|
Click Up back to Circuit page
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
|
capacitors: 0.1µF,
1µF 16V radial, 10µF 16V radial
|
diodes: 1N4148 ×6
|
LEDs: red, amber (or
yellow), green
|
1M preset, horizontal
|
555 timer IC, such as
NE555
|
4017 counter IC
|
DIL sockets for ICs:
8-pin, 16-pin
|
on/off switch
|
battery clip for 9V
PP3
|
strip board: 20 rows
× 21 holes |
| | | | | | | | | |
|
| Strip board Layout
|
|
Circuit
diagram
|
|
|
 |
 |
