digital pot as variable resistor

[Baran Ismen]

I'm here for the same question. Is it possible to make an automated expression pot, whose rate is set by an Arduino ?

[ElectricDruid]

I'm here for the same question. Is it possible to make an automated expression pot, whose rate is set by an Arduino ?

It's possible, but it's often largely unnecessary. Many "expression pedal" inputs are actually providing a +V and Ground across the expression pedal, and accepting a variable control voltage back in from the wiper. If you know what voltage the pedal is expecting (and you can easily stick a plug in the jack and test the pins to see what +V it provides) then you can simply feed in a control voltage of the correct level, with no need to mess about with digital pots. This is especially true on modern pedals where the expression inputs tend to be simply an input to one of the processor's ADC channels.

I have nothing against digital pots, but they're not always the simplest solution and they cause several other headcahes - if they're not updated rapidly enough, you get unpleasant digital stepping as they jump between values.

[Baran Ismen]

I'm here for the same question. Is it possible to make an automated expression pot, whose rate is set by an Arduino ?

It's possible, but it's often largely unnecessary. Many "expression pedal" inputs are actually providing a +V and Ground across the expression pedal, and accepting a variable control voltage back in from the wiper. If you know what voltage the pedal is expecting (and you can easily stick a plug in the jack and test the pins to see what +V it provides) then you can simply feed in a control voltage of the correct level, with no need to mess about with digital pots. This is especially true on modern pedals where the expression inputs tend to be simply an input to one of the processor's ADC channels.

I have nothing against digital pots, but they're not always the simplest solution and they cause several other headcahes - if they're not updated rapidly enough, you get unpleasant digital stepping as they jump between values.

What I ask is actually a quite spesific scenario, in between steps are irrelevant in my case, I just want this to make a hard A-B steps, like 0 to 100, because that's how this pedals Humanizer effect works, it steps in between vowels just as is.

[ElectricDruid]

What I ask is actually a quite spesific scenario, in between steps are irrelevant in my case, I just want this to make a hard A-B steps, like 0 to 100, because that's how this pedals Humanizer effect works, it steps in between vowels just as is.

Fair enough. Well, in that case, a digital pot might work for you. You'd still need to know what voltage the expression socket is expecting, since digital pots can only cope with voltages between their power supply voltages. It's not like a normal pot where you could stick 25V across it without worrying too much!

But again, if all you want to do is control the Humaniser pedal using an Arduino, you can probably do that without needing the digipot. If the expression input will accept a voltage, you can generate that more directly using the Arduino's PWM outputs (plus a bit of lowpass filtering). Saves you a chip and some messing about using SPI.

I'm just repeating stuff that's in the other thread though, so I'm going to post over there instead.