I would like to drive a 12V car fan motor with a fan driver that is sold for 20-30 dollars at ebay or amazon. These drivers have power MOSFET built in. Car computer sends 12V PWM to the unit. Duty cycle is kind of reversed. 90% 12V PWM will yield 10% fan operation.
I am not sure if I can connect arduino PWM directly to one of these units. Most likely not. So I plan to use an N-channel enhancement MOSFET. Connnect PWM pin to gate. Ground to source . Drain to the driver. Is my approach correct?
So the fan driver has 3 connections, ground, +12v, and a PWM pin? Depending on if it has one inside already, you may need a pullup on the pwm pin to +12v, in addition to the transistor to switch it.
You know there are computer fans that use 12v power, but 5v PWM signal for control, right? (not sure if it's suitable for your application, but if you're not aware of them, you should be) They're referred to as "4 wire fans" (power, ground, speed output, pwm input)
Yes, the fan has those pins, Ground, +12V, and PWM from car computer. By pullup, do you mean a resistor between PWM pin of the driver and drain of MOSFET switch? I don't know if the driver has it or not. Is 10k ohm a good number?
No, I didn't know about 4-wire computer fan. I will study it.
PS: I am not sure if I can post a link. Amazon.com
Pullup would be from pwm pin to +12v, otherwise how will the pwm pin get back up to 12v when the mosfet is off?
Oh, I need to watch more youtube videos to understand your comment. I will get back when I "pullup" my understanding. Thank you.
I remember reading this: these fan control modules will run the fan at full speed if computer fails to give pwm signal. My approach was only half correct. I need to provide full 12V PWM. 0 volt allows the module to run. 12V stops it. So I need to have a pullup resistor on my side. Thank you for the note.
12V ------10K pull-up resistor ---(A)----MOSFET-------Ground. And the fan module is connected to (A). Is this correct?