Charge Pump and Step Up DC DC Converter Solutions for Powering White LEDs in Series or Parallel Connections:  Maxim Application Note #1037 (app note added 11/06)

Christmas Star (grantronics):  (diagram added 05/07)

Christmas Star:  (electronic circuit added 10/05)

Christmas tree:  (diagram added 05/07)

Christmas Tree:  (electronic circuit added 4/05)

Circuit Delivers Dimming Control for White LED Driver:  10/28/04 EDN Design Ideas  / (added 1/05)  The demand for power in color cell-phone handsets is constantly increasing. New applications steadily emerge, making it imperative to reduce power consumption in the design. Examination of usage data shows that more than 50% of the power consumed is in providing backlighting for the color screen. People use the phones for playing games and MP-3s and a multitude of other heavy-duty, multimedia f...

Circuit Drives Mixed Types and Quantities of LEDs:  10/03/02 EDN Design Ideas  /  (added 1/05)  Portable systems often use LEDs of different colors and in varying quantities of each color. Some examples are white for the display backlight, green for keypad illumination, and red for power. Typically, the LEDs derive power from at least two power supplies: one for "standard" LEDs (red and green) and one for white LEDs....

Circuit Efficiently Switches Bipolar Led:  11/22/01 EDN Design Ideas  /  (added 1/05)  The circuit in Figure 1 represents one method to switch a bipolar, two-color LED using an SPDT mechanical switch or relay. This circuit wastes power and does not work properly if the power-supply voltage is not substantially more than the sum of the LEDs' forward voltages. The circuit is, therefore, marginal, to the point of being unusable, with a 5V supply and a red or green LED, which... ...

Circuit uses Simple LED for Near IR Light:  09/01/98 EDN-Design Ideas / (added 6/06)  

Clock Design using the PIC16c54 for LED Displays and Switch Inputs:  Microchip Application Note Published 26-Aug-97   (app note added 6/06)

Colour Shifting For Bi-Colour LED's:  (circuit added 05/07)

Compact Inductorless Boost Circuit Regulates White LED Bias Current:  Maxim Application Note #1116 (app note added 6/06)

Complementary LED Drive:  Microchip Application Note Published 6-Nov-98   (app note added 2/06)

Connecting LED to PIC Micro I/O Pins:  (electronic circuit added 7/03)

Constant Brightness LED Stroboscope: for Measuring the Speed of Small Motors :  The rotary switch is available for $5.00USD as of 2003 from DigiKey under part number EG1951-ND or EG1952-ND. It is a real pain to operate this circuit without a proper switch. You can put multiple 4017 ring counters in series to reduce the duty cycle in order to obtain a more focussed strobe image but you will have to increase LED current to maintain the same level of brightness and that will shorten LED life. This circuit can be improved a bit by using a more stable STROBE RATE oscillator or by using a regulator to power the oscillator and associated logic. If you do this you should switch to 74HC class devices.   (added 2/05)

Constant Current Constant Voltage Converter Drives White LEDs:  09/02/04 EDN Design Ideas  /  (added 1/05)  LEDs usually take their drive from a constant dc-current source to maintain constant luminescence. Most dc/dc converters, however, deliver a constant voltage by comparing a feedback voltage to an internal reference via an internal error amplifier. The easiest way to turn a simple dc/dc converter into a constant-current source is to use a sense resistor to convert the output current to a voltage......

Constant Off-Time Buck-Based LED Drivers using HV9910:  Supertex Semiconductors  (app note added 2/06)

Constant-Current DC/DC LED Driver in ThinSOT:  Linear Technology LT1932 (app note added 02/05)

Create Secondary Colors from Multicolored LEDs:  07)/24/03 EDN Design Ideas  /  (added 1/05)  It is well-known that simultaneously mixing two primary-color light sources, such as red and green, creates a secondary color, such as yellow. This mixing process commonly occurs in tricolor LEDs. One disadvantage of this method of generating a yellow color is that the LED must use twice the current because both the red and the green LEDs must be on....

Current Regulated Switched Capacitor LED Supply with Analog and PWM Brightness Control:  National Semiconductor Application Note LM2794/LM2795 March 2004 (app note added 02/05)

Current Regulators For Light Emitting Diodes:  (schematic / circuit added 05/07)