On Thu, Apr 26, 2012 at 7:35 PM, Robert Rolf wrot= e: > Varying the speed could be as simple as triac phase control of the AC inp= ut > to your motor. > Is there a triac or scr/bridge on the old controller? Well, I took another look at what I thought was a transistor and it turns out it is a BT139 triac. So that's interesting, in now we have a better idea of how they're doing it, but I'm not super interested in implementing full phase control in my circuit. I wonder if there's a way to cheat and get two speed control without going full on phase control. > When the voltage is dropped, there is more slipage in the magnetic field, > so the motor spins slower. > > I think what you may have is a normal capacitor run INDUCTION motor. > Can you feel any cogging of magnetic poles when no power is applied? > If you spin the rotor by hand, do you get anything out of the input leads= ? > If not, its more likely and simple induction motor, as commonly used for > fans, garage door openers, etc. This motor feels like it's got a gearbox internally, which means I can't spin the motor sadly. > Borrow or buy a 'fan speed control' commonly used for ceiling fans to see > if the > motor slows down smoothly. A fan dimmer is just like a like light dimmer, > except that the pot starts out at max voltage instead of minimum, > and often has a trimpot adjustment to set the minimum speed to > something other than zero output. Unfortunately this motor runs on roughly 18VAC, which makes it a bit harder to find a fan control for. Good thought though! Thanks! Josh --=20 A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. =A0 =A0 =A0 =A0 -Douglas Adams --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .