Eurorack Modular Power Panel Micro Switches
While planning out the case for our very first modular synthesizer I decided it would be nice to build a small panel with a power switch that would turn everything on and off instead of relying on the connection of the main power cable.
I was already familiar with the type of switches used on Eurorack modules, the little metal ones like the ones on the SQ816 Sequencer, so off I went to my local electronics supply store to pick one up.
They had switches in packages marked On Off On, (On) Off (On) and even On On, but no On Off switches so I decided to go for broke and pick up the On Off On (the red one in the photo).
I was thinking I would use it to interrupt the positive power input but upon returning home and conferring with someone whose knowledge of such matters far exceeds my own, it turned out you have to interrupt both the positive and negative lines (+V and -V) at the same time or risk destroying your modules with only a single power rail powered.
A caveat does exist in so far as you can use the switch to interrupt the mains power to the transformer, just like a light switch interrupts the power to a light bulb, but it can't be used in the same way on the 12 volt outputs from the transformer to the modules, which is what I was thinking of doing.
After another trip to my local electronics supply store I picked up the correct switch (the blue one in the photo). It's called a DPST (Double Pole Single Throw) switch and it can interrupt both the +V and -V power supplies to the power rail at the same time. It's like having two of the red SPST (Single Pole Single Throw) switches joined together into one switch.
Now that's all sorted out I'm looking into adding some LED's to confirm that mains power is connected, which may come in useful in a live situation one day.