REVERSE TAMER

This PICAXE based project was designed to limit the reverse speed of radio control model boats. Most speed controllers give full speed in both directions and while full speed may not be required for reverse use, it is often most undesirable to have it available! Apply too much speed in reverse and the stern dips under the water and the boat is swamped and may even sink. This is particularly easy to do with high speed launches where even relatively little throttle yields a speed which is dangerous in the reverse direction.

This unit was designed to intercept the throttle channel from the receiver and pass a processed speed demand signal to the ESC (Electronic Speed Controller). The forward speed demand remains unchanged, whereas any reverse speed demand is suitably scaled. A potentiometer allows the user to set the maximum reverse speed anywhere between 0 and 100%.

A transistor buffer is used to condition the signal from the receiver. The output voltage swing of some receivers (especially 2.4Ghz types) has been found to be insufficient to trigger the PICAXE 08M (Schmitt Trigger type) input.

Additional code is used to check the validity of the input signal and take appropriate action, including 'failsafe' - otherwise rubbish in = rubbish out, and you may get that full speed reverse you were trying to avoid!

As can be seen from the picture, the unit is easily constructed on stripboard and those of you wishing to build one for yourselves should follow the link http://www.technobotsonline.com/reverse-tamer-by-alan-bond.html where you will find additional technical detail, a stripboard layout diagram and parts list (all parts are available from Technobots).