Construction of a Simple USB Powered LED Light Source for Illuminating Optical Microscopes

Tungsten and halogen lamps are normally used for microscope illumination. However, if there is an electrical fault in any of these lamps, extra money to purchase a new one and the sacrifice of a long time for its arrival may be required to get the lamp replaced, especially in some developing countries. The aim of this study therefore is to develop a cheap and easily obtainable light source, built with Light Emitting Diodes (LEDs) to replace a faulty tungsten or halogen lamp. The LEDs are cheap to buy, easily available and operate at a much lower voltage. A light source, using LEDs, was designed and constructed to fit easily into the space previously occupied by the tungsten or halogen lamp. An integrated switching low power DC-DC converter, having a microcontroller unit at its heart and powered from a 5 Volt source, was also constructed to control the LED light source. It was observed that the contrast of the sample image obtained with the halogen lamp was reproduced by the LED light source. In this study, a replacement LED based light source for illuminating optical microscopes was constructed, and it gave a reasonable result compared to that obtained by using the halogen lamp. This work will be very useful in those places where it may be very difficult to get a quick replacement halogen or tungsten lamp or where electric power is not always available.