K8LH Novelty Single Chip Clock - Page 4 - Electronic Circuits Projects Diagrams Free

Mike, K8LH · 28th December 2008, 03:10 PM

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

SteveyD · 28th December 2008, 03:17 PM

Thanks Mike,

Any solution to the display brightness?

Mike, K8LH · 28th December 2008, 03:57 PM

Yes. Use something better than this one chip novelty design (grin).

More later. Gotta run.

Gayan Soyza · 26th January 2009, 05:38 AM

Hi Mike(K8LH) whats the frequency you driving the speaker on RA1?

Are you using any built in Timer modules to that?

Mike, K8LH · 26th January 2009, 09:01 AM

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.

Code:

/********************************************************************
 *  interrupt service routine, 1 msec Timer 2 interrupts            *
 ********************************************************************/

Code:

 /*                                                                 *
  *  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
  }

Gayan Soyza · 26th January 2009, 09:23 AM

Thanks

Now only I saw it.1mS is a nice rounded value.To drive piezos it needs about 2-3khz to get a smooth sound.It can be easily make this frequency by your software nice work.

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28th December 2008, 03:10 PM	#46
Mike, K8LH	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

28th December 2008, 03:17 PM	#47
SteveyD	Thanks Mike, Any solution to the display brightness?

28th December 2008, 03:57 PM	#48
Mike, K8LH	Yes. Use something better than this one chip novelty design (grin). More later. Gotta run.

26th January 2009, 05:38 AM	#49
Gayan Soyza	Hi Mike(K8LH) whats the frequency you driving the speaker on RA1? Are you using any built in Timer modules to that? __________________ Gayan My Website http://gsmicro.blogspot.com/

26th January 2009, 09:23 AM	#51
Gayan Soyza	Thanks Now only I saw it.1mS is a nice rounded value.To drive piezos it needs about 2-3khz to get a smooth sound.It can be easily make this frequency by your software nice work. __________________ Gayan My Website http://gsmicro.blogspot.com/