Design and fabrication of an electronic system for monitoring and controlling temperature, light illuminance and humidity in a greenhouse

Abstract

Climate uncertainities pose a challenge to the production of food to feed the growing billions on the globe. Climatic conditions can change abruptly ruining farming efforts and leading to food shortages. Greenhouses attempt to solve this problem by enclosing crops in a climatically controlled environment. Crop production in greenhouse has distinct characteristics. Data on these characteristics need to be collected at regular intervals. For each type of crop, these characteristics need to be controlled within the specified limits to achieve the maximum efficiency and yields. In the past, greenhouses employed electromechanical devices such as thermostats to monitor and control the environment. Mechanical systems lack the flexibility and precision required for greenhouse control. Some modern greenhouses use computers to control the environment. Computers require programming skills, are bulky and costly. A greenhouse monitoring and control system that is compact and thus portable, adaptable, cheap and easy to assemble hs been developed. Based on the Z80 microprocessor, the hardware consists of a Z80 CPU, two 8255 PIA's, a 2716 EPROM, a 6116 RAM, an HIH-4000 humidity sensor, an LM-35 temparature sensor and two ADC 0804 analogue to digital converters, a clock and reset circuitry and 7-segment displays and LEDs. The software has been coded in the Z80 assembly language. This system monitors temperature, humidity and light illuminance on a continuous basis. It measures and displays these parameters and activates appropriate devices whenever these variables fall outside predetermined ranges. Relative humidity is controlled by a water sprinkler, temperature by a fan and heater and light illuminance by a lighting system.