EEVblog #801 - How To Design A Digital Clock

[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.