EEVblog #801 - How To Design A Digital Clock

[EEVblog]

The next step for Ahmed Mohamed
How to design your own digital clock from 4000 series CMOS chips.
Dave reverse engineers a DIY clock he built back in the 1980's as a teenager (he lost the schematics, twice!)
Before the days of microcontrollers, cheap PCB's, and internet mail order parts, you built stuff on veroboard using discrete parts from your junk bin salvaged from old teardowns.
Does it use Texas Instruments chips from Radio Shack? :-D

Schematic: http://www.eevblog.com/files/DigitalClockSchematic.pdf

Datasheets of all your favourites:
https://www.fairchildsemi.com/datasheets/CD/CD4013BC.pdf
http://www.nxp.com/documents/data_sheet/HEF4040B.pdf
http://www.ti.com/lit/ds/symlink/cd4518b-mil.pdf
http://www.ti.com/lit/ds/symlink/cd4026b.pdf
http://www.ti.com/lit/ds/symlink/cd4511b.pdf

[Cliff Matthews]

Why was, or better put, who marked this as private?

[Delta]

Please sign in to see this video???

[AF6LJ]

I built one in the 70's using TTL it was a fun project.
This is a good beginner's project for someone learning digital logic, you really don't need a schematic, it is dead simple.

[zapta]

Why was, or better put, who marked this as private?

The clock had a Y2K bug. Dave is fixing it right now.

[WN1X]

Why was, or better put, who marked this as private?

I guess Dave doesn't want us to know what time it is 

[Cliff Matthews]

Please sign in to see this video???

I am signed-in and looking at my "EEVblog just uploaded a video" email. I'd guess there's so much activity, they've put restrictions on anything with this young lads name in it...
Update: After being posted 35 minutes ago, I can now watch it (screen grab from just 10 minutes ago..) - Draw your own conclusions...

[Barny]

One post on Twitter bevore he wrote that he shows his clock with many wires, he asked a company which uses explosives if he is allowed to visit them.

I think he have now some unwantet visitores which have many questions. 

[SeanB]

Works for me, don't know about the rest of you.........

CMOS, because you could drive LED displays directly from them at 5V without much risk of blowing up displays.

[Barny]

Strange.

Now, its working for me too.

[han]

Next step??


I found the frist step in youtube:
https://youtu.be/kHk_6Vh4Qeo

[EEVblog]

Why was, or better put, who marked this as private?

No one has access to my account but me.
I set it private because people were going to bitch about the 360p only. Turns out more people bitched about it being private 

[tggzzz]

Dave reverse engineers a DIY clock he built back in the 1980's as a teenager (he lost the schematics, twice!)
Before the days of microcontrollers, cheap PCB's, and internet mail order parts, you built stuff on veroboard using discrete parts from your junk bin salvaged from old teardowns.

Here's my variant, from around 1973: https://entertaininghacks.wordpress.com/2015/02/21/a-40-year-old-hack-disinterred/ and construction techniques: https://entertaininghacks.wordpress.com/2015/02/21/vintage-hacking-or-the-past-is-a-foreign-country-they-do-things-differently-there/

A few years earlier I built a 8 bit counter from discrete resistors capacitors and transistors, all salvaged from other equipment since I didn't have enough money to do otherwise. I used it to turn my radio off after a preset time.

[EEVblog]

I am signed-in and looking at my "EEVblog just uploaded a video" email. I'd guess there's so much activity, they've put restrictions on anything with this young lads name in it...
Update: After being posted 35 minutes ago, I can now watch it (screen grab from just 10 minutes ago..) - Draw your own conclusions...

There is no mystery, there is no restrictions being put on things. I made it private because it hadn't finished processing yet.

[EEVblog]

Here's my variant, from around 1973: https://entertaininghacks.wordpress.com/2015/02/21/a-40-year-old-hack-disinterred/ and construction techniques: https://entertaininghacks.wordpress.com/2015/02/21/vintage-hacking-or-the-past-is-a-foreign-country-they-do-things-differently-there/

Blah, it uses one of those new-fangled integrated clock chips, sacrilege!

[Delta]

Great video Dave.  I'm off upstairs to fire up the soldering iron! 😀

[Cliff Matthews]

Doesn't seem to be a 16-pin TTL version of the 4026, and the obsolete 24-pin 74143 would be pricey by now. Always loved the forward thinking of the 4000-series designs.

[SeanB]

IIL clock chips are nice, just that they run hot enough to cook on, and if the power fails battery life ( off that 9V battery they support) is only good for a few hours before it dies. CMOS will run for weeks off a coin cell, and I did hack in a LCD clock mechanism ( used the 32Hz backplane signal as a stable cheap clock source and a germanium transistor level translator because of the 0.5V swing it had) on one I did. 4V8 NiCd pack for backup with the display blanked, and the watch board was supplied using a simple resistor divider to give it 1V5 at the 100uA it needed. Selected resistors on test to get voltage to 1V5, just to get the value high.

Tossed it out a few years ago in a move. Sometimes I regret things.......

[SeanB]

Doesn't seem to be a 16-pin TTL version of the 4026, and the obsolete 24-pin 74143 would be pricey by now. Always loved the forward thinking of the 4000-series designs.

A lot of those designers were scratching their own itches, and designed stuff that solved problems they has come to experience, or that friends had experienced. That is why you had so many counters, especially the large number of ripple counters and the BCD dual ones.

[alexanderbrevig]

I love this video! Makes me want to throw out the µCU and try to get my hands dirty with CMOS

[asgard]

All well and good, Dave.  Righteous clock design.  However, I must call bullshit on the Ahmed bandwagon.  Here are the updated facts and context:

1.  Ahmed did not design that "clock" from scratch.  It was an existing Radio Shack clock removed from its enclosure and remounted into a briefcase.
2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.
4.  The entirety of the situation resembled nothing more than an improvised explosive detonator being taken into a public school.
5.  Ahmed Mohamed's father, instead of consulting with the school board (which is the legal and responsive authority on this matter), has contacted CAIR, which is in the process of manufacturing a racial incident out of this event.
6.  The same father, a known jihadist, has twice ran campaigns for the presidency of Sudan, which last I checked, is not known as a wellspring of democracy but is known for impressing children into suicide bombers, as part of President Bashir's policy of global jihad and arms supply to Hamas and Hizbullah.

[AF6LJ]

All well and good, Dave.  Righteous clock design.  However, I must call bullshit on the Ahmed bandwagon.  Here are the updated facts and context:

1.  Ahmed did not design that "clock" from scratch.  It was an existing Radio Shack clock removed from its enclosure and remounted into a briefcase.
2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.
4.  The entirety of the situation resembled nothing more than an improvised explosive detonator being taken into a public school.
5.  Ahmed Mohamed's father, instead of consulting with the school board (which is the legal and responsive authority on this matter), has contacted CAIR, which is in the process of manufacturing a racial incident out of this event.
6.  The same father, a known jihadist, has twice ran campaigns for the presidency of Sudan, which last I checked, is not known as a wellspring of democracy but is known for impressing children into suicide bombers, as part of President Bashir's policy of global jihad and arms supply to Hamas and Hizbullah.

Good Job, all factual.
I love it when someone posts the truth in such a concise form. 

[Delta]

Modified to be a countdown timer? Where did you read that?  From what I've seen, that sounds far above the young man's abilities...

[neotesla]

Get off of it, he's just a kid.

Geez... fighting the war on terror even here.

[Svuppe]

Ahh, that clock brings back memories.
I made one out of CD40192's back in my youth. They could count in both directions, and had a preset input so I could make it go from 00 to 59 when counting down (instead of 00 to 99).

[wraper]

All well and good, Dave.  Righteous clock design.  However, I must call bullshit on the Ahmed bandwagon.  Here are the updated facts and context:

1.  Ahmed did not design that "clock" from scratch.  It was an existing Radio Shack clock removed from its enclosure and remounted into a briefcase.
2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.
4.  The entirety of the situation resembled nothing more than an improvised explosive detonator being taken into a public school.
5.  Ahmed Mohamed's father, instead of consulting with the school board (which is the legal and responsive authority on this matter), has contacted CAIR, which is in the process of manufacturing a racial incident out of this event.
6.  The same father, a known jihadist, has twice ran campaigns for the presidency of Sudan, which last I checked, is not known as a wellspring of democracy but is known for impressing children into suicide bombers, as part of President Bashir's policy of global jihad and arms supply to Hamas and Hizbullah.

Good Job, all factual.
I love it when someone posts the truth in such a concise form. 

Crap job, reposting bullshit (consisting of lies mixed with some real information) found in sewers of internet.

[AF6LJ]

All well and good, Dave.  Righteous clock design.  However, I must call bullshit on the Ahmed bandwagon.  Here are the updated facts and context:

1.  Ahmed did not design that "clock" from scratch.  It was an existing Radio Shack clock removed from its enclosure and remounted into a briefcase.
2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.
4.  The entirety of the situation resembled nothing more than an improvised explosive detonator being taken into a public school.
5.  Ahmed Mohamed's father, instead of consulting with the school board (which is the legal and responsive authority on this matter), has contacted CAIR, which is in the process of manufacturing a racial incident out of this event.
6.  The same father, a known jihadist, has twice ran campaigns for the presidency of Sudan, which last I checked, is not known as a wellspring of democracy but is known for impressing children into suicide bombers, as part of President Bashir's policy of global jihad and arms supply to Hamas and Hizbullah.

Good Job, all factual.
I love it when someone posts the truth in such a concise form. 

Crap job, reposting bullshit (consisting of lies mixed with some real information) found in sewers of internet.

We all are entitled to our opinion.
One thing you and I have in common, we were not there to witness any of the facts.

[wraper]

We all are entitled to our opinion.
One thing you and I have in common, we were not there to witness any of the facts.

Then try to modify such clock into being countdown timer. That's where the credibility of that info ends. Also his father is not Jihadist (if you know what this word means).

[SeanB]

The IIL clock chip has a clock, alarm with snooze and a countdown timer, for it's designed use as a part of a clock radio, where you can have the radio on or off, or use it as a wake up aid ( like I do) or to fall asleep using the radio, while it turns off so as not to awaken you during the night. Hidden feature is that you can get a display of the minutes digit ( not 10's of minutes) and the seconds count on the display, just by holding down a combination of the input selector buttons.

 A lot of clock radios also use the redundant power switch on the small edge variable resistor volume control as a method to inject 100/120Hz or a 400Hz signal into the audio amplifier instead of the radio audio, with the open switch removing a short across a voltage divider, that is fed into the amplifier chip after the volume control at a fixed loud level.

[AF6LJ]

We all are entitled to our opinion.
One thing you and I have in common, we were not there to witness any of the facts.

Then try to modify such clock into being countdown timer. That's where the credibility of that info ends. Also his father is not Jihadist (if you know what this word means).

That shouldn't be so hard, I know where there is one of those clocks, might be fun.....
Most of those clock chips have a countdown timer function, just because it is in a table clock doesn't mean the chip doesn't have the functionality.

[SeanB]

MM5314 is one, amongst others.

TMS3450NL another. LM8560 yet another.

[AF6LJ]

OR;
You can just go to the Dollar Store and buy a kitchen timer.   

[free_electron]

7490 ( for decade dividers ) 7492 ( for /6 dividers ) 7447 or 7448(display decoders) and a few and gates

50 hz :
7490 div 5
7490 div 5
7590 div 2  -> 1hz 50% duty cycle clock

60hz :
7492 div 6
7490 div 5
7490 div 2 -> 1hz 50% duty clock

seconds
7490 one's
7492 tens
minutes
7490 one's
7492 tens
hours
7490 one's
7492 tens     ( you only count to 12 and add an AM pM indicator  . )
7400 NAND gate

[AF6LJ]

This use to be the go-to first project for those of us who wanted to play with digital logic.

[Howardlong]

7490 ( for decade dividers ) 7492 ( for /6 dividers ) 7447 or 7448(display decoders) and a few and gates

50 hz :
7490 div 5
7490 div 5
7590 div 2  -> 1hz 50% duty cycle clock

60hz :
7492 div 6
7490 div 5
7490 div 2 -> 1hz 50% duty clock

seconds
7490 one's
7492 tens
minutes
7490 one's
7492 tens
hours
7490 one's
7492 tens     ( you only count to 12 and add an AM pM indicator  . )
7400 NAND gate

Sounds very much like the one I made in the mid 70s. The tricky thing then for a 12yo was to work out how to make the hour display from a 7492 which is a div-by-6 plus div-by-2, and make it BCD to feed to a couple of 7447s. I designed some logic solution, I can't remember exactly what the design was, but it used two or three 74xx SSI devices to achieve it. That was the hardest part of the design, I spent a long while writing truth tables and dry running it while I saved up my pocket money for the parts.

[krivx]

Dave, did you not use PNPs at the time?

[Dave Turner]

I used to have great fun experimenting with TTL in the early 70's. This biggest problem was obtaining parts. unless you could find bargain bins or rare surplus/damaged equipment (rare because TTL was still relatively new). The cost new was anything upwards from 10 shillings (50p in decimal money) from hobby shops.

IC sockets and continual tear downs was the name of the game.

I spent more time with truth tables than I did with a soldering iron.

[SeanB]

NPN was a lot more common in old equipment, plus it made the logic easier not changing conventions.  It does not work well with DTL to mix PNP and NPN in gates, especially if one is driving the other. It either will be always on or always off, or will have even worse noise immunity than it already has. Worse it can sit in the middle of the indeterminate range and oscillate.

[LabSpokane]

Dave - outstanding!  I hope that a lot of people scrounge up the parts and give that a whirl.   

[apis]

Crap job, reposting bullshit (consisting of lies mixed with some real information) found in sewers of internet.

Yeah, indeed, that's how certain internet groups operate. They keep piling up the lies mixed with a gain of truth.

[apis]

Really cool clock Dave!

Clever using the mains frequency as clock, love the discrete diode/transistor logic and the 0.1 second display was a nice touch!

[Cliff Matthews]

Dave, did you not use PNPs at the time?

That was in the 60's germanium transistor era when PNP's were used more. I built my first 2-tranny kit radio on the 2N107 around the time when SCR color-organs were built from Christmas-tree lights jammed into old speaker boxes covered with Plexiglas diffusers     I'm sure the drugs made them look better (far out man..)

[nitro2k01]

3.  Said clock/timer was executing an active countdown when the incident occurred.

Source?

5.  Ahmed Mohamed's father, instead of consulting with the school board (which is the legal and responsive authority on this matter), has contacted CAIR, which is in the process of manufacturing a racial incident out of this event.
6.  The same father, a known jihadist, has twice ran campaigns for the presidency of Sudan, which last I checked, is not known as a wellspring of democracy but is known for impressing children into suicide bombers, as part of President Bashir's policy of global jihad and arms supply to Hamas and Hizbullah.

As much as Ahmed's father may be a less sympathetic person who took advantage of the situation after the fact, that proves nothing about the events leading up to it. Was Ahmed instructed to wear a NASA t-shirt too, to give that authentic "kid who's into STEM fields" look? In short, don't judge the son by the father.

[AF6LJ]

We do tend to use what we cut our teeth on.
Dave made a comment regarding microcontrollers in the video. We actually had the 8031 and the 8051 before 1980. One place I worked in 1979 was building ticket issuing machines for a number of airlines and their ticket printer used a 9 pin print head and an 8051 to control it. (I could be off on the numbers but Intel was building dedicated controllers back then.) The rest of the machine except for the data modem was controlled by an Intel 8080 SBC. (single board computer). The 300 baud modem was all discreet CMOS all wirewrapped together.

 

[int2str]

Dave,

How do you adjust that clock?
If it's all BCD overflow logic, does that mean you have to run to every 10th of a second to get to the right time?

[SeanB]

Would have been an 8748 for the development, and an 8048 for the production units. Still have some 8748 chips around, and a unit with one in it that I really should tear apart.

Clock setting was described, he had a switch pair that selected either the regular count input, or a 10x faster one, for both seconds and minutes. Reset was by depowering it then count up to right time.

[Howardlong]

The reminiscing over recycled parts took me back. My old recovered IC collection has seen better days.


Things like IC sockets were an unnecessary expense for most parts: still are today, but I gave the right tools now to replace them on the odd occasion it's necessary!

