hi is it possible to use a battery smoke alarm, take the board off it and solder two wires to the place where the piezo is connected to, and then connect the two wires at the end, to a relay? So when the smoke alarm detects smoke, it activates the relay and piezo?

This is a normal 9 VDC battery smoke alarm.

Chris.

 

It depends on the output voltage that is driving the piezo (It's probably 9V). Is the output high enough to latch the relay (You will probably need a 5V relay)? Will the output supply enough current for the relay and the piezo? Put the smoke into alarm and measure the output to the piezo. Your DMM may fluctuate a little in that there will probably be oscillations from the piezo. You will have to check what device is driving it to see if it can supply enough current to the load.

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