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Big digit LED people counter using arduino and sonar sensor
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C4AA Sonar People Counter

Project Website on github

Designed for our collaboration with Treatment Action Group for the 2018 AIDS Conference. Learn more.

This project uses sonar to detect when people walk through a doorway. The signal is sent to an arduino, which triggers lights (and possibly sounds) and counts the person on 8in LED numbers overhead.

The project uses:

  1. Arduino - we used a RedBoard
  2. LCD Button Shield V2 - note: this is now retired, but it seems similar shields are available.
  3. 6.5in tall 7-segment Display
  4. SparkFun Large Digit Driver

TO DO Part 1: Basic Systems & Testing

Strengthen wired connections between parts

Some of the wired connections were too delicate for use in the field.


  • Rebuilt circuitboard that sits alongside arduino and LED shield
  • added ethernet jacks to run connection between LED Number display and Arduino.
  • used JRT connectors between LED strip light and board.
  • kept pin header connections for connection to Sonar unit.


Part 2: Ideas for Improvements

Add sound

Bike bell + servo motor

Add positionable mount for sonar sensor


Build case for arduino, circuit board, and bell:


LED 7-Segment Display Box


Part 3: Documentation and Instructions

We should do this as we go along. It starts now!

Part 4: Physical door (if there’s time)

Experiment with designs, or creating specifications for building on site.

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