I have a serial keyboard that has 24 pins and works via one of the top 11 pins shorting to one of the bottom 13 pins when you press a button (top and bottom membranes touch) and this is picked up by an interface board. I would like to simulate this with an Arduino. There are potentially 143 different combinations but I only need to simulate 50. Normally I would use a relay to act as a switch (i.e. pin 1 and 12 are connected to relay, arduino renergizes relay and these pins get connected) but I don't want to buy/connect 50 different relays along with diodes, transistors, etc. to control them. Is there another way to do this?
I have tried shorting both pins to ground and this is not read by the interface board and I have tried just using a regular transistor but since these pins aren't energized the transistor doesn't conduct.