Dark-activated LED or Lamp Flasher -  This circuit adopts the rather unusual Bowes/White emitter coupled multivibrator circuit.  The oscillation frequency is about 1Hz and is set by C1 value.   __ Contact: Flavio Dellepiane, fladello @ tin.it

Dark-Detecting LED -  Here's a simple problem: "How do you make an LED turn on when it gets dark?" You might call it the "nightlight problem, " but the same sort of question comes up in a lot of familiar situations-- emergency lights, street lights, silly computer keyboard backlights, and the list goes on.  Solutions? Lots.  The time-honored tradition is to use a circuit with a CdS photoresistor, sometimes called a photocell or LDR, for "light-dependent resistor.  " 

Deliver Dimming Control for White-LED Driver -  10/28/04  EDN-Design Ideas 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 thatthan 50% of the power Design by Wallace Ly, National Semiconductor, Santa Clara, CA

Descrete Multistage Light Sequencer -  The drawing below illustrates a multistage light sequencer using descrete parts and no integrated circuits.  The idea is not new and I hear a similar circuit was developed about 40 years ago using germanium transistors.  The idea is to connect the lights so that as one turns off it causes the next to turn on, and so forth.  This is accomplished with a large capacitor between each stage that charges when a stage turns off and supplies base current to the next transistor, thus turning it on.  Any  __ Designed by Bill Bowden

Design Notes: 60V, Synchronous Step-Down High Current LED Driver -  03/01/14 EDN-Design Notes   This circuit provIdeas much better performance and higher power handling than a Zener diode The meaning of the term “high power LED” is rapidly evolving.  Although a 350mA LED could easily earn the stamp of “high power” a few years ago, it could not hold a candle to the 20A LEDs or the 40A laser diodes of today.  High power LEDs are now used in DLP projectors, surgical equipment, stage lighting, automotive lighting, and other applications traditionally served by high intensity bulbs Design by Hua  Walker Bai, also see Linear Technology Design Note 508

Desktop LED Emergency Light -  You can make an ultra-simple desktop emergency light using ‘discharged’ batteries.  You know that battery cells still have considerable energy left in them even when these become ‘weak’ for most battery-powered...__ Electronics Projects for You

Diagnose LEDs by Monitoring the switch-mode duty-cycle -  04/09/09  EDN-Design Ideas Engineers often monitor the forward voltage, VF, of HB LEDs  (high-brightness light-emitting diodes] to assess the LEDs’ health.  Big changes in forward voltage can indicate deterioration or even a complete failure of one or more LEDs  Design by Fons Janssen, Maxim Integrated Products Inc, Bilthoven, the Netherlands

Dice -  Press the push switch to 'throw' the dice: this makes the circuit rapidly cycle through the dice numbers so that an effectively random dice number is displayed by the LEDs when the push switch is released.   __ Designed by John Hewes

Digital Clock Timer-PIC16F628 -  This clock timer uses a PIC16F628 microcontroller to display 3 and 1/2 digit time and control an external load.  The clock includes a calendar with leap year and optional daylight savings adjustments.  The timer output can be set from 1 to 59 minutes and manually switched on and off.  The clock also has a correction feature that allows an additional second to be added every so many hours to compensate for a slightly slow running oscillator.  The oscillator uses a common 32.768 KHz watch crystal and the frequency can be adjusted slightly with the 24pF capacitor on the right side of the crystal __ Designed by Bill Bowden

Digital Fading Eyes using a PIC -  Another version of the circuit was done using a PIC microcontroller and a pair of high power 1/2 watt orange LEDs.  The software uses a non-linear scale to generate a more linear visual response.  LEDs are more efficient at lower power and a nonlinear reduction in current seems to obtain a more linear visual effect.  The controller produces a PWM output in 50 steps which is buffered with a medium power transistor to drive the LEDs.  The LEDs are connected to a 12 volt supply so that most any colored or white LEDs can be used in the range of 1.6 to 3.3 forward voltage.   __ Designed by Bill Bowden

Digital LED AM meter -  Measures current up to 10A with selected 100mA, 10mA and 1mA resolutions.  

Digital LED Chaser -  This circuit uses digital circuits such as a demultiplexer and a binary counter to create patterns of "moving" led lights.  This basic circuit is really cool when used in the dark or to light up a sign of some sort, as it creates a cool pattern that catches the eye __ Designed by Zaakid Mata @ kakinblogs @ gmail.com

Digital LED Lighting Controller for Chrismas Lights -  It's that time of year again when all those Christmas lighting devotees start planning and building their displays for the festive season.  They might have dozensif not hundredsof different light arrays and they will be thinking about buying even more.  Is this you? Have you thought about controlling lots of your lights in time to music? Well now you can!__ SiliconChip

Digital LED Voltmeter -  Measures voltages up to 199.9V with 0.1V resolution.  