The parts I still have don't quite go back to the 60s, although at one stage in the mid 70s I often substituted DTL parts for TTL parts which were from the late 60s. The oldest here looks like a 74153 from 1970. There are a couple of 2102 RAM chips in there, AY-5-1013 uarts, an 8080, and some recovered TTL with letters like AZ, HZ, or M22 in large characters for example. These were TTL rebadged, the Z meant high speed Schottky. Some of you may remember the sticky paper pinouts you could stick on your chips too.

[zapta]

Really cool clock Dave!

Clever using the mains frequency as clock, love the discrete diode/transistor logic and the 0.1 second display was a nice touch!

I read once that utility companies used to adjust the number of cycles during the day for the benefit of clocks like this.

Anybody knows if this is true?

[Fungus]

How do you adjust that clock?

You have to plug it in at exactly midnight!


(either that or sit and watch the whole first minute of an EEVBLOG video)

[rdl]

Nice video. I have a very similar clock built on a plastic breadboard that I was playing around with because I wanted one that displayed the seconds. Most commercial clocks are 4 digit only. I used the 4026 chips also, though the reset at 6 count is done differently. The only reason I stopped working on it was because I decided I wanted 12/24 hour capability, then I got sidetracked onto other things. I really need to go back and finish it up.

[LabSpokane]

Really cool clock Dave!

Clever using the mains frequency as clock, love the discrete diode/transistor logic and the 0.1 second display was a nice touch!

I read once that utility companies used to adjust the number of cycles during the day for the benefit of clocks like this.

Anybody knows if this is true?

True.  Using the mains frequency as a clock synchronizer is how clocks kept time for decades.  And the number of cycles was adjusted mainly as an efficiency and power plant capacity issue.  The frequency would slow down during the day as the load increased, then it would be correspondingly sped up at night so that each day would have the same number of mains frequency cycles. 

BPA, I believe, did a test recently to see how many systems were still dependent on mains synchronization for timing.  The answer was: not many.  They may actually allow the mains frequency counts to vary from day to day in the future.  You would need to check with the operators of your particular power grid to know how they are handling this now. 

[LabSpokane]

And could I request that everyone just shut up about the whole Ahmed situation now?  That is just going nowhere. 

This thread is about building a clock.  And that's something really damned cool - and a very accessible, basic-building block project for a lot of interested electronics folks. 

[SeanB]

Used to be true, but now most have decided that they will allow a certain number of cycles slippage with heavy load and will not recover them at night with low load. You might be lucky in that you only lose a few seconds per month, but they pretty much decided it was too expensive to get the controllers to aim for midnight on the master clock to agree with UTC.

[Macbeth]

All well and good, Dave.  Righteous clock design.  However, I must call bullshit on the Ahmed bandwagon.  Here are the updated facts and context:

2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.
4.  The entirety of the situation resembled nothing more than an improvised explosive detonator being taken into a public school.

Good Job, all factual.
I love it when someone posts the truth in such a concise form. 

Me too. This is great. Of course I am assuming you septics just using the kind of sardonic humour us limeys are known for? 

I mean as that great American John McEnroe stated "You cannot be serious!?"

As for Achmed, I think all of us and the media should just forget about it, at least until we find teachers being sacked for political correctness reasons or some other outrage. Dave closed the last thread, so I don't know why he effectively started another.

[Dinsdale]

Yeah, that clock is the bomb, Dave.

[Macbeth]

Used to be true, but now most have decided that they will allow a certain number of cycles slippage with heavy load and will not recover them at night with low load. You might be lucky in that you only lose a few seconds per month, but they pretty much decided it was too expensive to get the controllers to aim for midnight on the master clock to agree with UTC.

Kitchen clocks all used to run on the mains to keep time in the UK, but then cheap batteries and 32.768kHz crystals took over. Later we had accurate clocks using radio broadcasts for synchronisation. Now it's NTP.

[Howardlong]

And could I request that everyone just shut up about the whole Ahmed situation now?  That is just going nowhere. 

This thread is about building a clock.  And that's something really damned cool - and a very accessible, basic-building block project for a lot of interested electronics folks.

+1. Thank you.

[alien_douglas]

Great clock Dave.

I never ever made a clock. I did make frequency counter that did look very similar in construction to your clock.
I love veroboard 

Great stashes of old components, brings back memories.
My first ever job was as an electronics service engineer for IBM. I also collected many 7400 series chips from old faulty boards. The big problem was that IBM used to part number almost everything back in the eighties.
Although it may have been a standard TI 7401 TTL chip it would only have an IBM part number on it.  I could never remember all the IBM seven digit part numbers so a translation list was a must.

And yes, everything was part numbered especially for IBM, from SnapOn tools to Tektronics scopes.

And my favourite CMOS chip that I used everywhere was the 4017 (Not the 4026. Sorry Dave.)
I used to make blinky LED lights for my scale model projects. 4017 rocks...

Alien

[tggzzz]

I read once that utility companies used to adjust the number of cycles during the day for the benefit of clocks like this.

Not quite. For many decades non-clockwork clocks used the mains frequency as the time reference. LED digital clocks were a latecomer.

I believe that the average frequency is still required to be 50Hz. IIRC there are some moves to remove that restriction - not least because we are down to about a 2% capacity margin. Why? Due to the total failure of the market (with the complicity of government) to provide adequate generating capacity.

[tggzzz]

Here's my variant, from around 1973: https://entertaininghacks.wordpress.com/2015/02/21/a-40-year-old-hack-disinterred/ and construction techniques: https://entertaininghacks.wordpress.com/2015/02/21/vintage-hacking-or-the-past-is-a-foreign-country-they-do-things-differently-there/

Blah, it uses one of those new-fangled integrated clock chips, sacrilege!

Well, at that time TTL was very new, very expensive[1] and required an "accurate" 5V supply - all of which was a problem for an impecunious youngster.

[1] especially 7447s, looking at the adverts in http://www.americanradiohistory.com/Archive-Wireless-World/70s/Wireless-World-1973-02.pdf

[g0hjq]

My first major project was a TTL digital clock, built during the school summer holidays in 1977. It used a 4:12 decoder and a diode matrix for the 12 hours display.

More recently, I've just finished building a kit using discrete Diodes/Tranistor logic with around 200 transistors, 500 diodes and no ICs. http://www.transistorclock.com

[Howardlong]

My first major project was a TTL digital clock, built during the school summer holidays in 1977. It used a 4:12 decoder and a diode matrix for the 12 hours display.

More recently, I've just finished building a kit using discrete Diodes/Tranistor logic with around 200 transistors, 500 diodes and no ICs. http://www.transistorclock.com

Beautiful. Pornographic even.

[Macbeth]

[1] especially 7447s, looking at the adverts in http://www.americanradiohistory.com/Archive-Wireless-World/70s/Wireless-World-1973-02.pdf

Oh wow, I love going through old magazines... Page a16 "Candles are for eskimos" totally takes me back to the 70's, I can't remember a time when the 'leccy wasn't cut. The UK was worse than North Korea at the time. Though I think it wasn't just the national strikes but my parents being out of work and out of 50p's shillings for the meter just as often. I totally remember the candles. It's also why I loved my crystal set. Those Ever-Ready batteries never lasted more than 5 minutes 

ETA: The 50p's were for the, can you believe it, pay-slot colour TV. I preferred the black and white because we could have that on any time. To use the colour we had to put 50p in the slot and wind a dial and then it would tick away...  Oh fuck, life was grim in the '70s...

[EEVblog]

All well and good, Dave.  Righteous clock design.  However, I must call bullshit on the Ahmed bandwagon.  Here are the updated facts and context:
1.  Ahmed did not design that "clock" from scratch.  It was an existing Radio Shack clock removed from its enclosure and remounted into a briefcase.

For the 1 millionth time, everyone knows this. It was bleedingly obvious to anyone with electronics knowledge who saw that photo.
So what? Beginners have to start somewhere, many of us were in the exact same position.

2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.

I call bullshit. Provide proof.
Exactly how do you modify a commercial clock chip to down?
Please be precise and technical in your answer.
Because if experiences electronics people don't know how to do it, I'm pretty sure Ahmed, who is clearly a rank beginner has no clue how to do that.

[EEVblog]

All well and good, Dave.  Righteous clock design.  However, I must call bullshit on the Ahmed bandwagon.  Here are the updated facts and context:

1.  Ahmed did not design that "clock" from scratch.  It was an existing Radio Shack clock removed from its enclosure and remounted into a briefcase.
2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.
4.  The entirety of the situation resembled nothing more than an improvised explosive detonator being taken into a public school.
5.  Ahmed Mohamed's father, instead of consulting with the school board (which is the legal and responsive authority on this matter), has contacted CAIR, which is in the process of manufacturing a racial incident out of this event.
6.  The same father, a known jihadist, has twice ran campaigns for the presidency of Sudan, which last I checked, is not known as a wellspring of democracy but is known for impressing children into suicide bombers, as part of President Bashir's policy of global jihad and arms supply to Hamas and Hizbullah.

Good Job, all factual.
I love it when someone posts the truth in such a concise form. 

Crap job, reposting bullshit (consisting of lies mixed with some real information) found in sewers of internet.

We all are entitled to our opinion.
One thing you and I have in common, we were not there to witness any of the facts.

There is no need for opinion, this is purely a technical question. Please explain how a commercial desk clock chip can be modified into a countdown timer.

[EEVblog]

Dave, did you not use PNPs at the time?

Sure, but NPN's worked just fine.

[LabSpokane]

All well and good, Dave.  Righteous clock design.  However, I must call bullshit on the Ahmed bandwagon.  Here are the updated facts and context:
1.  Ahmed did not design that "clock" from scratch.  It was an existing Radio Shack clock removed from its enclosure and remounted into a briefcase.

For the 1 millionth time, everyone knows this. It was bleedingly obvious to anyone with electronics knowledge who saw that photo.
So what? Beginners have to start somewhere, many of us were in the exact same position.

2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.

I call bullshit. Provide proof.
Exactly how do you modify a commercial clock chip to down?
Please be precise and technical in your answer.
Because if experiences electronics people don't know how to do it, I'm pretty sure Ahmed, who is clearly a rank beginner has no clue how to do that.

Picture help:


http://www.ebay.com/itm/Micronta-Vintage-Digital-Alarm-Clock-with-Large-Red-Display-63-765A-/271992316574?hash=item3f5401629e

Buy this clock for over $150 and prove Dave and common sense wrong. 

[EEVblog]

We do tend to use what we cut our teeth on.
Dave made a comment regarding microcontrollers in the video. We actually had the 8031 and the 8051 before 1980.

Yes, but almost no one in the hobby field used micro's until basically the PIC16C84 came out in 1993 (no flash parts then).
It was not a cheap or easy field to get into like it is now.

[EEVblog]

How do you adjust that clock?
If it's all BCD overflow logic, does that mean you have to run to every 10th of a second to get to the right time?

By very careful fast forwarding.

[Macbeth]

There is no need for opinion, this is purely a technical question. Please explain how a commercial desk clock chip can be modified into a countdown timer.

Especially by a lad who clearly doesn't know one end of a soldering iron from the other. I mean it doesn't work both ways. He's either a rank amateur who knows how to twiddle a screwdriver, or a genius bomb-maker who goes to the extreme of reverse engineering a fucking radio alarm clock instead of going with a much simpler 555 timer or Arduino or the good old mechanical switch on the minute hand trick... In fact I remember using potassium permangate and glycerine as a fuse - no electronics or mechanics needed.

[EEVblog]

http://www.ebay.com/itm/Micronta-Vintage-Digital-Alarm-Clock-with-Large-Red-Display-63-765A-/271992316574?hash=item3f5401629e
Buy this clock for over $150 and prove Dave and common sense wrong.

As always, I'm happy to be proven wrong.
It might very well have a countdown timer in it, but can't say I've ever seen one.
And if it does require some form of technical hack to do it (no evidence of in photo), then Ahmed has much better skills then it seems half the world is shooting him down in flames for lack of.

[EEVblog]

More recently, I've just finished building a kit using discrete Diodes/Tranistor logic with around 200 transistors, 500 diodes and no ICs. http://www.transistorclock.com

Wow, very nice! 

[Deathwish]

[1] especially 7447s, looking at the adverts in http://www.americanradiohistory.com/Archive-Wireless-World/70s/Wireless-World-1973-02.pdf

Oh wow, I love going through old magazines... Page a16 "Candles are for eskimos" totally takes me back to the 70's, I can't remember a time when the 'leccy wasn't cut. The UK was worse than North Korea at the time. Though I think it wasn't just the national strikes but my parents being out of work and out of 50p's shillings for the meter just as often. I totally remember the candles. It's also why I loved my crystal set. Those Ever-Ready batteries never lasted more than 5 minutes 

ETA: The 50p's were for the, can you believe it, pay-slot colour TV. I preferred the black and white because we could have that on any time. To use the colour we had to put 50p in the slot and wind a dial and then it would tick away...  Oh fuck, life was grim in the '70s...

You must of lived next door to me !. ditto

[tggzzz]

[1] especially 7447s, looking at the adverts in http://www.americanradiohistory.com/Archive-Wireless-World/70s/Wireless-World-1973-02.pdf

Oh wow, I love going through old magazines... Page a16 "Candles are for eskimos" totally takes me back to the 70's, I can't remember a time when the 'leccy wasn't cut. The UK was worse than North Korea at the time.

I still keep candles, and have very occasionally used them.

I'll stock up next year, before the lights go out again - this time because we don't have the generating capacity. See https://www.ofgem.gov.uk/publications-and-updates/security-electricity-supply-faqs and read between the lines Or maybe the domestic lights won't go out, because the businesses on cheap rates will get "load shedded".

Though I think it wasn't just the national strikes but my parents being out of work and out of 50p's shillings for the meter just as often. I totally remember the candles. It's also why I loved my crystal set. Those Ever-Ready batteries never lasted more than 5 minutes 

ETA: The 50p's were for the, can you believe it, pay-slot colour TV. I preferred the black and white because we could have that on any time. To use the colour we had to put 50p in the slot and wind a dial and then it would tick away...  Oh fuck, life was grim in the '70s...

Some things were better (e.g chemistry lessons), some weren't (e.g. bicycle lights).

[kwass]

Yes, but almost no one in the hobby field used micro's until basically the PIC16C84 came out in 1993 (no flash parts then).
It was not a cheap or easy field to get into like it is now.

Maybe not that cheap but it was easy ... mostly becasue of Digikey (not sure if they sold outside of the US back then).

There was the INS8073 chip and development board.  The INS8073 had NSC Tiny Basic built in and the development board that Digikey sold (can't remember the model number of this)  provided the hardware for writing tokenized BASIC programs directly to EPROM. 
http://www.classiccmp.org/cini/pdf/NatSemi/INS8073_DataSheet.pdf

You didn't need anything more than a dumb terminal and simple power supply to start using this micro for projects.  It was on the expensive side but I made a few projects with them.  This was was back in 1981, way before the PIC and the BASIC Stamp, etc..  There were a few other single chip/development boards too that were targeted for hobbyists.

Back then and well before that, Digikey was only a hobbyist company.  They started off selling surplus electronics via a typewritten and hand drawn 8 page catalog.  Later they sold a lot of NSC clock modules and PCB kits to "make your own".  I used to make those to order for my family and friends, there were lots of options to pick from on these modules: alarms, temperature display, date display, etc..  Digikey had interesting stuff before they started selling to the industry.

[Macbeth]

Some things were better (e.g chemistry lessons), some weren't (e.g. bicycle lights).

I think that's why I went all rogue and started making explosives as a kid in the '80s. Because I was fucking annoyed that I never had the opportunity to choose my "options" which I was going to drop rubbish like Art, French, Knitting and concentrate on Chemistry, Physics, Maths. The school merged with another one and the politics involved meant that nerd subjects were elitist and they brought in "General Science" instead. It was nothing more than an excercise in reading comprehension - and the subjects were such as "what western capitalists put in your sausages - these are the evil chemicals... Wall's puts walls (brick dust) in your sausages..." (I kid you not!)

There is a reason the National Union of Teachers is the NUT.

Yep. Self taught. Badly taught no doubt, but much better than the NUTters in charge of the school tried to indoctrinate me with.

As for bicycle lights - back then we would use dynamos if lucky, otherwise just hope the Ever-Ready would last longer than 5 minutes (oh if only batteriser existed then!). But nowadays NOBODY uses lights even though they are effectively free in the 99p shop. All the local scallies think they are "well 'ard" by riding about at night on the wrong side of the road deliberately without any lights. Insanity! 

