DESIGN OF A LOW COST TEMPERATURE CONTROLLER FOR HIGH TEMPERATURE FURNACES USED IN CRYSTAL GROWTH

Temperature plays a very vital role in proper growth of crystals and compound semiconducting materials. Temperature also affects the properties of the materials. Therefore, it is desirable to accurately monitor and control the temperature of the furnace used for Growth of different types of Materials. This paper focuses on the design and construction of a low cost temperature controller for high temperature laboratory based furnaces used for crystal growth. It can also be used for industrial furnaces. The design is based on microcontroller (IC PIC16F873A). In the circuit K-type thermocouple is used as a temperature sensor. Suitable instrumentation and signal conditioning circuit is developed to give desired electrical signal to the microcontroller which is equivalent to the actual temperature. The actual temperature is monitored continuously. Because different materials have different melting points, facility is provided to program different temperature profiles. When the device exceeds a preset temperature level, power output of the circuit is switched OFF, hence switching of the heating device (Furnace). The developed circuit is reliable and cost effective. It has good accuracy better than ±1oC.The overall performance of the controller is tested and found it perfectly functional.