LED Driver Provides Software Controlled Intensity:  09/30/04 EDN Design Ideas  /  (added 1/05)  Recent advances in operating efficiency have expanded the use of LEDs from one of mere indicators to becoming driving forces in electronic lighting. Increased reliability and ruggedness (versus other lighting technologies) gives the LED a bright future indeed. Vendors in recent years have introduced many ICs for driving LEDs, but the problem of driving serial chains of LEDs has received less at......

LED drivers minimize power dissipation:  2/1/2007)  EDN Design Ideas  / (added 05/07)    Reference source and pullup resistor improve efficiency.

LED Flasher 2 Transistor:  (electronic circuit added 09/04)

LED Flasher and TRAC Pulser Work Off AC Line:  01/15/98 EDN-Design Ideas / (schematic / circuit added 11/03)  

LED Flasher Indicates Low Battery Condition:  01/02/97 EDN Design Ideas / (added 5/02)

LED flashers:  (schematic / circuit added 05/07)

LED Headlamps :  This article includes circuits of DC-DC LED drivers step downs to run LEDs on less than Battery Volts, Boost for above. (added 4/02)

LED Light Dimmers uses Only Two Lines:  03/21/02 EDN-Design Ideas / (added 05/03) -The circuit in Figure 1 provides 32 steps of brightness control—from 0 to 100%—for a backlight or instrument panel, using just two general-purpose-microprocessor signals. In addition, the circuit requires little board space, because it uses only three SOT-23s and one µMax package. Although Figure 1 shows the circuit driving white LEDs,...

LED Module with Low EMI:  Melexis Application Note  (app note added 2/06)

LED Mood Light (solorb):  (circuit / schematic design added 6/06)

LED Mood Light:  this LED circuit makes a nice lamp that is low power, runs cool, and has a long lifetime, operates from12V, puts out a warm yellow shade of light, the color may be adjusted by changing the number of red or green LED strings (added 4/02)

LED Night Light for 120Vac :  Reverse engineered circuit diagram of an LED night light made by a north american manufacturer. Remarkably it only draws 100mW and has some surge voltage immunity. A clear plastic light pipe is used to diffuse the light from the LED into the room. I do not gaurantee the accuracy or safety of any information herein. (added 2/05)

LED or Lamp Flasher :  Minimum parts counting. Designed for3V battery operation (added 9/04)

LED or Lamp Pulser :  Astonishing effect4.5 Volt supply (added 9/04)

LED Photo Sensor Circuit:  Here's a circuit that takes advantage of the photo-voltaic voltage of an ordinary LED. The LED voltage is buffered by a junction FET transistor and then applied to the inverting input of an op-amp with a gain of about 20. This produces a change of about 5 volts at the output from darkness to bright light. The 100K potentiometer can be set so that the output is around 7 volts in darkness and falls to about 2 volts in bright light... (added 4/05)

LED Photo Sensor:  (electronic design added 11/06)

LED Photodetector:  Using the light-emitting diode as the photodetector (circuit added 11/06)

LED Pilot Light (AC or DC):  LED current is constant between 6 and 8 mA at5 to30Vdc (added 4/02)

LED senses and displays ambient-light intensity:  11/9/2006    EDN Design Ideas  / (added 05/07)    LED doubles as photosensor and visual indicator of ambient-light intensity.

LED Sign:  uses two LED arrays to form a 7 X 10 matrix. It produces moving messages or animations stored in an EPROM. (added 7/03)

LED Strobe:  This circuit drives a high brightness LED as a strobe.  The BD136 (I had one spare) transistor can be used to drive an LED from a higher voltage source than the PIC operates from if required….   (added 6/06)

LED Stroboscope:  This simple LED Stroboscope circuit which I designed, maintains constant

LED Torch :  A white LED torch that consumes just24 mW (added 4/02)

LED Torch:  (electronic design added 11/06)

LED Traffic Lights:  (electronic circuit added 4/05)

LED Traffic Lights:  The LED traffic Light circuit controls 6 LEDs (red, yellow and green) for both north/south directions and east/west directions. The timing sequence is generated using a CMOS 4017 decade counter and a 555 timer. Counter outputs 1 through 4 are wire ORed using 4 diodes so that the (Red - North/South) and (Green - East/West) LEDs will be on during .... (added 05/07)

LED7 Solar Tracker:  (electronic circuit added 7/03)

LED-Based Message Display:  (electronic Circuit / Schematic added 10/04)

LEDs Flasher Alternately:  Classic astable multivibrator using2 transistors. Transistor is not critical. Try these:2N4401,2N2222, NTE123A, NTE123AP, NTE159, TUP/TUN and those in your junk box, you may find that most of them will work. (added 4/02)

LEDs or Lamps Sequencer:  Very simple, versatile modular design No limits to the number of modules used in the ring (added 9/04)

Light a White LED from Half a Cell:  06/12/03 EDN Design Ideas  /  (added 1/05)  Whether you use them as indicators or to provide illumination, LEDs are hard to beat in efficiency, reliability, and cost. White LEDs are rapidly gaining popularity as sources of illumination, as in LCD backlights, but with forward voltages typically ranging from 3 to 5V, operating them from a single cell presents obvious difficulties....

Light Flasher(Blinking Lights):  This is a very basic circuit for flashing one or more LEDS and also to alternately flash one or more LEDs.
It uses a 555 timer setup as an astable multivibrator with a variable frequency.
With the preset at its max. the flashing rate of the LED is about 1/2 a second. It can be increased by increasing the value of the capacitor from 10uF to a higher value. For example if it is increased to 22uF the flashing rate becomes 1 second. (added 10/05)

Light Pollution Meter :  LED brightness control circuit and a millimeter to compare light levels to LED level. (added 4/02)

Lighting Management System for Six White LEDs and One RGB or Flash LEDs:  National Semiconductor Application Note LP3936 June 2004 (app note added 02/05)

Lighting Management System for Six White LEDs and Two RGB or Flash LEDs:  National Semiconductor Application Note LP3933 March 2004 (app note added 02/05)

Line Powered White LEDs:  (electronic circuit added 1/06)

Linear Constant Current LED Lamp Dimmer:  This circuits drives24 white light LEDs with an adjustable constant current. (added 4/02)

Line-powered driver lights up high-power LEDs:  6/8/06  EDN Design Ideas  /  (added 11/06)  LED array reduces power and maintenance expenses.

Line-powered driver lights up high-power LEDs:  6/8/2006    EDN Design Ideas  / (added 05/07)

LM27961-Dual-Display White LED Driver with 3/2x Switched Capacitor Boost:  National Semiconductor Application Note   (app note added 2/06)

LM3485 LED Demo Board:  National Semiconductor Application Note   (app note added 2/06)

LM3570:  National Semiconductor Application Note   (app note added 2/06)

LM3909 LED Flasher:  (electronic circuit added 4/05)

LM3909 LED flasher:  (electronic schematic added 05/07)

LM3909 replacement using discrete components:  (diagram added 05/07)

LM555 LED Blinker Circuits:  (diagram added 05/07)

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

Low battery voltage flasher:  (diagram added 05/07)

Low current LED flasher:  (electronic circuit added 05/07)

Low Power LED Flasher :  based on LM3909 (added 4/02)

Low Power LED Volt Meter:  (circuit / schematic design added 6/06)

Low Power Reader Based on the MLX90121:  Melexis Application Note  (app note added 2/06)

Luxeon LED Heat Sinking Requirements:  Luxeon Application Note  (app note added 2/06)

LX1995 LED Driver: Camera Flash Application (AN-30):  Application Note 30 from Microsem  (app note added 6/06)