Published November 8, 2025

Hall Sensor Based Mail Detector

This device tracks two different doors using Hall effect sensors, I used it to track when mail is in my mailbox.

IntermediateFull instructions provided1

Things used in this project

Hardware components

Particle Photon 2

Hall Effect Sensor

LED (generic)

Story

TheGoal

Spam mail is a curse, and removing curses is what home automation is for. I could just burn whatever's in the mailbox, but that's unsafe and probably illegal. So instead I figured I'd design something to eliminate any unnecessary, fruitless trips to the mailbox by sensing when mail has arrived.

I used a Hall effect sensor to detect a magnet attached to each mailbox door, and to indicate when something arrived I used an LED.

Hardware

I began with a Particle Photon 2 on a breadboard.
Connect the positive bus to the Photon's USB (5 volt) pin and the negative bus to ground.
Attach the first pin of the Hall effect sensor to 5 volt power, the second pin to ground, and the third pin to a digital pin on the Photon.
Connect the first pin to the third pin with a 10 Ω resistor.

In theory

In practice

This process can be repeated for the second Hall effect sensor, and then the LED (or any other device for signalling to the user-- using Particle's event feature you could even use things like email) can be installed.

Installation

I taped small neodymium magnets to each door, in a position close to the edge. The Hall effect sensors can be extended from the breadboard using male to female wires. I used a chain of these wires to extend the sensors far enough to reach the magnets, and then taped the sensors in place. If replicating this project, be sure to secure the wires snugly to the walls of the mailbox, or you could risk incoming mail damaging the system.

Results

(I was a little too scared I would drop the tiny neodymium magnet into the bushes outside my house if I taped it on the outside door, so for the sake of demonstration I tweaked the code so that the magnet touching the outside sensor would make the machine think the door was open, and here's the result...)

Magnets!!!

Code

Source Code

#include "Particle.h"
SYSTEM_MODE(AUTOMATIC);
SerialLogHandler logHandler(LOG_LEVEL_INFO);

//Declaring which pin the sensors are attached to.
int LED = 1;
int HALL1 = 14;
int HALL2 = 13;
bool on = false;
//

void setup() {
  pinMode(LED, OUTPUT);
  pinMode(HALL1, INPUT);
  pinMode(HALL2, INPUT);
  digitalWrite(LED, LOW);
  Serial.begin(9600);
  delay(1000);
}

void loop() {
    
    //The following code is for troubleshooting with the serial monitor. 
    Serial.print("Hall1: ");
    //Serial.print(analogRead(HALL1));
    //Hall sensors really only use digitalRead, so these are commented out. 
    //Serial.print(" D: ");
    Serial.print(digitalRead(HALL1));
    Serial.print(" Hall 2: ");
    //Serial.print(analogRead(HALL2));
    //Serial.print(" D: ");
    Serial.print(digitalRead(HALL2));
    Serial.println(" ");
    delay(500);
      
    //Tells LED to turn on or off depending on the boolean 'on'.
    if(on == true){
      digitalWrite(LED, HIGH);
    }
    else{
      digitalWrite(LED, LOW);
    }
    //

    /*This turns the light on when the mailbox's outside door opens (when mail is dropped in), and back off when the inside door opens (mail is taken out). Note that in this design a hall sensor reading 'LOW' means it detects a magnet nearby, ie. the door is closed*/ 
    if((digitalRead(HALL1) == HIGH)){
      on = true;
    }
    if((digitalRead(HALL2) == HIGH)){
      on = false;
    }
    //
}

Credits

Andrew Plencner

1 project • 0 followers

Hall Sensor Based Mail Detector

Things used in this project

Hardware components

Story

Hardware

Installation

Results

Schematics

Full Diagram

Code

Source Code

Credits

Andrew Plencner

Comments

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Hall Sensor Based Mail Detector

Hall Sensor Based Mail Detector

Things used in this project

Hardware components

Story

Hardware

Installation

Results

Schematics

Full Diagram

Code

Source Code

Credits

Andrew Plencner

Comments

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