103 projects with light-emitting diodes

Electroluminescent semiconductor devices are assuming a great importance in electronic world. There are now many devices related to this family. The electroluminescent panels, laser diode, infra red diode, light emitting diode (LED) and LED Displays are some of the important members of this family.
The electroluminescence is a phenomenon occurring when a semiconductor material emits light under the influence of electric field.
We are concerned here with the LEDs and the LED Displays which are now increasingly used by the equipment manufacturers. The LEDs have very wide variety of applications, especially in read-out circuits and indicators. They are now used where fast and low power devices of the greatest possible life—10,000 to 10,00,000 hours—are required.
The LEDs were first made in 1954 since then they made a rapid progress in workmanship, shape, size and life. Although the modern LED is with us since more than 10 years. It was not popular with experimenters and amateurs owing to its high cost. Now its price is below Rs. 2/ and in near future the price will come down to the level of a filament lamp. This is how most suitable time to experiment with the twinkling tiny LEDs. The LEDs have multitude of applications in many areas.
The readers will be surprised to find a wide variety of applications covered in this work.