John,

Is this for a battery powered or mains device?

If mains, and your mains frequency is 50hz, then you can pick up
100 Hz after the bridge rectifier.

I have used this clock source in South Africa - I found that although
there was quite a bit of drift on a daily cycle, the AVE frequency is
very accurate. The clock would drift by 30sec or so, but at the end
of the year it was still within 30 sec. (fast in the day, slower
at peak loads)

Don't know if that helps. USA is 60Hz (120hz rectified). The UK
also use 50Hz if memory serves.

If you're using a portable solution then I'd go with a higher frequency
crystal and a binary divider chain, such as the suggestion made by
Barry.


Regards

Anton Schoultz
mailto:antons@ePOS.co.za
tel: +27 11 267-9564




-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Barry King
Sent: Thu.16 November 2000 23:02
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC]: Cheap and easy 100 Hz MPU clock? (prefix added)


John,

You asked:

>I am looking for a cheap and easy 100 Hz clock (yes, 100 cycles per
>second) for externally clocking a pic. I considered a 3909, but they
>are not very cheap and not that easy to find.

>Any ideas?

If I wanted to run that slow, I'd use a (CMOS) 4060, with a 32 kHz
watch crystal, and tap off one of the last divider taps.

But if you are doing it so that you use less power than a PIC witha
32 kHz clock, this won't help, since the 4060 will draw the few uA
instead of the PIC LP osc.  What are you trying to do?

-Barry.
------------
Barry King
NRG Systems "Measuring the Wind's Energy"
http://www.nrgsystems.com
Check out the accumulated (PIC) wisdom of the ages at:
PIC/PICList FAQ: http://www.piclist.org

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