Team Group 21:

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Published April 18, 2019

IoT LED Temperature Monitor

The LED Temperature monitor can tell yo if your room is hot or if it's just your mind playing tricks with a blink of the eye!

IntermediateFull instructions provided6 hours865

Things used in this project

Hardware components

Jumper wires (generic)

DHT22 Temperature Sensor

Solderless Breadboard Half Size

Photo resistor

USB-A to Mini-USB Cable

Resistor 4.75k ohm

Particle Photon

Software apps and online services

IFTTT Maker service

Google Sheets

Story

Background:

Temperature sensor technology is in a lot of applications.For example, a smart refrigerator or cooler will notify you when its internal temperature is above a certain temperature if left open for too long. Each fridge has a form of temperature control to maintain a certain temperature value. In this experiment we do a deep analysis of the technology behind the temperature sensor. The possibilities are endless when it comes to manipulating code to trigger an output. One output could be opening and closing door or notifying you via text message. For our experiment we use LED lights to notify us when the temperature is above a certain limit.

How it works:

The first step of this project was to build a circuit with the DHT22 temperature/humidity and a photo resistor. The DHT22 sensor detects the temperature and humidity and sends the values to the photon by uploading code to the photons firmware. The photo resistor is connected to the A0 pin on the photon and measures the amount of light in the room based off of the resistance in the photo resistor.

The next step of this project was to build a circuit with another photon to be in communication with the photon connected to the temperature sensor. The purpose of this photon is to receive and read the temperature values provided from the first photon. It then used this data to control green and yellow LEDs based off of the readings from the temperature sensor. It was then time to build the code for the first photon (shown below) to receive the data from the temperature sensor to be published in the particle console. Then, code for the second photon was created to receive the temperature data and create two if/elseif statements to turn off and on the green and yellow LEDs.

Finally, it was time to set up IFTTT to send the data being published to google sheets where it was then graphed by three graphs; temperature, humidity, and light vs. time (shown below).

Analysis:

From the graphs, it is easily seen that sometimes the temperature sensor received a bad reading and ultimately gave us a 0 for the temperature which was obviously not true. This is typical, however, as the temperature sensor is not the best and most accurate of temperature sensors, but is sufficient enough to determine the actual temperature as the bad readings can be ignored. The data was taken as the temperature sensor was being heated up and this trend can be seen from the graphs.

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() {
    
    // temp 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("temperature", String(temperature), PRIVATE);
    digitalWrite(D7,HIGH);
    delay(5000);
    digitalWrite(D7,LOW);
    Particle.publish("humidity", String(humidity) + "%", PRIVATE);
    delay(5000);
    Particle.publish("light", String(light) + "%", PRIVATE);
    delay(5000);
   
    }

//Sets pin D4 as the power toggle pin
const int tog = D4;
const int tog1 = D2;
//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);
    pinMode(tog1, 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(tog1, HIGH);
    //Subscribes the device to the  temperature data coming from the first photon and send it to the temperature handler function
    Particle.subscribe("temperature", 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 >= 23){
        //At a temperature greater than 23 deg C it close the circuit and turns on the Yellow light
        digitalWrite(tog, HIGH);
    }
    else if (temperature <= 22){
        //At temperatures lower than 22 deg C it will open the circuit and turn off the Yellow light
        digitalWrite(tog, LOW);
    }
    if (temperature <= 22){
        //At a temperature greater than 20 deg C it closes the circuit and turns on the Green light
        digitalWrite(tog1, HIGH);
    }
    else if (temperature >= 22){
        //At temperatures lower than 19 deg C it will close the circuit and turn off the Green light
        digitalWrite(tog1, 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

Luke Shevlin

1 project • 0 followers

Elijah Mateola

1 project • 0 followers

IoT LED Temperature Monitor