Hi. I am trying to control the switches on a old musical keyboard. I had planned to put a npn transistor across the switch and use the arduino to control the base through a resistor. It didn't work. The keyboard is powered by a split rail 15v supply. One side of the switch measures -15 volts the ot…

Using transistors as switches.. problems

EVP October 16, 2012, 1:12pm 3

Thanks MarkT that's good advice the opto isolators are the way to go.

The switch actually measures -11 volt when open and -9 when closed. A npn and a opto isolator?

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