[AF6LJ]

All well and good, Dave.  Righteous clock design.  However, I must call bullshit on the Ahmed bandwagon.  Here are the updated facts and context:

1.  Ahmed did not design that "clock" from scratch.  It was an existing Radio Shack clock removed from its enclosure and remounted into a briefcase.
2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.
4.  The entirety of the situation resembled nothing more than an improvised explosive detonator being taken into a public school.
5.  Ahmed Mohamed's father, instead of consulting with the school board (which is the legal and responsive authority on this matter), has contacted CAIR, which is in the process of manufacturing a racial incident out of this event.
6.  The same father, a known jihadist, has twice ran campaigns for the presidency of Sudan, which last I checked, is not known as a wellspring of democracy but is known for impressing children into suicide bombers, as part of President Bashir's policy of global jihad and arms supply to Hamas and Hizbullah.

Good Job, all factual.
I love it when someone posts the truth in such a concise form. 

Crap job, reposting bullshit (consisting of lies mixed with some real information) found in sewers of internet.

We all are entitled to our opinion.
One thing you and I have in common, we were not there to witness any of the facts.

There is no need for opinion, this is purely a technical question. Please explain how a commercial desk clock chip can be modified into a countdown timer.

The indivudal that posted after me gave you part numbers for commonly used clock chips that end up in every;thing from actual colcks to microwave ovens.
No opinion just fact. You really don't think companies like Radio Shack would have their own clock chip rolled for them? I knew you didn't, boils down to economics the cheapest chip for the job is most likely the one that is used in the most appliances.
Seriously. Odds are that chip used in said clock is also used on some brand of microwave oven...
 

[Deathwish]

I once told one of my sons I would put solar panels on his bike for his lights, he asked me what he was meant to do if it was night or no sunlight, I told him he should be at home watching TV or in bed. I wont repeat his reply.

[AF6LJ]

My first major project was a TTL digital clock, built during the school summer holidays in 1977. It used a 4:12 decoder and a diode matrix for the 12 hours display.

More recently, I've just finished building a kit using discrete Diodes/Tranistor logic with around 200 transistors, 500 diodes and no ICs. http://www.transistorclock.com

That is too Cool, nice workmanship.

[pickle9000]

@dave

That's a pretty good format, covers a massive amount of material in a short time.

[EEVblog]

Maybe not that cheap but it was easy ... mostly becasue of Digikey (not sure if they sold outside of the US back then).

If they technically did it would have been difficult (before online e-commerce).
I had never heard of Digikey until the Internet era.
We had Farnell & RS back then, but you had to be a business and have a credit account.

[EEVblog]

That's a pretty good format, covers a massive amount of material in a short time.

40 minutes was much longer than I wanted!

[trophosphere]

I made a clock back in High School that is still running to this day (~10 years old) that I did a write-up for way back when located here

[Stupid Beard]

I still keep candles, and have very occasionally used them.

Same here. They get used every time there's a power cut. A couple of christmases ago we had no power for about a week. In the end they parked a big mobile genny in the street to give everyone power on christmas eve. I was actually a bit disappointed; I was looking forward to a BBQ in the cold/rain.

The frequency of power cuts was also a large part of my reasoning behind getting a butane soldering iron many years ago. The idea being it would give me something to do in a power cut. There's been lots of power cuts since and I don't think I've ever used the butane iron during one, so that turned out well. Nowadays I mostly use it to shrink heatshrink.

[EEVblog]

The indivudal that posted after me gave you part numbers for commonly used clock chips that end up in every;thing from actual colcks to microwave ovens.
No opinion just fact. You really don't think companies like Radio Shack would have their own clock chip rolled for them? I knew you didn't, boils down to economics the cheapest chip for the job is most likely the one that is used in the most appliances.
Seriously. Odds are that chip used in said clock is also used on some brand of microwave oven...
 

More words and guesses.
Come back when you have identified the chip used in Ahmeds clock, and how it's possible to make it count down. And if it requires a hardware hack, please point that out where that is on the photo.
I'm not doubting it might be possible, but where is the real evidence?

[EEVblog]

I made a clock back in High School that is still running to this day (~10 years old) that I did a write-up for way back when located here

Wow, that's detailed, nice work.
And sweet wiring too!
http://www.mshieh.com/Hardware/Projects/DigitalClock_2/16.php

[zapta]

And could I request that everyone just shut up about the whole Ahmed situation now?  That is just going nowhere. 

Read the first post. This thread about the next step for Ahmed and how he can really design a clock.

I don't understand why Ahmed ticks you off.

[Macbeth]

I still keep candles, and have very occasionally used them.

Same here. They get used every time there's a power cut. A couple of christmases ago we had no power for about a week. In the end they parked a big mobile genny in the street to give everyone power on christmas eve. I was actually a bit disappointed; I was looking forward to a BBQ in the cold/rain.

The frequency of power cuts was also a large part of my reasoning behind getting a butane soldering iron many years ago. The idea being it would give me something to do in a power cut. There's been lots of power cuts since and I don't think I've ever used the butane iron during one, so that turned out well. Nowadays I mostly use it to shrink heatshrink.

Blimey, where do you live? The only time we had a power cut since the glory days of trade unions in the 70's was a year ago when I noticed my server powering down and rebooting and then the house lights dimming randomly. I chucked one of those power meters into a socket and found the mains had dropped as much as USA levels but hovered around 160VAC. Out on the street all the sodium lamps were flickering or off. Turns out on the high street the underground transformer caught fire and there were flames coming up from the paving stones. Quite bizzarre experience.

As for butane iron. I got one thinking it would be good for fixing stuff on the car... erm... maybe not 

[AF6LJ]

The indivudal that posted after me gave you part numbers for commonly used clock chips that end up in every;thing from actual colcks to microwave ovens.
No opinion just fact. You really don't think companies like Radio Shack would have their own clock chip rolled for them? I knew you didn't, boils down to economics the cheapest chip for the job is most likely the one that is used in the most appliances.
Seriously. Odds are that chip used in said clock is also used on some brand of microwave oven...
 

More words and guesses.
Come back when you have identified the chip used in Ahmeds clock, and how it's possible to make it count down. And if it requires a hardware hack, please point that out where that is on the photo.
I'm not doubting it might be possible, but where is the real evidence?

The same applies to you, you have No idea what chip is in that clock.
Even if I bought the same brand of clock that doesn't mean it would use the same chip.
You are also guessing.

[LabSpokane]

And could I request that everyone just shut up about the whole Ahmed situation now?  That is just going nowhere. 

Read the first post. This thread about the next step for Ahmed and how he can really design a clock.

I don't understand why Ahmed ticks you off.

I like Ahmed fine.  I'm tired of reading about all the guessing about the poor kid's motivations. 

[TerminalJack505]

Nice time machine, Doc.

[EEVblog]

The same applies to you, you have No idea what chip is in that clock.
Even if I bought the same brand of clock that doesn't mean it would use the same chip.
You are also guessing.

I'm not the one making claims!

[EEVblog]

Read the first post. This thread about the next step for Ahmed and how he can really design a clock.

Err, no, that's a just a throw-away line because of recent events.
I did not make this video for Ahmed.

[EEVblog]

Blimey, where do you live? The only time we had a power cut since the glory days of trade unions in the 70's was a year ago when I noticed my server powering down and rebooting and then the house lights dimming randomly.

We rarely get power cuts or brownouts here.
At home, maybe once a year at worst, and it's usually just for a few seconds. Maybe one major blackout in the 10+ years we've been there that lasted long enough for us to go "we'll, what do we do now?".
At the lab I've never had a single blackout (don't know about nights when not here), just maybe 3-4 glitches in the 4 years I've been here. Coincidently I got one this morning actually. Didn't reboot the computer, but dimmed the lights.

[AF6LJ]

The same applies to you, you have No idea what chip is in that clock.
Even if I bought the same brand of clock that doesn't mean it would use the same chip.
You are also guessing.

I'm not the one making claims!

I have seen universal clock chips before while browsing data sheets.
I think it is silly for you to just catigorically say I am wrong.

Men can't live with them, can't live with out them.

[adprom]

I have seen universal clock chips before while browsing data sheets.
I think it is silly for you to just catigorically say I am wrong.

Men can't live with them, can't live with out them.

Dude, whether it is possible or not is irrelevant. Conspiracies are being stated as fact. On one had, the conspiracy nutters are saying well he didn't design anything and just disassembled a clock and reassembled in another receptacle to discredit him technically.

Then the very next point, to continue the conspiracy theory, saying how it had been modified into a countdown timer. Even if it had, then it would require more than just disassembly.

You can't have it both ways, but more importantly you can't state conspiracy as fact.

[EEVblog]

I have seen universal clock chips before while browsing data sheets.
I think it is silly for you to just catigorically say I am wrong.

 
Again, I'm not the one making claims!
You made a claim (well, you backed up someone else's claim, saying it's "factual") that the clock counted down. You get to prove it, that's how it works.
I'm not saying it's not possible, but it seems unlikely. It's a reasonable position to hold until you actually provide evidence or proof.

You said, and I quote:

Good Job, all factual.

in response to these supposed facts:

2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.

Prove it.

[6581]

Thank you so much Dave for #801! I hope I learnt something - all that logic gate stuff to reset at specific condition, tricking 7-segment to show something else than counter state is - all good stuff for someone like me taking baby steps into using old school relatively easy to understand 4000 or 7400 series chips. Love it. Huge amount of information in a video like this. Thanks! 

[mswhin63]

Thanks Dave, bring back memories for me too.

Just a quick question, on the resetting of the 4026's how are you using the carry before it has finished its count?

[EEVblog]

Just a quick question, on the resetting of the 4026's how are you using the carry before it has finished its count?

IIRC (from 25 years ago!) the carry will still work when you force the reset.

[bitwelder]

Great video, Dave! 
Not that microcontroller rubbish, thankyouverymuch.

[sbprojects]

As it so happens I have build my own 24 hour CMOS clock a few months ago, just for fun. The parts had been sleeping in my junk box for over 30 years.
Check out the detailed description of it if  you like at http://www.sbprojects.net/projects/cmosclock/

[Howardlong]

Just a quick question, on the resetting of the 4026's how are you using the carry before it has finished its count?

IIRC (from 25 years ago!) the carry will still work when you force the reset.

There was a bone of contention back in the day (when I did my TTL clock) about using ripple counter outputs on non-synchronous resets because it is possible, if the data sheets are taken literally, that the counter may not fully reset on the required condition combination. As no minimum propagation delays are generally quoted,  technically they "should" be considered to be zero. Of course, in reality this was not what happened and the practice tying outputs to reset inputs this was very common because it worked.

On the clock I made, not having enough experience, I chose to do it the hard way, and cobbled together all sorts of SSI logic to make it work technically correctly within the data sheet spec, but it added a fair bit of extra complication. But as a 12yo, it taught me an awful lot about digital design logic, reading datasheets, and being analytical.

The 4026 is a Johnson counter (plus decode) rather than a ripple counter but the same concepts still apply, that it is possible that the counter may end up in an undefined state if the reset pulse is too short. Again, of course, in practice there was always sufficient propagation delay between input and output as well as "give" in the real life specs that this worked: use of the technique was very common.

[krivx]

Dave, did you not use PNPs at the time?

Sure, but NPN's worked just fine.

Cheers Dave. I ask because I know I tended to "think in NPN" (and still do, to some extent) and will often grab NPNs first even if a PNP circuit could do the same thing with fewer parts.

[SeanB]

The simplest way to ensure that you meet the minimum reset pulse length is to use a capacitor of around 10n  across the DTL logic gate, which means it has a built in delay on going high so meeting the required width. Going low is fast, but a delay going high. Might cause an issue if you are using a ripple counter with a fast clock input ( clock period less than reset pulse width) where you might get an incorrect count as some gates reset threshold is slightly different from the others so they might reset as a clock arrives and miscount, but for low frequency or with a short pulse no worry.

You can see that on Dave's board.

[tggzzz]

I made a clock back in High School that is still running to this day (~10 years old) that I did a write-up for way back when located here

Mine 1973-ish clock still runs, and I updated it to become more "interesting": https://entertaininghacks.wordpress.com/2015/02/23/vetinari-digital-clock/

[tggzzz]

The frequency of power cuts was also a large part of my reasoning behind getting a butane soldering iron many years ago. The idea being it would give me something to do in a power cut. There's been lots of power cuts since and I don't think I've ever used the butane iron during one, so that turned out well. Nowadays I mostly use it to shrink heatshrink.

I remember using a soldering iron that was a lump of copper that you heated up on the gas stove - but not for semiconductor-scale things. It would probably still be useful where large amounts of heat are needed, e.g. soldering two sheets of copper together when making a shield. I'll try and find it sometime.

[Stupid Beard]

Blimey, where do you live? The only time we had a power cut since the glory days of trade unions in the 70's was a year ago when I noticed my server powering down and rebooting and then the house lights dimming randomly.

I'm in West Sussex. I think http://www.bbc.co.uk/news/uk-25515310 is the christmas one I was thinking of, and it was the worst one that we've had in a long time. We do have the odd 1 or 2 every year or two when there's bad storms, but they usually only last around a day.

On a slightly more on topic note, I found my old clock project. Just hooked it up to my bench supply and it still works. It's PIC based rather than CMOS, sorry about that. I lashed it together over a few days whilst bored one christmas many years ago after finding a bit of MDF in the cupboard. It's funny where inspiration comes from sometimes.



The unlit LED on the outer ring indicates the hour, the center LEDs are the minutes in binary (blue flashes once per second, green is the 10s of minutes, orangey red the rest). I nicknamed it the clock of doom because the minutes LEDs were initially so damn bright you couldn't actually look at the clock. I remember trying to add PWM for the LEDs, then realising I fucked up and did PFM instead and never got around to fixing it.

The two extra holes on the front were going to be for an LDR (for auto dimming the LEDs) and the DS1820, but I never got around to adding the LDR and I made the leads for the DS1820 far too short and couldn't be arsed to fix it.



It uses a PIC18F448 (which was seriously overkill), a DS1307 with inappropriately loaded crystal, and a DS1820 for the temperature. I was actually surprised when I turned it back on to find that it was only 5 minutes fast. I think it has been a couple of years since I adjusted the time.

The hours LEDs are charlieplexed and the minutes LEDs are just connected straight to GPIO pins. The debouncing on the buttons is terrible so they frequently miss presses. They do let you set the time, however, as well as turn off the (extremely annoying) flashing blue LED, the seconds display and the temperature.

For years I've been meaning to redo this project properly and fix all it's many quirks and idiotic mistakes. Maybe I'll finally get around to it; the discrete clock was particularly inspiring.

[SeanB]

I have seen universal clock chips before while browsing data sheets.
I think it is silly for you to just catigorically say I am wrong.

 
Again, I'm not the one making claims!
You made a claim (well, you backed up someone else's claim, saying it's "factual") that the clock counted down. You get to prove it, that's how it works.
I'm not saying it's not possible, but it seems unlikely. It's a reasonable position to hold until you actually provide evidence or proof.

You said, and I quote:

Good Job, all factual.

in response to these supposed facts:

2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.

Prove it.

http://www.nteinc.com/specs/2000to2099/pdf/nte2062.pdf

Datasheet of a pretty common clock chip. Page 2 table 5 shows how to get the display to show a countdown timer on the sleep function.

On some clocks that use a diode matrix to change the arrangement of the switches ( you have a time set switch to press first) You need to have time set pressed first along with alarm set and sleep to get this display to show, and an active sleep running.

[GK]

Here's my teen clock; just pulled from the junkbox. I'm surprised it's still so intact.

HH.MM.SS display, 74LS90+74LS47 for each digit. A 2MHz XTAL oscillator based on a single 4011 gate is divided down to 1Hz by six 4017 decade counters and 1/2 a 4013 DFF wired to toggle in series. 555 timers wired as monostables to de-bounce the time-setting push-buttons. Discrete RTL gates for handling the manual-set functions.

The 2MHz XTAL doesn't appear to be on the board anymore. I abandoned this project and never packaged it because I could never get it to keep accurate time - it would loose several minutes per day IIRC. I didn't know enough about XTAL loading/capacitance specifications at the time and the trimmer cap visible was just some random (unknown value) that I salvaged from a radio or something. I do recall soldering in different kinds of values. This was before the internet and all I had for reference was my Dick Smith Funway and Tandy Forrest M Mimms books.

My workshop is currently without a clock. Hmmm.....I think that I should finally fix the oscillator properly and commission this clock by fixing the wiring and mounting it on a wall-hanging board with a sheet of perspex over the front.

