Easy plug & play answer: Get a serial servo controller and use it to run an RC speed control. Those are what electric RC cars and trucks use to power their drive motors. $20-$30 for the serial servo interface, and the same maybe for speed control.
I've been reading data sheets for weeks now... I can get an analog out, at 1ma, but how to I "amplify" that to control a blower motor? I don't even really know how much amperage the motor takes... right now, the "stock" system uses a resistor box; and I'd prefer use a pic, to control it on a scalar level.
Anyone have any more information other than "google op-amps"? lol
I'm not really an electronics engineer, but I play one on TV. Seriously... I have a good grasp on how most things work, but without having the stuff infront of me, I can't really make sence of half of the numbers in the datasheets.
EDIT1: btw, what I'm looking at now, is the IRFP250NPBF http://www.irf.com/product-info/data...a/irfp250n.pdf ... it "seems" like it would work. but again, I'm no electronics engineer. According to the Datasheet, it says that the source drain peaks at 1ma, and the emitter constant drain can be 30A, with a peak of 120A...
Not sure if those RC speed controllers can handle 30 amps..
for (HIGH) speed, the blower runs P=220W, V=12v, R=0.65ohms, I=18.33A
Plenty of them can handle that load. I googles "30amp speed control 12v" and found lots of matches. Just let your browser do the walking.
You know.... It might be cheaper to get, instead of a speed controller, a servo. Attach it to the old controls behind the dash and make it "turn" the knob.
If you have a low amp 0-12V signal (or even 0-5V), you could use a power transistor (commonly found in Hondas, comes with a big heatsink, and doesn't require PWM input). Heatsink should go in airstream, just like a blower resistor.
The HB-25 can't be controlled by a servo interface out of the box, unfortunately. It needs 5 ms delays between pulses and only expects to receive instruction when there's a change, instead of a constant PWM stream like RC servo interfaces provide. You could use some of Parallax's sample code to rough together a control for this through your analog output, but it'd be a little work.