Arduino project · Motors and movement · Hard
Tachometer (IR Sensor and LCD)
An IR sensor sees a mark on a spinning shaft once per turn. The time between marks gives the speed in revolutions per minute.
What you will learn
- How a tachometer measures rpm
- Why rpm = 60000 divided by the time of one turn in ms
- How a stopwatch can measure speed
How it works
Each time the mark passes the sensor the program reads the time since the last mark, restarts the stopwatch and divides 60000 by it. The red LED lights above 1500 rpm. The first reading after power-on is not correct.
Try this next
- Use two marks per turn and halve the result.
- Show the speed of a fan or a motor.
- Add a buzzer for over-speed.
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 tachometer on a wheel
A reflective mark on the wheel passes the sensor once per turn. Counting passes gives the speed in RPM.
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 = sees the mark
- LED = pulse indicator