As a
technical project I plan to design a system that will completely automate a
greenhouse. Using the C++ programming
language I plan to develop software that will monitor various conditions within
the greenhouse and perform task such as watering and cooling automatically.
Thus eliminating the need for human labour. Data will be collect and stored in
spreadsheet format file(s) and presented in graphical form through the use of
the Graphical Programming Language LabVIEW. The entire software system will be
presented as a stand-alone test executive developed with National Instruments
LabVIEW and/ or TestSTAND programming software that can be installed on any
standard Intel 80486 or higher system running Windows 95 of higher. LabVIEW
will also execute the C++ program in its own environment. The hardware portions
will be designed to connect directly to a standard IBM PC parallel port located
up to 50 feet away (standard specification).
This system will be designed to monitor both the
temperature within the greenhouse and the moisture of soil in the greenhouse.
As part of the automated process the temperature transducer will be associated
with a heating and cooling system. If the temperature within the greenhouse
exceeds a high temperature limit motorized fans will be turned on and remain on
until the temperature fall back into an acceptable range. Subsequently, if the
temperature falls below a low temperature limit a central heating system will
be turned on. The system will also have the ability to monitor the moisture of
the soil in the greenhouse to determine if water needs to be added. If the soil
moisture transducer determines that there is a lack of water in the soil it
will have the system turn on water valves for a set time to water the plants.
Interfacing Software:
As stated earlier the interface
software will be developed in the C++ environment. Using parallel port
addresses 378H (output), 379H (input), and 37AH (Bi-directional) the software
will use 8-bit parallel data to monitor the greenhouse and display its findings
on the screen. The system operator will set the sampling rate and acceptable
temperature range. The collected data, which will include date, time and
measured values, will all be written to a spreadsheet file at the time of
sampling. A simplified flowchart of the program is shown if Fig. 1-1 below.
Fig. 1-1: Program Flow Chart
LabVIEW Software:
LabVIEW
will be used to develop a complete windows based test executive. This program
will provide security features such as password protection to the system. Only
authorized operators will be able to start up the test plan. Furthermore,
LabVIEW will be used to execute the C++ program and display the acquired data
stored in the spreadsheet file whenever the operator wishes to do so. The
display will consist of graphs, tables, and charts.
Hardware:
The
hardware consists of a fan, heater, thermistor, soil moisture transducer, light
bulb (to simulate watering system), and various other discrete components. To
the analog signals from the transducers will be signal conditioned to produce
0-5VDC signals and converted to 8-bit digital signals with ADC0804, 8-bit
analog-to-digital converters. Since the 80x86 PC only allows 8 bits of data
to be inputted at a time a 74157 multiplexer will be used to input the
digital signal 4-bits at a time. Fig. 1-2 below shows a conceptual block
diagram of the overall circuit.
Fig. 1-2: Conceptual block diagram
Soil
Moisture Transducer: Various soil moisture
transducers have been researched but I have yet to find one in my price range.
Research has indicated that one alternative is to use two electrodes and
measure the resistance of dry soil and highly saturated soil and uses this as a
linear relationship for signal conditioning purposes. Additional research is
underway and this area will be updated shortly.
Cooling
System: To reduce cost a large
computer-cooling fan will be used rather then an industrial or residential one
that would be used in an actual greenhouse. The fan will be connect such that a
short hi pulse from the PC will latch it into operation and it will remain on
until the program checks the temperature again. At that time, if the temp. is
still to high the fan will remain on. If the temp falls back into range the fan
will be turned off.
Heating
System: Once again a small heating element
will be used to produce heat rather then an industrial or residential one that
would be used in an actual greenhouse. The heater will be connect such that a
short hi pulse from the PC will latch it into operation and it will remain on
until the program checks the temperature again. At that time, if the temp. is
still to low the heater will remain on. If the temp rises back into range the
heater will be turned off.
Watering
System: A small light bulb will be used to
simulate the watering of plants. I plan to use a LM555 timer to keep the water
(light bulb) running for a 30 seconds before it cuts off.
This
system is to be designed as a practical consumer product. For this reason I
plan to package it in an enclosed case. The circuit will be constructed on
either a wire wrap board or a PCB. If I can gain access to the facilities
required to make a PCB we will use a PCB development program such as OrCAD or
Electronic Workbench 6: Ultiboard.
I expect
the cost of this project including the production stages to be in the range of
$150 - $200.
Demonstration
Currently
I plan to use my notebook computer to run all software and connect hardware
directly to it.
Week of |
Scheduled work |
May 11,
2001 |
-
First Class -
Order evaluation software
from Nation Instruments |
May 18,
2001 |
-
Submit project proposal
(objective, goals, and timeline). -
Block outline and
conceptual circuit -
Start Ordering Parts -
Start C++ Program. |
May 25,
2001 |
-
Determine all parts and
order them. -
Continue with C++ program
and start LabVIEW program. -
Work on hardware design. |
Jun. 1,
2001 |
-
Complete C++ program -
Complete LabVIEW program -
Work on hardware design and
troubleshooting. |
Jun. 8, 2001 |
-
Complete hardware. -
Interface hardware, C++
software and LabVIEW software. |
Jun. 15,
2001 |
-
Work on construction
stages. -
Write final report and
design power point presentation. |
Jun. 22,
2001 |
-
Complete construction
stages before Friday. |
Jun. 29,
2001 |
-
Presentation. |