Measurement of Temperature Using ADT75 and Particle Photon

ADT75 is a highly accurate, digital temperature sensor. It comprises of a band gap temperature sensor and a 12-bit analog to digital converter for monitoring and digitizing the temperature. Its highly sensitive sensor makes it competent enough to measure the ambient temperature accurately.

In this tutorial the interfacing of the ADT75 sensor module with particle photon has been illustrated. To read the temperature values, we have used arduino with an I2c adapter.This I2C adapter makes the connection to the sensor module easy and more reliable.

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

1. ADT75

2. Particle Photon

3. I2C Cable

4. I2C Shield for particle photon

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

The ADT75 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.

Lets start with the particle code now.

While using the sensor module with the arduino, we include application.h and spark_wiring_i2c.h library. "application.h" and spark_wiring_i2c.h library contains the functions which facilitate the i2c communication between the sensor and the particle.

The entire particle code is given below for the convenience of the user:

#include<application.h> 
#include<spark_wiring_i2c.h> 
// ADT75 I2C address is 0x48(72)
#define Addr 0x48
float cTemp = 0.0, fTemp = 0.0;
int temp = 0;
void setup()
{  
// Set variable  
Particle.variable("i2cdevice", "ADT75");  
Particle.variable("cTemp", cTemp);
// Initialise I2C communication as Master  
Wire.begin();  
// Initialise serial communication, set baud rate = 9600  
Serial.begin(9600);  
delay(300);
}
void loop()
{  
unsigned int data[2];
// Start I2C transmission  
Wire.beginTransmission(Addr);  
// Select data register  
Wire.write(0x00);  
// Stop I2C transmission  
Wire.endTransmission();
// Request 2 byte of data  
Wire.requestFrom(Addr, 2);
// Read 2 bytes of data  
// temp msb, temp lsb  
if (Wire.available() == 2)  
{    
data[0] = Wire.read();    
data[1] = Wire.read();  
}
// Convert the data to 12 bits  
temp = ((data[0] * 256) + data[1]) / 16;  
if(temp > 2047)  
{    
temp -= 4096;	  
}  
cTemp = temp * 0.0625;  
fTemp = (cTemp * 1.8) + 32;
// Output data to dashboard  
Particle.publish("Temperature in Celsius : ", String(cTemp));  
Particle.publish("Temperature in Fahrenheit : ", String(fTemp));  
delay(1000);
}

Particle.variable() function creates the variables to store the output of the sensor and Particle.publish() function displays the output on the dashboard of the site.

The sensor output is shown in the picture above for your reference.

ADT75 is a highly accurate, digital temperature sensor. It can be employed in a wide range of systems including environmental control systems, computer thermal monitoring etc. It can also be incorporated in industrial process controls as well as power system monitors.