[SeanB]

Probably the biggest thing leading to the poor time keeping is the lack of decoupling capacitors. Those are definitely needed on the oscillator to keep it stable, as the fast edges will affect thresholds on the gates and leads to jitter on the clock. Also a thick short wire from the crystal capacitors to the Vss pin and a similar one on the longer lead of the supply decoupling cap. Might even benefit from the Vdd supply being fed through a ferrite bead and a decoupling capacitor before and after it.

Slap a few across random counters, a 10uF electrolytic on the input 5v rail and it should work better.

Other than that it should be nice to have on the wall.

[GK]

Yes, it appears to have rather spartan power supply decoupling.

[Fungus]

http://www.nteinc.com/specs/2000to2099/pdf/nte2062.pdf

Datasheet of a pretty common clock chip. Page 2 table 5 shows how to get the display to show a countdown timer on the sleep function.

 

Yes, but was the clock in question actually modified that way? Was it counting down when he took it to school?

[f4eru]

Hello Dave,

Nice optimizations and tricks in your clock

For the hour counting, I would have used half a 4520 wired as modulo 12 counter, and a similar bit of glue logic to convert that to the needed 1,5 digit signals...
This way you could replace the 4013 used for the AM/PM by the second half of that 4520 (with no reset, just use the LSB and let it count modulo 16) -> spare one IC.

Or in fact, I would in fact have made a 24 hour clock, as this format is more common here than AM/PM...

When I was young, I made a LED clock with a bunch of leds arranged in two concentric rings.
I also brought it to school, and no one freaked out.
It was made on two self made PCBs with hand drawn traces + decals directly on copper clad ..... Wow, when I think about that .....
The design came from a elektor or elex.

Elex was a very very funny electronics magazine with a lot of funny illustrations :

look at p4/5 here for a nice story how 7 segment displays are organized )) :

http://docsenstock.free.fr/a/elex/LX1989-13+.pdf

(yeah it's french, but you will understand the story from the pictures anyway.)
Wanted : complete scans of the "Elex" magazines ....

At the lab I've never had a single blackout (don't know about nights when not here)

Your clock has a nice side effect feature of detecting power losses in the night by resetting

Blah, it uses one of those new-fangled integrated clock chips, sacrilege!

Yep, that IC is definitely not in production any more, whereas all the logic IC you used can be bought for 10-50cent today.

a genius bomb-maker who goes to the extreme of reverse engineering a fucking radio alarm clock instead of going with a much simpler 555 timer or Arduino or the good old mechanical switch

A 555 is not a good idea for a bomb timer, or any similar long timing : at long times it becomes unreliable because of the leakage current overcoming the capacitive charge current.
I suggest using a 4060 with a much faster oscillator and a big division factor instead.

[johnwa]

Nice clock Dave! I found the circuit vaguely familiar as I was watching, and, after a bit of rummaging through old magazines, I think I have tracked down what it reminded me of: the Talking Electronics clock project. This appears to use the same count-to-12 arrangement, though the display format is different. Perhaps this might have been an inspiration for you - I know you were a big fan of Colin's work.

The 10Hz fast set is a nice touch - I think some of the designs using stray 50Hz might have been a bit temperamental.

[zapta]

Err, no, that's a just a throw-away line because of recent events.
I did not make this video for Ahmed.

This explains the lack of detonator output in your design.

;-)

[Ed.Kloonk]

Must have been awful waiting 10,12 and 24 hours to debug that hour circuit.

I believe we don't have precise power frequency anymore. I recall in the news a while back that they were abandoning the daily clock watching/adjustment at the power stations.

Does anyone know more about this?

[AF6LJ]

I have seen universal clock chips before while browsing data sheets.
I think it is silly for you to just catigorically say I am wrong.

Men can't live with them, can't live with out them.

Dude, whether it is possible or not is irrelevant. Conspiracies are being stated as fact. On one had, the conspiracy nutters are saying well he didn't design anything and just disassembled a clock and reassembled in another receptacle to discredit him technically.

First off I am not a DUDE, I am female. Perhaps you should check people's profiles once and a while.
And no I am not going to address your comment, not worth the bandwidth here.

Then the very next point, to continue the conspiracy theory, saying how it had been modified into a countdown timer. Even if it had, then it would require more than just disassembly.

And you have evidence the clock was only disassembled? please lets see it.

You can't have it both ways, but more importantly you can't state conspiracy as fact.

When you have provable facts please come back with them and their sources.

[AF6LJ]

I have seen universal clock chips before while browsing data sheets.
I think it is silly for you to just catigorically say I am wrong.

 
Again, I'm not the one making claims!
You made a claim (well, you backed up someone else's claim, saying it's "factual") that the clock counted down. You get to prove it, that's how it works.
I'm not saying it's not possible, but it seems unlikely. It's a reasonable position to hold until you actually provide evidence or proof.

You said, and I quote:

Good Job, all factual.

in response to these supposed facts:

2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.

Prove it.

I am simply backing up what was reported in the news. You are making the claim I am somehow wrong without anything to back it up.
But hay..
I get it.

[AF6LJ]

I have seen universal clock chips before while browsing data sheets.
I think it is silly for you to just catigorically say I am wrong.

 
Again, I'm not the one making claims!
You made a claim (well, you backed up someone else's claim, saying it's "factual") that the clock counted down. You get to prove it, that's how it works.
I'm not saying it's not possible, but it seems unlikely. It's a reasonable position to hold until you actually provide evidence or proof.

You said, and I quote:

Good Job, all factual.

in response to these supposed facts:

2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.

Prove it.

http://www.nteinc.com/specs/2000to2099/pdf/nte2062.pdf

Datasheet of a pretty common clock chip. Page 2 table 5 shows how to get the display to show a countdown timer on the sleep function.

On some clocks that use a diode matrix to change the arrangement of the switches ( you have a time set switch to press first) You need to have time set pressed first along with alarm set and sleep to get this display to show, and an active sleep running.

Thank You...

[f4eru]

It depends heavily on how the grid is managed.

Here in Europe, a frequency is guaranteed at normal times, there is very little variation, due to phase sync of a big number of grids.
The reason is that there is still a lot of domestic appliances keeping time based on the grid.
Advantage is the drift is limited to, say, 30s. With a quartz based clock, the drift is not limited, and you have to trim the clock time every few months.
Drawback is the non deterministic drift. 50/60 Hz automatic switching can be done if the uC has an internal clock with 5% frequency accuracy.


https://www.swissgrid.ch/swissgrid/en/home/experts/topics/frequency.html
https://en.wikipedia.org/wiki/Synchronous_grid_of_Continental_Europe
http://wwwhome.cs.utwente.nl/~ptdeboer/misc/mains.html


Now, if the whole synchronized grid is in an emergency situation, or if one part falls out of sync, there could be a significant frequency deviation
This frequency deviation is how the power companies decide to do load shedding....
See for example here ( in german) http://blog.fefe.de/?ts=aba55ed4

One funny thing to notice is that the UK is, as usual, not playing ball with the rest of the EU, so their grid needs more reserve power ( they can exchange a "little bit" of power to the EU through inverters ), and this is one of the reasons (along with crumbling infrastructure) that they have a lot more power outages.

One of the problematic countries is Japan, separated in two zones : 50 and 60 Hz... These two zones are also connected by HVDC inverters

[rdl]

I found my old unfinished clock project in the closet. Plugged it in and it started fine. It looks like the hours counting logic is missing which would make sense because I think that's what I was working on when I shelved it 2 years ago. I'm thinking now that maybe I'll forget about the 12/24 switching and just finish it up as 12 hour am/pm because I know I had that much working correctly.

[zapta]

Here in Europe, a frequency is guaranteed at normal times, there is very little variation, due to phase sync of a big number of grids.
The reason is that there is still a lot of domestic appliances keeping time based on the grid.
Advantage is the drift is limited to, say, 30s. With a quartz based clock, the drift is not limited, and you have to trim the clock time every few months.
Drawback is the non deterministic drift. 50/60 Hz automatic switching can be done if the uC has an internal clock with 5% frequency accuracy.

How do they sync between all the power stations connected to the same grid?  Is there some master that determines the frequency/phase and everybody else locks to it?  Or, is it some symmetric system when they all lock to each other and a way that guarantees convergence?

It seems to be a very challanging problem, considering the scale and complexities of the grid and the energy levels involved.

[tggzzz]

Here in Europe, a frequency is guaranteed at normal times, there is very little variation, due to phase sync of a big number of grids.
The reason is that there is still a lot of domestic appliances keeping time based on the grid.
Advantage is the drift is limited to, say, 30s. With a quartz based clock, the drift is not limited, and you have to trim the clock time every few months.
Drawback is the non deterministic drift. 50/60 Hz automatic switching can be done if the uC has an internal clock with 5% frequency accuracy.

How do they sync between all the power stations connected to the same grid?  Is there some master that determines the frequency/phase and everybody else locks to it?  Or, is it some symmetric system when they all lock to each other and a way that guarantees convergence?

It seems to be a very challanging problem, considering the scale and complexities of the grid and the energy levels involved.

It is challenging. For one station re-attaching to a functioning grid, "all" it has to do it is sync with the cables going past the station.

The real problems would arise in a complete grid failure, not least because a power station needs an electricity supply to "get going" in the first place! This is the so-called "black start" problem: https://en.wikipedia.org/wiki/Black_start 

In the UK hydro plants are designated for black start capacity, e.g. https://en.wikipedia.org/wiki/Cruachan_Power_Station

[LabSpokane]

Here in Europe, a frequency is guaranteed at normal times, there is very little variation, due to phase sync of a big number of grids.
The reason is that there is still a lot of domestic appliances keeping time based on the grid.
Advantage is the drift is limited to, say, 30s. With a quartz based clock, the drift is not limited, and you have to trim the clock time every few months.
Drawback is the non deterministic drift. 50/60 Hz automatic switching can be done if the uC has an internal clock with 5% frequency accuracy.

How do they sync between all the power stations connected to the same grid?  Is there some master that determines the frequency/phase and everybody else locks to it?  Or, is it some symmetric system when they all lock to each other and a way that guarantees convergence?

It seems to be a very challanging problem, considering the scale and complexities of the grid and the energy levels involved.

It is a very challenging problem.  Phase synchronization issues can cause very large blackouts.  For power transmission, the phasor is used to convey magnitude and phase of the real and complex part of voltage and current in the form:



There is a master clock for each grid authority.  In the US we have three major grids:  West, East, and Texas ERCOT. 

In the US, we are moving to using synchrophasors http://energy.gov/articles/how-synchrophasors-are-bringing-grid-21st-century in order synchronize the phase angles between generation stations.  Synchrophasors are referenced to a common clock such as GPS and then transmitted to a common, coordinating authority.  Schweitzer Labs, has a good primer as well as live data to view:

https://www.selinc.com/synchrophasors/

[Howardlong]

I assume the same problem exists for renewable feed-ins, albeit at a much lower power. How do they synchronise for maximum power transfer?

[LabSpokane]

Interestingly enough, one of the things we got to do in the EE power lab was to synch generators up to the grid.  It's actually possible to do with three light bulbs, one for each phase.  When there is a difference in phase between your generator and the grid, the bulbs will illuminate proportionally to the phase difference.  As you bring your generator into sync, the bulbs go dark, and then you can transfer your generator onto the grid. 

Crude, to be sure, but it was a great visual introduction into phase synchronization. 

[LabSpokane]

I assume the same problem exists for renewable feed-ins, albeit at a much lower power. How do they synchronise for maximum power transfer?

I'll ask.  I know that it's a problem because the renewable generators like to push in 100% of the generation regardless of the demand.  This forces the utilities to not only follow the load, but also follow the renewables generation level. The phase synchronization technique varies with wind turbines since some are synchronous generators and some are induction, so the latter has slip. 

[jancumps]

...Perhaps you should check people's profiles once and a while.
...

I did, and the first hit was "Why has AG6K been Banned Here ?" Must use a different search mechanism...

[AF6LJ]

...Perhaps you should check people's profiles once and a while.
...

I did, and the first hit was "Why has AG6K been Banned Here ?" Must use a different search mechanism...

You obviously didn't click on my screen name over to the left did you?

[jancumps]

I didn't at first . I did now.

[AF6LJ]

I didn't at first . I did now.

Even in this day and age finding a female in this business is uncommon.
Think of what it was like when I started in the mid 70s.
If it wasn't for one acquaintance of my family that owned a service shop in Oregon I would likely not had made into electronics as a career let alone RF and two way radio.

[ez24]

Interestingly enough, one of the things we got to do in the EE power lab was to synch generators up to the grid.  It's actually possible to do with three light bulbs, one for each phase.  When there is a difference in phase between your generator and the grid, the bulbs will illuminate proportionally to the phase difference.  As you bring your generator into sync, the bulbs go dark, and then you can transfer your generator onto the grid. 

Crude, to be sure, but it was a great visual introduction into phase synchronization.

Do you know of any videos on this?

[LabSpokane]

Interestingly enough, one of the things we got to do in the EE power lab was to synch generators up to the grid.  It's actually possible to do with three light bulbs, one for each phase.  When there is a difference in phase between your generator and the grid, the bulbs will illuminate proportionally to the phase difference.  As you bring your generator into sync, the bulbs go dark, and then you can transfer your generator onto the grid. 

Crude, to be sure, but it was a great visual introduction into phase synchronization.

Do you know of any videos on this?

No.  Sorry.

[warp_foo]

I still keep candles, and have very occasionally used them.

Same here. They get used every time there's a power cut. A couple of christmases ago we had no power for about a week. In the end they parked a big mobile genny in the street to give everyone power on christmas eve. I was actually a bit disappointed; I was looking forward to a BBQ in the cold/rain.

The frequency of power cuts was also a large part of my reasoning behind getting a butane soldering iron many years ago. The idea being it would give me something to do in a power cut. There's been lots of power cuts since and I don't think I've ever used the butane iron during one, so that turned out well. Nowadays I mostly use it to shrink heatshrink.

Blimey, where do you live? The only time we had a power cut since the glory days of trade unions in the 70's was a year ago when I noticed my server powering down and rebooting and then the house lights dimming randomly. I chucked one of those power meters into a socket and found the mains had dropped as much as USA levels but hovered around 160VAC. Out on the street all the sodium lamps were flickering or off. Turns out on the high street the underground transformer caught fire and there were flames coming up from the paving stones. Quite bizzarre experience.

As for butane iron. I got one thinking it would be good for fixing stuff on the car... erm... maybe not 

In Minnesota we are very prepared for whatever may come in during the winter. North Carolina, not so much.

In general, an NC winter is usually a bit frigid, somewhat damp, and usually overcast. Every few years, however, NC gets some fairly severe ice storms. The last one I was there for - maybe '96 or '97 - we were out of power for 3 full days. Pretty much every major power company East of the Mississippi sent crews to assist in getting the power back online. (Pro Tip: Kerosene heaters are not capable of warming up much more than a mid sized bedroom.)

If it isn't an ice storm and NC gets any snow coverage, you'll see news reports of the stores getting cleared out of food and bottled water. Really...

m

[apis]

I have seen universal clock chips before while browsing data sheets.
I think it is silly for you to just catigorically say I am wrong.

 
Again, I'm not the one making claims!
You made a claim (well, you backed up someone else's claim, saying it's "factual") that the clock counted down. You get to prove it, that's how it works.
I'm not saying it's not possible, but it seems unlikely. It's a reasonable position to hold until you actually provide evidence or proof.

You said, and I quote:

Good Job, all factual.

in response to these supposed facts:

2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.

Prove it.

I am simply backing up what was reported in the news. You are making the claim I am somehow wrong without anything to back it up.
But hay..
I get it.

Really... do you have any links to the news reports saying he had modified the clock to be a countdown timer? (And no, the hate-sites doesn't count as "news", real news sites like wall street journal or new york times, etc.) He either smashed a clock with a rock and threw the remains into a pencil case or he shrewdly modified the clock to be  countdown timer, you can't have it both ways. And in the end it doesn't matter, because it was stupid of the teachers to call the cops either way. You complain you live in a police state, yet you applaud when teachers call the police when a kid brings a clock mod to school and show his science teacher.

[apis]

It depends heavily on how the grid is managed.

