# Electronic Circuits and Projects Forum

1. ## 1Hz timebase

How do I get a precice 1hz timebase for a digital clock. Even if its a sine wave generator, I can probably use a comparator or schmitt trigger to turn it to a square wave. I was wondering if you use an amplifier with the feedback component a quartz crystal, will it oscilate the resonant frequency of the crystal? (the problem is how to turn it to 1hz)

2. Just use digital dividers, if it's mains operated just divide down from the mains frequency, or use a 32KHz clock crystal and divide down from that - it's a well known (VERY old) technique.

3. Its Battery powered, the digital divider might work. But how to make the crystal resonate?

4. Originally Posted by catcat
How do I get a precice 1hz timebase for a digital clock. Even if its a sine wave generator, I can probably use a comparator or schmitt trigger to turn it to a square wave. I was wondering if you use an amplifier with the feedback component a quartz crystal, will it oscilate the resonant frequency of the crystal? (the problem is how to turn it to 1hz)
This is a good read on the subject:
http://www.pacificsites.com/~brooke/PClock.shtml#5369

Here is another one:
http://www.rentron.com/at89c205.htm

5. Originally Posted by catcat
Its Battery powered, the digital divider might work. But how to make the crystal resonate?
In a crystal oscillator circuit!.

6. How to make one? (And it should oscilate the resonant frequency of the crystal.)

7. Originally Posted by catcat
How to make one?

8. A 32768Hz crystal and a CD4060 will give you 2Hz. A simple flip / flop will give you the 1Hz you're after.

http://www.efymagonline.com/pdf/circuit-2.pdf

9. Except that circuit uses a 4.194304MHz crystal.

You could try this circuit

http://www.mcamafia.de/nixie/ncp_en/ncp.htm

Other examples are:
http://hometown.aol.com/alka1/mcschp.gif
http://www.kpsec.freeuk.com/components/cmos.htm#4060

10. Improooooooooved.
Sounds like an ad on TV.

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Electronic Circuits  |  Learning Electronics

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