Safety Flasher:  This circuit alternately flashes two high-brightness LEDs as a safety measure during jogging or walking. The LED’s can be mounted on clothing or a belt. The circuit draws a precisely controlled 10mA in order to conserve battery life. Also, the battery voltage can drop to the LED voltage plus about .5 volts before there is a noticeable change in performance.   The LEDs actually act like voltage regulators. Because the blue LED has a higher drop voltage, it will dim rapidly and then go out first (about 3 volts) with decreasing battery voltage. The yellow LED will keep blinking unaffected to about 2 volts of battery voltage. Also due to the higher voltage drop of the blue LED, the blue LED is on for less time than the yellow LED at normal battery voltage.  Designed by Andrew R. Morris  (added 09/05)

Scheme Provides High Side Current Sensing for White LED Drivers:  02/19/04 EDN Design Ideas  /  (added 1/05)  White LEDs find wide use in backlighting color-LCD screens in most portable devices, such as cellular phones, PDAs, and MP3 players. Multiple LEDs often connect in series to ensure that the same current flows through every LED. To forward-bias these LEDs, a voltage of 10 to 16V comes from an inductor-based boost regulator, such as an SP6690....

Sequential LED Flasher :  for10 LEDs (added 4/02)

Serial Comms to LED Driver:  (circuit / schematic added 2/03)

Series White LED Driver:  National Semiconductor Application Note LM3590 November 2003 (app note added 02/05)

Seven Component Regulated LED Lamp :  (electronic design added 9/02)

Signal Processor Adds LED Display:  06/06/96 EDN Design Ideas  / (added 6/05)  Designers using the Texas Instruments TSS400, a versatile 4-bit sensor-signal processor, may find the circuit in Figure 1 useful as a replacement for, or an adjunct to, the IC's built-in display capabilities.

Simple Logic Probe uses Bicolor Led:  03/13/98 EDN-Design Ideas / (added 03/03)  

Simplified White LED Flasher Operates from One Cell:  05/26/05 EDN Design Ideas  / (added 1/06)  The white-LED flasher in Figure 1 offers an alternative approach to a previously published idea (Reference 1). Targeting use in portable appliances and products powered by a single cell, this circuit flashes an LED to provide a highly visible warning signal—for example, to indicate power on, battery low, or another eye-catching visual signal. However, white LEDs typically present a forward-voltage drop of 3 to 5V. Given that a single cell's end-of-life output voltage decreases to 1V, flashing a white LED from such a low voltage demands special circuit techniques. The circuit in Figure 1 exploits the low-voltage capabilities of Fairchild's universally configurable two-input NC7SV57 logic gate. The NC7SV57 operates from a supply voltage as low as 0.9V, a key requirement for single-cell applications....

Single and Two Cell White LED Drivers Without Inductors:  (diagram added 05/07)

Single Cell Flashes White LED:  12/11/03 EDN Design Ideas  / (added 2/06)   Many portable appliances and other products that must operate from a single cell are restricted to working at very low voltages. It is thus difficult to drive white LEDs that typically have a forward voltage of 3 to 5V. The ability to flash the LED with a supply voltage as low as 1V presents additional complications.

Single Cell Lights Any LED:  07)/05/01 EDN Design Ideas  /  (added 1/05)  The circuit in Figure 1 allows you to light any type of LED from a single cell whose voltage ranges from 1 to 1.5V. This range accommodates alkaline, carbon-zinc, NiCd, or NiMH single cells. The circuit's principal application is in LED-based flashlights, such as a red LED in an astronomer's flashlight, which doesn't interfere with night vision....

Single Cell TPS61041 LED Driver (Slva136.Htm, 1 Kb):  TI Application Note  (added 2/06)

Single FET Controls 2nd LED Array in Switchmode LED Backlight:  Maxim APP1871: Feb03,2003 / (app note added 7/03) -A design in which the display is backlit (or frontlit) for extended periods needs an efficient circuit that drives the LEDs with a controlled current, and eliminates the wasted power associated with current-limiting resistors. A switch-mode boost design that regulates current instead of voltage accomplishes this purpose.

Single FET Controls LED Array:  04/12/01 EDN-Design Ideas / (added 11/05)

Single LED Indicates Two Power States:  12/05/96 EDN-Design Ideas / (added 6/03)   -Uses a single bicolor LED to indicate both power-on and blown-fuse conditions

Single Port Pin Drives Dual Led:  10/13/05   EDN -Design Ideas  / (added 11/05)   Single-line LED driving can be versatile.

Sky writer - displays 'in air' messages and features inertia switch:  (schematic / circuit added 05/07)

Solar Charged LED Flashlight:  (electronic design added 9/02)

Special Lighting :  experiments with white LEDs (added 4/02)

Spectroscopy with Optical Linear Arrays:  Melexis Application Note  (app note added 2/06)

Speed Control of MLX90401 with PWM Input:  Melexis Application Note  (app note added 2/06)

Stealth-mode LED controls itself:  5/25/06  EDN Design Ideas  /  (added 11/06)  High-efficiency LED doubles as a light detector

Stealth-mode LED controls itself:  5/25/2006    EDN Design Ideas  / (added 05/07)    High-efficiency LED doubles as a light detector

Step Up Converter for LED:  Melexis Application Note  (app note added 2/06)

Step-Down Conversion Concept for a Pwm-Mode Boost Converter:  TI Application Note  (added 2/06)

Strange LED Sequencer:  This bizzare but simple PWM circuit fades from LED to LED. This deceptively simple sequencer actually pulse width modulates the LEDs as it fades from one LED to the next. Bulbs will last much longer when driven in this gentle manner; add FETs or transistors to the outputs if you wish to drive bulbs. You can reconfigure the capacitors from a delta configuration to a star configuration, or you can remove one of them entirely and the circuit will still function. Use high efficiency red LEDs for best results. This circuit was inspired by the BEAM sequencer circuits on the web. I simply reversed the roles of the resistors-capacitors and 'floated' the capacitors to create this monstrosity which incidentally chirps out RF interference as it hobbles along. (added 2/05)

Switching regulator efficiently controls white-LED current:  4/27/06  EDN Design Ideas  /  (added 11/06)  Circuit has 93% efficiency and beats 64% efficiency of series resistor approach.

Synchronous Buck/Boost High Power White LED Driver:  Linear Technology LT3453 (app note added 02/05)

Synchronous Step-Up DC/DC Converter for White LED Application:  National Semiconductor Application Note LM3500 February 05 (app note added 02/05)