Here in Europe, a frequency is guaranteed at normal times, there is very little variation, due to phase sync of a big number of grids.
The reason is that there is still a lot of domestic appliances keeping time based on the grid.
Advantage is the drift is limited to, say, 30s. With a quartz based clock, the drift is not limited, and you have to trim the clock time every few months.

Do you know how they do it in fennoscandia, I know there is a HVDC connection from southern Sweden to Germany. I think there is a link via the bridge to Copenhagen as well, Not sure if that is AC or DC though. I have a vague memory of reading the mains frequency is kept synchronized here as well but it was some time ago.

[cezar]

You guys have too many semiconductors in your clocks
http://thestuffwebuild.com/2015/07/the-electromechanical-relay-clock-project-is-complete/

Sent from my LG-D802 using Tapatalk

[apis]

Love the clicking of the relays, but wouldn't wan't it in my bedroom.

[Delta]

If you throw a three phase alternator onto a bus, it will either trip its breakers or lock to the bus frequency.  How close to synchronization it is when you throw the switch determines what happens. Like a previous poster said, lamps can be used, but there was always a syncrometer for the tech to use. I'll try to find a video, probably someone doing it on a ship...

AC generators on a common bus are phase locked by definition.  The amount of power they contribute (or consume! that's why there are always reverse power trips) depends purely on the torque provide by the prime mover.

[Macbeth]

I was just idly thinking what a waste of energy bench electronic loads are, chucking it away as heat, surely it could just be fed back into the mains? Not necessarily back into the grid (especially considering the pathetic amount paid for it these days), but just to take the burden from all the other lab gear, washing machine, microwave, lights, etc. on the mains from the electricity company and your bill.

Extra advantage - no need to dissipate all that heat. Run your load cool.

I found what look like some expensive commercial versions of this. Any DIY?

[EEVblog]

You guys have too many semiconductors in your clocks
http://thestuffwebuild.com/2015/07/the-electromechanical-relay-clock-project-is-complete/

That would drive the wife nuts! 

[Tac Eht Xilef]

You guys have too many semiconductors in your clocks
http://thestuffwebuild.com/2015/07/the-electromechanical-relay-clock-project-is-complete/

I need to find the pics of the uniselector & RP / one-plane readout clock I built during a few lunchtimes 30-odd years ago.

Now, where did I put those old Polaroids...?

[AF6LJ]

You guys have too many semiconductors in your clocks
http://thestuffwebuild.com/2015/07/the-electromechanical-relay-clock-project-is-complete/

Sent from my LG-D802 using Tapatalk

I like that soothing, I could go to sleep listening to that.

[AF6LJ]

I have seen universal clock chips before while browsing data sheets.
I think it is silly for you to just catigorically say I am wrong.

 
Again, I'm not the one making claims!
You made a claim (well, you backed up someone else's claim, saying it's "factual") that the clock counted down. You get to prove it, that's how it works.
I'm not saying it's not possible, but it seems unlikely. It's a reasonable position to hold until you actually provide evidence or proof.

You said, and I quote:

Good Job, all factual.

in response to these supposed facts:

2.  The clock was altered into a countdown timer, rather than an RTC.
3.  Said clock/timer was executing an active countdown when the incident occurred.

Prove it.

I am simply backing up what was reported in the news. You are making the claim I am somehow wrong without anything to back it up.
But hay..
I get it.

Really... do you have any links to the news reports saying he had modified the clock to be a countdown timer? (And no, the hate-sites doesn't count as "news", real news sites like wall street journal or new york times, etc.) He either smashed a clock with a rock and threw the remains into a pencil case or he shrewdly modified the clock to be  countdown timer, you can't have it both ways. And in the end it doesn't matter, because it was stupid of the teachers to call the cops either way. You complain you live in a police state, yet you applaud when teachers call the police when a kid brings a clock mod to school and show his science teacher.

To be honest any information I post here you would consider hate, as is usual often the truth is seen as hate speech by some.
Good Day.

[apis]

To be honest any information I post here you would consider hate, as is usual often the truth is seen as hate speech by some.
Good Day.

It doesn't matter what I consider hate speech, you said it was reported in the news and a fact.

The truth isn't hate speech (at least not if it's the truth the whole truth and nothing but the truth), but if people make up lies and spread rumors that are not true in order to discredit someone because they have a certain religion that is hate-speech in my book.

[adprom]

Dude, whether it is possible or not is irrelevant. Conspiracies are being stated as fact. On one had, the conspiracy nutters are saying well he didn't design anything and just disassembled a clock and reassembled in another receptacle to discredit him technically.

First off I am not a DUDE, I am female. Perhaps you should check people's profiles once and a while.
And no I am not going to address your comment, not worth the bandwidth here.

Firstly, in Australia dude is regularly used as a general reference without implying gender. No need to get your knickers in a knot.

What you have stated so far is no more than an unproven conspiracy.

And you have evidence the clock was only disassembled? please lets see it.

You don't seem to understand how this works. You are making claims without evidence, the impetus is on you to prove it - not for others to prove the negative assertion. This is basic stuff (something which conspiracy theorists and 'truthers' tend not make a mistake with.

When you have provable facts please come back with them and their sources.

I'm not the one making a claim - it is up to you when saying something is true to back it up. I am simply questioning the claims - it is not up to me to provide evidence that it isn't true. That isn't how it works.

So that's the point, if you make a claim, it is up to you to prove them with evidence. Not for me to provide evidence otherwise.

[bartm]

Hi Dave,

fun stuff to watch as usual. Just wondering about the carry from the seconds to the minute, and the minutes to the hour.
Shouldn't it be the reset there in stead of the carry ? the carry will only pulse on a 9->0 transition i presume.
See my scrible on the schematic.

regards,
Bart

[Macbeth]

Hi Dave,

fun stuff to watch as usual. Just wondering about the carry from the seconds to the minute, and the minutes to the hour.
Shouldn't it be the reset there in stead of the carry ? the carry will only pulse on a 9->0 transition i presume.
See my scrible on the schematic.

regards,
Bart

Well spotted, that makes sense to me. Now enough of that, can we get back to all the bomb talk  and conspiracy theories please? 

[EEVblog]

fun stuff to watch as usual. Just wondering about the carry from the seconds to the minute, and the minutes to the hour.
Shouldn't it be the reset there in stead of the carry ? the carry will only pulse on a 9->0 transition i presume.

No, the carry goes low once it hits 5 (see timing diagram) so the reset then switches it back high. So it works for any count >=5
http://www.ti.com/lit/ds/symlink/cd4026b.pdf

[linux-works]

Used to be true, but now most have decided that they will allow a certain number of cycles slippage with heavy load and will not recover them at night with low load. You might be lucky in that you only lose a few seconds per month, but they pretty much decided it was too expensive to get the controllers to aim for midnight on the master clock to agree with UTC.

Kitchen clocks all used to run on the mains to keep time in the UK, but then cheap batteries and 32.768kHz crystals took over. Later we had accurate clocks using radio broadcasts for synchronisation. Now it's NTP.

more and more, its GPS.  or some other IoT message transfer protocol that includes 'time' as a reportable variable

OT: I should dig up my own binary led clock that I built as a kid (late 70's).  I was given a handful of point source red and green leds and I used 7490's (etc) to show HH:MM:SS in red and green groups of those pt-src leds.  it had a funky 'use what you can find in a craft store' look for the chassis, too.  and it did use the local 60hz for its timebase; I supplied a wallwart with 9v ac into it, used a 7805 and local bridge/cap to create dc.

if seen today, it might be scary to someone who didn't know; but for those who could not understand binary, whether it was currently counting UP or DOWN would be totally lost on them

if I find the clock in my storage boxes, I'll snap some photos of it.  I built it when I was late teens and I'm over 50 now, so its been in storage for a long time..

[AF6LJ]

Dude, whether it is possible or not is irrelevant. Conspiracies are being stated as fact. On one had, the conspiracy nutters are saying well he didn't design anything and just disassembled a clock and reassembled in another receptacle to discredit him technically.

First off I am not a DUDE, I am female. Perhaps you should check people's profiles once and a while.
And no I am not going to address your comment, not worth the bandwidth here.

Firstly, in Australia dude is regularly used as a general reference without implying gender. No need to get your knickers in a knot.

Okay I can accept that, even though it may be considered impolite, that's okay there are a number of cultural differences between AU and US.

What you have stated so far is no more than an unproven conspiracy.

Perhaps; but consider what we don't know about the story.
Far too many details missing to rule out any one source of information at this time.

And you have evidence the clock was only disassembled? please lets see it.

You don't seem to understand how this works. You are making claims without evidence, the impetus is on you to prove it - not for others to prove the negative assertion. This is basic stuff (something which conspiracy theorists and 'truthers' tend not make a mistake with.

When you have provable facts please come back with them and their sources.

I'm not the one making a claim - it is up to you when saying something is true to back it up. I am simply questioning the claims - it is not up to me to provide evidence that it isn't true. That isn't how it works.

So that's the point, if you make a claim, it is up to you to prove them with evidence. Not for me to provide evidence otherwise.

I get that but it needs to be applied all the way around, including to those stories you and others like Dave favor.
One related thought;
The difference between a skeptic and a debunker is a skeptic is always after the truth, a debunker could care less about the truth when it doesn't fit his or her agenda.
I am the skeptic. And for now I am done with this urinating contest, I have better things to do like get on the radio and talk to my friends in Northern Kalifornia.

[EEVblog]

Firstly, in Australia dude is regularly used as a general reference without implying gender. No need to get your knickers in a knot.

Okay I can accept that, even though it may be considered impolite, that's okay there are a number of cultural differences between AU and US.

Another example: I call girls "guys" all the time. If I see a bunch of girls I know I go "hi guys". Guys is just the common collective term.

What you have stated so far is no more than an unproven conspiracy.

Perhaps; but consider what we don't know about the story.

Why are people unable to simply leave it at that?
This whole thing has bought out the worse in people, it's embarrassing.
When I first released the video and that blog post about the clock being a Radio Shack thing hadn't been posted yet, almost everyone was in support of Ahmed.
But then suddenly it went viral that it wasn't his design (even though that was obvious and even he said it was a 10-20min job), and the world went ape shit and turned on him. As if it's the greatest fraud in history that a 14yo kid overated his skills and used the wrong word to describe what he did.
And people accuse me of being manipulated by the media 

Far too many details missing to rule out any one source of information at this time.

You have zero sources of information that confirm your assertion.
You and others just want to ride the Ahmed hate train because *insert reason here*

So that's the point, if you make a claim, it is up to you to prove them with evidence. Not for me to provide evidence otherwise.

I get that, but

No, you don't get it. There is no but. You made a claim, you provide the evidence, or you get rightfully get shot down in flames for it.

but it needs to be applied all the way around, including to those stories you and others like Dave favor.

The only story I favor is giving a 14yo electronics hobbyists the benefit of any doubt. I'm guilty as charged.
If it turns out all the conspiracy stuff is all true, so be it. People can say "I told you so" all they like, they will still be the ones who were too pathetic enough to give a 14yo kid the benefit of the doubt.

The difference between a skeptic and a debunker is a skeptic is always after the truth, a debunker could care less about the truth when it doesn't fit his or her agenda.
I am the skeptic.

No, you are not. You have stated certain facts as being, and I quote you "all factual.". When pressed for evidence for that statement you haven't giving any. An agenda if there ever was one!

Many people know my strong thoughts on religion, Islam, and you can likely guess what I think of Ahmed's father, and yet I still support Ahmed - why?
Well, I can either give up on a 14yo kid and join the whole world in chorus about how he's a "fraud", and crap on about his family ties etc, but how is that going to help him?
Why are so many people now willing to throw a 14yo kid to the fire?
This story has turned an order of magnitude sader than I thought it was at the beginning.
And I'm sad for Ahmed that his father is dragging him off on some pilgrimage to Mecca. The kid needs to stay in school and keep learning. And he needs to hang out at a maker space after school with like minded people.

[adprom]

Okay I can accept that, even though it may be considered impolite, that's okay there are a number of cultural differences between AU and US.

It's just slang - not impolite. Blog forum of an aussie blogger - I'm willing to take a punt that our slang is fine here

Perhaps; but consider what we don't know about the story.
Far too many details missing to rule out any one source of information at this time.

Quoting unsubstantiated sources is akin to making it up which will always attract scrutiny. The problem is that claims were cited as fact, without any evidence. Quite rightfully, the obligation is on the party making said claims to prove they are correct. It is not up to another party to prove them wrong.

Otherwise I could say Ahmed's mother was a prostitute and state it as a fact and then argue against those who disagree demanding they show evidence to show I was wrong. Obviously this would be absurd.

And you have evidence the clock was only disassembled? please lets see it.

You don't seem to understand how this works. You are making claims without evidence, the impetus is on you to prove it - not for others to prove the negative assertion. This is basic stuff (something which conspiracy theorists and 'truthers' tend not make a mistake with.

I get that but it needs to be applied all the way around, including to those stories you and others like Dave favor.

No - it really doesn't that would be completely flawed. Someone who is introducing new information has the burden upon them to provide satisfactory proof that it is true.

One related thought;
The difference between a skeptic and a debunker is a skeptic is always after the truth, a debunker could care less about the truth when it doesn't fit his or her agenda.
I am the skeptic. And for now I am done with this urinating contest, I have better things to do like get on the radio and talk to my friends in Northern Kalifornia.

Not quite true. A sceptic is someone who habitually doubts the claims made. There is no assumption that this is rational. Rationality may or may not exist. There is no shortage of irrational sceptics out there (climate change, 9/11 truthers etc etc).

A debunker  is someone who takes a demonstrably false claim and shows it to be so. They don't necessarily take a particular position. To expose a false belief or idea as false is to debunk. In scientific circles, debunking is quite an objective process which requires clear evidence (as dave has done with Batteriser).

[EEVblog]

A debunker  is someone who takes a demonstrably false claim and shows it to be so. They don't necessarily take a particular position. To expose a false belief or idea as false is to debunk. In scientific circles, debunking is quite an objective process which requires clear evidence (as dave has done with Batteriser).

"Debunking" is quite an interesting concept. As often a debunker might indeed start out from an opinionated viewpoint, and sets about to prove it. That could be looked upon as bad, as starting out from a viewpoint can introduce bias etc, but a good debunking is one that sticks to the facts that are verifiable by others knowledgeable in the field, and even gives benefit of the doubt (playing devils advocate) as part of the debunking process. Ultimately though it always falls down to demonstrable facts to prove your case of course.

[AF6LJ]

Firstly, in Australia dude is regularly used as a general reference without implying gender. No need to get your knickers in a knot.

Okay I can accept that, even though it may be considered impolite, that's okay there are a number of cultural differences between AU and US.

Another example: I call girls "guys" all the time. If I see a bunch of girls I know I go "hi guys". Guys is just the common collective term.

No big deal the same happens here. You guys" has no gender attached to it here also. 

What you have stated so far is no more than an unproven conspiracy.

Perhaps; but consider what we don't know about the story.

Why are people unable to simply leave it at that?
This whole thing has bought out the worse in people, it's embarrassing.
When I first released the video and that blog post about the clock being a Radio Shack thing hadn't been posted yet, almost everyone was in support of Ahmed.
But then suddenly it went viral that it wasn't his design (even though that was obvious and even he said it was a 10-20min job), and the world went ape shit and turned on him. As if it's the greatest fraud in history that a 14yo kid overated his skills and used the wrong word to describe what he did.
And people accuse me of being manipulated by the media 

There were other issues; had his father simply been a manager at a 7-11 or something there would be no uproar over the incident.
Obama getting involved added to the suspicion.
There is a lot of internal politics involved in this issue including a known race pimping president.

Far too many details missing to rule out any one source of information at this time.

You have zero sources of information that confirm your assertion.
You and others just want to ride the Ahmed hate train because *insert reason here*

Sorry but that isn't true, I appeal to your sense of logic, at best we only have third hand testimony.
The news report wouldn't stand up in court if it were admitted as the testimony of a witness.
Dave I know you are too smart to fall for the "hate" canard.

So that's the point, if you make a claim, it is up to you to prove them with evidence. Not for me to provide evidence otherwise.

I get that, but

No, you don't get it. There is no but. You made a claim, you provide the evidence, or you get rightfully get shot down in flames for it.

I totally get it Dave; I don't gulp media Kool Aid or engorge myself in a banquet of media bullshit.

but it needs to be applied all the way around, including to those stories you and others like Dave favor.

