Category: Electronics

The first thing that came to my mind when I started microcontroller programming was to set an automatic room heating cum humidifier system.

First off – bought a DHT11 sensor module. Then went about setting up the circuit. Added the LCD to boot – to show the temperature and humidity.

Set up the circuit as follows:

Code as follows:

#include 
#include 
#define DHT11PIN 13
#define RELAY1 2 // Connect humidifier to Relay1
#define RELAY2 3 // Connect heater to Relay2
#define TEMP_SET 20.0
#define HUM_SET 35.0

dht11 DHT11;
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

void setup() {
  lcd.begin(16, 2);
  pinMode(DHT11PIN, INPUT);
  pinMode(RELAY1, OUTPUT);
  pinMode(RELAY2, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly: 
  int chk = DHT11.read(DHT11PIN);
  // Serial.print("Read sensor: ");
  switch (chk)
  {
    case DHTLIB_OK: 
               // Serial.println("OK"); 
                break;
    case DHTLIB_ERROR_CHECKSUM: 
               // Serial.println("Checksum error"); 
                break;
    case DHTLIB_ERROR_TIMEOUT: 
               // Serial.println("Time out error"); 
                break;
    default: 
                lcd.println("Unknown error"); 
                break;
  }
  lcd.setCursor(0, 0);
  lcd.print("Humidity: ");
  lcd.print((float)DHT11.humidity, 2);
  lcd.setCursor(0, 1);
  lcd.print("Temp: ");
  lcd.print((float)DHT11.temperature, 2);
  if(DHT11.humidity < 50){ 
    digitalWrite(RELAY1, HIGH);
    lcd.print("H1");
  }
  else {
    digitalWrite(RELAY1,LOW);
    // lcd.print("H0");
  }
  if(DHT11.temperature < 25){ 
    digitalWrite(RELAY2, HIGH);
    // lcd.print("T1");
  }
  else {
  digitalWrite(RELAY2,LOW);
  lcd.print("T0");
  }
  delay(900000);
}

Worked like a charm – next steps:

1. Add two buttons to change the temperature presets – save preset in EEPROM
2. Create a standalone arduino so that I don’t have to give up my Induino for this small project

 

After the workshop, I plugged in my Indiuno with the LCD and within half an hour had the LCD working.

Source: http://arduino.cc/en/Tutorial/LiquidCrystal

Photos:

Next up was using the 7-segment display and the shift register. After a lot of googling and experimenting – finally managed to set it up so that it counts from 0 to 9. I used the on-board switch on pin # 7. Had to use a lot of binary to decimal conversions to get the numbers correct – but finally got it down pat 🙂

Attached circuit diagram and sketch if anyone’s interested.

//Pin connected to ST_CP of 74HC595
int latchPin = 4;
//Pin connected to SH_CP of 74HC595
int clockPin = 3;
////Pin connected to DS of 74HC595
int dataPin = 2;
int buttonPin = 7;
int numberToDisplay = 0;
int segNumbers[10] = {126,48,109,121,51,91,95,112,127,123};

void setup() {
  //set pins to output so you can control the shift register
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  pinMode(buttonPin,INPUT_PULLUP);
}

void loop() {
      // take the latchPin low so 
      // the LEDs don't change while you're sending in bits:
      digitalWrite(latchPin, LOW);
      // shift out the bits:
      shiftOut(dataPin, clockPin, LSBFIRST, segNumbers[numberToDisplay]);  
      //take the latch pin high so the LEDs will light up:
      digitalWrite(latchPin, HIGH);
      if (digitalRead(buttonPin) == LOW){
        numberToDisplay++;
        if (numberToDisplay > 9) {numberToDisplay = 0;}
      }
      while(digitalRead(buttonPin)==0);
      delay(100);
}

Have always been fascinated with electronics and computers – but never knew how to go about it.

Finally got a chance to experiment – when Abhiram decided to hold a small electronics workshop. Well – got up early (comparatively) on a Saturday and went to see what could happen.

 

The workshop was great – Abhiram started right from the basics of analog circuits and went on to explain how digital circuits are created using microcontrollers. In addition to all this – he arranged for starter kits for us – which included an Induino and lots of LEDs, resistors, sensors, et al to get us started. (Though he did warn us that this was an expensive hobby :-))

Anyways – long story short – I had a lot of fun and am now hooked to microcontroller programming.