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By xpzwhisper
#97479
Hi, everyone

i'm posting first time here :)
I have a problem with a 32768Hz crystal. I have set it up like shown on the picture I've provided and I divided the frequnecy with three 4024 7-bit (÷128) ripple counters. It works but the length of the "second" is too short (i'd say maybe 900ms), I noticed it by watching obviously but confirmed it with a stopwatch.. I don't get what is wrong.. I have some suspicions, though. I think the 1M resistor has got something to do with the time, because when I change its value the length of the time changes as well.. That makes me ask a question: how come the frequency can be dependant on the resistor, I thought the crystal has got its natural oscillating frequency..And if you're asking where did I get this configuration it's from A level Electronics book.

but yeah, I am a little confused.

hope you guys know what i'm doing wrong :)
thanks in advance
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By xpzwhisper
#97509
Thanks you for your replies.
I don't know much about crystal. I will try this "32.768 KHz oscillator using a watch crystal". I'd like to understand how does the crystal physically work and also I would like to know what sort of crystal should I use in order to use the circuit I have.
By n1ist
#98029
If you look at the link in your last post, the crystal is *across* the inverter, not in series with the signal. As for the cap, I'd guess a 30 or so pF trimcap. You could also just try caps around 30pF and see if things are close enough.
/mike