The only story I favor is giving a 14yo electronics hobbyists the benefit of any doubt. I'm guilty as charged.
If it turns out all the conspiracy stuff is all true, so be it. People can say "I told you so" all they like, they will still be the ones who were too pathetic enough to give a 14yo kid the benefit of the doubt.

It is sad the child was used like this. Keep in mind you are talking about a country where the school droids suspend a child for eating a pop tart into the shape of a gun. You need to live here to fully understand the high degree of fear and stupidity that rules this country as it is being destroyed from within.

The difference between a skeptic and a debunker is a skeptic is always after the truth, a debunker could care less about the truth when it doesn't fit his or her agenda.
I am the skeptic.

No, you are not. You have stated certain facts as being, and I quote you "all factual.". When pressed for evidence for that statement you haven't giving any. An agenda if there ever was one!

So now I have to go and buy a radio shack alarm clock and modify it to count down, just so you can say it was not the same alarm clock or it didn't use the same chip, when you have no idea whatsoever what chip or how the board had been modified in said clock? That is a stretch sir.

Many people know my strong thoughts on religion, Islam, and you can likely guess what I think of Ahmed's father, and yet I still support Ahmed - why?
Well, I can either give up on a 14yo kid and join the whole world in chorus about how he's a "fraud", and crap on about his family ties etc, but how is that going to help him?
Why are so many people now willing to throw a 14yo kid to the fire?
This story has turned an order of magnitude sader than I thought it was at the beginning.
And I'm sad for Ahmed that his father is dragging him off on some pilgrimage to Mecca. The kid needs to stay in school and keep learning. And he needs to hang out at a maker space after school with like minded people.

I know why you support him and I am all with you on that, however we still don't know all the facts.
Again I appeal to your inner sense of logic.
We, including you know next to nothing about the actual events in question.

[zapta]

There is a master clock for each grid authority.  In the US we have three major grids:  West, East, and Texas ERCOT. 

The west coast is long and thus has significant phase difference between the ends, right? 

Assigning the optimal phase for each node on the grid is an interesting computational problem which I am sure was researched extensively. It's interesting to know how well it is solved by the local approach where each node just phase locks to its feed. It's also interesting to know if when they design the grid (e.g. adding lines), the include phase consistency considerations.

Dave had an episode where he visited a TV station. Would be interesting to see a similar one with a power station.

[EEVblog]

There were other issues; had his father simply been a manager at a 7-11 or something there would be no uproar over the incident.
Obama getting involved added to the suspicion.
There is a lot of internal politics involved in this issue including a known race pimping president.

Of course, no argument from me.

You have zero sources of information that confirm your assertion.

Sorry but that isn't true

That part is. Your continued inability to provide evidence to back up your claim is still noted.

I totally get it Dave; I don't gulp media Kool Aid or engorge myself in a banquet of media bullshit.

As above.

It is sad the child was used like this.

He is getting and will get use, yes, it's sad. His father and anyone else who can will ride this dog and pony show for all it's worth.

You need to live here to fully understand the high degree of fear and stupidity that rules this country as it is being destroyed from within.

Err, could have sworn I made a video talking about that...

So now I have to go and buy a radio shack alarm clock and modify it to count down, just so you can say it was not the same alarm clock or it didn't use the same chip, when you have no idea whatsoever what chip or how the board had been modified in said clock? That is a stretch sir.

You made a claim, you get to prove it. This is getting tiring.

I know why you support him and I am all with you on that, however we still don't know all the facts.

You'll get no argument from me on that.

Again I appeal to your inner sense of logic.
We, including you know next to nothing about the actual events in question.

Again, no argument.
So why try and shoot me down in flames for giving a 14yo kid the benefit of the doubt until facts do actually come in that tell a different story?
And BTW, even if it turns out he was setup/used/whatever, it's still ok to support a 14yo kid and help him. You can still support the kid and believe the conspiracies, they aren't mutually exclusive positions.
Personally I hope the kid does get a scholarship and moves to a school where he is surrounded by nothing but secular technical minded people.
Does he "deserve it" based on merit?, of course not, he seems to have little to no real technical skills or accomplishments, but I can still hope that happens for him.

[EEVblog]

Dave had an episode where he visited a TV station. Would be interesting to see a similar one with a power station.

It's on my blog wish-list (a.k.a get off my arse list).

[linux-works]

I don't really want to re-open this (now old) debate; but when people throw around things that have no citations, they need to be called out for it.

I looked and tried but could not find a single credible citation for this 'count down' notion that some posters are trying to have us believe.

either post something credible, applogize that you simply repeated conservative talking points on some blog, or shut the hell up already.  I think we've had enough spin on this from people trying to use this to forward their agenda.  put up or PLEASE just shut up.

(I start to wonder; should there be time-outs for people who insist on posting blatant lies and when called on it, cannot provide any backup?  if there is no negative consequences for posting lies, people will continue to do it.)

[asgard]

http://www.thedailybeast.com/articles/2015/09/21/nerds-rage-over-ahmed-s-clock.html

http://news.investors.com/ibd-editorials/092215-772291-did-muslim-clock-boy-perpetuate-hoax.htm

http://www.theguardian.com/science/2015/sep/20/richard-dawkins-questions-ahmed-mohamed-motive-backlash

http://www.nationalreview.com/corner/ahmed-mohamed-clock-bomb-media-narrative-ian-tuttle

http://toprightnews.com/uh-oh-this-is-what-happened-when-ahmeds-clock-invention-was-reverse-engineered/

http://ethicsalarms.com/2015/09/24/it-looks-like-ahmeds-cool-clock-was-a-hoax-after-all-now-what/

http://dfwci.com/blog4/ahmeds-clock-is-not-an-invention/

[LabSpokane]

There is a master clock for each grid authority.  In the US we have three major grids:  West, East, and Texas ERCOT. 

The west coast is long and thus has significant phase difference between the ends, right? 

I think that has historically been the issue with large grids, which leads to instability. That's the idea with synchrophasors that each generator station has a very accurate reference to a common clock. 

[KedasProbe]

Why was, or better put, who marked this as private?

Obviously he is hiding a bomb 

[linux-works]

(mess of blogs, bullshit and right-wing nutterscreeds deleted)

what point were you trying to make?

none of those are trusted sources.  not sure what your purpose was in posting that crap.  actually, I suspect I know ;(

[AF6LJ]

There were other issues; had his father simply been a manager at a 7-11 or something there would be no uproar over the incident.
Obama getting involved added to the suspicion.
There is a lot of internal politics involved in this issue including a known race pimping president.

Of course, no argument from me.

You have zero sources of information that confirm your assertion.

Sorry but that isn't true

That part is. Your continued inability to provide evidence to back up your claim is still noted.

I totally get it Dave; I don't gulp media Kool Aid or engorge myself in a banquet of media bullshit.

As above.

It is sad the child was used like this.

He is getting and will get use, yes, it's sad. His father and anyone else who can will ride this dog and pony show for all it's worth.

You need to live here to fully understand the high degree of fear and stupidity that rules this country as it is being destroyed from within.

Err, could have sworn I made a video talking about that...

So now I have to go and buy a radio shack alarm clock and modify it to count down, just so you can say it was not the same alarm clock or it didn't use the same chip, when you have no idea whatsoever what chip or how the board had been modified in said clock? That is a stretch sir.

You made a claim, you get to prove it. This is getting tiring.

I know why you support him and I am all with you on that, however we still don't know all the facts.

You'll get no argument from me on that.

Again I appeal to your inner sense of logic.
We, including you know next to nothing about the actual events in question.

Again, no argument.
So why try and shoot me down in flames for giving a 14yo kid the benefit of the doubt until facts do actually come in that tell a different story?
And BTW, even if it turns out he was setup/used/whatever, it's still ok to support a 14yo kid and help him. You can still support the kid and believe the conspiracies, they aren't mutually exclusive positions.
Personally I hope the kid does get a scholarship and moves to a school where he is surrounded by nothing but secular technical minded people.
Does he "deserve it" based on merit?, of course not, he seems to have little to no real technical skills or accomplishments, but I can still hope that happens for him.

I am going to address two things; then I am done not because of there being any "winner or looser" in this discussion; but because we are getting nowhere here.

First off.
As I stated we have no real information regarding the actual events surrounding this child, or the incident, we only have third hand testimony, hearsay, as a matter of fact it could be considered gossip, but some people take the word of the news media as the word of God. What passes for news in this day and age is seldom real news.

The other issue Dave;
I am not attacking you, just your position. There is a difference.
I respect you, I just think you give the news media the credit it doesn't deserve.

I am done you and everyone else get the last word.
 

[Fungus]

So now I have to go and buy a radio shack alarm clock and modify it to count down, just so you can say it was not the same alarm clock or it didn't use the same chip, when you have no idea whatsoever what chip or how the board had been modified in said clock? That is a stretch sir.

Nope. This is the fail.

You don't have to prove that it can be done, you have to prove that it WAS done.

[linux-works]

As I stated we have no real information regarding the actual events surrounding this child

so, just STFU then!

but actually, we do have info.  we know that if there was a 'count-down' feature added, that it would have been mentioned day-0 or day-1 at worst.  why is this being added to the conservate hate-blog talking points?  because they don't have enough real stuff to hate on this poor boy and, as faux news watchers regularly do, they make anything up they want and label it as 'fact' just to try to own the discussion and swerve it their way.

if you have facts, show an API or other news source and not some stupid hate-mongers blog!

or, again, just stfu.

[zapta]

...they don't have enough real stuff to hate on this poor boy...

Linux Works, you come to a conclusion without having the facts and then you complain that others  do the same and arrive to a different conclusion.

Your strong opinion is as unjustified as theirs.

[drws]

If I may just take the thread off topic and ask about the video... 

The part where the e, f, g segments are tapped to reset the chip, I just can't get my head around (and I know it will be simple).
I can see why, you don't have BCD output to do the reset, its more the voltage and current flow parts I'm trying to understand.
In the image I've attached, is the up arrow and resistor (in the blue circle) attached to the supply voltage / common 'logic high' voltage (not sure on the correct term, I don't mean 240v)?

The LEDs are common cathode where you set e, f and g 'high' if you want to light them, so then I see that conventional current travels down (the red highlighted cables) to the diodes which are reversed-biased from that perspective?
Then I got confused.

I've tried to go off and understand what is going on and come to this conclusion below. If the more experienced people (and to be honest Probes the Monkey is probably more experienced than me) could let me know if I'm in the right ballpark please.
Is it because when the segments are off, the red and green circled parts are 0v which means the right-hand side of the three diodes must be +0.6v or +1.8v? (because of diode forward Vdrop or 3x Vdrop?) and the resistor has to drop the supply voltage down to 0.6v/1.8v?
Then when the segments e,f and g go 'high' to Vsupply then the right of the diodes is Vsupply-0.6v which turns on the transistor? (i.e. the resistor doesn't need to drop as much voltage now.)

Not sure what happens when just one segment (or two) are high. The concept of an And gate I get, it just doesn't look like an And gate to me.
What is the voltage on the right of the three diodes when just one segment is lit?

*edit for some grammar.

[zapta]

The concept of an And gate I get, it just doesn't look like an And gate.

It is an AND gate. The output on the right side of the diodes is high only when the three inputs are high. A single low input forces the output to be low.  Draw the truth table and see what you get.

The only issue here is the inputs to the and gate are not standard 0-5V signals. That's why one transistor to amplify and another one to invert (other wise you would and with a NAND gate).

Dave could save one transistor and implement a NOR gate but I presume the seven segments sequence doesn't happen to have a set of output that are all low at 6 but not at 0-5. It's a kind of an opportunistic or trick design.

[drws]

I see, so the presence of even one diode with 0v on the left side will make the right side where all three meet always be 0.6v.
I'm ok with the truth table side of it, just trying to understand the physical side of it. I've only had the pleasure of using gates in the CMOS DIP variety. Maybe I should try and build one from just diodes.

[zapta]

I see, so the presence of even one diode with 0v on the left side will make the right side where all three meet always be 0.6v.
I'm ok with the truth table side of it, just trying to understand the physical side of it. I've only had the pleasure of using gates in the CMOS DIP variety. Maybe I should try and build one from just diodes.

This may help

https://en.wikipedia.org/wiki/Diode%E2%80%93transistor_logic

[Jr460]

Dave had an episode where he visited a TV station. Would be interesting to see a similar one with a power station.

It's on my blog wish-list (a.k.a get off my arse list).

Started off as a EE at a power station.  Not that much that is cool from an EE perspective unless you really know where to look.  The size and scale of things is very amazing.

I ended up mainly being the turbine guy for outages.  Each year a unit is taken down for a week or more for maintenance work.  Depending on what you know needs to be done, and what you suspect needs to be done, you must have all the spare parts around and ready to go.  Lots of planning.  Bring a unit back online after outage is timed so that someone else in the region can take their unit down.  I heard an unscheduled outage cost about $1,000,000 a day.

In terms of overall system control, that is handled not a at each station, but at some central company office.  That gets fun. 

One task is to keep the overall system freq. good over a 24 hour period.  So the software keeps a running total of how slow or fast the system has been.  Another goal is to generate what your local customers are using.  The next goal is to let X power flow in or out of your system based on who much you owe other companies, or they owe you.  (Some units are jointly owned and while you run the unit, someone else pays X%, you owe them X% of the power that unit generates).  And last but not least, tweak the amount of each of your units so that overall you are getting that power with the least amount of fuel.

The last part requires that you have curves for each unit of Heat Rate vs Mega Watts.  Most units get inefficient to run when under 50% loaded.  Those curves get computed by detailed load tests at least once a year under a bunch of conditions.  Not only do you need additional sets of temp, press, and flow measurements from all over the unit, you need exact careful lab work on the coal that was used during the test.  (Each barge of coal is different in the BTU per pound, water, ash and sulfur.  The coal lab at each plant runs almost all the time.)

Let me know, I'll be glad to answer anything I can remember.

[zapta]

Let me know, I'll be glad to answer anything I can remember.

I have many questions but they will be out of topic here. ;-)

Just a quick one, when you work in a power station, are you busy all time or just letting the computers do their job and waiting for the next incident?

[drws]

I see, so the presence of even one diode with 0v on the left side will make the right side where all three meet always be 0.6v.
I'm ok with the truth table side of it, just trying to understand the physical side of it. I've only had the pleasure of using gates in the CMOS DIP variety. Maybe I should try and build one from just diodes.

This may help

https://en.wikipedia.org/wiki/Diode%E2%80%93transistor_logic

Excellent, thanks. Its starting to sink in now. I knocked up a quick simulation and I can see the effect now of all off, some on and all on for the DTL AND gate, current paths and voltages etc.

Another noobie follow on question...
When I first saw the diagram (at the part where Dave paused the video for us to guess what was wrong) I was expecting the current to flow down through the resistor, then left through all three diodes (with a slight voltage drop) up through the three segments of the display (e,f,g - lighting them permanently) and through the common cathode+resistor to ground to complete the circuit. This would be whilst the 4026 was low for those segments.

Does the 4026 sink the current as well when its low on those pins or does the total path have too much resistance/voltage drop to light the segments?

[zapta]

Does the 4026 sink the current as well when its low on those pins or does the total path have too much resistance/voltage drop to light the segments?

The voltage at the right side of the diodes can be at most ~1.4v (voltage drop of two diodes, one of them in the transistor between B and E) so the pullup resistor can induce at most ~0.7v on the three inputs (1.4 - one diode drop) which is insufficient to light the LEDs.

[zapta]

fun stuff to watch as usual. Just wondering about the carry from the seconds to the minute, and the minutes to the hour.
Shouldn't it be the reset there in stead of the carry ? the carry will only pulse on a 9->0 transition i presume.

No, the carry goes low once it hits 5 (see timing diagram) so the reset then switches it back high. So it works for any count >=5
http://www.ti.com/lit/ds/symlink/cd4026b.pdf

What prevents it from starting at 7 (invalid value) on power up? 

[Jr460]

Let me know, I'll be glad to answer anything I can remember.

I have many questions but they will be out of topic here. ;-)

Just a quick one, when you work in a power station, are you busy all time or just letting the computers do their job and waiting for the next incident?

Just to keep it on topic.  I did build a digital clock when I was about 11-12 years old, mid 1970s.  Based on one of those fancy all-in-one clock chips. 

Computers, even in the newer units of the time did nothing in terms of running a unit.  The computer downtown, a PDP/11, sent commands to the tribune control to bump up or down the power set point.  But one push of a button on the controls and the turbine was all local, and would either stay at the load set, or follow the load.  The control systems took care of fuel feed rates air dampers, valve settings, etc.  I suspect that even new units, the control systems might get some "assist" from a computer, but can keep things running just fine without one. 

