Momentary footswitch expression control like Rubberneck or Ricochet

[Aentons]

Does something like that where you can set the rate exist as a standalone?

[madbean]

I'm afraid I don't quite understand what you are asking. Could you explain a little more?

[Aentons]

I'm afraid I don't quite understand what you are asking. Could you explain a little more?

Ok, sorry, I definitely could have been clearer...

I'd like to hold down a footswitch and have it change it's resistance over time like an expression pedal does when you rock it from heel to toe. The rate at which it changes is controlled by another pot.

It's what happens when you hold down one of the footswitches on the DOD Rubberneck Delay. The left "effect on" footswitch adjusts the delay time at the rate the little lighted "Rubberneck" rate pot is set to.

Was thinking it would be nice to have a control like that as a separate switch box for other pedals that accept expression input

[madbean]

It kinda depends on how the expression pedal input is operating. IOW, as TS (variable resistance) or TRS (voltage divider aka volume control). The first one is a lot easier. Use an octocoupler where the output comes from the two ends on the internal LDR. For the internal LED, you make a little a transistor based circuit that uses a time constant to charge up the LED brightness. You can find an example of this in the Multiplex Echo Machine from our local friend 1776 effects. There is an example circuit used to control delay time, but it could also be used to control any variable resistance with some tweaking.

[Aentons]

Hmm, I think most expression pedals are the trs/voltage divider type so I'd be much more interested in that. I've been looking at the tappy to see if it could be adapted in some way

[madbean]

Hmm, I think most expression pedals are the trs/voltage divider type so I'd be much more interested in that. I've been looking at the tappy to see if it could be adapted in some way

It just depends on what you are trying to control. For a rate pot on an LFO, or a delay pot on a PT2399 delay you only need to vary the resistance (ie TS). You can use an expression pedal that has TRS output all the same...you'll just being using two legs instead of three on the expression pot!

[Aentons]

I think I'm looking for something with 0-5v CV output. If I'm not mistaken, I can then use that with a "floating ring" TRS cable to plug into pedals with a regular TRS voltage divider style expression jack.

I think the Tappy will do 0-5v output if ground the bipolar pin8. From there, just need to figure out the momentary switching.