Literature review is an important step before proceed to the project. Collecting all the required information about the 433MHz RF module from the books, journals and website. The literature review also can provide a useful information to complete the project. The idea for this project comes from the problem faced when the data that have been transmitted becomes losses with the range that provided. In this chapter it will be explained more details about all the flow and also the components that will be used in this project.
The frequency of 433MHz that used in the wireless sensor network can test the sending and receiving the data for this range. 433MHz RF Modules required the 17cm of the antenna to support the range to send the data. Range is the one of the most important parameter of any wireless system which is it defined how the transmitter and receiver can be apart from each other. 433MHz RF Modules are used to build the wireless connection between two points. For the outside with few obstacles the data can go through hundreds meters. While for the indoor, the data can go for over 50 meters through multiple walls. The external antenna will be soldering to the “ANT” on the transmitter to get more range which is 17cm of the length for the antenna.
The Arduino Pro is a microcontroller board based on the ATmega328. This microcontroller is an open-source hardware and software. The version that used in this project is 3.3V/8MHz. this version can be powered with a battery or external power supply. It has 14 digital inputs and output pins which is 6 of it can be used as PWM output, another 6 pins for the analog input, battery power jack, an ICSP header and reset button. Arduino Pro needs to connect with FTDI cable through six pins header to provide the USB power and have a communication with the board.
Each of the 14 digital pins on the Pro can be used as an input and output which is operate at 3.3V. Each of the pin can provide or receive a maximum of 40mA, and has internal pull-up resistor (disconnect by default) of 20 until 50 kohm. The ATmega328 has 32KB and running 8MHz of the external resonator. It also has 2KB of SRAM and 1KB of EEPROM that can read and written with the EEPROM library. That’s figure 2.1 is the Arduino Pro board.
The operation of the Arduino microcontroller is based on the connection made on the pins. The application can be done by using the Arduino software where Arduino function can be edited according to the applications in this software. This software can work on by using the C or C++ language.
The program that have been create can be upload to the microcontroller by using the USB cable. If there are error detected, the program can be edited to make a correction on the process and then the program can be upload once again. Other than that, there is another option which is using the reset button to delete all the previous program that have been upload before this.
In this board, there are pins with their functions such as:-
• Serial: 0 (RX) and 1(TX). They are used to receive (RX) and transmit (TX) TTL serial data. These pins are connected to the TX-0 and RX-1 pins on the six pins header.
• External interrupts: 2 and 3 which is these pins can trigger an interrupt on a low value, a rising or falling edge or a change in value.
• PWM: 3, 5, 6, 9, 10 and 11 that provide 8-bit PWM output.
• SPI: 10(SS), 11(MOSI), 12(MISO), 13(SCK). These pins support the SPI communication.
• LED: There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is ON, while when the pin is LOW, it is OFF.
• Reset: This line LOW to reset the microcontroller.
In this project, the RFM69HCW which is 433MHz RF Module version that has been chosen because it is an inexpensive and versatile radio module that operates in the unlicensed ISM (Industry Science and Medicine) radio band. It’s available for using in the building inexpensive short range wireless networks of sensors. This types can operates on the 433MHz frequency and can capable of transmitting at up to 100mW and up to 300kbps. In addition, this types can be maximize range by increasing the transmit power and reducing the data rate or it can be reduce both for short-range sensor that sip battery power.
DHT11 is a digital temperature and humidity sensor.
Micro-B is the smallest USB connector type. Nearly uses in every new cell phone uses that Micro-B connector that you might already have one or two cables laying around.
Using this board because the standard FTDI board cannot supply the enough current to run the RFM69 433MHz RF Modules.