Traffic light from a 555, a CD4017 and ten diodes
Open in the lab ▸Make my own copy
No microcontroller: a 555 ticks once a second and a CD4017 counts 0 to 9. Diodes gather the counts into three groups, so red stays on for four seconds, green for four, and yellow for two, then it starts again. Change the timing by moving diodes: give red five counts and green three, and the light favours the side road. Change C1 to 22 µF to slow the whole cycle down.
What is on the bench
45 parts, 65 wires.
| Signal diode | 10 |
|---|---|
| Resistor | 5 |
| LED | 3 |
| 9 V battery | 1 |
| 555 timer | 1 |
| Electrolytic capacitor | 1 |
| Ceramic capacitor | 1 |
| CD4017 decade counter | 1 |
Put it on your page
The project runs live inside the frame: readers can press buttons, turn knobs and read the meters.
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Link
https://zencircuitlab.com/p/zcltraffic4017
Published by its author under the lab's community terms: it may be opened, copied and changed by anyone. Simulation results are for learning; check a real build against the parts' datasheets.