Simple Relay Bypass

[electrosonic]

I have been considering the options for using relay bypass.

If you want to use a SPST latching switch you can use mictester's circuit from the free stomp box forum. I have used this and it works great.

If you want to use a momentary switch you can use CMOS logic to drive the above circuit or use a microcontroller based circuit.

The very simplest circuit I have found uses a DPDT to send a pulse through the relay as a capacitor either charges or discharges based on the switch position. This is my kinda ugly schematic  of that idea. It includes a Schottky diode for polarity protection and some power supply filtering to keep any clicks out of the audio and the fx send is muted during bypass.




I got some boards made by OSH Park, they are 0.8" by 0.9", so it costs $3.70 for 3 boards. The 3mm LED points down through the board. The board itself is attached by double sided tape (I use a hole (paper) punch to make a hole for the LED in the double sided tape). I have also made a version with a SMD LED on the bottom, instead of the 3mm LED poking through the board.

I now realize I need low profile caps to fit under the input jacks in a 125B enclosure. I will probably revise the board to put the caps in the middle of the board so it is not an issue.



Test build



I will post the wiring layout and OSH Park link later if anyone is interested.

Andrew.