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

[scaecrow]

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

 

[canadaelk]

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

 

[ben7]

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

 

[canadaelk]

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

 

[jbeng]

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

 

[MikeMl]

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

This should fix it.

Dr Mike ML

 

[scaecrow]

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

Glenn