I've taken some stock I have and am bodging together a blower for either a fireplace or for an out-door fire pit. The sole purpose is to force air into the firebox to get a better / hotter burn. Not looking for anything serious in the way of temperatures, just want to reduce the amount of smoke. So from stock, I've taken an old light dimmer from a 1989 Toyota Celica. It functions as a PWM. The "Sink" terminal is either ground or open. The circuit below shows a 10KΩ resistor to pull up an N channel MOSFET (also from stock); a 2SK1277 out of a pool spa controller board. It's rated at 250 V, which is enough for what I'm doing. I intend to vary the speed of the blower so that I can control the oxygen without blowing ashes out of the pit or blow the flame out.
My question concerns whether I need to include a flyback diode or not. I certainly can put one in, but why do so if one is not needed? So I'm turning to you experts in such matters. As far as the blower motor goes - it comes out of a BMW automobile, and I have no idea whether it's a permanent magnet type or series wound. I suppose I could check, but it's out in the garage and I'm sequestered in the basement tinkering with junk.
My question concerns whether I need to include a flyback diode or not. I certainly can put one in, but why do so if one is not needed? So I'm turning to you experts in such matters. As far as the blower motor goes - it comes out of a BMW automobile, and I have no idea whether it's a permanent magnet type or series wound. I suppose I could check, but it's out in the garage and I'm sequestered in the basement tinkering with junk.
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