Electronic – Arduino PIR relay with manual override switch

arduinorelayswitches

I'm setting up a PIR activated relay (connected to some lights) using an Arduino Nano.

I have the PIR code working (obtained from a 3rd party site) but I'd like the option to override the PIR input based on an input from a push button switch. To add even more complexity, I'd like to have an LED lit up to let me know when the PIR is being manually overridden (relay always on).

The button is a simple push button.

By default, I want the unit to be in PIR mode. The relay is activated if motion is detected, and then after X seconds it switches off. If I press the button once, it's manually overridden and the relay is switched on (constantly) and the blue LED is activated to inform me that the unit is on constantly. If the button is pressed again, the unit switches back to PIR mode.

Here's the code I've got so far – but the LED and relay seem to be constantly active. The PIR is still reading (according to the serial monitor).

/*
 * PIR sensor tester
 */ 


int PIR_override = 3;         // the number of the switch pin
int overridestatus = 12;       // the number of the led pin

int relaypin = 13;                // choose the pin for the LED
int inputPin = 2;               // choose the input pin (for PIR sensor)
int pirState = LOW;             // we start, assuming no motion detected
int val = 0;                    // variable for reading the pin status
int DELVAR = 3000;             // Delay in milliseconds
int override_state = LOW;      // the current state of the output pin

// set states for PIR override switch
int state = LOW;      // the current state of the output pin
int reading;           // the current reading from the input pin
int previous = HIGH;    // the previous reading from the input pin

///////////////////////////////////////////////////////
void setup() {
  pinMode(relaypin, OUTPUT);      // declare LED as output
  pinMode(inputPin, INPUT);     // declare sensor as input

  Serial.begin(9600);
}

void loop()
{
    digitalRead(PIR_override);  // read input value of PIR override switch
    if (val == LOW)
    {            // check if the input is LOW
        val = digitalRead(inputPin);  // read input value
        if (val == HIGH)
        {            // check if the input is HIGH
            digitalWrite(relaypin, HIGH);  // turn LED ON
            if (pirState == LOW)
            {
                // we have just turned on
                Serial.println("Motion detected!");
                // We only want to print on the output change, not state
                pirState = HIGH;
                delay(DELVAR);    // maximum delay is 32776 millisecons,
                //  delay(DELVAR);    // so add multiple delays together to get
                // delay(DELVAR);    // so add multiple delays together to get
            }
        }
        else
        {
            digitalWrite(relaypin, LOW); // turn LED OFF
            if (pirState == HIGH)
            {
                // we have just turned of
                Serial.println("Motion ended!");
                // We only want to print on the output change, not state
                pirState = LOW;
            }
            else
            {
                digitalWrite(overridestatus, HIGH);  // turn override status LED ON
                digitalWrite(relaypin, HIGH);  // turn relay ON
            }
        }
    }
}

Here's the code I've got so far – but the LED and relay seem to be constantly active. The PIR is still reading (according to the serial monitor).

There's clearly something wrong with my if-else loop but I'm not entirely sure where I need to start looking.

I'm also including a basic breadboard image of the circuit (it's my first Fritz so be gentle!) Also, please ignore the pin in on the relay board. I am using an SRD-05VDC-SL-C but it's on a slightly different board with only 3 pins (IN, VCC, GND).

enter image description here

Best Answer

I think your main problem is that you aren't assigning a variable or using an if statement with your digitalRead(PIR_override);, but even with that you may miss the button press in the loop. If it's a momentary switch then it goes high/low for only the time that it's pressed, so the processor would have to see this at the right time in the while loop. You could just hold the button down for about a second or you could connect the button to pin 2 or 3 and use an interrupt, which it looks like your button is connected to pin 3 according to your code. I think this is a better solution. In the embedded world interrupts are your friend.

So, according to the documentation (https://www.arduino.cc/en/Reference/AttachInterrupt), you could do something like this:

const byte PIR_override = 3;        // the number of the switch pin
volatile boolean override = false;          // Use this to know if your currently  in override mode or not when looking at the button press

Inside Setup() add:

pinMode(PIR_override, INPUT);
attachInterrupt(digitalPinToInterrupt(PIR_override), motionOverride, LOW); // the sense may need to be changed - from your image it looks like the button goes low when pressed

So now motionOverride will be called when the button is pressed. Just put what you want to happen inside this function. Something like this:

void motionOverride()
{
    if(override) // overriding motion and the button has been pressed - got to PIR mode
    {
        digitalWrite(overridestatus, LOW);  // turn override status LED OFF
        digitalWrite(relaypin, LOW);  // turn relay OFF - you may not want to do this... depends on what you want
        override = false;               // set the override flag
    }
    else // not overriding motion and the button has been pressed - go to override mode
    {
        digitalWrite(overridestatus, HIGH);  // turn override status LED ON
        digitalWrite(relaypin, HIGH);  // turn relay ON
        override = true;                // set the override flag
    }

   // I guess Arduino takes care of clearing the interrupt for you
}

Then inside your main loop() just look at the override flag (Note: I did not check any of your PIR motion detection logic, and hopefully I didn't mess up your brackets there):

void loop()
{
     if(!override)
     {
         val = digitalRead(inputPin);  // read PIR input value
         if (val == HIGH)  // check if the input is HIGH
         {           
              digitalWrite(relaypin, HIGH);  // turn LED ON
              if (pirState == LOW) 
              {
                   // we have just turned on
                   Serial.println("Motion detected!");
                   // We only want to print on the output change, not state
                   pirState = HIGH;
                   delay(DELVAR);    // maximum delay is 32776 millisecons,
                   //  delay(DELVAR);    // so add multiple delays together to get
                   // delay(DELVAR);    // so add multiple delays together to get
             }
        } 
        else
        {
            digitalWrite(relaypin, LOW); // turn LED OFF
            if (pirState == HIGH)
            {
                 // we have just turned of
                 Serial.println("Motion ended!");
                 // We only want to print on the output change, not state
                 pirState = LOW;
            } 
        }
     }
}

Try that out if you want. If there's a mistake I'll try and help with it.

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