The following are current regulator circuits that could be used to drive light emitting diodes and small incandescent lamps.
They can also be used for many other applications as well.
Test these circuits at the bench before using them in practical applications.
The following is a current regulator built around the LM317 voltage regulator IC. For additional information, see the datasheet for the LM317 series regulators.
The following are current regulators built with PNP and NPN transistors.
Circuit B is more accurate and has better regulation over a larger input range than circuit A.
Circuit B can be replaced with (fixed) current regulating diodes similar to those in the datasheet links below.
The following links are for Current Limiting Diode data sheets.
The following links is for the LM334 current regulator data sheet.
Low Voltage Power Supplies For LEDs Or Lamps
The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.
If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.
Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.
18 February, 2011