# Generate a 200kHz varying voltage signal

I have a 12V DC supply from just a normal household converter. We have to make a circuit which will output an 200kHz AC signal with a p2p voltage of 3-12 volts depending on a strain gauge. 3 being no load and 12 being complete failure.

We have been given 2 555 timer ICs but I really don't see where to start with this; anyone able to give me a push in the right direction with any part of this?

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This is an amplitude modulation problem, Gricey. You need to condition your strain gage signal to provide the correct signal, and then multiply (i.e., modulate) it by the 200KHz wave. That's a push in the right direction, and if you can convince me this isn't coursework that you're supposed to be doing on your own, we'll see if we can dig up something more specific. –  Scott Seidman Oct 4 '12 at 12:42
Use the strain gauge in the RC timing circuit on a triangle wave generator. –  Ignacio Vazquez-Abrams Oct 4 '12 at 13:32
@ScottSeidman it's University coursework; not trying to hide that by any means. Some 'modern teaching' thing where we are meant to learn from eachother and the internet; no lectures or textbook. Stupidest thing ever, anyway, my ranting is irrelevant. –  Gricey Oct 4 '12 at 14:15
@ScottSeidman thanks for the push onto a new topic of research, I'll go read some more theory then see if I can't get closer –  Gricey Oct 4 '12 at 14:17
The easiest thing you could do would be to vary the frequency, but that doesn't seem to satisfy the requirement. A likely plausible sort of signal you could try to generate would be a 200 KHz triangle wave which builds to a peak amplitude varying based on the strain gauge reading. You could do this either as something which charges a capacitor at a varying rate for the full duration of the each 1/200Khz period, or something which charges it with a fixed circuit for a variable fraction of each period. –  Chris Stratton Nov 3 '12 at 17:18