Please visit my Instructable "555 Timer Hacks: Cable Testers, Magnetic Stirrers, and Lego Grabbers Oh My!" to see a demonstration of 555 timer IC Pulse Width Modulation (PWM) to use in your robotics projects: http://www.instructables.com/id/Hack-Your-Snap-Circuits-a-Minimalist-Very-Few-Co/?ALLSTEPS
This is a companion discussion topic for the original entry at https://community.robotshop.com/robots/show/555-timer-pwm-controls-lego-grabber