The speed of the motor connected to this circuit depends on the amount of light that strikes the sensor. The capacitor is dimensioned according to the motor, so that vibrations do not occur. With the BD136 the maximum current is 500mA but motors up to 2A can be controlled with the TIP32. The input and motor voltage is typically 5 to 12V. The circuit is from the book Mechatronics for the Evil Genius by Newton C. Braga.
