Learning Circuit Failure

A project log for Rittenhouse 520 Sequencer

Replacement sequencer for a Rittenhouse 520 doorbell

MichaelMichael 04/08/2021 at 15:510 Comments

After creating the design for the power supply, the next piece that I needed to create was the interface to ring the chimes.  Because I started without any idea about the intricacies of circuit design, I started testing with a out of the box relay module from Sainsmart:

Hooking this up to a test circuit just to try and ring the bell through a button and connecting the relay to the solenoids...fried the board.  Not understanding inductive loads, I had not given any thought to inductive flyback, and even after frying the Sainsmart board, I went to to fry some more solid state relays before understanding the circuit design necessary to protect against this type of problem.   After coming to this realization,  I added a TVS diode across the relay, and this has fixed the problem for now, but as always I am happy to be criticized to update the circuit and add more protection.  The design of this part of the circuit is below: