PROJECT PROPOSAL

 

Brief Description of the Automated Greenhouse (Objective):

            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.

Proposed Design Specifications

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

 

Temperature Transducer: Currently I have chosen to use the LM56 IC as a temperature-sensing device because it is capable of measuring temperature in a range of –50 to +100 degrees Celsius. Furthermore the LM56 IC contains two operational amplifiers that can be configured as a window comparator to set the upper and lower temperatures. If however This IC cannot be obtained I will resort to using a LM35 thermocouple and two LM741 op-amps to do the same thing. Further details of this signal conditioning will be shown in future updates.

 

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.

 

 

Construction

 

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.

 

Cost

 

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.

Project Schedule

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.