now i know this query must have been posted a million times not only in this forum, but in all the other forums that have anything to do with electronics.

here goes: HOW TO BUILD A DAMN DIGITAL CLOCk?!!

why not be the first in history of the internet to answer it?
yep! i have serched all the possible sites, no simple answer anywhere. this is my last hope.

ok guys, pls answer. i am not an electronics student, but an IT student. So I hope you understand my problem.

i know how to build a clock using a 555 timer with a counter. but it aint accurate enough, or so it seems.

i don't need any fancy mechanism to set the time, alarm etc etc..., just a simple clock that runs on DC power. i repeat, 'DC'. it may start from 00:00 no problem.

preferably a microcontroller without using a crystal ocsillator.
or just tell me how to get a pulse for half a sec, so that it can be fed to a counter and 7 segment display and stuff. and don't forget to explain how it works, only the clock generator part, i'll manage the remaining counter and 7 seg display part.

pls excuse me for a long post, but pls try to answer.

 

If you use a micro-controller, then that's all you need - no counters or anything else.

If you check the MicroChip website there are old application notes for just such devices.

It's really a VERY common simple project for a micro-controller.

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hi,
I just Googled for: LED digital clock circuits

how many would you like.

http://ourworld.compuserve.com/homep...den/dclock.htm

http://www.hobbyprojects.com/C/Clock_Circuits.html

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Well if you don't want to use a crystal that begs the question, how accurate is "accurate enough"?

Mike

 

If you're interested, I hope to post a single chip Charlieplexed Clock based on the experiment below in the Projects sub-forum this weekend.

The first installment is just the Clock portion of the experiment below and the source is written using the free/lite version of BoostC. Features include;

<> run and set modes (a display 'group' flashes at 2 Hz in set mode)
<> switch debouce (press and release states)
<> switch press beep feedback

Subsequent installments will include the Calendar, Alarm, and (appliance) Timer functions using the same base hardware (PIC, six digit display, four switches, etc.) as I finish moving the code over from assembly language to C.

Please note that the drawing is misleading in that the displays are wired in a Charlieplexed matrix even though the drawing suggests they're wired as a standard multiplexed matrix. I'm working on a new drawing.

Regards, Mike

Attached Thumbnails

     

 

Here's some links to simple clocks I've built. Might give you some ideas.

http://ghmicro.com/index.php/pic/25-...ockthermometer
http://ghmicro.com/index.php/pic/15-...-lcd-interface
http://ghmicro.com/index.php/project...2-simple-clock

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Futz's Microcontrollers & Robotics
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Mike! Dial your ISO way down. Those pics are grainy as hell (well lit though ). Auto-ISO has no place in electronic macros. Keep it under at or under 100. 50 or 80 is good.

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Futz's Microcontrollers & Robotics
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okay, so can you name one micro controller reliable & cheap enough to use?

 

well mike, i need it to work as long as the batteries last without any significant error, 555 delivers about 15 min error every day, astronomical!

 

hey mike, can u pls explain the workin of this clock?
http://www.electro-tech-online.com/a...v2-1-chip-.png

is that the one thats misleading?? finally, looks like a simple enough clock to build, eagerly awaiting a reply..

 

Any PIC with enough pins, the number of which depends on how you actually construct it.

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It's the Charlieplexed display wiring that's misleading in that schematic. I've attached a display wiring detail (below). A Charlieplexed matrix uses a "floating" segment line which means you can't use standard multiplexed 2-digit, 3-digit, or 4-digit displays. I used non-multiplexed 2-digit displays in this project which means there's a lot more wiring to be done.

A clock is a clock, is a clock, is a clock (grin). They all work the same. I'll attach working BoostC code if you want to take a peek at the program but I still have to add repeat capability for the up and down arrow keys. Again, I hope to post a better schematic and final code for a plain vanilla Clock in the Projects forum this coming weekend.

Regards, Mike

Attached Thumbnails

 

Attached Files

LED Clock.c.txt (12.1 KB, 35 views)

 

I forgot to tell you that I tried running the clock off of the internal 8 MHz oscillator yesterday afternoon.

The internal oscillator drifts up and down a bit with temperature so I wasn't too surprised to see the time drift by tens of seconds per hour.

The crystal and caps' are definately worth the extra $1 (usd) in parts.

Mike

 

Batteries? On a 7 segment LED clock? Well unless it's on a big honkin' lantern battery you should probably forget it (grin).

Mike

 

Make that a car battery!

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