Electronic gearbox

Since others are posting their electronic gear ratio controls which are remarkably similar to mine, I figured I would post mine that I have been using for a while for many of my vehicles. My design allows for the full range of ratios to be used in forwards or reverse.

I found with my crawler builds that the dc motors would not provide enough torque to turn the large wheels that I was using yet the servo motors were too slow and had no control over the exact speed using the slider. With my ratio design allowing the full range in reverse also, I found that the servos could be accurately controlled in reverse and with much higher speeds. So by changing them to counter clockwise rotation and starting with the vehicle in reverse, I could get high speeds, high torque and full speed control while going forwards. Problem was that when decelerating, it was either stop or go. By adding a Ceil to turn the power source off when the slider was at zero, it would allow the servo to coast.