Development of Stepper Motor-Based Programmable Autotransformer Output Power Regulating System

Electric heating is essential for many research and industrial applications, including multi-chamber furnaces for heat treatment and plasma vacuum chambers. Heating elements, such as heating tapes, coils, etc., are conveniently used for these kinds of heating operations. Variable auto-transformers, also known as Variacs, are used to regulate the power input to these heating components because of their versatility. With the use of auto-transformers, the user can change the input voltage to the heater, which in turn changes the input current to the heaters, thus changing the input power (hence the process temperature). In many processes, a constant power input needs to be supplied to these heaters through out the operation. The user must continuously monitor the process power input and manually adjust the auto-transformer voltage as necessary. This is a tedious and error prone task. In this work the automation for supplying constant power to heating element utilizing a stepper motor controller to regulate a variable auto transformer is described in detailed. The design has the provision of setting desired power input by the user and the control system will achieve and maintain it accordingly. The system utilizes both programmable logic control and an algorithm to achieve efficient control. The design uses the ATmega328P micro-controller based Arduino UNO for control and operating purposes. The code development is done in the Arduino Integrated Development Environment (IDE). Experimental findings have confirmed the better controlling of the auto-transformer's power output. The auto-transformer controlling mechanism described in this paper is power-efficient, less expensive (in terms of components' total cost), and best suited for all resistance heaters and motors' speed control and other similar applications. Project files available at: https://github.com/Nikhil-Gangwar/SPARS