Magnetic Field Strength Measurement using Arduin
Magnetic Field Measurement
using Arduino Uno
In
this project we are using the concept of ADC (Analog to Digital Conversion) in ARDUINO UNO. We are going to use a Hall Effect sensor and Arduino
uno to measure the field strength of a magnet. The sensor which we have used here is UGN3503U. This is a hall sensor which senses the magnetic
field strength and provides a varying voltage at output proportional to the
field strength.
This sensor picks up field
strength in the units of ‘GAUSS’.
So
with this sensor we will have field strength as varying voltage. By using ADC feature we will convert this voltage
to a number.
This number represents the
field strength and is shown on LCD. [Also
check: 16x2
LCD Interfacing with Arduino]
Arduino
has six ADC channels. In those any one or all of
them can be used as inputs for analog voltage. The UNO ADC is of 10 bit resolution (so the integer values from (0-(2^10) 1023)). This
means that it will map input voltages between 0 and 5 volts into integer values
between 0 and 1023. So for every (5/1024= 4.9mV) per unit.
In all
of this we are going to connect a potentiometer or pot to the ‘A0’ channel,
and we are going to show the ADC result in a simple display. The simple displays are 16x1 and 16x2 display
units.
The 16x1 display unit will
have 16 characters and are in one line. The 16x2 will have 32 characters in total 16in 1st line and another 16 in 2nd line. Here
one must understand that in each character there are 5x10=50 pixels so to display one character all 50
pixels must work together, but we need not have to worry about that because
there a another controller (HD44780) in the display unit which does the job of
controlling the pixels (you can see it in LCD unit,
it is the black eye at the back).
Components Required
Hardware: ARDUINO UNO, power supply (5v),
JHD_162ALCD (16x2LCD),
100uF capacitor (2pieces),
UGn3503U.
Software: arduino IDE (Arduino nightly)
Circuit Diagram and Explanation
The
above figure shows the circuit diagram for magnetic field measurement
using arduino uno.
In
16x2 LCD there are 16 pins over all if there is a back light, if there is no
back light there will be 14 pins. One
can power or leave the back light pins. Now in the 14 pins there are 8 data pins (7-14 or
D0-D7), 2
power supply pins (1&2 or VSS&VDD or
GND&+5v), 3rd pin for contrast control (VEE-controls
how thick the characters should be shown) and 3 control pins (RS&RW&E).
In the
circuit above, you can observe I have only took two control pins, the contrast
bit and READ/WRITE are not often used so they can be shorted to
ground.
This puts LCD in highest
contrast and read mode. We just need to control
ENABLE and RS pins to send characters and data accordingly.
The
connections which are done for LCD are given below:
PIN1
or VSS to ground
PIN2
or VDD or VCC to +5v power
PIN3
or VEE to ground (gives maximum contrast best for a beginner)
PIN4
or RS (Register Selection) to PIN8 of ARDUINO UNO
PIN5
or RW (Read/Write) to ground (puts LCD in read mode eases the communication for user)
PIN6
or E (Enable) to
PIN9 of ARDUINO UNO
PIN11
or D4 to PIN10 of ARDUINO UNO
PIN12
or D5 to PIN11 of ARDUINO UNO
PIN13
or D6 to PIN12 of ARDUINO UNO
PIN14
or D7 to PIN13 of ARDUINO UNO
The
ARDUINO IDE allows the user to use LCD in 4 bit mode. This type of communication enables the user to
decrease the pin usage on ARDUINO, unlike other the ARDUINO need not be
programmed separately for using it in 4 it mode because by default the ARDUINO
is set up to communicate in 4 bit mode. In the circuit you can see we used 4bit communication (D4-D7). So from mere observation from above table we
are connecting 6 pins of LCD to controller in which 4 pins are data pins and 2
pins for control.
Working
For
interfacing an LCD to the ARDUINO UNO, we need to know a few things.
1.
analogRead(pin);
2.
analogReference();
3.
analogReadResolution(bits);
|
First
of all the UNO ADC channels has a default reference value of 5V. This means we can give a maximum input voltage of
5V for ADC conversion at any input channel. Since some sensors provide voltages from 0-2.5V,
with a 5V reference we get lesser accuracy, so we have a instruction that
enables us to change this reference value. So for changing the reference value we have (“analogReference();”)
As
default we get the maximum board ADC resolution which is 10bits, this
resolution can be changed by using instruction (“analogReadResolution(bits);”). This resolution change can come in handy for some
cases.
Now if
the above conditions are set to default, we can read value from ADC of
channel ‘0’ by
directly calling function “analogRead(pin);”, here “pin” represents pin where we connected analog signal,
in this case it would be “A0”. The value from ADC can be taken into an
integer as “int ADCVALUE = analogRead(A0); ”, by
this instruction the value after ADC gets stored in the integer “ADCVALUE”.
NOW
let’s talk a bit about 16x2 LCD. First we need to enable the header file (‘#include <LiquidCrystal.h>’), this
header file has instructions written in it, which enables the user to interface
an LCD to UNO in 4 bit mode without any fuzz. With this header file we need not have to send
data to LCD bit by bit, this will all be taken care of and we don’t have to write a program for sending data or a
command to LCD bit by bit.
Second
we need to tell the board which type of LCD we are using here. Since we have so many different types of LCD (like 20x4, 16x2, 16x1 etc.). In here we are going to interface a 16x2 LCD to
the UNO so we get ‘lcd.begin(16, 2);’. For
16x1 we get ‘lcd.begin(16, 1);’.
In
this instruction we are going to tell the board where we connected the pins,
The pins which are connected are to be represented in order as “RS, En, D4, D5, D6, D7”. These pins are to be represented correctly. Since we connected RS to PIN0 and so on as
show in circuit diagram, We represent the pin number to board as “LiquidCrystal lcd(0, 1, 8, 9, 10, 11);”.
After
above there all there is left is to send data, the data which needs to be
displayed in LCD should be written as “ cd.print("hello, world!");”.
With this command the LCD
displays ‘hello, world!’. As you can see we need not worry about any
this else, we just have to initialize and the UNO will be ready to display data. We don’t have
to write a program loop to send the data BYTE by BYTE here.
Once a
magnet is brought near the sensor the sensor represents a voltage at output
proportional to field, this value is taken up by Uno and shown in LCD. Working of this magnetic field measurement
project is further explained through the below C code.
Demo & Code
Magnetic Field Strength Measurement using Arduin
Reviewed by XXX
on
สิงหาคม 27, 2560
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