Hi,
I am hoping to modify an audio mixing desk so that when a latching pushbutton switch is depressed, a miniature LED will illuminate to indicate activation (as it is currently very difficult to see with black (non indicating) pushbuttons on a black background used in dim lighting conditions !!).
The problem I have is that the switches are DPDT latching, and BOTH poles are currently used to route audio signals. I presume that it is not possible to connect an LED to one of these poles as it will introduce voltage / current where the original design wasn't expecting it....
I had thought about miniature DPDT relays... re-route one 'pole' of the audio signal off the existing switch onto one pole of the relay, use the freed-up pole on the existing switch to drive the relay and use the spare pole on the relay to switch the LED. However, with thirty switches to deal with, this could be expensive and cause quite a power drain.
Is there any easier way (transistor ?) to switch an LED when you only have a DPDT switch (with both poles used for other things !) ??
Many thanks for any help you can give.
Cheers,
Kev.