(Sorry to ruin it for all folks that think a hacker on the inter-webs can take over power plants.)

If all the computers were dead everywhere, then the units would run, and follow the load.  You wouldn't have adjustments for 24 hour freq. control, and you wouldn't get the best mix of loads across units for fuel usage.

The plant I worked at started with two units in 1917, those where gone by the time I got there, and that space was used by one of the newer units.  Two more units were mothballed.  Ripping out all the asbestos would have cost a lot, and the space wasn't needed at that time.  The next newest unit was built in the 1950, the next in the 1960, the next in the early 70s, and the newest in the late 70s.  That plant is still running.  I can tell from the outside that have added to the two largest units SOx scrubbers.  I suspect the oldest unit that ran when I was there has been shutdown.  It was designed for lower operating pressures, thus was not very efficient.

The oldest running unit had a very basic control system.  Lines from the control room to the plant were all pneumatic.  The two newest ones each had a room with about 24 racks full of analog controls for the turbine and boiler.  They may have had some 7400 type logic chips.  No one ever touched that stuff expect for once a year when the unit was down, techs from the respective manufactures would come in and help tweak and align the feedback controls.

Back to your basic question.  The "operations" staff were the guys that sat in the control rooms.  If everything was fine, they sat around and waited for something to show up on the panel.  If a unit's load went way down, they might have to shutdown a coal mill, and then later start one back up.  That required someone to follow a procedure to start motors and change valves, and light off the burners from that mill.  Sometimes going out into the plant and cranking something open or closed.  Full unit startup and shutdown, they were busy as hell and you stayed away from the control room and out of the way.  I think it was requirement that you were a member of the local biker club to be in operations.

"coal yard" was busy all the time, got to keep getting coal out of the barges.  The "maint" department always had someone in the plant, with most of them being in on the day shift.  Something always needed fixing.  I think they had the most people of any department. 

"Instruments and Controls" was always busy with scheduled work.  They would pull sensors on a schedule and bring them back in and calibrate them.  Service all the chart recorders,  file/catalog the charts.

I was mainly in "Tech Srvcs"  We had the lab.  Coal was analyzed, boiler water chemistry was monitored and adjusted.  We did the engineering for new projects, did all the efficiency studies.  Adjusted the feed water heaters and the electrostatic ash precips.

The precips might be fun for Dave to see.  Big hockey puck SCRs and control that are fast to detect and ramp back power before an arc can jump between the wires and plates.

Other than that it was few office people, management, cleaning staff, etc.

[drws]

Does the 4026 sink the current as well when its low on those pins or does the total path have too much resistance/voltage drop to light the segments?

The voltage at the right side of the diodes can be at most ~1.4v (voltage drop of two diodes, one of them in the transistor between B and E) so the pullup resistor can induce at most ~0.7v on the three inputs (1.4 - one diode drop) which is insufficient to light the LEDs.

of course! I'd completely forgot to consider a voltage drop to ground via the base-emitter of the transistor.
All makes sense now. Really appreciate you taking the time to explain it for me zapta. 

[NiHaoMike]

I was just idly thinking what a waste of energy bench electronic loads are, chucking it away as heat, surely it could just be fed back into the mains? Not necessarily back into the grid (especially considering the pathetic amount paid for it these days), but just to take the burden from all the other lab gear, washing machine, microwave, lights, etc. on the mains from the electricity company and your bill.

Extra advantage - no need to dissipate all that heat. Run your load cool.

I found what look like some expensive commercial versions of this. Any DIY?

Most electronic loads are not used enough to be worth doing that. It's mostly the problem of efficiently accepting power over a very wide voltage range.

[zapta]

Really appreciate you taking the time to explain it for me zapta. 

That stretched my electronic knowledge to its limit.  ;-)

[EEVblog]

I am done you and everyone else get the last word.

Good, because you couldn't back up a single claim you made.
Now, how about that 4000 series logic huh?

[sbprojects]

I love Dave's videos, but I've never got myself to join the forum. Especially for this topic I created an account to showcase my own series 4000 CMOS clock, which I have finished just a couple of months ago. http://www.sbprojects.net/projects/cmosclock/



Unfortunately I was brutally reminded why I'm not a forum person. I thought this forum, being an electronics engineering forum, would be different. I really can't understand why all these useless flames are going on here about whether Ahmed is a dangerous bomber or not. These discussions are pointless and leading us nowhere. There are people who believe every Muslim is a dangerous killer, while (fortunately) most other free thinking spirits know better than that. There's no way any of us can make either side think differently. There is simply no reasoning between the two camps. And the rest of us don't even care.
I appreciate that Dave doesn't sensor any of the messages. But perhaps he could flag some of the replies as “flame” so those of us who don't care can filter them out.

[EEVblog]

What prevents it from starting at 7 (invalid value) on power up?

Nothing. I showed that in the video. Just forward to fix.

[AF6LJ]

I am done you and everyone else get the last word.

Good, because you couldn't back up a single claim you made.
Now, how about that 4000 series logic huh?

4000 series is fine, I have seen it do some real great things back in 1974 like a 2-12 MHz PLL synthesizer in a man pack radio. The stuff wasn't real fast back then. I was just out of high school and a friend was a project engineer for a local communications equipment manufacturer. Learned a lot back in those days.

Besides;
The only person I have anything to prove to is Me.

[linux-works]

I appreciate that Dave doesn't sensor any of the messages.

his lm75 is just stuck, is all.

(sorry, bad joke.)

[Macbeth]

I love Dave's videos, but I've never got myself to join the forum. Especially for this topic I created an account to showcase my own series 4000 CMOS clock, which I have finished just a couple of months ago. http://www.sbprojects.net/projects/cmosclock/

Very nice, I like your breakdown of the circuit. Unadblocked, and ahem, interesting links clicked too... Apparently I have >1000 Russian or Ukranian beauties looking for a guy just like me 

I appreciate that Dave doesn't sensor any of the messages. But perhaps he could flag some of the replies as “flame” so those of us who don't care can filter them out.

Seriously, I think you are asking too much. He can't be a mindreader on what people find offensive. Or watch every freakin' thread for it either 

Also why post in a thread that would have this flame moniker in the first place?

[zapta]

Now, how about that 4000 series logic huh?

It's awesome. I remember when I switched from TTL to 4000. I measured the supply current of a 4xNAND and the needle didn't move. I remember that moment, I was impressed.

It opened the door for new possibilities, with a little bit of creativity you can simplify the design. For example, I built once a phone pules dialer with only two 4000 ICs. I don't remember the details but one had inverters or gates and the other was a counter with 10 decoded outputs. The 'buttons' where an aluminum plate with 10 holes, each has a screw head isolated from the plate. You dialed by touching a screw head and the plate around it and the body resistance activated it.

At the time I was not ware of ESD so had no issues with it.

Also built a clock with TTls. Some binary counter IC and a high voltage decoder that drove nixies. High voltage came from rectified mains.

I like it much more today today those small and cheap MCUs, Digikey online ordering, internet communities, affordable oscilloscopes, and datasheets that are one click away. Life is good.

[zapta]

...I appreciate that Dave doesn't sensor any of the messages. But perhaps he could flag some of the replies as “flame” so those of us who don't care can filter them out.

Like your own message?

;-)

[Tac Eht Xilef]

You are not alone.  I am sure there are a great many people who come here would like to find an oasis where some respite can be found from such things.

^This^.

[cimmo]

Blimey, where do you live? The only time we had a power cut since the glory days of trade unions in the 70's was a year ago when I noticed my server powering down and rebooting and then the house lights dimming randomly.

We rarely get power cuts or brownouts here.
At home, maybe once a year at worst, and it's usually just for a few seconds. Maybe one major blackout in the 10+ years we've been there that lasted long enough for us to go "we'll, what do we do now?".
At the lab I've never had a single blackout (don't know about nights when not here), just maybe 3-4 glitches in the 4 years I've been here. Coincidently I got one this morning actually. Didn't reboot the computer, but dimmed the lights.

This weather event caused a seven day blackout (screenshot taken literally seconds before we went back to medieval living):

[boffin]

There is no need for opinion, this is purely a technical question. Please explain how a commercial desk clock chip can be modified into a countdown timer.

I think FOX News have a tutorial on their website.

[cimmo]

Did someone mention old-school clocks?

I do believe this one is based on Strowger Relays:
https://en.wikipedia.org/wiki/Strowger_switch


And here's one with Dekatrons:


http://wv7u.com/cwc/hourglass.html
Transistor free - but still digital!

[sbprojects]

However all hope is not lost. You can add the people whose posts you would prefer to not see to your personal "ignore" list by going to your Profile --> Forum Profile --> Modify Profile --> Buddies/Ignore List.

Thanks for the tip. It might help me stick around for a while longer.
Hmmm, but I can't block Dave, can I?
So I will still see part of the flames.
We'll see.

[sbprojects]

Very nice, I like your breakdown of the circuit. Unadblocked, and ahem, interesting links clicked too...

Thnax man, now I can buy myself a beer from today's earnings. Problem is, I don't drink beer though. Well at least you have some nice company in the near future. Fortunately for you the language of love is universal.

[SeanB]

Just saw this "interesting" clock on Reddit, so thought the humour might be appreciated here.

http://imgur.com/a/HOSEC

Luckily living in South Africa I do have the ability to have off grid power, and have enough fuel to be able to survive a few days without power, though the longest I have had to do so was 2 days after a drunk gentleman parked his car in the minisub and they had to dig up the road to get to the 11kV cabling to rejoin them, then place a new unit on the new slab they brought in by crane. The other was a shade over 5 hours after the other minisub did an impressive flash and burn after the 11kV incoming cable arced over, probably from a rat, though there was not enough left around the big charred hole to be sure. 3 20 hour outages after the cable thieves broke in and stole the neutrals and earth bonds.

Last night was watching a crew at 10PM up a wooden pole replacing an insulator on the one 230V phase, as it was arcing ( again) to the pole. The whole street is scheduled for a rewire soon, going from bare 25mm copper cable to 35mm aluminium Aerial bundle cable. The copper scrap value pays for the upgrade.

[bartm]

No, the carry goes low once it hits 5 (see timing diagram) so the reset then switches it back high. So it works for any count >=5

Ah i see... Asumption is the mother of all f**kup's..

[SeanB]

Same as the 4017 carry out, which is not surprising as they are basically the same chip, with one having 10 decoded outputs and the other a 7 segment decode.

The question of the DTL pulling the digits to light is simple, all CMOS chips, aside from a few designated as having open drain outputs, are push pull outputs, having an active device to pull up or pull down the output.

[timb]

We riddin' spinnaz, also clocks.


Sent from my Tablet

[RedOwen1177]

Hello Everyone!

I'm a new person here, but I love the EEVBlog. Dave, keep up the good work! I have a question about the clock project(I'm going to make one). With the "6 Decoder Reset", where do the outputs(?) go from the transistors and the diodes? Do they go to the reset pin? To ground? To Vcc? I really want to make a clock, so please help!

[EEVblog]

I'm a new person here, but I love the EEVBlog. Dave, keep up the good work! I have a question about the clock project(I'm going to make one). With the "6 Decoder Reset", where do the outputs(?) go from the transistors and the diodes? Do they go to the reset pin? To ground? To Vcc? I really want to make a clock, so please help!

Exactly as per the schematic.

[Cliff Matthews]

I really want to make a clock, so please help!

Schematic: http://www.eevblog.com/files/DigitalClockSchematic.pdf
You may have to wear one of these the first time you power it up (these things are sensitive you know..) 
http://vangogh.teespring.com/shirt_pic/2895042/3290084/2/581/front.png

[RedOwen1177]

I'm a new person here, but I love the EEVBlog. Dave, keep up the good work! I have a question about the clock project(I'm going to make one). With the "6 Decoder Reset", where do the outputs(?) go from the transistors and the diodes? Do they go to the reset pin? To ground? To Vcc? I really want to make a clock, so please help!

Exactly as per the schematic.

The problem I'm having is with the arrows. I can't tell where they go, I don't know much about electrical engineering. Do they go to reset? And if not, where do they go? That is what I'm trying to ask.

[RedOwen1177]

The arrows pointing up go to V_cc

Thank you! That is what i was looking for! I'll post the results when I'm done!

[alexanderbrevig]

I made a sharable project on Mouser for this.
http://www.mouser.com/tools/projectcartsharing.aspx
Access id: 52b77a006e

Feel free to correct errors, and use or misuse it to your heart's content

[AF6LJ]

I made a sharable project on Mouser for this.
http://www.mouser.com/tools/projectcartsharing.aspx
Access id: 52b77a006e

Feel free to correct errors, and use or misuse it to your heart's content

Very Cool.
 

[Macbeth]

I have to admit going back to discrete logic gates instead of easy stuff like programming AVR's is kinda fun, but surely a modern logic implemented clock should be done using a CPLD or FPGA? Having said that I've never programmed one (other than by flashing JTAG) so it's more intriguing to me. I know there is some kind of VHDL or something used for programming them, but is there a way to just draw logic gates and counters using schematics etc and program them that way?    (and I don't mean by paying megabucks to Altium or something like that)

[Kilrah]

but surely a modern logic implemented clock should be done using a CPLD or FPGA?

You of course do what you want, and if you feel like you're gonna like (and get an occasion to learn) FPGA design by all means go for it.
But many consider that as a "back to basics" approach and the challenge of making something with the only things that were available decades ago without the sophisticated devices and tools we have now.
Granted, it might be because most actually lived and worked with those things back then and it's a nice memory more than anything else

[TerminalJack505]

I have to admit going back to discrete logic gates instead of easy stuff like programming AVR's is kinda fun, but surely a modern logic implemented clock should be done using a CPLD or FPGA? Having said that I've never programmed one (other than by flashing JTAG) so it's more intriguing to me. I know there is some kind of VHDL or something used for programming them, but is there a way to just draw logic gates and counters using schematics etc and program them that way?    (and I don't mean by paying megabucks to Altium or something like that)

Xilinx ISE supports schematic entry.  I don't know how good it is, however, since I have only ever used VHDL for circuit definitions.

I'm guessing the other vendors support it as well but I can't say for sure since I've never used their software.

The attached screenshot is one of Xilinx's examples.

[Macbeth]

Cheers Jack, I decided to investigate a little. I already had Quartus II on my PC which I had only used for reading/flashing CPLDs on my 'scope with a cheap Altera USB Blaster. (Talk about sledgehammer to crack a nut!).

Playing with Quartus, I found the schematic editor and a whole load of 74 series logic to use. I ordered a really cheap dev board on ebay with Altera MAX II EPM240 so I'll have a go learning this stuff while waiting for the post 

[Stonent]

I made a sharable project on Mouser for this.
http://www.mouser.com/tools/projectcartsharing.aspx
Access id: 52b77a006e

Feel free to correct errors, and use or misuse it to your heart's content

Very Cool.

I tried the same thing on Tayda. There were two parts they didn'thave.

Code: [Select]

Product Name Unit Price Qty Subtotal
1N5817 Diode Schottky 1A 20V $0.06 24 $1.44
CD4013 4013 IC CMOS DUAL D FLIP FLOP $0.26 2 $0.52
2N3904 NPN General Purpose Transistor $0.02 10 $0.20
CD4040BE CD4040 4040 Ripple-Carry Binary Counter/Divider IC $0.36 2 $0.72
CD4026 4026 IC CMOS Counters Decade/Divider $0.33 6 $1.98
CD4511BE CD4511 4511 BCD to 7 segment Latch Decoder IC $0.23 2 $0.46
LED Display 7 Segment 2 Digit 0.36 inch Common Cathode Hi Red $0.36 2 $0.72
LED Display 7 Segment 3 Digit 0.36 inch Common Cathode Hi Red $0.42 2 $0.42
LED 3mm Red $0.02 4 $0.08


They don't stock 4518's and did not have any single digit .40" 7 segment displays.  (And I didn't bother with the transformer)

But out of what I found, less than $7

[JoeO]

Ahmed is a trouble maker.  The last thing he needs is an education in engineering.

He has been suspended from school MULTIPLE times.

