Reading a Push-Button with Arduino Uno

                   This example will explain you how to interface a Push Button(Push to ON switch) with Arduino UNO. The Push Button is connected to the Pin No.7 of Arduino and a LED is connected to the Pin No.13 of Arduino as shown in the Schematic below. A 1K ohm resistor is being used along with Push Button for connecting it to Pin no.7, this is to normally pull down the Pin No.7 to ground when the pin is not read otherwise the pin will foat sometimes and lead to wrong reading by Arduino.

                     Another 220 ohm resistor is also being used with LED, this is to limit the current to the LED approximately to 23mA (5V/220 ohm = 23 mA). After wiring the complete schematic, write the code shown below into the Arduino IDE and build it. Now, if you press the Push Button, immediately the LED becomes ON, if you leave the Push Button, immediately the LED becomes OFF.

Code 1:

// Reading a Push Button through Arduino UNO.
int ledPin = 13;                        // Pin for the LED
int inputPin = 7;                       // Pin for Push Button
int val = 0;                               // variable for reading the pin status

void setup()
{
pinMode(ledPin, OUTPUT); // configure ledPin as output
pinMode(inputPin, INPUT);  // configure inputPin as input
}

void loop()
{
val = digitalRead(inputPin);       // read input value
if (val == HIGH) // check if the input is HIGH (button released)
{
digitalWrite(ledPin, HIGH);       // turn LED ON
}
else
{
digitalWrite(ledPin, LOW);       // turn LED OFF
}
}

Same above code can be simply modified as for blinking of LED when the Push Butt
on is pressed totally OFF the LED when the Push Button is released from pressing.

Code 2:

// Reading a Push Button through Arduino UNO.
int ledPin = 13;                        // Pin for the LED
int inputPin = 7;                       // Pin for Push Button
int val = 0;                                // variable for reading the pin status

void setup()
{
pinMode(ledPin, OUTPUT);   // configure ledPin as output
pinMode(inputPin, INPUT);   // configure inputPin as input
}

void loop()
{
val = digitalRead(inputPin);   // read input value
if (val == HIGH) // check if the input is HIGH (button released)
{
digitalWrite(ledPin, HIGH);   // Blinking of LED starts here
delay(100);                              // set the delay of 100 milli Seconds for blinking
digitalWrite(ledPin, LOW);
delay(100);
}
else
{
digitalWrite(ledPin, LOW);  // turn LED OFF
}
}

Blinking a LED

Blinking a LED

            This example will explain you how to make a LED to blink continuously with a set time delay. The digital out put pin being used in the following circuit is 13 of Arduino Uno. Any LED should not be directly connected to the digital output of Arduino. You have to control the current to the LED. In this schematic a resistor of 220 ohm, 1/4 w is used to limit the current to 23 mA (5V/220 ohm = 23 mA). Anode of the LED is to be connected to Pin 13 of Arduino through a 220 ohm resistor. Cathode of the LED is to be connected to the ground. Both +5V and Ground terminals are available in the Arduino Board itself. After making the following wiring, write code in the Arduino IDE.

      

Code 1:

/*

  Blink

  LED connected to the pin of Arduino is made ON and OFF for one second each alternatively.

This is repeated for ever. 

 */

int led = 13;

void setup()

{                

  // initialize the digital pin as an output.

  pinMode(led, OUTPUT);     

}

void loop()

{

  digitalWrite(led, HIGH);   // turn ON the LED (HIGH  = 1 level)

  delay(1000);                    // wait for a second (i.e. 1000 mS)

  digitalWrite(led, LOW);   // turn OFF the LED (LOW = 0 level)

  delay(1000);                      // wait for a second  (i.e. 1000 mS)

}

compile the above code with the Arduino IDE you can see the magic in the LED burning. If you want to make LED to blink fast, the milli second delay can be reduced and checked. If you want to experiment another circuit mentioned below, you can do so.

       By making the above circuit, you can have the circuit as decorative lamps running. For making the above circuit, either you can use same colour LEDs or different colour LEDs. For the above circuit, you can use the following code.

