Crystal Oscillator

IronMan2010 · Jul 2, 2011

I had this cuicuit that generate 1 hz using crystal oscillator.. it is working fine with 9v supply but when i connect 5v it becomes more faster ,, why is that happening ?

audioguru · Jul 2, 2011

Most of your ICs do not have any supply voltage and an important supply bypass capacitor is not shown.

RCinFLA · Jul 2, 2011

You are overdriving the crystal. The only thing keeping it from fracturing is the 100 pF loading the output buffer.

Put about 220k ohms in series with output buffer to crystal and two 18 pF on either side of crystal.

32.768 kHz crystal oscillator can take several seconds to start up.

Diver300 · Jul 3, 2011

RCinFLA said:
You are overdriving the crystal. The only thing keeping it from fracturing is the 100 pF loading the output buffer.

Put about 220k ohms in series with output buffer to crystal and two 18 pF on either side of crystal.

I agree, but I would have explained it differently. You should keep the output of IC1a connected to the input of IC1b, and put a 220k ohm resistor instead of the wire that goes from the output of IC1a to the crystal.

MrAl · Jul 3, 2011

IronMan2010 said:
I had this cuicuit that generate 1 hz using crystal oscillator.. it is working fine with 9v supply but when i connect 5v it becomes more faster ,, why is that happening ?

Hi,

My question would be what is the frequency at 9v and what is the frequency at 5v. That is, how much does it change.

Crystal Oscillator

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Crystal Oscillator

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