A hardware arcade game built from three ICs — no microcontroller, no code. A bouncing LED tests your reaction time: stop it on the centre light to score.
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A 555 timer generates a ~7 Hz clock that drives a 4017 decade counter, which advances one LED per pulse — creating a light that bounces back and forth across 5 LEDs. A 4011 NAND SR latch handles the Start/Stop buttons: pressing Start enables the counter, pressing Stop freezes it. Whatever LED is lit at that exact moment is your result.
| Property | Value |
|---|---|
| Clock IC | 555 Timer (astable) |
| Sequencer IC | 4017 Decade Counter |
| Latch IC | 4011 NAND (SR latch) |
| Clock frequency | ~7 Hz |
| Supply | 9V battery |
| LEDs | 2× red, 2× blue, 1× green (centre) |
| Position | Points |
|---|---|
| Centre green LED | 10 pts |
| Adjacent yellow LEDs | 5 pts |
| Outer red LEDs | 0 pts |
First to 50 wins. Swap R1/R2 values to adjust difficulty.
- 555 Timer IC (NE555)
- 4017 Decade Counter IC (CD4017)
- 4011 NAND Gate IC (CD4011)
- Resistors: 100kΩ, 10kΩ, 1kΩ ×2, 100Ω ×10
- Capacitor: 1µF electrolytic
- LEDs: 2× red, 2× blue, 1× green
- 2× push-buttons
- Full-size breadboard (60+ rows), jumper wires, 9V battery
- Testing each subsystem in isolation (555 → 4017 → latch) saved a lot of debugging time
- The 4017 notch orientation is easy to get wrong — always double-check before powering up
- SR latch needs pull-up resistors on button inputs, otherwise it triggers randomly from noise
- A full-size 60-row breadboard is not optional — 3 ICs + 5 LEDs + 2 buttons won't fit on smaller ones
- Replace R2 with a potentiometer for real-time speed control
- Add a 7-segment display to track score automatically
- Extend to 7–9 LEDs for more scoring zones
- Port to PCB for a permanent build