The simple touch of the fingers on a sensor causes this circuit to drive a motor that goes into immediate operation. The circuit shown in the figure uses two transistors in the Darlington configuration. The drive can be done in two ways: The first consists in the simultaneous touching of two metal plugs, one next to the other, connected in X and Y. The current circulating through the fingers of the one who touches is enough to drive the circuit. The second is to connect point X to earth (any large metal object in contact with earth). In this case, just touch Y to start the motor. The transistor must be provided with a small heat radiator, and depending on the desired sensitivity or gain of the power transistor it may be necessary to reduce the resistor from 10 k ohm to a minimum value of 1 k ohm.