Code 2:

/*

  Blink3Led

  LED connected to the pins of Arduino are made ON and OFF one by one with a delay of one second. 

This repeated for ever. 

 */

int led1 = 11;

int led2 = 12;

int led3 = 13;

void setup()

{                

  // initialize the digital pins as outputs.

pinMode(led1, OUTPUT);

pinMode(led2, OUTPUT);

pinMode(led3, OUTPUT);     

}

void loop()

{

  digitalWrite(led1, HIGH);   // turn ON the LED1 (HIGH  = 1 level)

  digitalWrite(led2, LOW);   // turn OFF the LED2(LOW = 0 level)

  digitalWrite(led3, LOW);   // turn OFF the LED3 (LOW = 0 level)

  delay(1000);                      // wait for a second  (i.e. 1000 mS)

  digitalWrite(led1, LOW);   // turn OFF the LED1(LOW = 0 level)

  digitalWrite(led2, HIGH);   // turn ON the LED2 (HIGH  = 1 level)

  digitalWrite(led3, LOW);   // turn OFF the LED3 (LOW = 0 level)

  delay(1000);                      // wait for a second  (i.e. 1000 mS)

  digitalWrite(led1, LOW);   // turn OFF the LED1(LOW = 0 level)

  digitalWrite(led2, LOW);   // turn OFF the LED2(LOW = 0 level)

  digitalWrite(led3, HIGH);   // turn ON the LED3 (HIGH  = 1 level)

  delay(1000);                      // wait for a second (i.e. 1000 mS)

}

 While experimenting the above, you can learn some thing in the field of micro-controller programming and hardware. If you really enjoyed my posts. Please comment, that will encourage me to post many more. You can also comment in both ways!     

      

  

           

12 x 16 Characters Display interfacing with Arduino Uno

12 x 16 Characters Display interfacing with Arduino Uno

This example shows how to interface a 2 x 16 Characters LCD Display with an Arduino UNO

Hardware required

·         Arduino Board

·         Potentiometer

·         JHD 162a LCD Display

·    Some of the jumper wires

Circuit

To build this circuit, a JHD 162a 2 x 16 Character LCD Display is wired up with an Arduino Uno as shown in the Schematic and a potentiometer of 2K ohm is also connected with the LCD Display, this is being used to adjust the brightness of theback light in the LCD Display. Then plug your Arduino board into your computer, and enter the code below

Schematic

Code

/*

LiquidCrystal Library - Hello World

Demonstrates the use a 16x2 LCD display.  The LiquidCrystal

library works with all LCD displays that are compatible with the

Hitachi HD44780/JHD 162a drivers.

 This sketch prints "Hello World!" into the LCD

and shows the time.

  The circuit:

 * LCD RS pin to digital pin 12

 * LCD Enable pin to digital pin 11

 * LCD D4 pin to digital pin 5

 * LCD D5 pin to digital pin 4

 * LCD D6 pin to digital pin 3

 * LCD D7 pin to digital pin 2

 * LCD R/W pin to ground

* 10K resistor:

 * ends to +5V and ground

 * wiper to LCD VO pin (pin 3)

 */

// include the library code:

#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins

LiquidCrystallcd(12, 11, 5, 4, 3, 2);

void setup() {

  // set up the LCD's number of columns and rows:

lcd.begin(16, 2);

  // Print a message to the LCD.

lcd.print("hello, world!");

}

void loop() {

  // set the cursor to column 0, line 1

  // (note: line 1 is the second row, since counting begins with 0):

lcd.setCursor(0, 1);

  // print the number of seconds since reset:

lcd.print(millis()/1000);

}

Arduino - An Introduction

Arduino Uno Overview:
The Arduino Uno is a microcontroller board based on the ATmega328. It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz ceramic resonator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started.

The Uno differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it features the Atmega16U2 (Atmega8U2 up to version R2) programmed as a USB-to-serialconverter.
Revision2 of the Uno board has a resistor pulling the 8U2 HWB line to ground, making it easier to put into DFU mode.
Revision3 of the board has the following new features:

· 1.0 pin out: added SDA and SCL pins that are near to the AREF pin and two other new pins placed near to the RESET pin, the IOREF that allow the shields to adapt to the voltage provided from the board. In future, shields will be compatible with both the board that uses the AVR, which operates with 5V and with the Arduino Due that operates with 3.3V. The second one is a not connected pin, that is reserved for future purposes.

