There are many cars on the road that could do with an extra brake light, particularly one high up that can be seen by the third, fourth or fifth car behind it. The proposed here consists of a running-light bar of LEDs that starts again and again when all LEDs light. In some countries, this may not be allowed check with your local highway or police department, but it can be used. anyway, in model cars.
Power is taken from the terminals of the present brake lights. Because of bridle rectifier D1-D4, the polarity of that voltage is immaterial. The voltage is kept steady at 5 V by 1C4.
An oscillator, based on ICI. provides Clock pulses to shift registers IC2 and IC3 as long as the brake pedal is pressed. The p.p.r. (pulse repetition rate) is set with P1.
LEDs are connected to the outputs of the shift registers via series resistors. Because input pins 1 and 2 of IC2 are connected to the positive supply line, each clock pulse generates a logic high at successive output pins, so that more and more LEDs will light. Since the last output of IC2 is linked, to input pins 1 and 2 of IC3, the outputs of that register will also be supplied successively with logic Is when all LEDs connected to the IC2 light. When, finally, the last output of IC3 goes high. T1 is switched on, which results in a reset of the shift registers and all LEDs going out. If the brake pedal is still pressed. the LEDs will light one by one again.
Network R19-C9 ensures that the shift registers are reset and thus the LEDs go out the instant T1 is switched on.
A pulse generator is either an electronic circuit or a piece of electronic test equipment used to generate rectangular pulses. Pulse generators are used primarily for working with digital circuits; related function generators are used primarily for analog circuits.