DC controller using push button switch.
http://www.zen22142.zen.co.uk/Circuits/Switching/dcmotor.html
for example an electric drill, designed for 115V AC
http://home.maine.rr.com/randylinscott/aug99.htm
This circuit is designed for 24V-dc up to 2.5A motor that comes with a worm gear.
http://www.edn.com/article/CA193190.html
Motion-control systems often use a PWM signal to control the duty cycle for a motor driver or amplifier module. Typical designs generate the PWM signals using µCs with dedicated PWM output lines.
http://www.edn.com/archives/1998/091198/19di.htm