· Stronger RESET circuit.

· Atmega 16U2 replace the 8U2.

"Uno" means one in Italian and is named to mark the upcoming release of Arduino 1.0. The Uno and version 1.0 will be the reference versions of Arduino, moving forward. The Uno is the latest in a series of USB Arduino boards, and the reference model for the Arduino platform; for a comparison with previous versions, see the index of Arduino boards.

Summary:
Microcontroller                                  :  ATmega328
Operating Voltage                             :   5V
Input Voltage (recommended)           :   7-12V

Input Voltage (limits)                         :   6-20V
Digital I/O Pins                                 :   14 (of which 6 provide PWM output)
Analog Input Pins                             :    6
DC Current per I/O Pin                    :   40 mA
DC Current for 3.3V Pin                  :   50 mA
Flash Memory                                  :   32 KB (ATmega328) of which 0.5 KB used by boot loader
SRAM                                             :   2 KB (ATmega328)

EEPROM                                        :   1 KB (ATmega328)
Clock Speed                                    :   16 MHz

Schematic & Reference Design
EAGLE files: arduino-uno-Rev3-reference-design.zip
(NOTE: works with Eagle 6.0 and newer)
Schematic: arduino-uno-Rev3-schematic.pdf

Note: The Arduino reference design can use an Atmega8, 168, or 328, Current models use an ATmega328, but an Atmega8 is shown in the schematic for reference. The pin configuration is identical on all three processors.

Power:

The Arduino Uno can be powered via the USB connection or with an external power supply. The power source is selected automatically.

External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can be inserted in the Gnd and Vin pin headers of the POWER connector.

The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.

The power pins are as follows:

· VIN. The input voltage to the Arduino board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.

· 5V.This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.

· 3V3. A 3.3 volt supply generated by the on-board regulator. Maximum current draw is 50 mA.

· GND. Ground pins.

· IOREF. This pin on the Arduino board provides the voltage reference with which the microcontroller operates. A properly configured shield can read the IOREF pin voltage and select the appropriate power source or enable voltage translators on the outputs for working with the 5V or 3.3V.

Memory:

The ATmega328 has 32 KB (with 0.5 KB used for the boot loader). It also has 2 KB of SRAM and 1 KB of EEPROM (which can be read and written with the EEPROM library).

Input and Output:

Each of the 14 digital pins on the Uno can be used as an input or output, using pin Mode(), digitalWrite(), and digitalRead()functions. They operate at 5 volts. Each pin can provide or receive a maximum of 40 mA and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms. In addition, some pins have specialized functions:

· Serial: 0 (RX) and 1 (TX). Used to receive (RX) and transmit (TX) TTL serial data. These pins are connected to the corresponding pins of the ATmega8U2 USB-to-TTL Serial chip.

· External Interrupts: 2 and 3. These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value. See the attachInterrupt() function for details.

· PWM: 3, 5, 6, 9, 10, and 11. Provide 8-bit PWM output with the analogWrite() function.

· SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). These pins support SPI communication using the SPI library.

· LED: 13. There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it's off.

The Uno has 6 analog inputs, labeled A0 through A5, each of which provide 10 bits of resolution (i.e. 1024 different values). By default they measure from ground to 5 volts, though is it possible to change the upper end of their range using the AREF pin and the analogReference() function. Additionally, some pins have specialized functionality:

· TWI: A4 or SDA pin and A5 or SCL pin. Support TWI communication using the Wire library.

There are a couple of other pins on the board:

· AREF. Reference voltage for the analog inputs. Used with analogReference().

· Reset. Bring this line LOW to reset the microcontroller. Typically used to add a reset button to shields which block the one on the board.

See also the mapping between Arduino pins and ATmega328 ports. The mapping for the Atmega8, 168, and 328 is identical.

