Archive for October 14th, 2013

14 Oct 2013 Standalone Arduino
 |  Category: Electronics  | Tags:  | 7 Comments

Now that the circuit for my Temperature and Humidity Control is working – its time to create a standalone micro-controller circuit so that I can free up my Induino.


Shopping List:

  1. Atmega 328P-PU (without bootloader)
  2. 16 MHz Crystal
  3. 2 x 22 pf capacitors
  4. LM 7805
  5. 1 uF + 10uF Electrolytic capacitors
  6. 10k Resistor
  7. General purpose PCB

All-in ~250 bucks. Had a 9V 1A power supply at home – so that was free. Needed a 9V for the relays that I had – otherwise you can use a 5V USB adapter that comes with most mobiles and gadgets. I have 8-10 lying at home 🙂

Wiring the Components:

Wire up the components as per the diagram below:

Arduino Standalone_bb

Burning the Bootloader:

  1. Connect your arduino to your computer using the USB cable.
  2. Select your board type and port from the Tools Menu
  3. Open the Arduino ISP sketch from examples
  4. Upload to your Arduino (clone)
  5. For the Induino – you can modify the LED numbers as follows: Lines 49-51 in the code. LED_HB 13; LED_ERR 12; LED_PMODE 11; Edit: Just realised – pins 11, 12, 13 are used for actual programming and should not have LEDs attached to them.
  6. This would allow you to use the in-built LEDs to show the bootloading process (purely optional)
  7. Select Tools->Board->Arduino Uno (the sources say use either Nano or Duemilanove – but Uno works just fine; I selected Uno so that I don’t have to keep changing the board every time I program my standalone kit)
  8. Select Tools->Programmer->Arduino as ISP
  9. Select Tools->Burn Bootloader
  10. Congrats – you have a working standalone arduino (albeit with some limitations)

You can disconnect the cables from your Arduino to the standalone board

 Uploading Sketches

Since our clone doesn’t have a USB-TTL interface, we have to use our arduino to program it. (this is one of the limitations :-))

  1. Remove the micro-controller from your Arduino (I’m trying to skip this step – so if anyone knows a better way – I’m all ears)
  2. Connect Rx pin to Pin 2 on the micro-controller
  3. Connect Tx pin to Pin 3 on the micro-controller
  4. Connect RST pin to Pin 1 on the micro-controller
  5. Connect power to the board (either through arduino or separate)
  6. Connect your arduino to the computer
  7. Upload sketch as usual



14 Oct 2013 Thermometer and Humidity Control
 |  Category: Electronics  | Tags:  | 2 Comments

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:

#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 =;
  // Serial.print("Read sensor: ");
  switch (chk)
    case DHTLIB_OK: 
               // Serial.println("OK"); 
               // Serial.println("Checksum error"); 
               // Serial.println("Time out error"); 
                lcd.println("Unknown error"); 
  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);
  else {
    // lcd.print("H0");
  if(DHT11.temperature < 25){ 
    digitalWrite(RELAY2, HIGH);
    // lcd.print("T1");
  else {

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


14 Oct 2013 Mango Pi
 |  Category: Electronics  | Leave a Comment

Continuing my saga with electronics – went for an electronics workshop by Kits’n’Spares – the workshop was nothing to talk about – however did get me a Mango Pi – a development board for the PIC processors.

Well surprise – surprise – doesn’t support Mac OS, at least I couldn’t get it to work. Finally gave up, started Windows XP in parallels, downloaded the software and started programming. Its not as easy as the arduino, but fun nevertheless. Took me a whole day to program the LCD. The code samples provided with the kit didn’t work and had to troll through the net to understand how to make it work. Finally got it working, here’s the code:


 * File:   LCT Trial.c
 * Created on October 6, 2013, 7:56 PM


// PIC16F877A Configuration Bit Settings


// #pragma config statements should precede project file includes.
// Use project enums instead of #define for ON and OFF.

#pragma config FOSC = XT        // Oscillator Selection bits (XT oscillator)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = OFF      // Brown-out Reset Enable bit (BOR disabled)
#pragma config LVP = ON         // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3/PGM pin has PGM function; low-voltage programming enabled)
#pragma config CPD = OFF        // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF        // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF         // Flash Program Memory Code Protection bit (Code protection off)

char name1[32]={"Lots of Love -- Dushyant        "};
int counter=0;

void delay(int x)
	 int d,l;

void instwrt(int x)

void datawrt(int x)
    if (counter==16){
    if (counter==32){
void lcdin()

void main(void) {
    int a;
    TRISB = 0x00;
    PORTB = 0b00000010;
        // PORTD=
         //       PORTB=name1[a];
14 Oct 2013 My First Arduino Circuit
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After the workshop, I plugged in my Indiuno with the LCD and within half an hour had the LCD working.



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);

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){
        if (numberToDisplay > 9) {numberToDisplay = 0;}
14 Oct 2013 My start in the electronics world
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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.