Arduino project · Displays and counters · Hard
Two-Way People Counter with Room Light
Two IR sensors at a door count people going in and out. The room light stays on while at least one person is inside.
What you will learn
- How two sensors can tell the direction of a person
- How a counter goes up and down but never below 0
- How a smart room saves energy
How it works
IR sensor 1 is outside, sensor 2 is inside. Whichever fires first tells the direction: sensor 1 first means a person enters (count up), sensor 2 first means a person leaves (count down). A short wait lets the person pass, then both sensors must be clear. In the simulator, switch sensor 1 and then sensor 2 on and off to walk in.
Try this next
- Show the count on a 7-segment display.
- Add a buzzer when the room is full (more than 10).
- Sound a chime for each person entering.
The simulator program and explanation on this page are original. The idea follows a classic Arduino project that students have built for years.
Caution: single-phase mains (230 V AC). The wall socket, relay contacts and load in this circuit carry mains voltage, which can kill. Work only with an adult, with the plug out of the wall, switch the LIVE wire only, fit a fuse or MCB, join Earth to metal bodies, use a closed insulated box, and have an electrician check it before you power it. In the simulator everything is safe. In real life, test with a low-voltage lamp first.
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 room that counts who walks in
Each time the IR sensor is blocked a person passes through the door and the count goes up.
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 = a person in the doorway
- Relay = the room light (where used)