I plan on using a wiper motor to run some things in my new mechanical display for Christmas this year, but I am having a few issues. I have a few P-Channel power MOSFETs from Fairchild (https://www.fairchild...FQ/FQP47P06.pdf)lying around that I thought would work fine. The wiper runs fine with a 5V source, so I thought that if I used a PIC and put out a 400Hz 50% duty cycle I could halve the speed.
I connected ground to the wiper's ground, then I connected 5V to the Source of the MOSFET, and I use the Gate as my input switch. That means the Drain becomes the power source for the wiper.
The input switch seems to work OK with a constant +5V/GND (with GND turning the motor on, and +5V turning it off), but when I hook up the Gate to PWM, things seems to go awry. The PIC goes haywire and the MOSFET seems to lock-up.
I am wondering if I need to be using a transistor to switch the MOSFET (not sure why), of if I need to use a snubber of some kind to knock down any EMI (I know nothing about snubbers).
Does anyone have any thoughts how I can clean this problem up some? I would prefer something simple (who wouldn't) that lets me run everything off of the 5V, but if I must, I can probably throw 12V into the circuit (though I would prefer not to).
I connected ground to the wiper's ground, then I connected 5V to the Source of the MOSFET, and I use the Gate as my input switch. That means the Drain becomes the power source for the wiper.
The input switch seems to work OK with a constant +5V/GND (with GND turning the motor on, and +5V turning it off), but when I hook up the Gate to PWM, things seems to go awry. The PIC goes haywire and the MOSFET seems to lock-up.
I am wondering if I need to be using a transistor to switch the MOSFET (not sure why), of if I need to use a snubber of some kind to knock down any EMI (I know nothing about snubbers).
Does anyone have any thoughts how I can clean this problem up some? I would prefer something simple (who wouldn't) that lets me run everything off of the 5V, but if I must, I can probably throw 12V into the circuit (though I would prefer not to).