Introduction: Temperature Measurement Using MCP9803 and Raspberry Pi

MCP9803 is a 2-wire high accuracy temperature sensor. They are embodied with user- programmable registers that facilitate temperature sensing applications. This sensor is suited for highly sophisticated multi-zone temperature monitoring system.

In this tutorial the interfacing of the MCP9803 sensor module with raspberry pi is demonstrated and its programming using Java language has also been illustrated. To read the temperature values, we have used raspberry pi with an I2C adapter.This I2C adapter makes the connection to the sensor module easy and more reliable.

Step 1: Hardware Required:

Picture of Hardware Required:

The materials that we need for accomplishing our goal includes the following hardware components:

1. MCP9803

2. Raspberry pi

3. I2C Cable

4. I2C Shield for raspberry pi

5. Ethernet Cable

Step 2: Hardware Hookup:

Picture of Hardware Hookup:

The hardware hookup section basically explains the wiring connections required between the sensor and the raspberry pi. Ensuring correct connections is the basic necessity while working on any system for the desired output. So, the requisite connections are as follows:

The MCP9803 will work over I2C . Here is the example wiring diagram, demonstrating how to wire up each interface of the sensor.

Out-of-the-box, the board is configured for an I2C interface, as such we recommend using this hookup if you’re otherwise agnostic.

All you need is four wires! Only four connections are required Vcc, Gnd, SCL and SDA pins and these are connected with the help of I2C cable.

These connections are demonstrated in the pictures above.

Step 3: Code for Temperature Measurement:

Picture of Code for Temperature Measurement:

The advantage of using raspberry pi is, that is provides you the flexibility of the programming language in which you want to program the board in order to interface the sensor with it. Harnessing this advantage of this board, we are demonstrating here its programming in the Java. The java code for MCP9803 can be downloaded from our github community that is Control Everything Community.

As well as for the ease of the users, we are explaining the code here also:

As the first step of coding you need to download the pi4j library in case of java, because this library supports the functions used in the code. So, to download the library you can visit the following link:

http://pi4j.com/install.html

You can copy the working java code for this sensor from here also:

import com.pi4j.io.i2c.I2CBus;

import com.pi4j.io.i2c.I2CDevice;

import com.pi4j.io.i2c.I2CFactory;

import java.io.IOException;
public class MCP9803

{

public static void main(String args[]) throws Exception

{

// Create I2C bus

I2CBus Bus = I2CFactory.getInstance(I2CBus.BUS_1);

// Get I2C device, MCP9803 I2C address is 0x48(72)

I2CDevice device = Bus.getDevice(0x48);

// Select configuration register

// Continuous conversion mode, Power-up, comparator mode, 12-bit resolution

device.write(0x01, (byte)0x60);

Thread.sleep(500);

// Read 2 bytes of data from address 0x00(0)

// temp msb, temp lsb

byte[] data = new byte[2];

device.read(0x00, data, 0, 2);

// Convert the data to 12-bits

int temp = ((data[0] & 0xFF) * 256 + (data[1] & 0xF0)) / 16;

if(temp > 2047)

{

temp -= 4096;

}

double cTemp = temp * 0.0625;

double fTemp = cTemp * 1.8 + 32;

// Output data to screen

System.out.printf("Temperature in Celsius is : %.2f C %n", cTemp);

System.out.printf("Temperature in Fahrenheit is : %.2f F %n", fTemp);

}

}

The library which facilitates i2c communication between the sensor and the board is pi4j, its various packages I2CBus, I2CDevice and I2CFactory help to establish the connection.

import com.pi4j.io.i2c.I2CBus;

import com.pi4j.io.i2c.I2CDevice;

import com.pi4j.io.i2c.I2CFactory;

import java.io.IOException;

write() and read() functions are used to write some particular commands to the sensor to make it work in a particular mode and read the sensor output respectively.

The output of the sensor is also shown in the picture above.

Step 4: Applications:

Picture of Applications:

MCP9803 can be employed in a wide arena of devices which include personal computer and peripherals, hard disk drives, various entertainment systems, office systems and data communication systems. This sensor can be incorporated in various sophisticated systems.

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