This LED lamp was originally designed for use on a budget solar-charged 12V electrical system. It is bright enough for comfortable reading at night and features constant LED brightness with diminishing battery voltage. The circuit uses six high-brightness white LEDs mounted in a 90mm diameter reflector. The upper half of a stainless steel ice cream bowl makes a good reflector but almost any torch reflector of a similar size will do. As shown, two banks of three series-connected LEDs are powered from a 12V (nominal) DC supply. The LEDs used are rated at 20mA maximum with a measured voltage drop of 3.2V. Circuit diagram: Economical Desk Lamp Circuit Diagram For Camping Each bank combines an inexpensive LM334 current source IC with a BC558 transistor to provide a constant 20mA to the LED string. Basically, the LM334 controls the base current of the BC558 such that 64mV appears between its "R" and "V-" terminals. With the 3.3O resistor shown, this results in close to th...