He is no hero.  He did not invent ANYTHING.

http://www.dailymail.co.uk/news/article-3254317/Ahmed-Mohamed-s-former-teachers-say-teen-trouble-maker-suspended-weeks-time.html

[linux-works]

let me give you a hint, joe; quoting the DAILY FAIL as a source of trusted info only gets you laughed at.

give it up, guys.  if you have to show your hate, do it at some other forum.  we've had enough of this "I just HAVE to find some reason to hate this kid" stuff.    seriously, give it a rest already!  the horse has been beaten past death, at this point.

[AF6LJ]

let me give you a hint, joe; quoting the DAILY FAIL as a source of trusted info only gets you laughed at.

give it up, guys.  if you have to show your hate, do it at some other forum.  we've had enough of this "I just HAVE to find some reason to hate this kid" stuff.    seriously, give it a rest already!  the horse has been beaten past death, at this point.

I agree this is beating a dead horse, however how is posting an article that seems to be factual being hateful. Have we really sunk to that level where the truth can be considered hate speech?

[mtdoc]

Ahmed is a trouble maker.  The last thing he needs is an education in engineering.

He has been suspended from school MULTIPLE times.

He is no hero.  He did not invent ANYTHING.

http://www.dailymail.co.uk/news/article-3254317/Ahmed-Mohamed-s-former-teachers-say-teen-trouble-maker-suspended-weeks-time.html

Dead horse indeed!

Reading the story, it seems the only facts are that he was suspended once for blowing bubbles in the bathroom and once for defending himself in a hallway fight.

Yep, it's pretty clear who the troublemaker troll is.

[Macbeth]

I read the pathetic Daily Mail article and the headline bore no relation to the story whatsoever. It seems they really had to scrape the barrel to find he was suspended for being the victim defending himself (remember the zero tolerance nonsense? both the victim and the perpetrator get suspended). Then another incident he was blowing soap bubbles. Oooh wow! As for him inventing a remote control to switch off the projector, we know he can't even make a clock I seriously doubt he invented a remote control. Can't have it both ways. From his clock making ability I would guess he just used a universal android IR remote app from the Play store.

So pretty much the sort of shit I would get in trouble at school for. Never had to be suspended or police called in though. The odd half hour detention or a letter home to me mum was about the worst. I'd have stuff confiscated too.

[Simon]

Ahmed is a trouble maker.  The last thing he needs is an education in engineering.

He has been suspended from school MULTIPLE times.

He is no hero.  He did not invent ANYTHING.

http://www.dailymail.co.uk/news/article-3254317/Ahmed-Mohamed-s-former-teachers-say-teen-trouble-maker-suspended-weeks-time.html

And you are asking to be banned. This topic is clearly not about Ahmed and the subject has been done over and over.

[tggzzz]

let me give you a hint, joe; quoting the DAILY FAIL as a source of trusted info only gets you laughed at.

Just so. Except that it is often called the "Daily Wail" since its primary audience is the middle-aged housewife that really doesn't have too much to be worried about. This means the above-the-fold headlines tend to scream "why oh why did they let this happen?", even when it isn't a problem or was dealt with years ago. It is also infamous for its ongoing project to divide all the inanimate objects in the world into the ones that either cause or prevent cancer.

It does sometimes have good large-scale photos, though, for example http://www.dailymail.co.uk/news/article-1311828/Shoreham-air-crash-pilot-escapes-stunt-glider-smashes-runway.html

[Simon]

And perhaps we can stay a bit more on topic

[ez24]

http://www.dailymail.co.uk/news/article-1311828/Shoreham-air-crash-pilot-escapes-stunt-glider-smashes-runway.html

Nice photos, first time I have see a crash like this.  NOW if he had a good custom made digital clock, maybe this would not have happened.  Wonder what kind of camera was used, no simple one I bet,  AND I bet it had a clock that was not custom made, BUT I have seen custom clocks connected to cameras.  ps I do not know Daily Mail

[EEVblog]

PLEASE keep this thread on-topic, because I won't lock a comment thread on one of my videos (they exist for a reason), so the only thing left is to start deleting off-topic posts.

[Dave]

I have a question about the clock project(I'm going to make one).

There is one small modification you need to make to make it count right.
Your mains frequency is 60Hz, as opposed to 50Hz used in Australia, therefore you need to divide the mains clock by 6 instead of 5.
This can very easily be done by connecting the two diodes in the lower right part of the circuit to Q2 and Q3 instead of Q1 and Q3. That way the 4040 gets reset when it reaches 6 instead of 5.

[hayatepilot]

I'm thinking of building a clock like this. But I'd like it to display in 24H format.
How would the scematic have to be modified to do this?

Greetings

[sbprojects]

I'm thinking of building a clock like this. But I'd like it to display in 24H format.
How would the scematic have to be modified to do this?

If you don't need the seconds display you could build mine: http://www.sbprojects.net/projects/cmosclock/

[Dave]

I'm thinking of building a clock like this. But I'd like it to display in 24H format.
How would the scematic have to be modified to do this?

I've played with some ideas and came up with this.
It goes from 0 to 23 and it also blanks the leading digit if it happens to be 0 (so you get 6:29:32.9 instead of 06:29:32.9).

I kept the tradition of shitty hand-drawn circuits, I hope you like it.

[hayatepilot]

I kept the tradition of shitty hand-drawn circuits, I hope you like it.

WOW, thank you very much! That's exactly what I had in mind. 
Now where can I find some vintage 4000 series CMOS chips.... 

Greetings

[Dave]

You're welcome.

The chips used in this clock are still readily available from most major distributors.
CD4026BE
CD4040BE

[rdl]

The older chips get used a lot more than you would think. Here in the US, Mouser has a little over 15,000 of the 4026 stocked, in three different packages. I'm sure Digi-Key has them too.

[EEVblog]

Now where can I find some vintage 4000 series CMOS chips.... 

Still common as mud, that's the great thing about discrete logic like this.

[Stonent]

Now where can I find some vintage 4000 series CMOS chips.... 

Still common as mud, that's the great thing about discrete logic like this.

All of them except 2 were available from Tayda electronics. All were cheaper than the major distributor quote.

I made a sharable project on Mouser for this.
http://www.mouser.com/tools/projectcartsharing.aspx
Access id: 52b77a006e

Feel free to correct errors, and use or misuse it to your heart's content

Very Cool.

I tried the same thing on Tayda. There were two parts they didn'thave.

Code: [Select]

Product Name Unit Price Qty Subtotal
1N5817 Diode Schottky 1A 20V $0.06 24 $1.44
CD4013 4013 IC CMOS DUAL D FLIP FLOP $0.26 2 $0.52
2N3904 NPN General Purpose Transistor $0.02 10 $0.20
CD4040BE CD4040 4040 Ripple-Carry Binary Counter/Divider IC $0.36 2 $0.72
CD4026 4026 IC CMOS Counters Decade/Divider $0.33 6 $1.98
CD4511BE CD4511 4511 BCD to 7 segment Latch Decoder IC $0.23 2 $0.46
LED Display 7 Segment 2 Digit 0.36 inch Common Cathode Hi Red $0.36 2 $0.72
LED Display 7 Segment 3 Digit 0.36 inch Common Cathode Hi Red $0.42 2 $0.42
LED 3mm Red $0.02 4 $0.08


They don't stock 4518's and did not have any single digit .40" 7 segment displays.  (And I didn't bother with the transformer)

But out of what I found, less than $7

[GK]

You need nothing but 4011s.

[AF6LJ]

You need nothing but 4011s.

Well if you are going to do that, you din't need anything more than a box of resistors, and diodes and a gross of 2N2222s.

[sbprojects]

You need nothing but 4011s.

Well if you are going to do that, you din't need anything more than a box of resistors, and diodes and a gross of 2N2222s.

That wouldn't make a CMOS clock. You would need a 2N7000 instead of the 2N2222.

[Godzil]

This videos (and some others from Dave) just remind me that I never ever made any power supply nor any clock, does that mean I failed my EE learning? 

[Macbeth]

This videos (and some others from Dave) just remind me that I never ever made any power supply nor any clock, does that mean I failed my EE learning? 

I think as long as you've made something with a 555 and/or 741 then you will be fine 

[AF6LJ]

This videos (and some others from Dave) just remind me that I never ever made any power supply nor any clock, does that mean I failed my EE learning? 

In a word No.
Does having practical experience building stuff help? Yes.

[zapta]

If Dave would have at the time the same cheap technology we have now (MCUs, LCD/OLED, CPLD, network time sources, etc), I doubt if he would still build the clock from discrete logic.

I also built a discrete logic clock (74xx, Nixies) but there was not much else to do at the time if you were not into audio and radio.

[AF6LJ]

If Dave would have at the time the same cheap technology we have now (MCUs, LCD/OLED, CPLD, network time sources, etc), I doubt if he would still build the clock from discrete logic.

I also built a discrete logic clock (74xx, Nixies) but there was not much else to do at the time if you were not into audio and radio.

That's true, we could have combined radio with this project and synchronized the clock with WWVB or WWVL.

[Dave Turner]

I'm all for old school as a learning media it's fun and more importantly lays a foundation for true understanding.

In my view it is potentially (sic) dangerous for any engineer to focus only on the latest/greatest developments without having, at least, a basic understanding of where the technology came from.

[f4eru]

That would drive the wife nuts! 

I think we need a "wife compatible" electromagnetic clock done with low noise relays (e.g. reed relays or such)

[Brumby]

As I started reading through this thread, my mind went back to my very own attempt at designing and building a digital clock.  That was in the days of 7400 series ICs around the time the LS versions were appearing.  CMOS chips were some time later and looked rather magical with logic levels more relative to Vcc than absolute volts.  With my 5v TTL thinking, that was a real head spin.

It has been too long to remember the specific chips I used - but I'm sure there were some 7490s in there.

Like Dave, I also used the 50Hz mains as my clock reference, as this was the only low cost (i.e. free) frequency reference available.  Also, like Dave, it was constructed on Veroboard - but I didn't have a finished project in mind, I just wanted to know I could make something that worked - so everything was laid out on a single full-sized piece (very extravagant).  I went with a 24 hour clock format because I wanted hours, minutes and seconds and (at the time) didn't have any more displays for an AM/PM indicator.  It also felt more 'scientific'.

The display consisted of the regulation 7 segment red LED displays of the day, but I was intrigued with the idea of multiplexing them - so I went down that path.  With the multiplexing and generous number of Veroboard tracks available, most interconnects were simply tinned copper links, so I didn't have the mass of wires seen in Dave's project.  In my early days, this was probably for the best.

For the multiplexing, I needed something to provide a suitable clock speed so I went for an NE555 timer circuit, but made it with variable frequency so I could slow it down (to around 1Hz) and see it in action.  This worked really well and I spent far too much time twiddling that pot, fascinated by the magic.  Somewhere along the line, however, I killed one of the outputs from the digit select chip (forget what it was).  Since this chip cycled through more than 6 outputs, I simply used one of the free ones for the affected digit.  This changed the scanning sequence from 1-2-3-4-5-6-*-*-... to  1-2-7-4-5-6-*-*-... which was both annoying and satisfying.  While very obvious at slow scanning speeds, it soon became invisible as the speed was increased.  But I still knew it was there....

When it came to setting the clock, I took an easy path - just varying the clock pulse into the first counter. This was done with a 3 way switch.  In the 'Run' position, my mains derived pulse was connected.  Then there was the 'Stop' position where there were no pulses.  The idea of this was, if you overshot the fast forward, you could pause the clock until the world caught up and then you just flicked the switch to 'Run'.  For 'Fast forward', I just went for the obvious and tapped into the multiplexing circuitry.  Being variable frequency, it made it convenient for zipping forward quickly (up to 86,400 seconds) and then slowing down as the correct time approached.  Yes, slowing down the rate made the display a bit jittery to look at, but it was still quite readable and was only during the time set process.

So, there was my clock.  At last it was finished and working.  Over the next couple of hours my checks on its accuracy made me feel really chuffed, so I left it running overnight and went to sleep with that satisfying red glow over on my desk, silently ticking the seconds away.  It was a good night's sleep.

When I woke in the morning, I first checked my (wind-up) watch and then looked over at my clock, expecting to see a discrepancy of, maybe, a few seconds - but I was aghast to see my clock had gained something like 10-15 minutes!!!

What has happened here?!!  What's gone wrong?!!  I was devastated.  This shouldn't be!  Shock soon gave way to a determination.  I set out to check, re-check, test and re-test .... Did I have a dodgy solder joint?  Did my multiplexing signal get into the counter somehow?  Was it this?  Was it that?  After a couple of days, I was at a loss and I was just about over it.

However, late one evening, when I was just sitting there staring at it, I saw it jump into fast forward for a couple of seconds and then drop back to normal pace.  What the ...?  Then it happened again.  My first reaction was - is there some RF being picked up?  But how?  Where?  What can I do about it?  But then it happened a third time, which is when I noticed something else.... a faint buzz.  Over the next minute I saw the buzz and my clock's odd behaviour in perfect step.

The buzz did not come from my clock - it was part of the normal background noise of the home environment, often heard emanating from the odd electrical device at particular times of the day.  When I realised what was happening, it hit me like a piano dropped from the roof of the AMP building (the tallest building in Sydney at the time).  I was relieved - and miffed.

For those of you who haven't worked it out, it was the ripple control signals (off-peak switching tones) superimposed on the mains that run around the 1KHz mark which caused my problem.  Well that, and my all-too-simplistic circuit to produce my clock pulses.  It was picking these up and it would give me bursts of pulses 20 times too fast.  Once I worked this out, it was somewhat fascinating to watch and entirely annoying at the same time.

Having identified the problem, I had had enough and just put it aside.  Eventually, it ended up in a box in my garage marked "Electronics Assemblies" - a place where various circuit boards went to await reincarnation.  I had a bit of a clean up last year, but I don't think I would have ditched it.  I might see if I can dig it out.

[Brumby]

Interestingly enough, one of the things we got to do in the EE power lab was to synch generators up to the grid.  It's actually possible to do with three light bulbs, one for each phase.  When there is a difference in phase between your generator and the grid, the bulbs will illuminate proportionally to the phase difference.  As you bring your generator into sync, the bulbs go dark, and then you can transfer your generator onto the grid. 

Crude, to be sure, but it was a great visual introduction into phase synchronization.

I like it.  Beautifully simple.

[sean0118]

I'm just getting around to making my own version of this clock, but I have a few questions about the 4026B.

Are these really made to connect directly to 7 segment displays? The 4511B lists Ioh source current values of 0-25mA, however the CD4026B can only source 3.2mA (when Vdd is 5V). Or is the listed Ioh of the CD4026B only for 1 segment (giving 22.5mA total)?

In the applications section of the CD4026B datasheet they use a CA3082 to interface to the 7 segment display. However there is also a note saying buffers are only required for the A series... thoughts? 




http://www.ti.com/lit/ds/symlink/cd4026b.pdf

[EEVblog]

I'm just getting around to making my own version of this clock, but I have a few questions about the 4026B.

Are these really made to connect directly to 7 segment displays? The 4511B lists Ioh source current values of 0-25mA, however the CD4026B can only source 3.2mA (when Vdd is 5V). Or is the listed Ioh of the CD4026B only for 1 segment (giving 22.5mA total)?

It's per pin. You can source more for the entire power rail. IIRC it's speced in terms of maximum package dissipation.

[sean0118]

Thanks Dave! I'll post some pics when it's done. 

[n3vti]

My first ever attempt at a clock was about 20 years ago, when I was just getting started with electronics. I didn't have any CMOS chips; instead I had TTL. (7490s for the counting and 7448s for the displays) For the timing part, I tried to use a 555 timer (this was before I knew about temperature drifts years later  ) At one point I had wanted to use some old TIL-311 displays I had lying around. Someday, I hope to build one again.

Finally decided to join the forum  I have a lot of ideas and projects in mind; of course they'll be in the proper threads.

~Chuck

[EEVblog]

Finally decided to join the forum  I have a lot of ideas and projects in mind; of course they'll be in the proper threads.

Welcome, and please do publish your projects here.

[n3vti]

Welcome, and please do publish your projects here.

Will do; thanks Dave! Maybe I might send you something for a future mailbag/teardown. I collect clocks (over 200 of them!) and calculators (mostly TIs, but I have Casios, too! ) as a side hobby. 

[SteveyG]

I'm thinking of building a clock like this. But I'd like it to display in 24H format.
How would the scematic have to be modified to do this?

Greetings

I know SB Projects replied, I also have one on my website linked below.

https://sdgelectronics.co.uk/led-circuits/build-a-2-3-6-digit-led-clock/