In this case, they’re being used to create a basic PWM motor controller. The trick is to set the 555 up in astable mode, and use diodes and a potentiometer in the charge/discharge loop.

He hooks up the SN754410 to two motors, giving him speed and direction control for both based on the duty cycle of a PWM signal entering the chip for less than $2.50.

This is an easy tutorial showing how you can control the brightness of an LED or adjust the speed of a DC fan using Arduino Board, a small BC547 transistor and a potentiometer. In my example the whole ...

Maxon Precision Motor's ESCON 50/5 OEM module is a 4 quadrant Pulse Width Modulated (PWM) servo motor controller that can efficiently control permanent magnet brushed DC motors (PMDC motors) and ...