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Author Topic: Motion & Light Activated Night-light (lights up if it's dark & there is motion)  (Read 3054 times)
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I'm trying to build a night-light for the bedroom, that is motion activated AND will only light up if the room is dark (i.e. - for when you have to wake up in the middle of the night)

I'm having a problem getting the photoresistor part working.  This is one of my first projects so I'm sure I either wired it all wrong, wrong resistor, or wrong code. I got the motion sensor code online from the source listed in the comments, but couldn't find any examples for my photoresistor so most likely my code is wrong.

The Motion sensor part works good (LED lights up when it detects motion).  But the serial monitor isn't showing any photosensor values (which I need so I can adjust the code so it only turns the light on if it's below or above a certain value.

Here is what I have so far:

Parts:
Arduino Uno
5mm LED w/ 100 Ohm resistor
Photoresistor - VT935G-B  https://www.parallax.com/desktopmodules/catalookstore/ProductDetails.aspx?ProductID=175
18k Ohm resistor for Photoresistor
PIR Sensor (Rev B) https://www.parallax.com/desktopmodules/catalookstore/ProductDetails.aspx?ProductID=83


This is how my breadboard is set up:



NOTE: first time using Fritzing, so I'm not 100% sure if I drew the breadboard correct and if this schematic is correct, but here is what it converted the schematic to:




The motion detector turns on the LED when it senses motion.

What doesn't work is:

- getting a  readout on the serial monitor from the photoresister (so I can then adjust the code with correct value)

- I'm not sure my code is right (for now I have " if(digitalRead(pirPin) == HIGH && lightVal < 200) { "   and I'm hoping to just adjust this value once I can see readouts on the serial monitor.


My code is below.  Any advice would be very much appreciated. Thank you.


Code:
/*
 * //////////////////////////////////////////////////
 * //making sense of the Parallax PIR sensor's output
 * //////////////////////////////////////////////////
 *
 * Switches a LED according to the state of the sensors output pin.
 * Determines the beginning and end of continuous motion sequences.
 *
 * @author: Kristian Gohlke / krigoo (_) gmail (_) com / http://krx.at
 * @date:   3. September 2006
 *
 * kr1 (cleft) 2006
 * released under a creative commons "Attribution-NonCommercial-ShareAlike 2.0" license
 * http://creativecommons.org/licenses/by-nc-sa/2.0/de/
 *
 *
 * The Parallax PIR Sensor is an easy to use digital infrared motion sensor module.
 * (http://www.parallax.com/detail.asp?product_id=555-28027)
 *
 * The sensor's output pin goes to HIGH if motion is present.
 * However, even if motion is present it goes to LOW from time to time,
 * which might give the impression no motion is present.
 * This program deals with this issue by ignoring LOW-phases shorter than a given time,
 * assuming continuous motion is present during these phases.
 * 
 */

/////////////////////////////
//VARS
//the time we give the sensor to calibrate (10-60 secs according to the datasheet)
int calibrationTime = 20;       

//the time when the sensor outputs a low impulse
long unsigned int lowIn;         

//the amount of milliseconds the sensor has to be low
//before we assume all motion has stopped
long unsigned int pause = 5000; 

boolean lockLow = true;
boolean takeLowTime; 

int pirPin = 2;    //the digital pin connected to the PIR sensor's output PIR Sensor (Rev B) 555-28027
int ledPin = 7;
int lightPin = 0;  //Photoresistor - VT935G-B  350-00009
int lightVal = analogRead(lightPin);

/////////////////////////////
//SETUP
void setup(){
  Serial.begin(9600);
  pinMode(pirPin, INPUT);
  pinMode(ledPin, OUTPUT);
  digitalWrite(pirPin, LOW);
  pinMode(lightPin, INPUT);
  //give the sensor some time to calibrate
  Serial.print("calibrating sensor ");
    for(int i = 0; i < calibrationTime; i++){
      Serial.print(".");
      delay(1000);
      }
    Serial.println(" done");
    Serial.println("SENSOR ACTIVE");
    Serial.println(lightVal);
    delay(50);
  }

////////////////////////////
//LOOP
void loop(){

       
 
 
     if(digitalRead(pirPin) == HIGH && lightVal < 200) {
       digitalWrite(ledPin, HIGH);   //the led visualizes the sensors output pin state
       if(lockLow){ 
         //makes sure we wait for a transition to LOW before any further output is made:
         lockLow = false;           
         Serial.println("---");
         Serial.print("motion detected at ");
         Serial.print(millis()/1000);
         Serial.println(" sec");
         Serial.println(lightVal);
         delay(50);
         }         
         takeLowTime = true;
       }

     if(digitalRead(pirPin) == LOW){       
       digitalWrite(ledPin, LOW);  //the led visualizes the sensors output pin state

       if(takeLowTime){
        lowIn = millis();          //save the time of the transition from high to LOW
        takeLowTime = false;       //make sure this is only done at the start of a LOW phase
        }
       //if the sensor is low for more than the given pause,
       //we assume that no more motion is going to happen
       if(!lockLow && millis() - lowIn > pause){ 
           //makes sure this block of code is only executed again after
           //a new motion sequence has been detected
           lockLow = true;                       
           Serial.print("motion ended at ");      //output
           Serial.print((millis() - pause)/1000);
           Serial.println(" sec");
           Serial.println(lightVal);
           delay(50);
           }
       }
  }


