The circuit of the
running light comprises two integrated circuits (ICs), a resistor, a
capacitor and seven light-emitting diodes (LEDs), Decade scaler IC2 ensures that the LEDs
light sequentially. The rate at which this happens is determined by the
clock at pin 14. The clock is generated by IC1, which is arranged as an
astable multivibrator. Its frequency is determined by R1-C1. The touch
switch, consisting of two small metal disks is optional. When switch S1
is in position ‘off’, the circuit may be actuated by the touch switch.
By the way, this enables the circuit to be used as an electronic die (in
which case the LEDs have to be numbered from 1
to 6). The running light is powered by a 9 V battery or mains adapter.
It draws a current not exceeding 20 mA.
Author: L. v/d Heeden
Copyright: Elektor Electronics 1998