Arduino project · Displays and counters · Medium
Lap Timer with an IR Sensor
Each time a toy car passes the sensor the LCD shows how long the last lap took.
What you will learn
- How to time repeating events
- How one sensor can start and stop the stopwatch
- How lap timers work in racing
How it works
The time since the previous pass is read and the stopwatch restarts. The first reading after switch-on is not a real lap.
Try this next
- Keep the best lap in a variable.
- Count the laps.
- Show laps on a 7-segment display.
The simulator program and explanation on this page are original. The idea follows a classic Arduino project that students have built for years.
Parts: sensors and actuators (tap to show or hide)
Try the inputs (virtual sensors)
Pins (you can change them)
| Part | Arduino pin (change it here) | How to wire it |
|---|
Every wire, one by one
Red rail = 5 V from the Arduino 5V pin. Black rail = GND. The coloured wires carry signals. Match the wire colours on the drawing to this list.
| # | Colour | From (part and leg) | To |
|---|
Steps run from top to bottom, then start again. While the simulation runs, the active step is highlighted in green.
Quantities come from the parts you added. The store links open a search for that item on Robu.in, Amazon.in and ThinkRobotics, so you always see what is in stock today. Check the model, voltage and price before you order.
| # | Item | Qty | Search term | Buy / compare |
|---|
The PDF has the circuit sketch, pin table, every wire, sequence, full code, the parts list with store links, do’s and don’ts for each part, and the safety notes. The project file lets you come back and keep editing.
In the real world
A lap timer
Every time the car breaks the beam it finishes a lap.
Tip: use the gold tab at the bottom of the circuit drawing to pull the real-world view up over the Arduino board. Your parts stay visible above it, so you can press a button and watch the real scene react.
- IR sensor = the finish line