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НаименованиеAutomated control system for hothouse growing concerns

 

In growing agricultural products in hothouses, the precision with which the temperature is maintained inside the hothouse can affect the size of the harvest. The temperature, in turn, depends on the temperature and pressure within the heating system, the proper operation of equipment and the piping system, the condition of the hothouse material and the staff.

The ROSA hothouse concern (in Sosnoviy Bor, Leningrad Oblast) developed and implemented an automated system called ROSA-T for controlling these parameters. The core of the system is a network based on the RS-485 interface, attached to an IBM-compatible PC, an Advantech ADAM-4000 measurements module and an MT-2000 heat flowmeter. The PC is connected through the COM1 port to an ADAM-4520 isolated RS-232 to RS485 converter that allows for connecting up to 32 measurement modules at a distance of up to 1,200 meters. An ADAM-4050 digital I/O module is connected on two lines to the ADAM-4520, along with an ADAM-4013 analog RTD input module for temperature measurement, an ADAM-4012 module for measuring pressure and flow, and an MT-2000 heat flowmeter positioned 120 meters from the measurement modules. To connect a large number of sensors to the single-channel ADAM-4012 and -4013, four Advantech PCLD-788 16-channel relay multiplexer boards are used, controlled by an ADAM-4050 module.

Through the boards, 23 temperature sensors are queried, along with 15 sensors that detect the positions of mechanisms and four that detect steam and water pressure in pipes. The heat flowmeter controls the pressure, temperature and flow of water in the pipes. A PWR-243 switching power supply runs the measurement modules and the multiplexer boards.

Software for the system, developed in Borland PASCAL 7.0 for MS-DOS 3.3 and higher, includes the execution modules, a program for visualizing archived technical parameters (the "black box") and an equipment-testing program.

Every five minutes, the system queries the sensors and records the measurements. Should some parameter exceed the setting, the operator is given a warning signal. Data are archived at the end of the each shift.

Tests showed that the main degree of error occurs at the sensors, while thee margin of error caused by the ADAM modules was negligible. Six months of use showed the system to be highly reliable under difficult conditions.

The ADAM-4000 module allowed the system to go from design to pilot in two months, at a cost of 25 million rubles. ROSA expects harvests to increase by 1 to 2 percent, or 70 to 140 million rubles. Savings from reduced heating costs are expected to be from 2 to 3 million rubles per month. There will also be savings from the increased ability to detect and address accidents.


This is what the hothouse concern looks
like from the outside....

...and on the inside. Here, plants grow
even in winter.

By Valeriy Alyukov, Vladimir Kurtov and Nikolay Kurtov

Valeriy Alyukov,  Vladimir Kurtov,  Nikolay Kurtov