Fareed Mohmed← All projects

Arduino project · Displays and counters · Medium

Reaction Timer Game

The red LED lights up after 2 seconds. Press the button as fast as you can and the LCD shows your reaction time.

What you will learn

  • How the stopwatch measures short times
  • How reaction time is measured
  • Why people react in about 200 to 300 ms

How it works

The stopwatch starts at the moment the LED lights. When the button is pressed the milliseconds are read and shown. In the simulator the press is slow because you must click, so try the hold control.

Try this next

  • Add a random waiting time.
  • Show a message "too slow" above 500 ms.
  • Make a two-player version.

The simulator program and explanation on this page are original. The idea follows a classic Arduino project that students have built for years.

1Choose your Arduino board
2Build the circuit
Parts: sensors and actuators (tap to show or hide)

Try the inputs (virtual sensors)

Pins (you can change them)

PartArduino 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.

#ColourFrom (part and leg)To
3Define the sequence

Steps run from top to bottom, then start again. While the simulation runs, the active step is highlighted in green.

4Arduino code





5Parts list and where to buy


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.


#ItemQtySearch termBuy / compare



6Export








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.



7Learn: do’s, don’ts, cautions and tips





In the real world
A reaction game
Wait for the red light, then press as fast as you can. The board shows your time.
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.