Pic pulling to much current. Help quick please.

[czwalga]

I have the output of a pic chip setup to a power mosfet. The output works for the electromagnet i have. However when I goto power the motor (same setup different output) The source power of the pic chip jumps to 1A. It's killing my chips. I'm not sure why it would work with the electromagnet that is using a battery and pulling about 5 amps; but the motor just kills it.

 

[dknguyen]

Did you try putting a reverse biased diode in parallel with the motor to give the flyback current a return path? If you don't this can cause the motor to produce large voltage spikes when power is cut to the motor which might be causing this (but I am not sure if it would cause what you are describing).

 

[kchriste]

why it would work with the electromagnet that is using a battery and pulling about 5 amps; but the motor just kills it

It is probably the back EMF that is killing your PIC via the power supply lines/ regulator. Make sure you have diodes across the motor and the electromagnet. Put the cathode on the positive motor terminal and the anode on the negative motor terminal. Same goes for the electromagnet.

 

[czwalga]

thanks guys.


All kinda of problems; now the mosfets arent shutting off once they turn on. Never had so many problems before in my life.

 

[dknguyen]

Try adding a pull-down resistor onto the gate.

 

[Sceadwian]

The inductance of the motor must be significantly higher than the electromagnet.

 

[kchriste]

All kinda of problems; now the mosfets arent shutting off once they turn on.

Measure the voltage between the gate and source. It should be zero when they are supposed to be off. It is highly possible that the spikes that killed your PIC chips injured your MOSFETs, and they now have damaged gates.
To make sure it is not the PIC causing this, disconnect the PIC from the gate of the MOSFET, connect a 100K resistor between the gate and the source of the MOSFET and leave the load connected. The MOSFET should remain off with no voltage on the gate. Voltage on the gate, and/or the load turned on indicates a damaged MOSFET.