I need to speed control a 12 VDC 1 amp brushless fan using some somewhat limited resources. I have:
- 6 open collector transistors that I can control from a SW interface. I plan to use that as sort of a DAC.
- Radio Shack for parts - IRF510 N channel fet for drive, LM324, caps and resistors.
- A preference toward driving linear rather than PWMing because adding another noise source to test setups is kind of a pain. I know the brushless fan commutating will cause some but I have to have the fan.
My question:
I know(imagine?) the IRF510 is going to heat up and increase resistance. Does using a simple circuit similar to the power amplifier shown in National LM324 datasheet applications cover the bases for thermal drift? I probably also need to filter the commutation noise I would see on the feedback.
Any thoughts, comments and suggestions are welcome.
Thanks!
Ed V.