I am trying to make an arduino based system to control the brake lights of a vehicle. I have only used N-channel mosfets before. My bulb has x2 12v inputs (low & high beam) and a common ground. Since I only want to control the high beam, I believe a P-mosfet is required before the bulb
My arduino is powered by the vehicles 12v battery and regulated to 9v, and then to 5v.
The gate directly connected to an output pin
The source is 12v
The drain is leading to the high beam on the bulb
The seller of the mosfets claimed to be logic level yet the datasheet does not say anything about logic level but it still should work (i think)
The problem is, the high beam on always on. Switching the gate HIGH or LOW makes no difference and ive tested the mosfet with the multimeter and it doesnt seem to be blown
Since the difference between my gate and source is 7v, and the datasheet mentions RDSon between -4.5V & -10V, shouldnt this work?
As i understand the whole negative voltage is not compared to ground but to source?