Introduction: Room Occupancy Counter

About: I am Paolo Reyes engineering leader in FRC and FTC team WinT 3794.

I am Paolo Reyes a Mexican that loves to create and make things. That is why I Made this Room Occupancy Counter.

Due to COVID-19 circumstances, I decided to develop this project to limit virus spread, by controlling the number of people that can be in a room at the same time.

So how does this works? I am using two ultrasonic sensors that provide real distance information to the next wall, door or object, and when someone crosses between that space, the sensors will detect it, and according to the order in the sensors readings, it will count as a person entering or leaving the room.


  • Ultrasonic sensor (x2)


  • DHT11 Temperature and humidity sensor (x1)


  • Active Buzzer (x1)


  • LCD 16x2 (x1)


  • Green LED (x1)


  • Red LED (x1)


  • 10k potenciometer PT10-2(x1)


  • Push button (x3)


  • Arduino Uno (x1)


  • ON/OFF Switch (x1)

ON/ OFF_Switch

  • AC/DC Adapter (x1)


Step 1: Remove DHT 11 and Arduino Connectors

Remove DHT 11 connectors and arduino uno female input .

Step 2: Making the Case

Print the case with a 3D-printer if you want a case. Otherwise you can test the device without a case on a breadboard or you can make a cardboard box... Just keep in mind that there has to be a hole for every component, I suggest to make one for the arduino as well to change or upload the sketch.

Step 3: Wiring and Soldering

Wire all components according to the circuit plan.

If you want to make the PCB-prototype version, then arrange the components like in the diagram and use wires to connect the components.

Step 4: Upload Sketch to the Arduino

Feel free to modify and play with the code.

Step 5: Use the Device

You can now put some glue or tape to add it on the wall and. LET THE DEVICE START WORKING!