I'd like to add two footswitch controlled mods to the RC-3:

  • External Down Button that does not require holding a momentary switch (which is what the FC-7 can provide to the RC-3)

  • Save Button


What I'm trying to do

External Down Button is not fire and forget: The down button is available on a standard footswitch by holding the switch more than two seconds. This two second hold is a pain. It requires attention to trigger and more attenton to avoid overshoot via a repeat feature. I'd like to have a single, momentary press that activates down. Undecided as to the best way to handle repeat (hold or queue up multiple presses at 2.x second delays).

No footswitch for Save button: I'd like to save phrases via a footswitch.

The external save button is a nice to have.
The down button is pretty important.

Initial Thoughts

For just the Down mod, I could avoid modding the RC-3 by creating my own footswitch which simulates the 2 second hold after a single press. I'd also add an input for another switch (the normal up button and would pass that through as long as the down feature is not active (or add multiple footswitches). Leaning toward this approach even if it's just a starter project that I replace later.

Or I could achieve the Down mod directly on the FS-7. The FS-7 is much more than just a two mechanical switches; lots of IC's (including TLP4206G and TLP202A photo-relays, a dual flip flop, and debouncer chips) which allows it to be configurable (and presumably use cheaper surface mount switches). Curious how this device works fine without power in the standard non-latching, non-inverted config other than not driving the led. There's not much on the internals of this device as most people who clone the FS-7 do it mechanically. Thinking there's a simple way to add another signal to the debouncer or the relay. If this is simple and low risk, I'd go this route.

I could also achieve the down mod by modding the RC-3 directly. While I;d need to go this route for the Save mod, I think I'd prefer to start with the two other approaches above.

For the Save mod I could mod the RC-3 directly. The cable from the i/o daughter board looks to be a good place to start.

I would likely use a microcontroller of some sort for each mod. At the least, I will prototype with an Arduino. Glad we've moved beyond 555's.


Questions

For just the Down Button mod, which approach is going to be simpler, safer, and effective? I'm leaning towards the simply adding a box inline with the FS7 and not directly modding it. This box may grow into my own three button version of an FS-7.

Should I switch the RC-3 externally by a transistor or should I use a relay? The FS-7 uses two photo relays. I suspect I could build this with an NPN, but that might lead to secondary issues like hum now that there is a coupling. In general, what do people use for electronically controlled offboard switches? Anything available off the shelf for this?

How would I directly mod the signal inside the effects themselves? Is there a standard way people do this? An NPN? Is the approach different to for a mod to the FS-7 versus the RC-3 (save)? Anything to watch out for here (physical or electronic)?

Is it worth it to try to keep use of the onboard buttons as well as the external ones I add? Is a breakout from the ribbon cable the best approach (versus the pcb with tiny surface mount pads and buried traces)? Is there a situation when it's OK to attach another wire/signal to a pad or will that burnout the drivers already in the pedal? Do I need to cutout the original connection, add an interface that handles both, etc.

Any recommendations for a microcontroller to use in this simple setup? Any particular models which are better or worse in this application. I'm thinking things that simplify the power regulation (or leverage the onboard one), change how you drive other components, reduce part count, reduce size to fit inside an already cramped box. I may be overthinking this for a one off mod!

Has anyone built something similar to either of the two mods this that I can buy or leverage. Looking forward to getting my feet wet in building mods, but no need to reinvent the wheel.

Any general advice related to these types of mods?


Reference Info:
https://music-electronics-forum.com/...ad.php?t=45622
https://music-electronics-forum.com/...l=1#post528171


Thanks in advance for your help. I realized I've asked a lot of questions that cover a bit of ground.