An H bridge is a type of circuit that you can use to control the direction of electric motors. In this video I show you how an H bridge works and show you how to build one that can control the speed and direction of a brushed DC motor using PWM.

Parts list:
NE555 timer:
http://octopart.com/partsearch#!?q=NE555
N-channel MOSFET:
http://octopart.com/partsearch#!?q=psmn022-30PL.127
P-channel MOSFET:
http://octopart.com/partsearch#!?q=FQP27P06