Digital Lighting Controller for Christmas Light Shows, Pt.2 -  Everyone who has seen this has been pretty impressed and no wonder! While we originally intended it to make your Christmas Lights display the best in your suburb, with up to 32 channels and total power limited only by your power outlets, it's capable of controlling just about any lighting sequencing task you want to throw at it.  Now we get on with the good stuff: putting it all together!__ SiliconChip

Digital Lighting Controller for Christmas Light Shows, Pt.3 -  Christmas is just about here! Have you got your Digital Lighting Controller ready yet? In the first two articles we explained how the Digital Lighting Controller works and how to build it.  This third article explains how to use the softwareprimarily the Windows-based sequencing program.__ SiliconChip

Digital Logic Based LED Christmas Tree with 64 LEDs -  The Holidays are once again upon us and we wanted to give our readers the edge in decorating this year.  Continuing our all-digital-hardware theme to coincide with our Kickstarter for a Digital Electronics Course at PyroEDU, we have created an LED Christmas tree controlled entirely by digital logic __ Designed by PyroElectro

Digital Thermostat with LED Temperature Display -  I needed to replace two old, unreliable thermostats for controlling the heating and cooling for a large garden shed.  Commercial basic digital thermostats are available quite cheaply, but some lack the ability to control heavy loads or have the extra features that I require for saving energy when the door is often left open or to indicate temperature being out of range etc.  I like the PIC18F1320 microcontroller used in my previous project, so decided to use it again in a very similar design to drive three multiplexed LED displays and read the temperature from a Dallas/DS18x20 "1-Wire" digital sensor.   __ Designed by D. Thorpe, 2006

Digital Voltmeter with LED Display -  This is an easy to build, but nevertheless very accurate and useful digital voltmeter.  It has been designed as a panel meter and can be used in DC power supplies or anywhere else it is necessary to have an accurate indication of the voltage present.  The circuit employs the ADC  (Analogue to Digital Converter) I.  C.  CL7107 made by INTERSI - L __ Designed by © of this circuit belongs to smart kit electronics

Dimmable LED Desk Lamp -  This circuit was used to convert a portable fluorescent desk lamp to LEDs.  It is dimmable from "night light" level to "retina burner" level.72 high-brightness LEDs put out a lot of light.  Without a diffuser, the light output is very directional, like __ Designed by Andrew R. Morris

Dimmable LED Desk Lamp -  30-Nov-12 -Design News:   Andrew Morris designed a dimmable LED driver circuit that is simple and energy efficient.  He then installed the circuit into a portable fluorescent lamp. __ Designed by Andrew R. Morris, Gadget Freak-Case #230

Discrete LED Color Organ -  Here is a new version of the classic color organ, where different color lights are triggered by different frequencies of sound, resulting in a display that flashes along to music.  In this case the newer type high intensity LEDs  (30005000mcd) were used along with a very simple discrete transistor drive circuit.  The design goals included small size and excellent portability, as well as long battery life. __ Designed by Chester Winowiecki

Displays: LED Matrix -  Information for the Common Anode LED Matrix Display for SA04-11EWA, NFM-12882BEG-11, LEDM88RG  (Updated 7/03/2006)  __ Designed by Jose Pino

Does Power Line have 120 VAC or 240 VAC? -  Two LEDs indicate if a power line has 120vac or 240vac voltage on it. . . Circuit by Dave Johnson P.E.-July, 2006

Dot matrix LED running display -  Brightness settings The user can select the brightness level in 8 steps or select an auto mode.  To change the brightness from Settings menu, select Bright and press SET.  The display will show the current bright level  (from Bright 1 __ Designed by Ivailo Vasilev

Drive 12 LEDs with One I/O Line -  4-Feb-10 EDN-Design Ideas Use a binary counter to generate LED-lighting codes Design by Charaf Laissoub, Maisons Alfort, France

Drive 16 LEDs with One I/O Line -  Over the last few years, several Design Ideas have described how to use just a few microcontroller I/O pins to drive many LEDs  (references 1 through 7) .  The circuit in Figure 1 can drive 16 LEDs with just one pin and two shift registers.  You can use the circuit to drive long-dot-bar or two seven-segment-digit displays.  Adding multiplexing to the same circuit enables it to drive eight seven-segment LED digits.    Design by Zoran Mijanovic and Nedjeljko Lekic, University of Montenegro, Podgorica, Montenegro

Drive a blue LED from a 3V battery -  02/15/07  EDN-Design Ideas Two 1.5V cells and a few components can light a blue LED Design by Sergi Sánchez, Federal Signal Vama SA, Vilassar de Dalt, Spain

Drive a LED with an Intensity Ramping Mode -  The circuit below was designed to drive a LED with an intensity ramping mode.  Two 555 timers generate two different triangle waveforms.  The upper device generates a 10KHz signal while the lower unit produces a 1Hz signal.  The two signals are fed to a . . . Hobby Circuit designed by Dave Johnson P.E.-December, 2007

Drive latching relays -  02/01/96 EDN-Design Ideas Figure 1 shows a low-parts-count circuit that can drive one- or two-coil latching relays.  Latching relays are useful in sensitive analog designs.  The 74ACT174 hex flip-flop has ample capability to drive the Aromat TQ2E series of latching relays.  Both windings for the TQ2E-L2-5V two-coil relay are on the same magnetic element, so the windings' fields add.  You Design by Roy McCammon, 3M Austin, TX

Drive mixed types & quantities of LEDs -  10/03/02 EDN-Design Ideas 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 Design by Mark Pearson, Maxim Integrated Products, Sunnyvale, CA