Using Hall Effect Sensors with the Arduino-ATMEGA168

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Using Hall Effect Sensors with the Arduino-ATMEGA168

by Lewis Loflin

In the You Tube video above I demonstrated the use of a ratiometric Hall sensor with an Arduino-Atmega168 connected to a liquid crystal display. This page will show how to connect Hall sensors to the Arduino.

See the two previous pages on Hall sensors the video covered:

Hall Switch connected to LED

Pictured above is a Hall effect switch connected to a light emitting diode. (LED) In the off condition TP2 will be "HIGH" or 5 volts measured relative to ground. The LED will be off. When switched on by a magnet TP2 will measure about .5 volts and the LED will be on.

This can be directly connected to the input port of a micro-controller or other 5-volt digital logic.

Hall effect sensor

We can use the above circuit to read the output from the sensor. The voltage reading will give us an idea of the polarity and strength of a magnet. Instead of a voltmeter, we use Arduino. In this case I'll be using a 5-volt UGN3502 and not 12-volts, which will damage the controller.

A ratiometric Hall effect sensor outputs an analog voltage proportional to the magnetic field intensity. With no magnetic field applied the output is about one-half the supply voltage. The voltage will increase with the south magnetic pole on the face or decrease with the north magnetic pole on the face. The range is from about 1 to 4 volts.

Hall effect measure current

Here is a direct application. A calibrated linear Hall device in this example will measure the current through the wire. The higher the current the stronger the magnetic field and thus a higher output voltage. We could sound an alarm with excessive or low current, etc.

About the Program

An analog to digital converter (ADC) in the ATMEGA168 or ATMEGA328 are 10-bit (1024 steps) and over a range at 5 volts is 5.0/1024 = 4.882 mV per step. Here we simply measure the output voltage from the sensor and display that voltage. It's simply a modified version of my TMP37 program and uses the exact same schematic. See Using the TMP37Temperature Sensor with Arduino

See Arduino Project Mainpage



/*
 Demonstrates the use a 16x2 LCD display

The ratiometric Hall sensor I'm using is the UGN3503 
 and is connected to analog pin 0 (AD0)
 
Note the schematic below.

*/


 
// include the library code:
#include "LiquidCrystal.h"


 float refVoltage = 5.0 / 1024; // volts per step on ADC
 float sensorVolts;
 int val;

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() {
  // set up the LCD's number of columns and rows: 
  lcd.begin(16, 2);  // 16 char by 2 lines
  lcd.noCursor(); // Hides the LCD cursor.
}

void loop() {

    // read AD0
    val = analogRead(0);
    sensorVolts = refVoltage * val;
    
    
    // set the cursor to column 0, line 1
    // (note: line 1 is the second row, since counting begins with 0):
    lcd.setCursor(0, 0);
    lcd.print("Hall Volts ="); 
    
    lcd.setCursor(0, 1);
    lcd.print(sensorVolts); 
    delay(500); // 500 mSec

}  // end loop

Arduino connected to LCD display
Typical 2 line by 16 character LCD connection to a generic Arduino module.
R1 is used to adjust LCD contrast, pins 15 and 16 are the back light.

Using Hall Effect Switches and Sensors
Using Ratiometric Hall Effect Sensors
Using Hall Effect Sensors with the Arduino-ATMEGA168
TL173C 12-Volt Ratiometric Hall Sensor (PDF file)
UGN3503 5-Volt Ratiometric Hall Effect Sensor (PDF file)
SS466 Hall Latch (PDF file)

To purchase Hall sensors or explore the many varied types of sensors see www.allegromicro.com. If one wants a kit of parts to perform the above experiments contact me at lewis@bvunet.net for information.

Added January 2012: PICAXE Micro-controller Projects!

The PICAXE series of micro-controllers rank as the easiest and most cost effective way to use Microchip processors. I wanted an easier and less expensive way to introduce my students to the "PIC" micro-controller. Here I hope to get those starting out past poorly written literature and lack of simple working code examples.

The next groups of links below go to specific electronic/electrical devices on how to use and test them.