Sebastian Kuzminsky wrote: > Jon Elson <[EMAIL PROTECTED]> wrote: > >>You need a lot more voltage supplying the H bridge. At 55% duty >>cycle, you are getting 12 * 0.55 = 6.6 V at the motor. I am a >>little surprised the motor doesn't start to turn before this, it >>must have a lot of friction. Have you measured the motor >>current just before it starts to turn? That would be >>interesting to know. > > > It's a cheap used motor from the local surplus place, so maybe it's > been abused. The manufacturer's specs say: > > Friction Torque: 0.35 oz * in > Rotor inertia: 0.00014 oz * in * s^2 > > I dont know how to think about these numbers, really, or how they compare > to other motors. Well, .35 Oz-In friction on a motor with 1.6 Oz-In continuous torque is a mechanical efficiency of 78%, which doesn't sound real good. Depending on your meter, it may or may not give a very good reading of current pulses. You could put an R-C network in to average out the pulse effect on the meter, using a low-value resistor as a shunt. That won't be perfectly accurate, but will eliminate the effects of the pulses on the meter's circuitry.
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