Published April 13, 2017 © GPL3+

Temperature Sensor

A photon that measures the temperature and humididty with a DHT 22 sensor and communicates the temperature data to another photon.

BeginnerFull instructions provided4 hours2,428

Things used in this project

Hardware components

Particle Photon

Comes with photon kit. Two to communicate between.

Solderless Breadboard Half Size

Comes with Photon Kit. Two to communicate between.

Photo resistor

Comes with Photon Kit.

DHT22 Temperature Sensor

Takes the temperature, humidity, and light measurements

Jumper wires (generic)

Resistor 10k ohm

SparkFun Resistor 4.7k Ohm

USB-A to Mini-USB Cable

Comes with Photon kit to power device. Keep in mind that there needs to be a power source connected to this, such as a wall outlet or a computer.

Software apps and online services

IFTTT Maker service

Google Sheets

Story

This is our IOT project that was assigned from our Instrumentation class at UNCC for the Spring 2017 semester. The purpose of our project was to tell when a room reached a specific temperature, which will cause another particle photon to turn on the D7 LED. Since the summer is coming around the corner, we will be able to tell if a room or a car is too hot. This will allow us to better prepare ourselves for the heat.

To change it up for the cooler weather. These commands can be changed in the code to cause the D7 LED to light up when it gets too cold instead of causing the D7 LED to light up when the temperature is too hot. This can be achieved by simply changing the parameters in the particle subscribe code or by changing the Digital Write toggle commands. These commands will allow us to tell if a room or car has gotten too cold, and this will let us know if we need to bundle up to stay warm.

The breadboard below shows the wiring for the temperature sensor (DHT 22) and the particle photon. The temperature and humidity data are published into the cloud, which will then be picked up by the subscriber.

Temperature Sensor Breadboard

The breadboard shown below will act as the particle photon subscriber. This is the photon particle that retrieves temperature data from the cloud and will either Toggle Digital Write HIGH, if the temperature is greater than or equal to 20 degrees Celsius, or toggle a Digital Write LOW, if the temperature is less than or equal to 19 degrees Celsius. When it triggers the Digital Write HIGH, the D7 LED will light up. When it triggers the Digital Write LOW, the D7 LED will turn off or it won't light up at all.

Below shows the sample graph data that displays the Time vs Temperature, Time vs Humidity, and Light vs Humidity retrieved from the IFTTT and google docs programs.

This video shows the process of how our IOT temperature project works. It shows the communication between the two photons.

Code

// This #include statement was automatically added by the Particle IDE.
#include <Adafruit_DHT.h>

// This #include statement was automatically added by the Particle IDE.
#include "Adafruit_DHT/Adafruit_DHT.h"

// DHT parameters
#define DHTPIN 5
#define DHTTYPE DHT22

// Variables
int temperature;
int humidity;
int light;

// Pins
int light_sensor_pin = A0;

// DHT sensor
DHT dht(DHTPIN, DHTTYPE);

void setup() {
    
    // Start DHT sensor
    dht.begin();
}

void loop() {
    
    // Humidity measurement
    temperature = dht.getTempCelcius();
    
    // Humidity measurement
    humidity = dht.getHumidity();
    
    // Light level measurement
    float light_measurement = analogRead(light_sensor_pin);
    light = (int)(light_measurement/4096*100);
   
    // Publish data
    Particle.publish("temperature2807112", String(temperature), PRIVATE);
    digitalWrite(D7,HIGH);
    delay(2000);
    digitalWrite(D7,LOW);
    Particle.publish("humidity", String(humidity) + "%", PRIVATE);
    delay(2000);
    Particle.publish("light", String(light) + "%", PRIVATE);
    delay(2000);
   
    
  

    
}

//Sets pin D4 as the power toggle pin
const int tog = D7;

//initializes temperature
int temperature;



void setup() {
    pinMode(tog, OUTPUT);
    //The relay is wired as normally closed and is non-latching so that if the photon loses power the light will remain on, setting the pin value to high defaults the light to the off position by opening the relay circuit.
    digitalWrite(tog, HIGH);

    //Subscribes the device to the  temperature data coming from the first photon and send it to the temperature handler function
    Particle.subscribe("temperature2807112", temperatureHandler, MY_DEVICES);
    //Compares the temperature value pulled from the cloud to the values set by the user to prevent the well from freezing
}
void loop() {
    if (temperature >= 20){
        //At a temperature greater than 20 deg C it opens the circuit and turns off the light
        digitalWrite(tog, HIGH);
    }
    else if (temperature <= 19){
        //At temperatures lower than 19 deg C it will close the circuit and turn on the light
        digitalWrite(tog, LOW);
    }
    else{
        //Reading any temperature in the "deadzone" between 15 and 20deg C restarts the loop
    }

}
//Takes the string data retrieved from the cloud and converts it to an integer value for comparison
void temperatureHandler(const char *event, const char *data){
    //sets a new string, which i have defined as "pew" to take in the temperature data
    String pew = data;
    //Converts this new string "pew" into the previously defined integer "temperature"
    temperature = pew.toInt();
}

Credits

Melissa Thai

1 project • 3 followers

Fe Schultz

1 project • 2 followers

Temperature Sensor

Things used in this project

Hardware components

Software apps and online services

Story

Schematics