Emma NicholsDylan Moss

MEGR 3171 - That Car is HOT HOT HOT!

This project demonstrates the usage of a photon and temperature sensor programmed to notify you when your car reaches a certain temperature.

IntermediateFull instructions provided4 hours731
MEGR 3171 - That Car is HOT HOT HOT!

Things used in this project

Hardware components

Particle Photon
Jumper wires (generic)
Jumper wires (generic)
Particle Temperature Sensor - (sealed)
Resistor 4.75k ohm
Resistor 4.75k ohm

Software apps and online services

Maker service
IFTTT Maker service
Google Sheets
Google Sheets
Particle Build Web IDE
Particle Build Web IDE


Read more


Temperature Measuring Photon

Emma's Photon

Threshold Determining Photon

Dylan's Photon


Threshold Determination

This is the code for Dylan's Photon which establishes the temperature threshold and compares the data from Emma's Photon to establish if you're above or below the target temperature.
// ----------------------------------------------------------------------
// Determining Whether the Published Tmeperature has Crossed a Threshold
int boardLed = D7;
int tempThreshold;
int temperature;

// We start with the setup function.

void setup() {
  // Our on-board LED is output.

  // Here we are going to subscribe to smol_photon's event using Particle.subscribe:
  Particle.subscribe("smolphotonevent69", myHandler, "18002d001447363336383437");
  // Subscribe will listen for the event smolphotonevent69 and, when it finds it, will run the function myHandler()
  // myHandler() is declared later in this app.

  // First, the D7 LED will be off
  tempThreshold = 70;
  // Initialize a threshold as the desired temperature (in degrees fahrenheit) of the car.

void loop() {
  // This void begins a loop so ur_mom will continuously subscribe and publish.
// The myHandler function is called when the cloud tells us that smol_photon's event is published.
void myHandler(const char *event, const char *data)
     //ur_mom will blink for a second each time smol_photon publishes a new temperature

  int myValue = atoi(data); 
  //Convert the string received from the smolphotonevent69 into an integer.
  if (myValue>tempThreshold) {
    // Compare the incoming data with the chosen threshold.
    // Publish a public event announcing the temperature to be above the threshold.
    // If the temp is above the threshold, then the LED will keep blinking.

  else {
    // Publish a public event announcing the temperature to be below the threshold.
    // If the temp is below the threshold, the LED will stay on.

Temperature Sensor

This is the code on Emma's Photon for temperature measurement, slightly modified from the Particle Tutorial mentioned above.
// This #include statement was automatically added by the Particle IDE.
#include <OneWire.h>

This sketch reads the temperature from a 1-Wire device and then publishes
to the Particle cloud. From there, IFTTT can be used to log the date,
time, and temperature to a Google Spreadsheet. Read more in our tutorial
here: https://docs.particle.io/tutorials/topics/maker-kit

This sketch is the same as the example from the OneWire library, but
with the addition of three lines at the end to publish the data to the

Use this sketch to read the temperature from 1-Wire devices
you have attached to your Particle device (core, p0, p1, photon, electron)

Temperature is read from: DS18S20, DS18B20, DS1822, DS2438

Expanding on the enumeration process in the address scanner, this example
reads the temperature and outputs it from known device types as it scans.

I/O setup:
These made it easy to just 'plug in' my 18B20 (note that a bare TO-92
sensor may read higher than it should if it's right next to the Photon)

D3 - 1-wire ground, or just use regular pin and comment out below.
D4 - 1-wire signal, 2K-10K resistor to D5 (3v3)
D5 - 1-wire power, ditto ground comment.

A pull-up resistor is required on the signal line. The spec calls for a 4.7K.
I have used 1K-10K depending on the bus configuration and what I had out on the
bench. If you are powering the device, they all work. If you are using parisidic
power it gets more picky about the value.

