My question is, how to derive this frequency using the less amount of components, but only using discrete components, not ICs at all (that is a requirement).
1. Start with a watch crystal at 32.768kHz because these will require least stages of division. The division stages can also be discrete transistor flip flops. You will need 10 divide-by-2 stages to get from 32.878kHz down to 32Hz.
Without ICs I would suggest the two crystal approach but make sure the entire circuit is kept at the same temperature to minimize drift. I suggest two buffered oscillators and a mixer, if you try mixing the two oscillator outputs directly you will probably find they injection lock to each other. At 32Hz difference you can probably pull watch crystals far enough but there is no reason why higher frequencies can't be used.
Brian.
I suspected that the mixing is far simpler, despite I have seen some neat designs like the one in the second page of the attached pdf, but the output frequency depends somehow on the capacitor charge/discharge curve and the buffer threshold and it is not guaranteed to be stable.
Why don't you go for the digital divider solution that gives a very clean and stable output signal? This is what the professionals do when they want the best possible signal quality.
To get OCXO accuracy, you need at least an OCXO and a frequency divider that doesn't increase the drift and jitter.
Everything else, e.g. the mixer idea, is missing the stated accuracy by orders of magnitude.
So if you rely on a discrete solution (why, is it a competition?)
I know I said about oven stability in my post #1, but a 2-3Hz stability will suffice, so the thing can be relaxed a bit.
O/k integrated circuits are totally out for some reason ?Hi,
My application requires a about 32Hz reference oscillator (an OCXO accuracy will do), preferably square wave, but not essential.
My question is, how to derive this frequency using the less amount of components, but only using discrete components, not ICs at all (that is a requirement).
O/k integrated circuits are totally out for some reason ?
Least components....
How about a very simple LC oscillator.
Big pot core, thousands of turns, several Henries very easy to do.
A decent fairly stable sine wave should not be too hard
Just to put some very rough numbers on it, ten Henries and 2.5uF will get you close to 32Hz.
Both are very practical values, and a simple JFET oscillator would probably work out pretty well.
If you were dead keen, adding a suitable small proportion of NPO ceramic capacitors might get you a quite a respectable drift versus temperature characteristic over a reasonable ambient range.
Not exactly equal to a caesium time reference standard, but perhaps not too bad if you go to a bit of trouble to build and test it properly set it all up.....
If you are going to that amount of trouble, a conventional quartz crystal and a digital divider might be the way to go.
Another possibility for an ultra simple 32 Hz oscillator might be a tuning fork oscillator. Made of Invar that would have zero temperature coefficient.
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