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Mindsensors relay driver reversing a motor

Saw a circuit in on the 'net showing how to reverse an electric motor using a double pole changeover relay and wondered how it could be adapted to the Mindsensors relay/ motor driver. This can operate a powerful motor (18v at up to 10 amps) at variable speed but in only one direction.


On NXT ports B & C, only one of the two relay driver outputs can be active at a time. However, if you use a latching relay you can switch between contacts by just sending one signal; the next signal selects the the other contacts. Actual wiring layout would depend on the relay used.


I must state that I have never tried this and it is published as a suggestion only. LEDs in the relay circuit show which way it was set (or you would not be able to tell which way the motor would turn when switched on). A p push switch as shown will change the setting. See comment below about relay type required.


It was suggested that R and C should be 100R and 10nF but I have no idea whether these need to be changed to suit the actual voltages and currents used.


I can't find the article but this one explains the principles far better than I can -



It is in no way endorsed by Mindsensors -



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Uploaded on July 25, 2011