EEVblog #801 - How To Design A Digital Clock

[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.