All ESC means is just an electronic speed control, so what do you
mean and what kind of motor?
An H-bridge is a means of reversing current direction through any
motor coil using 4 switching elements in an H-configuration. It's
used for DC motors and for bipolar stepper motors coils, but a
unipolar stepper only requires a bank of four power transistors to
Another way to do without an H-bridge is to use a dual power
supply and use two switching elements top and bottom as a totem-pole
switch of the two supplies into the motor coil with reference to a
common ground into the other side of the motor coil.
Speed control is often done in single coil motors with PWM by
modulating the pulse width of the power supply using another
switching element and an oscillator to drive it. Speed in
steppers is controlled by the step rate.
ESC's are not necessarily H-bridges, and vice versa. An H-bridge allows
for reversing direction of the motor, and an ESC may or may not have
this ability. More ESCs are designed for a particular control input
signal (such as the 1.0-2.0 ms pulses used in R/C cars), whereas
H-bridges need a PWM signal best adapted to the kind of motor you are
Not all ESCs use fully electronic speed control. Some are mechanical,
and are meant to be controlled by a small R/C servo. The servo turns a
pot, which alters the output of the ESC. And of course some ESCs are
meant for manual control -- the speed control on a Dremel, for example.
Author: Constructing Robot Bases,
Robot Builder's Sourcebook, Robot Builder's Bonanza