which pic best for fan control

[glmclell]

Hi All

my question:

are there any pic's which I can remotely control via serial or setting i/o lines high and low (dip switch style) that can drive a transistor which drives a fan nice and smooth?

my story:

I'm trying to build myself a fan controller for my PC and possibly other tasks around the house, and have come to the conclusion that a PICmicro mcu is the best tool for the job.

When I started reading, most everything I can find is in refrence to "software" pwm that some of the pic's can generate ... but then they started talking about the frequency varying depending on duty cycle and needing this and that to smooth and integerate the output to make it compatible with a simple fan... quickly went over my head!

I have some nice little micrel chips that control fans via a simple mosfet transistor based on an analog voltage input, but I haven't found a way to control them automaticly (that is, I have to live with their pre-programed thermal response curve, etc)

so I'm thinking, if the pic has so much trouble generating a clean and stable pwm, maybe the D/A converter output is more useable?

All I really want to do is have a pic that I can send commands to and it takes those commands and varies the speed of a fan (or fans if that's possible) ... but as soon as they circuits get into inductors and logic gates and etc, it goes over my head

 

[Nigel Goodwin]

Hi All

my question:

are there any pic's which I can remotely control via serial or setting i/o lines high and low (dip switch style) that can drive a transistor which drives a fan nice and smooth?

my story:

I'm trying to build myself a fan controller for my PC and possibly other tasks around the house, and have come to the conclusion that a PICmicro mcu is the best tool for the job.

When I started reading, most everything I can find is in refrence to "software" pwm that some of the pic's can generate ... but then they started talking about the frequency varying depending on duty cycle and needing this and that to smooth and integerate the output to make it compatible with a simple fan... quickly went over my head!

I have some nice little micrel chips that control fans via a simple mosfet transistor based on an analog voltage input, but I haven't found a way to control them automaticly (that is, I have to live with their pre-programed thermal response curve, etc)

so I'm thinking, if the pic has so much trouble generating a clean and stable pwm, maybe the D/A converter output is more useable?

All I really want to do is have a pic that I can send commands to and it takes those commands and varies the speed of a fan (or fans if that's possible) ... but as soon as they circuits get into inductors and logic gates and etc, it goes over my head

Pretty well any PIC would do, but an easy choice would be the 16F628, this includes hardware PWM - making it very simple to vary the speed of your fan. It's also an EEPROM based chip, so it's easy to program and reprogram.

 

[RonH]

Very simple code to write about 20-30 lines I'd say, you just take the value received from the USART and drop it in the CCP module, done.

Are you running a DC fan? If so then the PIC can easily control it with PWM (through a transistor), just don't forget the diode!

Ron