2.1 Hardware set up
2.1.1 Schematic diagram
Figure 4
2.1.2 Arduino microcontroller
There are a couple of other pins on the board:
This indicates
that the codes
written for the
microcontroller can be loaded
on to Arduino
Uno using USB
cables, which are easier
to carry and
deal with. As
seen in the
figure, the Arduino Uno is
powered using ATmega328P microcontroller. The circuit board has a convenient
power management which allows the input
voltage up to
12V. The built-in
power regulatory mechanism then
permits the regulation
of this voltage into
5V and 3.3V.
The power can
be supplied by connecting
an adapter to the external
power supply or to
computers (or other
devices) using a
USB cable. The
figure clearly represents the existence of 14 digital I/O pins as well
as 6
analog I/O pins.
These pins are
the circuit board’s medium of
communication to external
devices. Apart from these
features, Arduino Uno
accommodates 32KB flash memory for the storage of programs.
Figure 5
The
power pins are as follows:
· Vin.
The input voltage to the Arduino/Genuino 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/Genuino 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 to work with the 5V or 3.3V.
Memory
The
ATmega328 has 32 KB (with 0.5 KB occupied by the bootloader). 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
See
the mapping between Arduino pins and ATmega328P ports. The mapping for the
Atmega8, 168, and 328 is identical.
Each
of the 14 digital pins on the Uno can be used as an input or output,
using pinMode(), digitalWrite(),
and digitalRead() functions. They operate at 5 volts. Each
pin can provide or receive 20 mA as recommended operating condition and has an
internal pull-up resistor (disconnected by default) of 20-50k ohm. A maximum of
40mA is the value that must not be exceeded on any I/O pin to avoid permanent
damage to the microcontroller.
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 driven by digital pin 13. When the pin is HIGH
value, the LED is on, when the pin is LOW, it's off.
· TWI:
A4 or SDA pin and A5 or SCL pin. Support TWI communication using the Wire
library.
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.
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.
2.1.3 External circuit
Figure 6
LCD was placed at the center of the box
Figure 7
Dot board with complete circuit is placed after LCD
Figure 8
LED's and BUTTONS is attached to the circuit
Figure 9
Arduino Uno
Figure 10
Arduino Uno with signed source code is being attached to the dot board
Figure 11
MQ2 gas sensor
Figure 12
MQ2 gas sensor is placed inside small box
Figure 13
Complete MQ2 gas sensor
Figure 14
Complete prototype