How can I keep the smoke in a hall effect? (Mr. Mike?)

Circuit works perfectly without a load, voltage changes from 0 to 12 with manual on. Turn manual switch off and V is still 12vdc - as it should be. Place magnet over Mr. Hall Effect and V drops to 0 - as it should. Over and over. Put the dc motor in place and the curcuit works fine the first time, may two or three. Then the smoke comes out ... Checked connections a billion times, replaced the 8 burned up halls, the npn and the cap -- no luck. The smoke keeps coming out. I am becoming Digikey's favorite customer. The relay is the larger automotive type, the motor is an auto wiper motor. How can the hall be protected, or is there a beefer hall I can use? Thankx in advance,
Glenn

Could be the back-EMF of the motor when the relay opens. Put a snubber diode or capacitor across the motor terminals. E

Yeah I would use a separate, clean, power supply for the hall sensor.

A 16volt zener diode and resistor will help reduce the spikes, and a large 4700uF capacitor will reduce the ripple on the power supply that is frying your hall sensor.

-Ben

PS: read 13-Application Information in the Melexis data sheet. E

Please ignore any ramblings you previously saw posted in this space. Lack of sleep will do that. My apologies.

Sorry for your troubles. You should have written back when you blew the second Hall sensor

This should fix it.

Dr Mike ML

Mr. Mike - Your a genius - can't wait to try it - Thankx ...

Glenn