Relay Switch uC for Guitar Effects Bypass

For use with Relay Switch PCB or with your own custom pcb.

Firmware various versions description:

3M-3RL: this versions uses 3 momentary footswitches N.O. to drive up to 3 relay+LED individually.
It's the noisest one but may depends on momentary footswitch type. You can hear pop and click when engage it.

2M-2RL-1O: this versions uses 2 momentary footswitches N.O. to drive up to 2 relay+LED individually plus an optocoupler.

Optocoupler can be made with GL4537-1 ldr and green ultrabright LED.
Less noisy than 3M-3RL, only a light click is heard when engage it. Still it can depend on footswitch type.
Slight volume drop for a few milliseconds when engage it.

3NM-3RL: this versions uses 3 hard footswitches non-momentary type (configuration can be SPST, SPDT, etc.) to drive up to 3 relay+LED individually.

Most silent.

3NM-2RL-1L: 3 hard footswitches (A, B, C) non-momentary type (configuration can be SPST, SPDT, etc.) to drive up to 3 relay+LED (A, B) plus an additionary LED(C) to select between different routing options: A, B, A+B.

Most silent.

Detailed description of 3NM-2RL-1L:

If relay+led A and relay+led B are off, pressing footswitch A turns relay+led A on. 

If relay+led A and relay+led B are off, pressing footswitch B turns relay+led B on.

If relay+led A is on, pressing footswitch B turns relay+led A off and relay+led B on.

If relay+led B is on, pressing footswitch A turns relay+led B off and relay+led A on.

If relay+led A (or relay+led B) is on, pressing footswitch C turns relay+led A, relay+led B and led C on.

If relay+led A and relay+led B are on, pressing footswitch C turns relay+led A, relay+led B and led C off.

If relay+led A and relay+led B are off, pressing footswitch C turns relay+led A, relay+led B and led C on.