Here’s one for you deep geeks in the hiz-ouse (you of fainter heads can turn away now).
Rick Bickle, of the Dallas Personal Robotics Group, has posted an awesomely simple circuit that turns a ubiquitous 555 Timer integrated circuit into a Pulse-Width Modulator that can be used to control DC motors.
Pulse-Width Modulation (or PWM) is a common way of controlling the speed of a motor (where pulses are sent to the motor at a given rate, turning the power on and off, which is used as a method of speed control). PWM is usually handled with a microcontroller chip and module, but this little circuit uses an el cheapo 8-pin 555 IC chip (which even Radio Shack still carries and they don’t carry much of anything anymore) and other common analog components. This would be a great way to control a BEAM or other type of robot where you were trying to reduce or eliminate reliance on computer control.