Using DSP hardware to control your world

In recent years, more and more students have been designing and implementing small systems using real-time DSP hardware. Given the decreasing cost and the increasing capability of DSP starter kits (DSKs) and evaluation modules (EVMs), these projects are being used by greater numbers of educators as a valuable pedagogical tool. To help keep the cost relatively low, most DSKs and EVMs are designed to work with audio input and output signals. Digital input/output pins are sometimes available, but the ability to control a number of electrical loads totaling several hundred watts easily does not readily exist. Yet DSP control of significant electrical loads can add depth and interest to many student projects. The paper discusses the design, construction, and use of a very compact, dual-tone multiple-frequency (DTMF) based decoder and power switching device. These devices have been successfully used by a number of undergraduate and graduate students to allow their DSP algorithms to control their world.