OneWire ds = OneWire(D4);  // 1-wire signal on pin D4

unsigned long lastUpdate = 0;
int led = D7;
float lastTemp;
void setup() {

void anything(const char *event, const char *data)

//if temp is below threshold, smol_photon will blink


// up to here, it is the same as the address acanner
// we need a few more variables for this example

void loop(void) {
  byte i;
  byte present = 0;
  byte type_s;
  byte data[12];
  byte addr[8];
  float celsius, fahrenheit;

  if ( !ds.search(addr)) {
    Serial.println("No more addresses.");

  // The order is changed a bit in this example
  // first the returned address is printed

  Serial.print("ROM =");
  for( i = 0; i < 8; i++) {
    Serial.write(' ');
    Serial.print(addr[i], HEX);

  // second the CRC is checked, on fail,
  // print error and just return to try again

  if (OneWire::crc8(addr, 7) != addr[7]) {
      Serial.println("CRC is not valid!");

  // we have a good address at this point
  // what kind of chip do we have?
  // we will set a type_s value for known types or just return

  // the first ROM byte indicates which chip
  switch (addr[0]) {
    case 0x10:
      Serial.println("  Chip = DS1820/DS18S20");
      type_s = 1;
    case 0x28:
      Serial.println("  Chip = DS18B20");
      type_s = 0;
    case 0x22:
      Serial.println("  Chip = DS1822");
      type_s = 0;
    case 0x26:
      Serial.println("  Chip = DS2438");
      type_s = 2;
      Serial.println("Unknown device type.");

  // this device has temp so let's read it

  ds.reset();               // first clear the 1-wire bus
  ds.select(addr);          // now select the device we just found
  // ds.write(0x44, 1);     // tell it to start a conversion, with parasite power on at the end
  ds.write(0x44, 0);        // or start conversion in powered mode (bus finishes low)

  // just wait a second while the conversion takes place
  // different chips have different conversion times, check the specs, 1 sec is worse case + 250ms
  // you could also communicate with other devices if you like but you would need
  // to already know their address to select them.

  delay(1000);     // maybe 750ms is enough, maybe not, wait 1 sec for conversion

  // we might do a ds.depower() (parasite) here, but the reset will take care of it.

  // first make sure current values are in the scratch pad

  present = ds.reset();
  ds.write(0xB8,0);         // Recall Memory 0
  ds.write(0x00,0);         // Recall Memory 0

  // now read the scratch pad

  present = ds.reset();
  ds.write(0xBE,0);         // Read Scratchpad
  if (type_s == 2) {
    ds.write(0x00,0);       // The DS2438 needs a page# to read

  // transfer and print the values

  Serial.print("  Data = ");
  Serial.print(present, HEX);
  Serial.print(" ");
  for ( i = 0; i < 9; i++) {           // we need 9 bytes
    data[i] = ds.read();
    Serial.print(data[i], HEX);
    Serial.print(" ");
  Serial.print(" CRC=");
  Serial.print(OneWire::crc8(data, 8), HEX);

  // Convert the data to actual temperature
  // because the result is a 16 bit signed integer, it should
  // be stored to an "int16_t" type, which is always 16 bits
  // even when compiled on a 32 bit processor.
  int16_t raw = (data[1] << 8) | data[0];
  if (type_s == 2) raw = (data[2] << 8) | data[1];
  byte cfg = (data[4] & 0x60);

  switch (type_s) {
    case 1:
      raw = raw << 3; // 9 bit resolution default
      if (data[7] == 0x10) {
        // "count remain" gives full 12 bit resolution
        raw = (raw & 0xFFF0) + 12 - data[6];
      celsius = (float)raw * 0.0625;
    case 0:
      // at lower res, the low bits are undefined, so let's zero them
      if (cfg == 0x00) raw = raw & ~7;  // 9 bit resolution, 93.75 ms
      if (cfg == 0x20) raw = raw & ~3; // 10 bit res, 187.5 ms
      if (cfg == 0x40) raw = raw & ~1; // 11 bit res, 375 ms
      // default is 12 bit resolution, 750 ms conversion time
      celsius = (float)raw * 0.0625;

    case 2:
      data[1] = (data[1] >> 3) & 0x1f;
      if (data[2] > 127) {
        celsius = (float)data[2] - ((float)data[1] * .03125);
        celsius = (float)data[2] + ((float)data[1] * .03125);

  // remove random errors
  if((((celsius <= 0 && celsius > -1) && lastTemp > 5)) || celsius > 125) {
      celsius = lastTemp;

  fahrenheit = celsius * 1.8 + 32.0;
  lastTemp = celsius;
  Serial.print("  Temperature = ");
  Serial.print(" Celsius, ");
  Serial.println(" Fahrenheit");
  // now that we have the readings, we can publish them to the cloud
  String temperature = String(fahrenheit); // store temp in "temperature" string
  Particle.publish("smolphotonevent69", temperature);// publish to cloud
  delay(5000);} // 5 second delay


Emma Nichols

Emma Nichols

1 project • 1 follower
Dylan Moss

Dylan Moss

1 project • 0 followers


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