Published May 7, 2021

Thermostat

A smart thermostat that you can manage via the cloud

IntermediateFull instructions provided2 hours321

Things used in this project

Hardware components

Particle Photon

Adafruit Waterproof DS18B20 Digital temperature sensor

Jumper wires (generic)

C&K Switches JS Series Switch

Breadboard (generic)

Software apps and online services

Microsoft VS Code

Particle Build Web IDE

Hand tools and fabrication machines

Multitool, Screwdriver

Story

This project is the representation of a smart thermostat, remotely controllable.For do this I use IoTReady Platform, where I claim my photon, and update all the function and the variables. You can see their documentation here.

IoTReady platform

The realization

I recently started a stage experience at IoTReady, in Bergamo. My tutor ask me to realize a smart thermostat, using their platform.So I built the circuit and the I wrote the code.

How the project works

Instead of the led and the Arduino I was using a relay, which was activated when the temperature became lower than the threshold, set from IoTReady platform, and the Photon. The thermostat only worked when the switch was on.

Part of code

Using the Particle cloud functions I realize a Particle.function() to modify the starting threshold of the thermostat. In the setup function I have declaired my function and variables.

void setup(){
    Particle.function("setSoglia", setPoint);
    Particle.variable("Bottone", button);
    Particle.variable("Soglia", soglia);
    Particle.variable("Tempreatura attuale", actualTemp);
}

Then, under the loop() I write the logic of my function.

int setPoint(String point){
    soglia = point.toFloat();
    return 1;
}

Code

Thermostat

#include <DS18B20.h>
/*
 * Project termostato
 * Description:
 * Author:
 * Date:
 */

// setup() runs once, when the device is first turned on.

int button, shiftStatus, relay1;
int latchPin = A3;
int dataPin = A4;
int clockPin = A2;
const int MAXRETRY = 4;
const int16_t dsData = D7;
const uint32_t msSAMPLE_INTERVAL = 5000;
double soglia = 0;
double actualTemp = 0;

DS18B20  ds18b20(dsData, true); 

double celsius;
uint32_t msLastMetric;
uint32_t msLastSample;

void setup() {
  // Put initialization like pinMode and begin functions here.
  pinMode(D3, INPUT);
  pinMode(latchPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  Particle.variable("bottone", button);
  Particle.variable("soglia", soglia);
  Particle.variable("Tempreatura attuale", actualTemp);
  Particle.function("setSoglia", setPoint);
  Particle.variable("Relay", relay1);

  Serial.begin(9600);
}

// loop() runs over and over again, as quickly as it can execute.
void loop() {
  // The core of your code will likely live here.
  button = digitalRead(D3);
  if (millis() - msLastSample >= msSAMPLE_INTERVAL){
    getTemp();
    actualTemp = celsius;
  }

  if(button == 1){
    if(actualTemp < soglia){
      relay1 = 1;
      registerWrite();
    }else{
      relay1 = 0;
      registerWrite();
    }
  }else{
    relay1 = 0;
    registerWrite();
  }

}

void registerWrite() {

    shiftStatus = 8*relay1;

    digitalWrite(latchPin, LOW);
    shiftOut(dataPin, clockPin, MSBFIRST, shiftStatus);
    digitalWrite(latchPin, HIGH);
}

void getTemp(){
  float _temp;
  int   i = 0;

  do {
    _temp = ds18b20.getTemperature();
  } while (!ds18b20.crcCheck() && MAXRETRY > i++);

  if (i < MAXRETRY) {
    celsius = _temp;
  }
  else {
    celsius = NAN;
    Serial.println("Invalid reading");
  }
  msLastSample = millis();
}

int setPoint(String point){
  soglia = point.toFloat();
  return 1;
}