Time Proportioning Computer Control of Resistive Heating

The design and construction of an interface to regulate electrical power to a heater (resistive load) for temperature control is described. An overview of various techniques is presented and a specific approach to heater power control is described in detail. The method, however, can be easily adapted to other applications, for example, the manipulation of a solenoid valve to control an average fluid flow rate. The interface described here has a linear relation between the numerical computer output value and the power delivered to the load. This is convenient for both calibration and scaling purposes.