Overview
The TM1637 is a dedicated LED driver IC that controls a 4-digit 7-segment display over a simple 2-wire protocol (CLK + DIO). It handles all the segment multiplexing internally, which means your Arduino only needs two GPIO pins and a tiny library to display any number from 0000 to 9999, show a colon separator, or write raw segments.
In this project we'll build three modes:
- Stopwatch — counts elapsed seconds since boot
- Up/Down counter — two buttons increment and decrement
- Countdown timer — 60-second countdown with buzzer at zero
💡 Tip
Install the **TM1637Display** library by Avishkar (search 'TM1637' in Arduino Library Manager). The `display.showNumberDecEx()` method handles the colon and leading-zero padding in a single call.
Components
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Wiring
The TM1637 module already includes current-limiting resistors on each segment, so direct wiring is safe:
| TM1637 Pin | Arduino Pin |
|---|---|
| CLK | D2 |
| DIO | D3 |
| VCC | 5V |
| GND | GND |
Button A (increment) → D5 with 10 kΩ pull-down to GND.
Button B (decrement) → D6 with 10 kΩ pull-down to GND.
Buzzer + → D7.
Live simulation
Steps
- 1Install 'TM1637Display' via Arduino Library Manager (search: TM1637)
- 2Wire the display and buttons per the table above
- 3Upload the sketch — the display should show '0000' on boot
- 4Mode 0 starts automatically as a MM:SS stopwatch
- 5Press BTN_UP to switch to Up/Down Counter mode
- 6Press BTN_DOWN to switch to 60-second Countdown mode
- 7In Countdown mode, hold both buttons simultaneously to reset to 60s
