Close Loop Control System Demo Using LED Light and LDR

1#include <LiquidCrystal.h>
2
3LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
4const  int LDR_pin = A0;    		// pin that the LDR sensor is attached to
5const int  set_pot_pin = A1;
6const int led_light_pin = 9;        	// pin that the LED array  is attached to
7
8// variables:
9int sensorValue = 0;         // the sensor  value
10int sensorMin = 1023;        // minimum sensor value
11int sensorMax =  0;           // maximum sensor value
12int threshold = 0;
13int light_intensity  = 55, led_intensity = 20;
14void setup()
15{
16  lcd.begin(16, 4);
17  lcd.clear();
18  lcd.print("calibrating.....");
19  analogWrite(led_light_pin, 0);
20  digitalWrite(13,  HIGH);
21  while (millis() < 10000)
22  {
23    sensorValue = analogRead(LDR_pin);
24    if (sensorValue > sensorMax) sensorMax = sensorValue;
25    if (sensorValue  < sensorMin) sensorMin = sensorValue;
26  }
27  lcd.clear();
28  lcd.print("calibration  over");
29  lcd.setCursor(0, 1);
30  lcd.print("max light:");
31  lcd.print(sensorMax);
32  lcd.setCursor(0, 2);
33  lcd.print("min light:");
34  lcd.print(sensorMin);
35  delay(2000);
36  lcd.clear();
37  lcd.print("light intensity");
38  lcd.setCursor(0,  2);
39  lcd.print("threshold:");
40  lcd.setCursor(0, 3);
41  lcd.print("LED  light:0%");
42}
43
44void loop()
45{
46  sensorValue = analogRead(LDR_pin);
47  sensorValue = map(sensorValue, sensorMin, sensorMax, 0, 100);
48  sensorValue  = constrain(sensorValue,0,100);
49  lcd.setCursor(0, 1);
50  lcd.print(sensorValue);
51  lcd.print('%');
52  threshold = analogRead(set_pot_pin);
53  threshold = map(threshold,  0, 1023, 0, 100);
54  lcd.setCursor(11, 2);
55  lcd.print(threshold);
56  lcd.print('%');
57  if (sensorValue < threshold)
58  {
59    analogWrite(led_light_pin, light_intensity);
60    lcd.setCursor(11, 3);
61    lcd.print(led_intensity);
62    lcd.print('%');
63    if(light_intensity<255)
64      {
65        light_intensity += 25;
66        led_intensity  += 10;
67      }    
68   }
69  delay(2000); 
70}
71