MICROPROCESSOR BASED PROGRAMMABLE TEMPERATURE CONTROLLER

Abstract

This dissertation deals with a microprocessor (Intel 8086) based programmable temperature controller which has been developed for controlling the temperature in a furnace as per set time schedule. Due - to nonavailability of furnace, all work of testing has been done in a waterbath. The thermocouple has been used as a temperature sensing element, because of its high stability and long range. The output of thermocouple is amplified by an instrumentation amplifier and then is converted into the digital signal by an analog to digital converter ADC 0809. Microprocessor processes the output of the ADC and uses look up table method to determine the current temperature value. Microprocessor compares this temperature to set point temperature and accordingly decides about the control action through final control element. Final control element is a TTL compatible solid state relay. The use of the relay avoids the use of digital to analog. converter (DAC) and power amplifier. Three types of controller namely on-off, proportional and proportional integral type has been incorporated in the scheme. As per the necessity the control action is selected as part of control strategy. The performance of the controller has been evaluated by generating different control profiles over sufficient temperature range.