A microcontroller-based programmable temperature controller

A microcontroller-based programmable temperature controller developed using an RTD sensor is described. A resistance-to-time converter is employed to obtain a time-interval linearly varying with the sensor resistance. Using a counter of the microcontroller and suitable software, temperature under control is determined and compared with a target temperature. The resulting error, through a DDC implementation of PID algorithm, is used to control the firing angle of an SCR for controlling the power applied to heater. Experimental results are given in support of the scheme proposed.