Ron Fial wrote:

> ... measure the back EMF from the motor when the voltage to the motor
> is momentarally off.

> This is probably to complex a method for an H bridge driver, but its
> quite easy for a PWM single direction of rotation application.

  Not too hard.  If the "H-bridge" uses FETs which are essentially
symmetrical switches when turned on, you simply leave the "lower" FET
turned on after the pulse and measure the voltage at the other end of
the motor.  It'll probably work with bipolar transistors too.

  This latter could be by diodes from each end of the motor, an extra
pair of FET switches from the two ends, or just a resistive divider
giving you half of the back EMF notwithstanding which direction the
motor is spinning.

  I believe the back EMF needs to be well integrated though!

  Cheers,
        Paul B.