MK120 + MK174 integration


I’m trying to integrate these two kits. The 174 has an input for an external switch and I’m wondering how straight forward it would be to get a switch to be activated instead of the buzzer. Maybe a transistor? Maybe the transistor that is already there in the schematic?

Is this possible?


Replace buzzer by a small 12V relay (max. 50mA).
Make sure to put a diode over the relay coil (cathode to the (+) of the coil).
Relay NO contact can trigger MK174 kit.