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K8LH Novelty Single Chip Clock

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New Member
Yes it does get hot... Total current comsumption is ~200mA. I think it should be ok. The clock is running little fast compared to my digital watch ~1 second on 24hrs.
Anyway thanks for sharing your work. Sananh


Forum Supporter
Good work. What kind of pcb etching method did you follow? Did you make it yourself. Can you explain it.


New Member
Good work. Nice job on your project. Can you provide specific links to the two projects you combined? I know one is at the beginning of this thread.

Mike, K8LH;
Not sure if you recall helping me last year on my led clock project from Sixca.com using the TPIC6B595N's But Its finally completed and ticking away. thanks again

Time to try a new one and I'd like to give this project a run, Do you have a BOM(Bill of Materials) needed for your project?

I'd like to build it as its presented, then make a second one or alter the first in a countdown format which incorporates an alarm.


Mike - K8LH

Well-Known Member
Hi Steve,

I prototyped this one chip Clock simply to verify the design. While it works well, the Charlieplexed display brightness is awful. You really should be able to figure out the small BOM from the schematic -- some 1N914 or 1N4148 diodes, three dual-digit non-multiplexed common anode 7 segment displays, seven NPN transistors (2N3904, 2N4401, etc.), four momentary contact push button switches, etc.

Regards, Mike

Mike - K8LH

Well-Known Member
Hi Gayan,

When the "beep task" is running it toggles the "speaker" pin during each 1 msec interrupt. Toggling the speaker at this 1 KHz rate produces a 500 Hz tone.

 *  interrupt service routine, 1 msec Timer 2 interrupts            *
 /*                                                                 *
  *  beep task produces a 500 Hz 'beep' with 1 msec interrupts      *
  *                                                                 */
  if(beepctr)                   // if beep task running
  { porta ^= 1 << spkr;         // toggle speaker pin
    beepctr--;                  // decrement msec counter


New Member
Hi Mike...

In your pictures, we can see some diodes, what is their values?



New Member
Hi Mike...

It´s very hard to find 16F88... I will try to use a 16F628 to see what happens.




Congratulations for your project!!
Last edited:


New Member
No sucess to convert it to run in 628A... :(


New Member
I am using BoostC 6.97 in MPLAB IDE 7.50.

I´ve just create a new project using PIC16F628A.

When I try to compile:

Clock.c(20): warning: unknown or invalid pragma (ignored)
Clock.c(21): warning: unknown or invalid pragma (ignored)
Clock.c(167:2): error: unknown identifier 'ansel'
Clock.c(167:2): error: invalid operand 'ansel'
Clock.c(167:8): error: failed to generate expression

So, to compile, I need to comment this:

// ansel = 0; // a2d off, digital i/o

In MPLAB with BoostC, there isn´t a dialog to set the fuses... So, I do this in the programmer, just set PWRTE to ON and other to OFF/DISBALE

In breadboard, I am trying to see what happens using only one display (seconds) and it show only a number 9.

Only these parts:

1x PIC16F628A
1x Xtal 16Mhz
1x 2N3904
2x 22pf

Merry Christmas
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