ic for variable range pot?

[snorky]

Hey all,

I'm thinking of building an expression pedal, and maybe this is silly, but it would be really cool to be able to change the range of the resistance offered by the pedal.  Is it possible to use an IC of some kind as a variable range pot?  I would guess the IC would have a set range that could be changed somehow by a multiplier (somehow??).

Can't hurt to ask...

TIA!  And apologies if this has been covered before - I did look around a bit...

- Mark

[Jason Stout]

it would be really cool to be able to change the range of the resistance offered by the pedal. Is it possible to use an IC of some kind as a variable range pot?

EDIT: If your expression pedal is a volume pedal:
It would be cool! You can do this with a few resistors and a rotary switch, or an other pot.

Wire it so that the resistors or pot get switched in to the circuit parallel to the expression pedal pot. the new range can be found by:

Code Select Expand

(R1 x R2) divided by (R1 + R2)
Where
R1 is the expression pedal pot
R2 is the resistance inserted in parallel

EDIT: If your expression pedal is control voltage source, you can use a pot wired as a variable resisror connected to the wiper (like paul suggests below)
Hope this helps.

[Paul Perry (Frostwave)]

It depends what you mean by "expression pedal" and what the thing it is plugged into expects to see.
Is the controlled device expecting to see a variable resistance to ground?
Is it sendign a voltage to this resistance? If so, what voltage?
All this will make a difference.
But, yes, it can be done.
But, it might (depending on all the above) be easiest to just put a second pot in series with the variable one, maybe with anotehr resistance across the original pot, to cut the upper end out, if that is what you want.
Similarly for the other end, if you want to cut out bottom end range.

[snorky]

OK.  This is very exciting.  :-)

I basically want to replace a pot's function with a pedal.  I want to be able to choose what pot on the pedal to control (if >1) so from what you're saying, I could just mount the proper sized resistor in the pedal to switch in when that pot is selected to be controlled.  This would allow me to use one pedal with a fixed range pot to control pedals of any range.  I think.

Wow!  I didn't know you could do this!!

Thanks!!!!

- Mark

[Paul Perry (Frostwave)]

Well it depends what the pot in the effect is doing.. sometimes it is easy to mod for an external pot, sometimes you need to run all 3 wires out, sometimes it will be a problem because the part of the circuit you are lookign at doesn't want cable capacitance added on and so forth.
So it can be more complex than you would have hoped.
But don't let me stop anyone!!
I guess someone would be able to give advice on any of the regular circuits that float around here! :wink: