On 7/6/06, Vasile Surducan wrote: > On 7/6/06, Gerhard Fiedler wrote: > > Vasile Surducan wrote: > > > > > On 7/6/06, Wouter van Ooijen wrote: > > >> I have a bunch of nice 7.2V geared DC motors. Could I run these motors > > >> at let's say 24V if I keep the PWM on-percentage sufficiently low, I > > >> would guess (7.2/24)^2 = 0.09 at 24V would corespond to 1.0 at 7.2V? Or > > >> doesn't it work that way with motors? > > > > > > I don't think. The current pulse at 24V will eat the brushes quite soon. > > > > Since the motor is basically inductive, there isn't really a "current > > pulse", is there? At least not one that you couldn't reduce by a higher PWM > > frequency. Given a high enough PWM frequency, the current should have > > little ripple and it should be possible to keep it in the same range as if > > the motor was driven with 7V. > > I think you have right. But if the frequency is too high, there will > not be a real PWM switching and the H bridge will become hot. 24-7=17V > Unfortunately I don't know the current flow through the motor. If it's indeed 1A, I have doubts will work, maybe someone could tell me why I'm wrong with math ecuations. thx, Vasile > > greetings, > Vasile > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist