TRAFFIC LIGHTS Circuit
Here's a clever circuit using two 555's to produce a set of traffic
lights for a model layout.
The animation shows the lighting sequence and this follows the Australian-standard.
The red LED has an equal on-off period and when it is off, the first
555 delivers power to the second 555. This illuminates the Green LED
and then the second 555 changes state to turn off the Green LED and
turn on the Orange LED for a short period of time before the first
555 changes state to turn off the second 555 and turn on the red
LED. A supply voltage of 9v to 12v is needed because the second 555
receives a supply of about 2v less than rail. This circuit also
shows how to connect LEDs high and low to a 555 and also turn off
the 555 by controlling the supply to pin 8. Connecting the
LEDs high and low to pin 3 will not work and since pin 7 is in phase
with pin 3, it can be used to advantage in this design.
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