I recently made an automatic chicken door opener. I have a 110vac photodetector wired to 110vac relay. When the relay trips it provides 12vdc to a motor to raise and lower a door. The 12vdc power supply keeps failing, only last a day or two. Do I need to provide diode protection or some other protection from the relay kickback? Is that what is killing my 12vdc power supplies?

 

Hard to say without seeing the circuit, but relay kickback occurs across the coil of the relay, not the contacts.

What is the power supply?

 

thanks,
the power supply is a wagner 12vdc 5amp from walmart, maybe the motor is pulling more than 5amps?

 

Do you have a link to the power supply you are using, as well as the motor you are using?

Simpler, output Current/Amp rating of power supply, and stall current of motor.

 

Post a complete circuit including motor model.

Motor windings have an inductance and a resistance. Relay contacts bounce when they open or close. Depending on your motor it may create voltage that affects your power supply.

 

http://www.walmart.com/ip/Wagan-EL9903-Wagan-5-Amp-AC-to-12v-DC-Power-Adapter/10928407

windshield wiper motor, do not have stall current

 

hope the crudeness does not offend anyone for I am only a chemical engineer, the photodector is just homedepot off the shelf