Designing Wireless Control and Monitoring Device For Irrigation System

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					Designing Wireless Control and Monitoring Device
For Irrigation System – Wally Grutza, School of Trades & Technology

The purpose of this project is to design and build a wireless device that is capable of
controlling and monitoring of irrigation systems and using a computer connected to one
of the transceivers to give a platform for the interface with the Ethernet. There are two
main pieces: the remote link unit consist out of the microprocessor, relays and transceiver
to control the pivot and the base station unit consist of a transceiver and the serial port
interface that is connected to a computer. The remote link unit is comprised of sensors to
measure the pivot position in the field in degrees, and using relays to control the run,
stop, water on/off functions. A microprocessor interprets each sensor’s input individually
and performs calculations to create data. Then the data is sent to an RF transmitter using
the microprocessor USART. The RF transmitter creates a modulated waveform and
transmits it to the base station transceiver at about 915 MHz. The receiver at the interface
unit will receive and demodulate the transmitted data and send it over the serial port to
the computer where it will be display on the control panel in Visual Basic. Figure 1
shows the overview of the project goals.

Goals this project should meet are as follows:
• measure the position of the field in degrees.
• perform the basic commends run, stop, water on/off.
• transmit data from the remote link unit to the base station unit.
• interface with Visual Basic.
• establish options for web page and database support.

Testing is necessary for the project. A quantifying value needs to be set on how well the
project works. There are key areas to concentrate on in the design of this wireless device:
RF transceivers, microprocessor, sensors, and the interface with the irrigation control
panel. The sensors used in this project are the same sensors being used with irrigation
systems. The microprocessor code is written in C using AVR Studio 5. The
microprocessor should translate readings using analog-to-digital conversion for the Pivot
position in degrees and be able to read all other sensors. The microprocessor will send the
data to the transceiver which will modulate and transmit the data to the base station
transceiver.

There are five stages of tests: RF link, microprocessor code, USART, sensors, and the
integrated system. Each has different requirements. The sensor tests guarantee that the
data sheets predict the output correctly. The code testing ensures that the program is
doing the right operations at the right times and giving the projected results. The
microprocessor code is a major part of the design because it affects every function, be it
analog-to-digital conversion, serial data transmission and reception. The USART section
of the code has to be tested and to ensure that the proper bound rate is used. Transceiver
tests are the first stage of the RF link testing. The link tests will determine the transmit
power of the transceivers and the power losses. The results will enable an accurate link
budget to be calculated.