Flashing Light

EE JULY/AUGUST 1988 02 FLASHING LIGHT This is a rather unusual application of IC1 the Type 317 voltage regulator. With only a handful of external components, it can be used for flashing a small 12 V lamp. The output voltage is not stabiliz- ed by the circuit: it is simply a few volts lower than the input voltage. The 317 is capable of delivering more than 1 A. The circuit automatically limits the switch-on current, so that lamp life is considerably extended. The waveforms at the four major points in the circuit are shown in the accompanying photo- graph. The component values given result in a flash frequency of about 4 Hz. Flashing can be stopped by driving Ti with a voltage of more than +1 V. Source: Lambda Power Supply Hand- book LM317