💬 Motion Sensor

[bgunnarb]

I have found in my experiments with the PIR motion sensor that at least the type that I am using is extremely sensitive to ripple in the Vcc voltage.

First of all, it is unstable as the feed voltage approaches 5V and then it triggers spontaneously again and again. I then tried to rise the voltage to around 11V which is the voltage that the battery eliminator gives. But that voltage has a ripple of 0.1 volt amplitude so this triggers the sensor again and again also since the arduino introduces small changes in the voltage when it processes the script.

The solution was to install a LM317 voltage regulator to bring down the voltage to 8V which is then ripple free and stable. Now the PIR works very well and does not give false triggers.

The arduino is fed from a separate voltage regulator giving 5V. I tried to connect the battery eliminator directly to RAW but that released the smoke from the on-board voltage regulator and as you know, when you let the smoke out from components, they no longer work. :grinning:

Apparently the battery eliminator also produces some voltage spikes that are not healthy.

[gohan]

I solved my random pir triggers with a Capacitor on the 5v pin.

[A Former User]

@Kieren-Perry said in 💬 Motion Sensor:

Hi all,

The motion sensor project is my first using Arduino and MySensors! I've managed to get the Gateway all up and running and the motion sensor to communicate with it (using the standard ino file from the project page), but I seem to have a couple of issues:

• Despite the default sleep time it seems to be communicating with the Gateway constantly.
• Permanently displayed as in an 'On' state in Domoticz.

I've tried adjusting the sensitivity and time but it doesn't seem to make a difference.

I don't know which bit is supposed to contain the values which I can decipher with the serial protocol guide so apologies if the answer is staring me in the face!

Gateway received
0;255;3;0;9;TSF:MSG:READ,1-1-0,s=1,c=1,t=16,pt=0,l=1,sg=0:1
1;1;1;0;16;1

Node sent
0
1383086 TSF:MSG:SEND,1-1-0-0,s=1,c=1,t=16,pt=0,l=1,sg=0,ft=0,st=OK:0
1383106 MCO:SLP:MS=120000,SMS=0,I1=1,M1=1,I2=255,M2=255
1383120 MCO:SLP:TPD
1383127 MCO:SLP:WUP=1

Any help would be appreciated :)

Thanks for all your comments! Tried the capacitor route but no dice. In the end, connected a 9v battery to the jack and the PIR to the VIN as the voltage from the 5v pin and USB was a little below what it should have been.

[Cliff Karlsson]

If I want something to run for 10 seconds after a motion have been detected, how would I make this happend?

[gohan]

Set a timer in the code, that's shouldn't be very hard to do.

[Cliff Karlsson]

I have never used timers but I looked at the blink without delay sketch from the arduino website. Do I replace the if -statement with a while loop?

const int ledPin =  LED_BUILTIN;// the number of the LED pin

// Variables will change :
int ledState = LOW;             // ledState used to set the LED

// Generally, you should use "unsigned long" for variables that hold time
// The value will quickly become too large for an int to store
unsigned long previousMillis = 0;        // will store last time LED was updated

// constants won't change :
const long interval = 1000;           // interval at which to blink (milliseconds)

void setup() {
  // set the digital pin as output:
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // here is where you'd put code that needs to be running all the time.

  // check to see if it's time to blink the LED; that is, if the
  // difference between the current time and last time you blinked
  // the LED is bigger than the interval at which you want to
  // blink the LED.
  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= interval) {
    // save the last time you blinked the LED
    previousMillis = currentMillis;

    // if the LED is off turn it on and vice-versa:
    if (ledState == LOW) {
      ledState = HIGH;
    } else {
      ledState = LOW;
    }

    // set the LED with the ledState of the variable:
    digitalWrite(ledPin, ledState);
  }
}

[gohan]

Just leave it as it is, just put a condition that will trigger the if statement only once the pir sensor got triggered

[LastSamurai]

I would actually not do this in a node but in the controller (at least if I get what you are trying to do right). I have done that with some scripting in domoticz. I have lights that that are switched on for 5 minutes when motion is detected and shut down 5 minutes after the last motion stopped. Motion sensor and rgbw controller are different mysensor nodes. Much more versatile then hardcoding this in you node's code.

[ben999]

@LastSamurai
Would you do that through "rules" ?

[gohan]

@ben999 yes.

@LastSamurai I know that hardcoding is less flexible, but at least it can work even if controller is down or disconnected, of course it depends how critical is the actuator.

[maghac]

So, I notice that the HC-SR501 has a 7133-1 voltage regulator on-board which I guess means that the logic is actually driven with 3.3V and not 5V.

Is it possible to bypass the regulator and power the sensor directly with the 3.3V I am using to power my nano with?

[maghac]

@maghac Aha, guess I should read old posts first :)

[gohan]

Just make sure the power source is stable otherwise you will end up with random triggers from pir sensor

[ben999]

@gohan @maghac

From my little experience : when running from 2 AA batteries with sketch as it is I got random triggers continuousely

Adding a delay() before entering sleep() sorted things out (something like 3 sec is necessary to get power stable again)

Not sure it's the smartest way of doing it, but it works...

Any comment on the security side of it? Could my node miss some action during these 3 sec ? Or the interrupt pin would still listen to the PIR sensor pin ?

[gohan]

I think it will miss the pir trigger

[ben999]

@gohan

Thank you for your reply

Could you please explain a bit further ?

Interrupt pin would still read the trigger during delay()?
Data would be lost as the sketch is frozen during delay() ?
Or data is saved in some buffer, ready to be used as soon as sketch comes back to life ?

My view is that it shouldn't matter too much if i miss a trigger after a trigger : the first trigger will wake my node and transmit to gateway. So job done. Alarm goes off.

On the other hand, I guess a millis() would be neater ?

Thanks a lot for your input

[gohan]

I am saying that during delay no code is executed and interrupt only attaches to pin when executing the sleep function, so if motion if triggered during the delay it will not be detected by interrupt; maybe it could detect the CHANGE when pir goes from high to low but it will then report "no motion" and it will not trigger alarm if it set to go off on "motion" only.

[ben999]

@gohan

Thanks a lot

Got it now

delay() to be avoided then !

I will have a look at millis() instead

[gohan]

Delay is not bad, depends how you use it. Maybe you could use an if statement to check pin state is low before entering sleep

[skywatch]

Millis won't work with the SLEEP funtion either. REcently added to the API....