LED Light Emitting Diode Electronic Circuits, page 13


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LED (Light Emitting Diodes) Circuits   Page 13
LED:   #     A      B      C       D - E       F - H      I - K     L      M - O      P- R      S      T     U - Z
Last Updated on: Friday, July 18, 2008 11:33 AM

Circuits Designed by Dave Johnson, P.E. :

Universal LED Flasher
This low power LED flasher circuit draws about 100ua from any DC power supply ranging from 3 volts to 24 volts. The 1.0Hz 10ms LED pulsed current is held to a constant 10ma.

Universal 3v LED Flasher   NEW
The circuit below will flash any LED color with fixed current pulses powered by a 3v battery. It uses a charge pump approach, which routes a constant current pulse through the LED, regardless of the LED voltage requirement. Using this approach, white and blue LEDs, which normally require about 3.6v can be flashed with a 3v battery. With the component values selected, the LED is hit with 15ma current pulses lasting about 10ms every two seconds. This keeps the average current draw from a 3v battery to about 200uA. The circuit relies on a cheap 74HC14 hex Schmitt trigger inverter IC. One inverter forms a pulse generating oscillator. Other inverters are ganged together to increase the drive current. A two transistor circuit forms a constant sinking current controller.

VOLTAGE TO FREQUENCY CONVERTER + 1uS LED PULSE DRIVER
This circuit receives the signal from the above amplifier and launches powerful 1uS infrared light pulses from a low cost LED that are frequency modulated by the audio information. The 10KHz center frequency of the pulse stream is low enough so a standard infrared LED can emit ten times more light than conventional long pulse techniques. The circuit is described in more detail in the transmitter section of my Handbook of Optical Through the Air Communications.

WHITE LED NIGHT LIGHT
This simple circuit is designed to plug into a standard AC electrical outlet. It uses four super bright white light emitting diodes (LED) in conjunction with a capacitor coupled full wave rectifier circuit. The LEDs are mounted in a box and are angled slightly to bounce the light off of a nearby wall. The light should last about 10 years. The circuit draws less than one half of one watt of power and can therefore run continuously. In spite of the low power, the LEDs provide sufficient illumination for most night light applications. Circuit component values for both 120vac and 240vac are shown.

Wig/wag LED Flasher
This simple circuit will flash two LEDs in an alternating fashion.

Links to electronic schematics, circuits, designs and/or diagrams for engineers, hobbyists, students & inventors:

Ultra-Bright LED Lamp: (electronic Circuit / Schematic added 10/04)

Universal Flasher Circuit: LED flasher with the LM3909 IC (added 2/06)

Universal Pots Interface Lightning Protection: Melexis Application Note (app note added 2/06)

Using the TPS61040 in High Voltage Applications: TI Application Note (added 2/06)

Using the Xitanium Driver : Luxeon Application Note (app note added 2/06)

Voltage to Current Converter Drives White LEDs: 06/27/02 EDN Design Ideas / (added 1/05) You sometimes need to drive a white LED from one 1.5V battery. Unfortunately, the forward voltage of a white LED is 3 to 4V. So, you would need a dc/dc converter to drive the LED from one battery. Using the simple circuit in Figure 1, you can drive one white LED or two series-connected green LEDs, using only a few components....

White LED Circuits: (electronic circuit added 4/05)

White LED Driver Backlights LCD and Keypad: 11/13/03 EDN Design Ideas / (added 1/05) Designers widely use white LEDs to backlight color LCDs and keypads in handheld devices, such as cell phones, MP3 players, GPS navigators, and PDAs. Their spectrum and brightness represent near-ideal light sources. One possible configuration for a phone or a phone/PDA combination is to have a group of three LEDs to light the display and six LEDs for the

White LED Driver in Tiny SC70 Package Achieves 84% Efficiency: Linear Technology Magazine Design Ideas August 2002 (app note added 02/05)

White LED Driver in Tiny SC70 Package Delivers High Efficiency and Uniform LED Brightness: DN315 Design Notes (Linear Technology) (app note added 1/06)

White LED Driver Minimizes Space Maximizes Efficiency and Flexibility: Linear Technology Magazine Design Feature December 2003 (app note added 02/05)

White LED Driver Provides 64 Step Logarithmic Dimming: 06/24/04 EDN Design Ideas Online (added 1/05) The circuit in this Design Idea is designed for portable-power applications that require white LEDs with adjustable, logarithmic dimming levels. The circuit drives as many as four white LEDs from a 3.3V source.

White LED Driver Touts High Efficiency: 06/12/03 EDN-Design Ideas / (added 7/03) White LEDs, the most recent addition to the LCD backlight, find common use in providing backlight for color LCDs. Thanks to their size and white-light output, they appear in small, portable devices with color displays, such as PDAs and cellular phones. Like other LEDs, a white LED needs a constant-current source—typically,....

White LED Head Lamp: A white LED head lamp which can operate with only two AA batteries. The LEDs are driven in constant current, so that the brightness is maintained until end of battery life. (added 10/05)

White LED Power Supply Design Techniques: TI Application Note (added 2/06)

White LED Step-Up Converter in SC70 and ThinSOT: Linear Technology LT1937 (app note added 02/05)

White Light LED Driver with Gradual Dimming: TI Application Note (added 2/06)

White-LED Driver Backlights LCD and Keypad: 11/13/03 EDN Design Ideas (added 1/05) Designers widely use white LEDs to backlight color LCDs and keypads in handheld devices, such as cell phones, MP3 players, GPS navigators, and PDAs. Their spectrum and brightness represent near-ideal light sources. One possible configuration for a phone or a phone/PDA combination is to have a group of three LEDs to light the display and six LEDs for the

White-LED Driver Provides 64-Step Logarithmic Dimming: 06/24/04 EDN Design Ideas Online (added 1/05) The circuit in this Design Idea is designed for portable-power applications that require white LEDs with adjustable, logarithmic dimming levels. The circuit drives as many as four white LEDs from a 3.3V source.

White-LED Driver Touts High Efficiency: 06/12/03 EDN Design Ideas (added 1/05) White LEDs, the most recent addition to the LCD backlight, find common use in providing backlight for color LCDs. Thanks to their size and white-light output, they appear in small, portable devices with color displays, such as PDAs and cellular phones. Like other LEDs, a white LED needs a constant-current source—typically, on the order of 15 to 20 mA....

Wide Input Range 1a LED Driver Powers High Brightness LEDs with Automotive and 12 VAC Supplies: DN1012 Design Notes (Linear Technology) (app note added 1/06)

ZXSC100 Single cell DC-DC converter LED driving applications: Zetec Semiconductors Applications Notes ZXSC100 single cell DC-DC converter offers an ideal solution to driving white LEDs in flashlights, enabling operation from a single NiCd or NiMH cell. (app note added 6/06)

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