Smart Relay MEGR-3171

A motion controlled/light sensing activated relay board to control your lights, fans, or any other household appliance.

IntermediateFull instructions provided2 hours741

Things used in this project

Hardware components

Particle Photon

Parts List & Prices • 3 Particle Photons ($20.00 per photon) • PIR sensor module ($2.00) • Particle Relay Board ($30.00) • 12V Wall Adapter Power Supply ($7.99) • Photo Resistor ($0.20) • 14-20 Jumper wires ($2.00) Total Project Cost = $102.19 Links to materials Relay Shield https://www.amazon.com/Particle-RLYSHLD-Other-Development-Shield/dp/B01GVI2RWI PIR motion sensor https://www.amazon.com/DIYmall-HC-SR501-Motion-Infrared- 12V 2Amp Wall Adapter power Supply https://www.amazon.com/Amamax%C2%AE-Wall-Adapter-Power- Particle Photon https://www.amazon.com/Particle-Reprogrammable-Development-Prototyping-Electronics/dp/B016YNU1A0/ref=sr_1_1_sspa?s=electronics&ie=UTF8&qid=1541910559&sr=1-1-spons&keywords=photon&psc=1 Photoresistor https://www.amazon.com/eBoot-Photoresistor-Sensitive-Resistor-Dependent/dp/B01N7V536K/ref=sr_1_1_sspa?s=electronics&ie=UTF8&qid=1541910734&sr=1-1-spons&keywords=photoresistor&psc=1 Jumper Wires https://www.amazon.com/McIgIcM-Solderless-Flexible-Breadboard-Arduino/dp/B071NVN87X/ref=sr_1_17?s=electronics&ie=UTF8&qid=1541910279&sr=1-17&keywords=jumper+wires

Solderless Breadboard Half Size

Male/Female Jumper Wires

Male/Male Jumper Wires

9V 1A Switching Wall Power Supply

Photo resistor

PIR Sensor (generic)

Software apps and online services

Particle Pi

Particle Build Web IDE

ThingSpeak API

Story

During our enrollment in a measurement and instrumentation course at UNC Charlotte, we were required to create an IOT project which would be developed throughout the semester. The criteria for the project was the number of group members must be equal to the number of particle photons used in the project. Also, for every group member a line of cloud communication between one photon and another had to be established. These lines of communication were to be integrated into the functionality of the project. Our group consisted of three members which meant we were required to have three photons communicating with one another. We spent weeks bouncing ideas around while tinkering with the photons and sensors included in our makers kit's we had bought at the beginning of the semester. We developed an array of tentative project ideas, however, the project we ended up creating seemed to arise in very organic way.

As the end of the semester was approaching Keaton and I had created multiple single function systems including; a light sensor using a photo resistor, a motion detection system using a PIR sensor, an alert screen using an OLED display, a servo controller app, and multiple bits of code which allowed photons to communicate through the particle cloud.

During this time a particle relay board became part of the tools at our disposal. The project solidified itself as an expandable smart relay board which for demonstration purposes, would be configured as an automated night light and low tech home security system. This was achieved by allowing a single photon to be designated as the "master" controller of the relay board. Subscribing this photon to published events, uploaded by the other two devices, we were able to automate and control the channels of the relay using three way communication between all of our devices. One photon determined the light intensity within a room and the other motion. The LED light wired to the relay board was then triggered on an off without the need for a manual switch, using conditional loops which compared the light and motion sensory data published by the other two photons.

The conditional loop which controls the relay switch are based on events published to the particle cloud by the photon's connected to the photo resistor and PIR sensor. The photon connected to the relay board is subscribed to these published events and uses the conditions listed below to determine what state the relay should be set to.

For the relay to be activated, "LED lights are on"

Condition 1 - The light intensity value measured by the photo resistor connected to photon 1 must less than 55, " This value of 55 indicates that the current lighting condition of the space reflect a dark room"

Condition 2 - A sufficient amount of infrared (IR) light radiating from objects in the PIR sensor its field of view, connected to photon two, must be achieved indicating that there is motion in the room.

If both of thee conditions are met then the photon controlling the relay board will send a digital signal of "HIGH" to the D5 pin, which will close the relay and supply power to the connected LED lighting strip.

For the relay to be deactivated "LED lights are off"

If either one of the conditions above are not met, ie: the room already has enough natural lighting, from windows or other appliances, or if there is no motion detected in the room for a duration of time when the room is dark. The photon connected to the relay board will send a digital signal value of "LOW" to the D5 pin, effectively closing the relay and the LED strip connected to it.

The photon connected to the PIR sensor for this project is also set up to function as a low tech security solution. Published events from this photon, indicating whether a space is occupied or not, were configured using a web-hook and ThingSpeak.com. This web-hook provides a live stream of events which generate a daily log of events indicating what times during the day a given room was occupied.

