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Analog Temperature Sensor

Grove - Temperature Sensor can convert temperature value to voltage value, which can be read by the Arch board. In this example, you'll make a thermometer. The temperature is displayed as LED blinks. LED4 blinks corresponding to tens place of temperature value(in deg C) and LED1 blinks according to units place.

Hardware

  • Arch Board
  • Grove - Temperature Sensor

http://xiongyihui.github.io/archcookbook/figures/temperature.png

Software

Import the following code to mbed online compiler

#include "mbed.h"

AnalogIn thermistor(P0_11);   /* Thermistor output connected to P0_11 */

DigitalOut tensplaceLED(LED4);  /* This led blinks as per tens place of temperature value(in deg C) */
DigitalOut unitsplaceLED(LED1); /* This led blinks as per units place of temperature value(in deg C) */

int main()
{
    unsigned int a, beta = 3975, units, tens;
    float temperature, resistance;

    while(1) {
        a = thermistor.read_u16(); /* Read analog value */
        
        /* Calculate the resistance of the thermistor from analog votage read. */
        resistance= (float) 10000.0 * ((65536.0 / a) - 1.0);
        
        /* Convert the resistance to temperature using Steinhart's Hart equation */
        temperature=(1/((log(resistance/5000.0)/beta) + (1.0/298.15)))-273.15; 
        
        units = (int) temperature % 10;
        tens  = (int) temperature / 10;
        
        
        for(int i=0; i< tens; i++)
        {
             tensplaceLED = 1;
             wait(.200);
             tensplaceLED = 0;
             wait(.200);
        }
        
        for(int i=0; i< units; i++)
        {
             unitsplaceLED = 1;
             wait(.200);
             unitsplaceLED = 0;
             wait(.200);
        }
      
        wait(0.5);
    }
}

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