Relays for motor power trips micro

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Relays for motor power trips micro

Postby JustRob » Thu Sep 29, 2016 12:05 pm

I am using the pic16f1937 micro along with MPLABX v3.35, C8 v1.38 and the ICD3 to develop the circuit board.

I have a three phase trolling motor and in its original design simply rooted +12 V and GND via relays to the various combinations of the four power lines.

I designed a circuit board that monitors the Y-axis of a joystick and I turn relays on to step up through 5 forward gears of the trolling motor or the 3 reverse gears. My problem is that when I turn on the relays to root the power to the power lines of the motor it causes my micro to trip out.

I was using 5 amp Omron relays and driving them straight through the pic I/O and that worked fine. But then the relays were discontinued and the replacement relays, though electrically identical according to the datasheet, needed to be driven via transistors and now I'm getting the problem where it trips out my micro.

Please see the attached schematic.

I'd appreciate any help!

Thank you
Circuit schematic
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Re: Relays for motor power trips micro

Postby Roche » Fri Sep 30, 2016 3:03 pm

What are the symptoms when it is "tripped out"
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Re: Relays for motor power trips micro

Postby ric » Mon Oct 03, 2016 12:51 am

Comes from
I'd agree with du00000001's comment at
if you needed transistors to drive these relays, then they are taking more current than your previous relays, and you only apppear to have a tiny capacitor (10uF) on the output of your regulator.
Isolating the relay supply from the PIC supply would be beneficial.
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