Boss RC-50 mod - control two with one - is it possible?

[bigsam]

Hey everyone,
I have a boss RC-50, and I'd like to be able to control a second RC-50 from the first one. So say I step on a pedal on RC-50_1, I'd like that same pedal to be pressed on RC-50_2. I see that under the footswitches are tiny little switches, so my question is, how do I accomplish this. I'm afraid to wire them together, is it possible to build some type of interface that sees when the first pedal is touched, it electronically controls the second one? Is this something I would need a microcontroller for, or is it possible with transistors? Sorry I'm pretty new to this, so I'm not even sure if I'm asking correctly, I just really want to have this functionality and I don't think there is a non-modding way to do it.

thanks!

[ElectricDruid]

If the switches in the RC-50 are just connected to the digital electronics, it might be quite easy.

It's fairly common for digital inputs on a processor to be set-up as pulled high by default, and then a switch just shorts them to ground.

In that case, you connect the collector of a transistor to the switch pin that goes to the processor, and you connect the emitter to the other pin, which should be ground (if it isn't, STOP because we're barking up the wrong tree!).
Switching the transistor on then acts in exactly the same way as pressing the switch, so connect a 10K resistor to the transistor's base.

If you do this on a few switches, you can then trigger them all by connecting the open end of the 10Ks to a switch and connecting the switch to +5V/+9V or something (it won't matter too much since the 10K limits the current and you only need a little bit to turn the transistor on).
If you want extra safety or you're going to put an external inputs on these switches (so you can trigger things remotely, say) then you should add a 1N4148/1N914 diode pointing from emitter to base to protect the transistor from negative input voltages in case anyone ever tries that.

It'd look like this (a similar thing from one of my own circuits):



The "to Tap Tempo" is your processor input, and the Tap Tempo Button is whatever Boss switch you've already got on the PCB.

HTH,
Tom

[bigsam]

Wow, what a thorough response! Thank you so much!!

It is certainly easier than I thought (if it is indeed just switches connecting the digital electronics to ground). I think I might try hooking this up on a breadboard and testing on one pedal.

So how do I know if it is just a switch? Test the voltage at both point with a multimeter? Anything else to keep in mind?

thanks again!!

[ElectricDruid]

So how do I know if it is just a switch? Test the voltage at both point with a multimeter? Anything else to keep in mind?

Well, that's a good question. Testing the voltage when powered on would be a good start. You'd see high voltage with the switch open and nothing with it closed. Find the power rails, both positive and ground, if you can, so you know what you're expecting - might be 3.3V, might be 5V. A pull-up resistor from the pin to positive would be a  dead give-away, but these days it's as likely to be done using internal pull-ups on the chip, so that's probably a non-starter.
Once you've found the switch connection that attaches to the pin and toggles high and low, you could confirm that the other end is connected to ground by *powering off* (don't forget!) and doing a continuity check between ground and the switch.


Edit: I suppose you could also test the other end of the switch like that too: With power off, you should only see continuity to ground when the switch is pressed.

[bigsam]

excellent, I'll give it a try and report my findings, thanks!!