9v Smoke detector signal to 240v

Thread Starter


Joined Sep 8, 2020
Hi, I am looking to design a circuit board that will take the 9v DC signal from a smoke detector which will trigger a 1-60sec timer which will then trigger a relay turning off and on an MVHR system(240AC), I am unsure about the transformer properties and bridge rectifier properties to make this work as I have little to no experience with electronics, Any suggestions would be great. (I am using software called Circuit Wizard 3 to design the circuit)


Joined Jul 18, 2013
Look into a opto isolator method, see Fairchild App notes AN-3006 and AN-3003.
This method you may not require the transformer etc.