Ultra Low Current 3v LED Flasher #3 -  This circuit takes advantage of a tiny LMC7215 low current draw voltage comparator from National Semiconductor and a super efficient green LED from King Bright. The 3v powered circuit forms a classic pulse generator circuit, which drives the LED. The pulse width is set at about 20ms, the pulse rate is about 0. 5Hz and the peak LED current is only 100ua . . . [Circuit by David Johnson P.E.,  02/27/11]

Ultra Low Power LED Flasher -  The efficiency of some newer LEDs is amazing. Some of the latest green LEDs can launch blinding light with just one milliamp of current. I take advantage of one of these newer devices in the circuit below. The flashing circuit uses a classic multivibrator . . . [Hobby Circuit designed by Dave Johnson P.E.,  12/21/08]

Ultra-Bright LED Lamp -  . . . 

Ultra-simple Voltage Probe -  Detects 1. 8 to 230 Volts DC or AC Minimum parts counting. Circuit diagram: Parts: D1 5 or 3mm. Red LED D2 5 or 3mm. Green or Yellow LED LP1 220V 6W Filament Lamp Bulb P1 Red Probe P2 Black Probe Device purpose: This circuit is not a novelty, but it. . .  [Flavio Dellepiane's web site]

Universal Flasher Circuit -  LED flasher with the LM3909 IC. . . .  [Tony van Roon's circuit]

Universal Input TRIAC Dimmable 14W LED Driver -  The LT3799 is an isolated flyback controller with power factor correction specifically designed for driving LEDs. The controller operates using critical conduction mode allowing the use of a small transformer. Using a novel current sensing scheme, the controller is able to deliver a well regulated current to the secondary side without using an opto-coupler. A strong gate driver is included to drive an external high voltage MOSFET. Utilizing an onboard multiplier, the LT3799 typically achieves power factors of 0. 97. . . .  [Linear Technology App Note - , Jun 21, 2010]

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 . . . [Circuit by David A. Johnson P.E.,  07/11/06]

Universal-3v-LED-Flasher -  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 . . . [Circuit by David Johnson P.E.,  06/22/08]

Up / Down Digital Counter With 7 Segment LED Displays -  REVISEDReally as Simple as you can get and has 4, 5 or 6 Displays. REVISEDThis Schematic and PCB's updated on Nov 2, 2011. . . .  [G.L. Chemelec, designer]

Up/Down Ramping Light Pushbutton Control -  There are times when you want a lamp to gradually change from dark to light and from light to dark, with each push of a pushbutton switch. The circuit below performs this control function using a flip/flop and a classic pulse width modulation or PWM . . . [Circuit by David Johnson P.E.,  03/22/09]

USB LED Light -  A simply and easy-to-make circuit, useful when working with the computer at night. (6/08/2006) . . .  [Jose Pino]

USB LED Load -  The board supports driving two separate tri-color LEDs. More can be setup inline if desired. Currently the software only uses the second LED and its color represents the CPU load of the system in real-time. Blue for idle and gradients light blue, green, yellow, orange, and finally red indicating heavy CPU utilization. If the system fails to respond, the LED begins flashing RED to indicate a lack of communication from the software. This lets you easily identify a crashed machine in a rack for example. . . . 

Use a CFL ballast to drive LEDs -  04/26/07  EDN Design Idea   A CFL ballast can drive a string of as many as 64 LEDs. . .  [by Christian Rausch, Unterhaching, Germany]

Use An LED Matrix Horizontally -  02/16/12  EDN Design Idea   Using one 5×7 LED matrix horizontally instead of vertically allows the display of two characters instead of one. LEDs provide a convenient way to electronically display information. Although the seven-segment LED display, arranged in the form of the digit 8, is common, it does not allow the display of some alphanumeric characters. A 5×7 LED matrix allows the display of all ASCII characters, as well as graphics shapes. LEDs provide a convenient way to electronically display information. Although the seven-segment LED display, arranged in the form of the digit 8, is common, it does not allow the display of some alphanumeric characters. A 5×7 LED matrix allows the display of all ASCII characters, as well as graphics shapes. The circuit in this Design Idea shows an unconventional way to use a 5×7 LED matrix. . .  [by Benabadji Noureddine]

Use LEDs As Photodiodes -  11/18/10 EDN Design Idea   Ambient light changes an LEDs resistance, making it act like a photodiode. . .  [by Raju R Baddi, Raman Research Institute, Bangalore, India

Use simple LED for near-IR light -  09/01/98 EDN Design Idea   (several Design Ideas listed, scroll to find this one)  You can successfully use LEDs as sources of near-infrared light. However, when you need a source of light with precisely controlled power, a feedback loop is necessary to compensate for the temporal and thermal changes of the LED parameters. Standard LED types come with neither these monitoring detectors nor an external monitoring photodiode to detect part of the emitted light and generate a feedback signal. The situation calls for some mechanical fixture to mount the photodiode. Such a solution, however, is bulky and cumbersome, especially when space is scarce. . .  [by Lukasz Sliwczynski, Marcin Lipinski, Institute of Electronics, Krakow, Poland]

Using Common Cathode or Anode LEDs As Bipolar LEDs -  . . . 

Using the LM317T With LED Lighting -  Use an LM317T to regulate the current in LED lighting projects. . . .  [REUK-Renewable Energy UK website]

Using the TPS61040 in High Voltage Applications -  TI Application Note . . . 

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