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After building the device by Ralph Hempel, I decided to build an interface that can be used with standard RCX firmware.

To be honest, the idea starts from the new capabilities of Dick Swan's 10x firmware.

Since it allows RCX to have 128 PWM levels motor ouput, it can vary its voltage from 0 to about 8 volts.

I used this voltage to control this circuit; unfortunately, it requires external 9V power.

The NE555 is used as astable oscillator; tuning the ZERO trimmer, you can adjust the outmost position of the shaft.

varying the output voltage (in PWM levels) of RCX motor port, you can move the servo shaft to the other extreme side.

This design is only a trial, since servo vibrates a lot and it's not very accurate in movements.

SEVERE WARNING: be careful while trying to use this device and DO NOT remove the transistor!

I'm NOT responsible if you crack out an expensive servo!

I did a little error while experimenting and I almost destroyed the nylon gear train of the servo!

September, 2005.