With this circuit we can control a load from 500 mA to 1 A, depending on the transistor, using a low current sensor or switch, for example, a reed switch. The power transistor must have a heat radiator and the load can be from 6 to 15 V. The excitation transistor can be the BC548 or equivalent. The circuit is from Newton C. Braga's Mechatronics Sourcebook, published in the United States.