The biggest issue we ran into while creating this project was developing the code and determining the best method of passing data from one photon to another to achieve hands free control of the relay board. We hope our page provides a foundation of resources for others who wish to create cheap, customizable, and adaptable home automation systems.

Code

int photoresistor = A1;
int power = A5;
int analogvalue;     

//This code set the inital values of the code and assigns each of them to a pin //on the particle photon

void setup() {
    pinMode(power,OUTPUT);
    pinMode(photoresistor, INPUT);
    Particle.variable("analogvalue", &analogvalue, INT);
    
}

//This code sets up which pins supply power, input and how the particle receives //the photoresistor input

void loop() {
    
    analogvalue = analogRead(photoresistor);
    delay(100);
    
    if (analogvalue > 55){
        Particle.publish("LightStatus_KphotonUNCC","Bright", PUBLIC);
        digitalWrite(led,HIGH);
        delay(4000);
      
    }
    else {
        Particle.publish("LightStatus_KphotonUNCC","Dark", PUBLIC);
        digitalWrite(led,LOW);
        delay(4000);
        
    }
    
}
    
//This void loop reads the analog values recieved from the photoresistor and if //the value is above 55, it publishes that the ambient light is bright. If it is //below 55, it publishes that the amblient light is dark. It then delays 4 //seconds to prevent the photon from publishing too often. The value of 55 has to //be fine tuned for each individual situation. Also, if the published values are //backwards, you can flip the greater than and less symbols in the loop.

int ledPin = D7;                 // choose the pin for the LED
int inputPin = D0;               // choose the PIR sensor pin
//VIN & GRN & D0 are the only wire required to plug in, D7 turns on when motion is detected
bool available;                  // status of room
int motionCounter = 0;           // variable to count motion events

Timer timer(4000, determineMotion); // software timer to check every 10s


void setup() {
  pinMode(ledPin, OUTPUT);       // set LED as output
  pinMode(inputPin, INPUT);      // set sensor as input
  timer.start(); // start the determineMotion timer
}




void determineMotion() {    // this function determines if there's motion
    if(motionCounter < 2) { // if very little motion was detected
        if(available == false) { // only publish if the status changed
            Particle.publish("MotionStatus_MasterPhotonUNCC","Roomisunoccupied",PUBLIC); //publish to the relay photon
            }
        available = true; // set the status to available
    } else if (motionCounter >= 2) {
        if(available == true) { // only publish if the status changed
            Particle.publish("MotionStatus_MasterPhotonUNCC","Roomisoccupied",PUBLIC); //publish to the relay photon
            }
        available = false; // set the status to in use
    }
    motionCounter = 0; // reset motion counter
}

void loop() {
  if (digitalRead(inputPin) == HIGH) {  // check if the input is HIGH
    digitalWrite(ledPin, HIGH);         // turn LED ON if high
    motionCounter++;                    // increment motion counter
  } else {
    digitalWrite(ledPin, LOW);          // turn LED OFF if no input
  }
  delay(500);                           // wait 0.5s
}

Photon 3 - Relay Board (Primary)

C/C++

Photon 3 is connected to the relay shield and is subscribed to the published events from photon 1 and 2.
Based on the events published by each photon the code is set up such that if the room is "Dark" and there is "Motion" detected in the room. The photon will turn a relay on which will supply power to the LED strip wired to it. However, if no motion is detected for a period of time or if the room is sufficient bright. Then the particle will turn the relay off.

int ledPin = D5;                 // choose the pin for the LED
 
bool x ; //sets a boolean value of x for photon 1
bool y ; //sets a boolean value of y for photon 2


void setup() {
pinMode(ledPin, OUTPUT);       // set LED as output
Particle.subscribe("LightStatus_KphotonUNCC",data,"280030000d47343438323536"); // subscribes to Photon 1 for light detection
Particle.subscribe("MotionStatus_MasterPhotonUNCC",anything,"500026000b51353432383931"); // subscribes to Photon 2 for motion detection
}

void data(const char *event, const char *data)          // light Publish
 {
     if (strcmp(data,"Bright"))
     x = true;
     else 
     x = false;
 }
 //reads published data from photon 1
 
void anything(const char *event, const char *data)    // motion sensor
{
    
   if (strcmp(data,"Roomisoccupied"))
    y = false;
    else 
    y = true;
}
//reads published data from photon 2
    

void loop() {
  if (x && y)
//if photon 1 is Dark, and photon 2 Roomisoccupied, then the relay is switched on
digitalWrite(D5, HIGH);
else
digitalWrite(D5,LOW);
}
//if not, the relay stays closed