Traffic Light Project

This project operates red, amber and green LEDs in the
correct sequence for a single UK traffic light. The time
taken for the complete red - red & amber - green - amber
sequence can be varied from about 7s to about 2½
minutes by adjusting the 1M preset. Some amber LEDs
emit light that is almost red so you may prefer to use a
yellow LED. The 555 astable circuit provides clock
pulses for the 4017 counter which has ten outputs (Q0 to
Q9). Each output becomes high in turn as the clock
pulses are received. Appropriate outputs are combined
with diodes to supply the amber and green LEDs. The
red LED is connected to the ÷10 output which is high for
the first 5 counts (Q0-Q4 high), this saves using 5 diodes
for red and simplifies the circuit.


Parts Required
• resistors: 470 × 3, 22k, 100k • 555 timer IC, such as NE555
• capacitors: 0.1μF, 1μF 16V radial, 10μF 16V radial • 4017 counter IC
• diodes: 1N4148 × 6 • DIL sockets: 8-pin, 16-pin
• LEDs: red, amber (or yellow), green • on/off switch
• 1M preset, horizontal • battery clip for 9V PP3
• stripboard: 20 rows × 21 holes