Pressure Measurement Using CPS120 and Arduino Nano

Pressure Measurement Using CPS120 and Arduino Nano

CPS120 is a high quality and low cost capacitive absolute pressure sensor with fully compensated output.

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Components and supplies

About this project

CPS120 is a high quality and low cost capacitive absolute pressure sensor with fully compensated output. It consumes much less power and comprises of an ultra small Micro-Electro-Mechanical Sensor (MEMS) for pressure measurement. A sigma-delta based ADC is also embodied in it to accomplish the requirement of compensated output.

In this tutorial, the interfacing of the CPS120 sensor module with Arduino Nano has been illustrated. To read the pressure values, we have used Photon with an I2C adapter. This I2C adapter makes the connection to the sensor module easy and more reliable.

Step 1: Hardware Required

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

1. CPS120

2. Arduino Nano

3. I2C Cable

4. I2C Shield for Arduino Nano

Step 2: Hardware Hookup

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

  • The CPS120 will work over I2C. Reference the example schematic 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. These are connected with the help of an I2C cable. These connections are demonstrated in the pictures above.

Step 3: Code for Pressure Measurement

Lets start with the Arduino code now.

While using the sensor module with the Arduino, we include Wire.h library. The Wire library contains the functions which facilitate the I2C communication between the sensor and the Arduino board.

The entire Arduino code is given in the below Code section for the convenience of the user.

In the Wire library, Wire.write() and Wire.read() are used to write the commands and read the sensor output. Serial.print() and Serial.println() are used to display the output of the sensor on the serial monitor of the Arduino IDE. The output of the sensor is shown in the picture above.

Step 4: Applications

CPS120 has a variety of applications. It can be employed in portable and stationary barometers, altimeters etc. Pressure is an important parameter to determine the weather conditions and considering that this sensor can be installed at weather stations too. It can be incorporated in air control systems as well as vacuum systems.

Code

Code snippet #1Arduino
#include
// CPS120 I2C address is 0x28(40)
#define Addr 0x28
void setup() 
{    
// Initialise I2C communication    
Wire.begin();    
// Initialise Serial Communication, set baud rate = 9600    
Serial.begin(9600);
}
void loop()
{        
unsigned int data[4];        
// Start I2C Transmission    
Wire.beginTransmission(Addr);        
// Request 4 byte of data    
Wire.requestFrom(Addr, 4);
// Read 4 bytes of data    
// pressure msb, pressure lsb, temp msb, temp lsb    
if(Wire.available() == 4)    
{      
data[0] = Wire.read();      
data[1] = Wire.read();      
data[2] = Wire.read();      
data[3] = Wire.read();      
delay(300);            
// Stop I2C Transmission      
Wire.endTransmission();          
// Convert the data to 14 bits      
float pressure = ((((data[0] & 0x3F) * 265 + data[1]) / 16384.0 ) * 90.0 ) + 30.0 ;      
float cTemp = ((((data[2] * 256) + (data[3] & 0xFC)) / 4.0 ) * (165.0 / 16384.0)) - 40.0;      
float fTemp = cTemp * 1.8 + 32;             
// Output data to serial monitor      
Serial.print("Pressure is :   ");      
Serial.print(pressure);      
Serial.println(" kPa");      
Serial.print("Temperature in Celsius : ");      
Serial.print(cTemp);      
Serial.println(" C");      
Serial.print("Temperature in Fahrenheit : ");      
Serial.print(fTemp);      
Serial.println(" F");      
delay(500);     
}  
}

Schematics

CPS120 Schematic
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