Transistor selection, PWM fan control

[124C41]

I intend to control an automotive radiator mounted fan using HPWM on a P16F690. I selected this transistor to drive the fan, but please look at it and tell me if this is a poor choice.

http://www.mouser.com/Search/Product...6VkK4YLw%3d%3d

The fans I have looked at range from about 9 to 14 amps. I’d like to use a 4KHz frequency.
Any advice appreciated.

[skimask]

I think you'd be better off using a Logic level N-channel enhancement mode MOSFET.
Took a quick look at that datasheet. You need quite a bit of current for saturation to pull any decent current thru it.
http://search.digikey.com/scripts/Dk...e=IRL540PBF-ND
I've used these quite a bit to drive things like pairs of foglamps, blower motors, etc.
Sometimes I connect the base directly to the PIC, sometimes I use an isolator. Depends on how picky the PIC is and how noisy the PWM ends up making the power supply.

[124C41]

Ok Thanks, I'll try some of those.
I like the to-220 package better. Do you think it will get hot mounted in a small project box with the rest of the circuit?

[skimask]

Ok Thanks, I'll try some of those.
I like the to-220 package better. Do you think it will get hot mounted in a small project box with the rest of the circuit?

Only one way to find out. You can do the calculations based on the fan's current, PWM rate, duty cycle, thermal resistance of the MOSFET, dissipation of the device based on voltage/Rds(on)/current flow, etc.etc.etc...or you can just try it. One thing for sure, if you use it without a heat sink to save a buck, it's a dumb way to find out if the pieces/parts will heat up or not.
What is the end result of this project anyways? Are you driving an automotive type radiator fan for the purpose of being an automotive type radiator fan or something else?

[124C41]

I knew there was a formula, I kept getting stuff about air conditioners and science projects when I searched.

Yeah, It reads a coolant temp. sensor and controls the radiator fan speed. This is my first time using PWM, got started yesterday on a breadboard with a 80mm PC fan. 4 kHz was noisy, 20kHz is working real well. I’m more excited about PWM than I should be, I’ve been connecting other things to the circuit to see how they respond.

Ordered some MOSFETs , looks like they will be useful for all sorts of mischief.
Thanks for you help.

[skimask]

Yeah, It reads a coolant temp. sensor and controls the radiator fan speed. This is my first time using PWM, got started yesterday on a breadboard with a 80mm PC fan. 4 kHz was noisy, 20kHz is working real well. I’m more excited about PWM than I should be, I’ve been connecting other things to the circuit to see how they respond.

I can't think of any vehicle application that actually uses full PWM to control a radiator cooling fan. 2, maybe 3 or even 4 settings, maybe...but not a full range of 0% to 100% duty cycle controller of a fan motor.
Sounds like some serious overkill...