Variable DC Power Supplies are required for performing experiments in electronics laboratory. It is an integral part of the experimental setup along with Oscilloscope, Function Generator, Multi-meter, breadboard and assorted components. The induction of computer technologies in laboratories is gaining considerable attention and acceptance. However, the cost of such equipment is exorbitant. Some work has been done to provide low cost solutions for PC based Oscilloscopes and Function Generators for undergraduate laboratories. However no such work has been reported in literature for Power Supply. Therefore, in this paper, the design and implementation of a low cost Programmable DC Power Supply is described for undergraduate laboratories. The Programmable DC Power Supply is interfaced to PC using ubiquitous Centronics Parallel Port, also known as Printer Parallel Port. The Power Supply is controlled through program written in LabVIEW. The over current protection is innovative as it is implemented with a reset-able fuse, thus reducing the power dissipation and thermal stress on components in fault condition and also providing the ease of operation. The Programmable DC Power Supply has been successfully tested. It has been used for performing experiments for plotting the characteristics curves of diodes and transistors etc. The design of Programmable DC Power Supply with minor modification has also been used for converting the existing Simple Fixed and Variable DC Power Supplies, which are widely available in Laboratories, into Programmable DC Power Supplies. This provides an affordable and easy to implement alternative for expensive commercially available Programmable Power Supply. Further, the same generic design with some modification has also been used for developing a Programmable DC Power Supply controlled through the analog output voltage signal available in Multifunction Data Acquisition Cards.
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