A 4.7W 24V fan is going to move a LOT of air. Assuming it's about the same as the one on Digikey's website, it's a 120CFM-ish fan. That's huge- we use smaller fans than that for ventilating our machines.

Does the speed control work?

oh boy, does it ever

Yessss. I'd been imagining using it for this application but I hadn't actually tested it.

I don't know that an IC like this exists- takes an analog input and turns it into PWM. It's a shame, because it's useful, but it's NOT a shame, because I can sell it.

Pat can use it to control the temp on his hot-wire cutter. For that matter, I can use it on MY hot-wire cutter.

Snort...wha? Ok, I'm paying attention now.

It's basically the same deal- a load that looks pretty much like a resistance (although the motor is going to look like a larger or smaller resistance based on its load). We can chop up the input voltage to it to control the power we deliver.

Except for the wire-cutter, we might want to intentionally limit the duty cycle to 50% or something. We can discuss tonight.

BTW, JT- if you change out that pot, make sure that the replacement pot is not more than a about a 5k pot, and that it's not a pot intended for audio signal control.