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How to get 100Hz frequency

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Lac

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What is the easiest and most stable way of getting a square 100Hz frequecy? I can't really make those crystals work, any other way of getting 100Hz.

Cheers!
Lac.
 
us a 74HC14 Schmitt HEX pack, use a cap and a resistor
 
The easiest and most stable is using crystals. But since you're having some problems whith those, why don't you try RC relaxation? Not as accurate as crystals, though.
 
okey-dokey! Looks like I have to get those crystals working then, since the frequency have to be rock solid.

Thanks§
Lac.
 
Just to give you a numerical sense :) ... The stability of a crystal oscillator is 0.01% upto about 0.001%. While for an RC oscillator, it is around 0.1%[/b]
 
What is it actually for? - if it's a mains powered device you can simply generate 100Hz by feeding a transformer through a bridge rectifier - the resulting ripple is 100Hz (twice the incoming AC). Mains generally has extremely good long term accuracy, which is why it's generally used for clocks.
 
What is your application?

for 90% of the application a simple RC oscillator will do the job very good.
I am posting a simple oscillator circuit, you can replace the logic gates with any inverting HC gates.

The formula for the fequency is F=1 / 2.2RC

So a 100Kohm and 45pF will give you 101.0101Hz, close enough...

You should consider that the resistors are 1%-5% accurate and the capacitors are most likely 10% but again this is not the most accurate oscillator.
 

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I'd use a clock oscillator module, then divide it's output to get my 100Hz. Example: use a 1MHz clock oscillator then send the output thru two 4518 dual BCD up counters (using both halves of each chip for a total of four counters). You'll get 1MHz -> 100KHz -> 10KHz -> 1KHz -> 100Hz.
Digi-Key has the clock oscillator @$1.88US and the 4518's @$0.88US each.
It's more expensive than an RC network, but a lot more accurate. JB
 
100Hz timebase

the frequency has to be rock solid

Then I'd use a crystal, not a RC oscillator.

jbeng describes a good way to make a stable, inexpensive & portable 100Hz timebase. Here's a similar approach using a (74HC or CD)4060 (includes an on-chip oscillator) and a divide-by-N counter. It describes how to get a 50 or 60Hz output from a crystal, the basic idea is the same for 100Hz.

https://www.electro-tech-online.com/threads/high-tech-flashlight.2869/
 
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