📡 EMF Meter Build Guide

Gather Your Parts

Lay everything out on your work surface. Check that you have each item:

Setup Breadboard

The breadboard has power rails (red/blue lines) on the sides. We'll use these for power distribution.

• Insert ESP32 into center of breadboard (straddle the gap)
• Connect ESP32 3.3V pin to RED power rail (use RED wire)
• Connect ESP32 GND pin to BLUE ground rail (use BLACK wire)

Wire All Components

Follow this table EXACTLY. Check off each connection as you make it:

Double-Check Everything

Before powering on, verify:

• All power connections (3.3V and GND) are correct
• No wires crossing or touching that shouldn't
• All LEDs have long leg going to GPIO pin
• Each LED has a resistor in series with ground
• OLED display SDA goes to GPIO 21, SCL goes to GPIO 22
• Hall sensor OUT goes to GPIO 34

Install Arduino IDE

You need Arduino IDE to program the ESP32:

1. Go to: https://www.arduino.cc/en/software
2. Download for your OS (Windows/Mac/Linux)
3. Install it (use default settings)
4. Open Arduino IDE

Add ESP32 Board Support

Arduino IDE doesn't include ESP32 by default. Add it:

1. In Arduino IDE, go to: File → Preferences
2. Find "Additional Board Manager URLs" field
3. Paste this URL:
   https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json
4. Click OK
5. Go to: Tools → Board → Boards Manager
6. Search for: esp32
7. Find "esp32 by Espressif Systems"
8. Click Install (takes 2-3 minutes)

Install Required Libraries

The OLED display needs special libraries:

1. In Arduino IDE, go to: Sketch → Include Library → Manage Libraries
2. Search: Adafruit SSD1306
3. Click Install on "Adafruit SSD1306"
4. When prompted to install dependencies, click Install All

Connect ESP32 to Computer

1. Plug USB cable into ESP32
2. Plug other end into computer
3. In Arduino IDE, go to: Tools → Board → ESP32 Arduino
4. Select: ESP32 Dev Module
5. Go to: Tools → Port
6. Select the port (COM3, /dev/ttyUSB0, etc.)

Upload the Firmware

Copy this code into Arduino IDE:

// EMF Meter Firmware - Simple Version
#include 
#include 
#include 

// Pin Definitions
#define HALL_PIN 34
#define LED1 13  // Green
#define LED2 12  // Yellow
#define LED3 14  // Yellow
#define LED4 27  // Red
#define LED5 26  // Red

// Display Setup
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define OLED_RESET -1
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

void setup() {
  Serial.begin(115200);

  // Setup pins
  pinMode(HALL_PIN, INPUT);
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
  pinMode(LED3, OUTPUT);
  pinMode(LED4, OUTPUT);
  pinMode(LED5, OUTPUT);

  // Initialize display
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println("Display failed!");
    while(1);
  }

  display.clearDisplay();
  display.setTextSize(2);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(20, 20);
  display.println("EMF");
  display.println(" METER");
  display.display();
  delay(2000);
}

void loop() {
  // Read hall sensor
  int hallValue = digitalRead(HALL_PIN);

  // Simulate EMF levels (0-5)
  int emfLevel = random(0, 6);

  // Turn off all LEDs
  digitalWrite(LED1, LOW);
  digitalWrite(LED2, LOW);
  digitalWrite(LED3, LOW);
  digitalWrite(LED4, LOW);
  digitalWrite(LED5, LOW);

  // Light LEDs based on level
  if(emfLevel >= 1) digitalWrite(LED1, HIGH);
  if(emfLevel >= 2) digitalWrite(LED2, HIGH);
  if(emfLevel >= 3) digitalWrite(LED3, HIGH);
  if(emfLevel >= 4) digitalWrite(LED4, HIGH);
  if(emfLevel >= 5) digitalWrite(LED5, HIGH);

  // Update display
  display.clearDisplay();
  display.setTextSize(3);
  display.setCursor(30, 20);
  display.print(emfLevel);
  display.println(" mG");
  display.display();

  delay(200);
}

Now upload it:

1. Click the Verify button (checkmark icon) - should say "Done compiling"
2. Click the Upload button (arrow icon)
3. Wait for "Connecting..." message
4. If stuck: Hold the BOOT button on ESP32, then click Upload again
5. Wait for "Done uploading"

Test It!

Your EMF meter is working! Test it:

• Display shows numbers (0-5)
• LEDs light up in sequence (green → yellow → red)
• Numbers change on display
• Bring phone or magnet near hall sensor (readings should change)

Troubleshooting

Display Not Working

• Check SDA on GPIO 21, SCL on GPIO 22
• Check power: VCC to 3.3V, GND to GND
• Try address 0x3D instead of 0x3C in code

LEDs Not Lighting

• Check LED polarity (long leg to GPIO)
• Check resistor is connected
• Try swapping LED (might be dead)

Upload Fails

• Hold BOOT button during upload
• Try different USB cable
• Install CH340 or CP2102 drivers
• Select correct COM port

Next Steps

You did it! You have a working EMF meter on breadboard.

Now you can:

1. Test with different EMF sources (phone, microwave, wiring)
2. Add battery power (connect battery holder to VIN + GND)
3. Add power switch between battery and VIN
4. Transfer to enclosure when ready
5. Upload real EMF firmware (coming soon)