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Subject: Re: Oscillator with small resistance change
Date: Mon, 16 Dec 2002 21:04:08 +1100
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
Thanks to all.
Have now used the wire as part of a voltage divider with 100ohm to limit
current and fed to an opamp to increase the votlage range. Fiddling around
to get this to vary an 8038 vco...
May give the 4046 a go.
Reason for the setup is to make a slide wire theremin (tannerin).
Big problem now is contact resistance between my sliding bit of wire and the
5 ohms of nichrome..not real good very scratchy.
"Richard Hosking" wrote in message
> If the resistance wire had a current through it you could amplify the
> voltage drop across it using an opamp
> One end of the wire would be the reference (+) while the other would be
> inverting input (-)
> The output of the opamp would drive a VCO ?4046 See the chip datasheet.
> Verdons wrote in message
> > I wish to make an oscillator whose frequency is controlled by a varying
> > resistance of 0 to 5ohms ( a bit of resistance wire). I require a
> > range of around 2:1 about 500 Hz. it seems hard to use such a small
> > resistance in the usual sort of oscillator circuits ( tends to short
> > out).
> > Does anyone have some ideas on how to achieve this. The circuits I have
> > breadboarded seem to stall with such a low resistance.
> > TIA
> > Russell
> > (Note Remove text spam from email or reply to NG)
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