Ruben J=F6nsson wrote:
>=20
> Hello all,
>=20
> I have a circuit with a potentiometer (value 1kohm) in it. This
> potentiometer is to be set when the equipment is first installed in
> its environment. I am looking at a way to replace this potentiometer
> with an automatic setting, done every time the circuit is powered up.
> I thought I had a solution with a digital potentiometer in reostat
> configuration (2 terminal) and a PIC to control it. The problem is
> that the wiper current of these circuits have to be lass than 1 mA (I
> need about 10mA).
>=20
> So my question is, does anyone know of a two terminal circuit (plus
> power and control) that acts as a variable resistor where the
> resistance is set by a voltage level or a variable resistor with less
> current through it?
>=20
> I'm sure there must be a nice litle OP-amp or transistor curcuit that
> does this but I just can't seem to figure it out.
>=20


Sounds like you to need to establish WHAT the pot normally connects to.
If it is used in some type of resistive divider to set a voltage you
can probably use a transistor when you know more of the spec of the
target circuit, ie whether it sinks or sources current.

As a curiosity, many modern cheap hifi units have a motorised
volume control, you may have seen these. You use the remote control
and the volume knob on the hifi winds itself up or down. Pretty
nifty! I have a couple of these I have pulled from dead hifi units.
I always thought they might be handy for times when I have no option
but to use a pot, and it needs to be electrically isolated etc.
They are usually 500k or 250k. And log probably, being volume
pots and all. :o)
-Roman

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