Communication:

The Arduino Uno has a number of facilities for communicating with a computer, another Arduino, or other microcontrollers. The ATmega328 provides UART TTL (5V) serial communication, which is available on digital pins 0 (RX) and 1 (TX). An ATmega16U2 on the board channels this serial communication over USB and appears as a virtual com port to software on the computer. The '16U2 firmware uses the standard USB COM drivers, and no external driver is needed. However, on Windows, a .inf file is required. The Arduino software includes a serial monitor which allows simple textual data to be sent to and from the Arduino board. The RX and TX LEDs on the board will flash when data is being transmitted via the USB-to-serial chip and USB connection to the computer (but not for serial communication on pins 0 and 1).

A SoftwareSerial library allows for serial communication on any of the Uno's digital pins.

The ATmega328 also supports I2C (TWI) and SPI communication. The Arduino software includes a Wire library to simplify use of the I2C bus; see the documentation for details. For SPI communication, use the SPI library.

Programming:

The Arduino Uno can be programmed with the Arduino software (download). Select "Arduino Uno from the Tools > Board menu (according to the microcontroller on your board). For details, see the reference and tutorials.

The ATmega328 on the Arduino Uno comes preburned with a bootloader that allows you to upload new code to it without the use of an external hardware programmer. It communicates using the original STK500 protocol (reference, C header files).

You can also bypass the bootloader and program the microcontroller through the ICSP (In-Circuit Serial Programming) header; see these instructions for details.

The ATmega16U2 (or 8U2 in the rev1 and rev2 boards) firmware source code is available . The ATmega16U2/8U2 is loaded with a DFU bootloader, which can be activated by:

· On Rev1 boards: connecting the solder jumper on the back of the board (near the map of Italy) and then resetting the 8U2.

· On Rev2 or later boards: there is a resistor that pulling the 8U2/16U2 HWB line to ground, making it easier to put into DFU mode.

You can then use Atmel's FLIP software (Windows) or the DFU programmer (Mac OS X and Linux) to load a new firmware. Or you can use the ISP header with an external programmer (overwriting the DFU bootloader). See this user-contributed tutorial for more information.

Automatic (Software) Reset:

Rather than requiring a physical press of the reset button before an upload, the Arduino Uno is designed in a way that allows it to be reset by software running on a connected computer. One of the hardware flow control lines (DTR) of theATmega8U2/16U2 is connected to the reset line of the ATmega328 via a 100 nanofarad capacitor. When this line is asserted (taken low), the reset line drops long enough to reset the chip. The Arduino software uses this capability to allow you to upload code by simply pressing the upload button in the Arduino environment. This means that the bootloader can have a shorter timeout, as the lowering of DTR can be well-coordinated with the start of the upload.

This setup has other implications. When the Uno is connected to either a computer running Mac OS X or Linux, it resets each time a connection is made to it from software (via USB). For the following half-second or so, the bootloader is running on the Uno. While it is programmed to ignore malformed data (i.e. anything besides an upload of new code), it will intercept the first few bytes of data sent to the board after a connection is opened. If a sketch running on the board receives one-time configuration or other data when it first starts, make sure that the software with which it communicates waits a second after opening the connection and before sending this data.

The Uno contains a trace that can be cut to disable the auto-reset. The pads on either side of the trace can be soldered together to re-enable it. It's labeled "RESET-EN". You may also be able to disable the auto-reset by connecting a 110 ohm resistor from 5V to the reset line; see this forum thread for details.

USB Overcurrent Protection:

The Arduino Uno has a resettable polyfuse that protects your computer's USB ports from shorts and overcurrent. Although most computers provide their own internal protection, the fuse provides an extra layer of protection. If more than 500 mA is applied to the USB port, the fuse will automatically break the connection until the short or overload is removed.

Physical Characteristics:

The maximum length and width of the Uno PCB are 2.7 and 2.1 inches respectively, with the USB connector and power jack extending beyond the former dimension. Four screw holes allow the board to be attached to a surface or case. Note that the distance between digital pins 7 and 8 is 160 mil (0.16"), not an even multiple of the 100 mil spacing of the other pins.