Arduino project · Distance and parking · Hard
Speed Trap with Two IR Gates
A vehicle passes two IR gates one metre apart. The Arduino measures the time between them and shows the speed. A buzzer sounds above 40 km/h.
What you will learn
- How speed is distance divided by time
- How a stopwatch step measures milliseconds
- How speed cameras and traffic radar work
How it works
When gate 1 sees the car, the stopwatch starts. When gate 2 sees it, the milliseconds are read. With 1 metre between the gates the speed in km/h is 3600 divided by the milliseconds. Wait a moment, switch gate 1 on, then gate 2.
Try this next
- Change the gate distance to 0.2 m for toy cars (use 720).
- Add a camera trigger for speeders.
- Save every speed on an SD card.
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 road speed trap
A car breaks the first beam, then the second. The time between them gives the speed.
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.
- Two IR sensors = two beams across the road
- Buzzer = speeding warning