Soft Latch Relay Bypass DaughterboardVerified

From the post

[12th June 2014 - perf version added]

I've wanted to do a layout for this one for a while, but it fell by the wayside as the board will just be too big to fit in a 1590B which I use the majority of the time. But there are a few builds I want to do now using 125B or 1590BB boxes and so this may now come in handy for me.

The idea is that you can use a SPST momentary stomp which are much nicer to use than the 3PDT stomps with no clunking, one stomp will energise the relay coil, the next stomp will de-energise it and it cycles like that.

With a footprint around 40mm x 30mm this may just about fit at the bottom of a 125B and my intention is to velcro it to that lower side so it's in the right vicinity but leaving plenty of room for the stomp.

I've got some 9V and some 12V relays, both of which should work fine with a 9V supply, but check the pull-in voltage of the ones you want to use. These look like they'll be fine:

http://www.rapidonline.com/electronic-components/g5v-2-12dc-dpco-pcb-relay-2a-12vdc-60-4446

and these are the stomps I will be using:

http://www.ebay.co.uk/itm/290619513732

So it won't be the cheapest bypass method but nice to do for certain "best builds".

Thanks to Paul from paulinthelab for the circuit.

And something unusual for this site, but if you want to keep the size to a minimum then perf may be a good option. This version also grounds the board input during bypass, and note that I have done this with 1/8W resistors in mind.