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It's hard to see from the schematic, but it looks like you wired up the photoresistor wrong. It should form a potential divider:

Quote
                                     ->  ->
+ ------\/\/\/\--------------\/\/\/\/\/\/-------------| 0V
                            |
                            |
                      analog pin
By the looks of it, you missed out the 0V connection.

http://www.techitoutuk.com/knowledge/electronics/buildingblocks/potentialdividers/index.html

Onions.
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Thanks so much, yes I had it all in serial and didn't divide the voltage you're right. I found this blog post which really put it into perspective in case this helps anyone else:

http://nakkaya.com/2009/10/29/connecting-a-photoresistor-to-an-arduino/


I think there may have been an issue with my code too, I ended up taking some bits from the above post instead of what I had and now it all works. Here is the (revised and working) breadboard and schematic and code for anyone else trying to create something similar:






Code:
/*
 * //////////////////////////////////////////////////
 * //making sense of the Parallax PIR sensor's output
 * //////////////////////////////////////////////////
 *
 * Switches a LED according to the state of the sensors output pin.
 * Determines the beginning and end of continuous motion sequences.
 *
 * @author: Kristian Gohlke / krigoo (_) gmail (_) com / http://krx.at
 * @date:   3. September 2006
 *
 * kr1 (cleft) 2006
 * released under a creative commons "Attribution-NonCommercial-ShareAlike 2.0" license
 * http://creativecommons.org/licenses/by-nc-sa/2.0/de/
 *
 *
 * The Parallax PIR Sensor is an easy to use digital infrared motion sensor module.
 * (http://www.parallax.com/detail.asp?product_id=555-28027)
 *
 * The sensor's output pin goes to HIGH if motion is present.
 * However, even if motion is present it goes to LOW from time to time,
 * which might give the impression no motion is present.
 * This program deals with this issue by ignoring LOW-phases shorter than a given time,
 * assuming continuous motion is present during these phases.
 * 
 */

/////////////////////////////
//VARS
//the time we give the sensor to calibrate (10-60 secs according to the datasheet)
int calibrationTime = 20;       

//the time when the sensor outputs a low impulse
long unsigned int lowIn;         

//the amount of milliseconds the sensor has to be low
//before we assume all motion has stopped
long unsigned int pause = 5000; 

boolean lockLow = true;
boolean takeLowTime; 

int pirPin = 2;    //the digital pin connected to the PIR sensor's output PIR Sensor (Rev B) 555-28027
int ledPin = 7;
int lightPin = 0;  //Photoresistor - VT935G-B  350-00009
int threshold = 120;

/////////////////////////////
//SETUP
void setup(){
  Serial.begin(9600);
  pinMode(pirPin, INPUT);
  pinMode(ledPin, OUTPUT);
  digitalWrite(pirPin, LOW);
  pinMode(lightPin, INPUT);
  //give the sensor some time to calibrate
  Serial.print("calibrating sensor ");
    for(int i = 0; i < calibrationTime; i++){
      Serial.print(".");
      delay(1000);
      }
    Serial.println(" done");
    Serial.println("SENSOR ACTIVE");
    Serial.println(analogRead(lightPin));
    delay(50);
  }

////////////////////////////
//LOOP
void loop(){

       
 
 
     if(digitalRead(pirPin) == HIGH && (analogRead(lightPin)) > threshold) {
       digitalWrite(ledPin, HIGH);   //the led visualizes the sensors output pin state
       if(lockLow){ 
         //makes sure we wait for a transition to LOW before any further output is made:
         lockLow = false;           
         Serial.println("---");
         Serial.print("motion detected at ");
         Serial.print(millis()/1000);
         Serial.println(" sec");
         Serial.println(analogRead(lightPin));
         delay(50);
         }         
         takeLowTime = true;
       }

     if(digitalRead(pirPin) == LOW){       
       digitalWrite(ledPin, LOW);  //the led visualizes the sensors output pin state

       if(takeLowTime){
        lowIn = millis();          //save the time of the transition from high to LOW
        takeLowTime = false;       //make sure this is only done at the start of a LOW phase
        }
       //if the sensor is low for more than the given pause,
       //we assume that no more motion is going to happen
       if(!lockLow && millis() - lowIn > pause){ 
           //makes sure this block of code is only executed again after
           //a new motion sequence has been detected
           lockLow = true;                       
           Serial.print("motion ended at ");      //output
           Serial.print((millis() - pause)/1000);
           Serial.println(" sec");
           Serial.println(analogRead(lightPin));
           delay(50);
           }
       }
  }


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Sorry unrelated question. What app did you use to do the drawing?
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Sorry unrelated question. What app did you use to do the drawing?
It's Fritzing. I think it currently is in alpha mode. But works well and creates great looking pics. Just google up Fritzing. But it doesnt have simulation of circuits like Yenka.
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