I have an older car which tends to over heat in the summer, so a 20 Amp electric fan was added in front of the radiator. Currently its driven by a on / off relay.
I want to build an Arduino PWM controller but I am not confident switching that much current especially in an automotive environment.
Been testing the VNP35n07 MOSFET but I dont think I am doing it correctly. When tested in the on state there is a noticeable difference in fan speed (noticed via noise) and the draw is about 1 amp less. Understand there will be lose from the MOSFET, but should it be that high?
The wiring for the test is as follows:
VNP35n07
Pin 1: +5.5V
Pin 2: Fan's ground wire
Pin 3: Ground
My intention is to connect the Arduino PWM signal directly to pin 1.
Any feedback / comments welcome.
Best Answer
You will need to have a higher input voltage to the FET to get it to the lowest RDS-ON. Right from the data sheet that you linked you can see the difference between having an input at 5V versus 10V.