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Light Emitting Diodes (LED) Circuits
LEDs:   #'s - B     C - G      H - L       M - P       Q - T     U - Z 
 

Last Updated: October 24, 2017 02:55 PM

 

Circuits Designed by Dave Johnson, P.E. :

 Circuit Indicates Battery Charge CurrentThis circuit was inspired by a company needing a DC current indicator light which was small enough to be molded into a medium size 28v rechargeable battery assembly.  They specified that they wanted the circuit to turn on the LED indicator light with 500ma or more of battery charge current . . . Hobby Circuit designed by Dave Johnson P.E.-January, 2011

 Circuit indicates Battery Charging CurrentAnyone who has ever had a shocking experience on an especially dry day is acutely aware of the kinds of high voltage that can be generated from a simple walk across a carpeted floor.  Those same finger to metal sparks can destroy or disrupt sensitive elect . . . Hobby Circuit designed by David A. Johnson P.E.-January, 2011

 Classic Linear 5v Supply using 6.3VAC TransformerThere are times when you wish to control a pulse width modulation (PWM) signal with a DC voltage, ranging from 0v to 5v.  This voltage is often created by a computer interface.  The circuit below performs this voltage to PWM conversion.  PWM signals are often . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2010

 Closet Light with Automatic 3-Minute TimeoutThe circuit below is powered by three 1.5v alkaline AA cells.  With a finger tap to the pushbutton trigger switch, a cluster of 6 wide angle white LEDs is turned on.  The lights remain on for about 3 minutes, then will turn off.  The circuit’s standby current is only a few microamps.  A set of fresh batteries should last at least 200 light applications.  The circuit uses a Schmitt trigger inverter and two transistors.  When the pushbutton switch S1 is pressed, the 10uF capacitor C1 is discharged. . . Circuit by Dave Johnson P.E.-November, 2010

 CMOS IC Flashes LEDJudging from the numerous references I have received, this electronic circuit, hobby circuit seems to be rather popular.  Many published circuits which flash LEDs need 3 or more volts.  This electronic circuit uses only a single inexpensive C-MOS IC and . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

 Computer Controlled PWM CircuitThere are times when you wish to control a pulse width modulation (PWM) signal with a DC voltage, ranging from 0v to 5v.  This voltage is often created by a computer interface.  The circuit below performs this voltage to PWM conversion.  PWM signals are often. . . Circuit by Dave Johnson P.E.-October, 2010

 Computer, Long Period, Watch Dog TimerThis circuit uses a simple 4060 IC oscillator/timer that is reset periodically by a computer.  Should the computer fail to send a pulse, the output changes state.  The time can easily be set from seconds to hours . . . Hobby Circuit designed by David A. Johnson P.E.-January, 1998

 Constant Current Drives LEDsLEDs are current driven devices.  The light they produce is proportional to the current flowing though them.  One way to maintain a fairly steady light output is to keep the current through the LED fixed, even as the supply voltage may change.  A classic . . . Hobby Circuit designed by Dave Johnson P.E.-December, 2010

 Constant Current LED DriverBob Pease from National Semiconductor came up with this circuit and I have used it many times.  It maintains a constant current through one or more LEDs.  A single resistor controls the desired current. . . . Hobby Circuit designed by Dave Johnson P.E.-November, 2004

 Control Variable LED IntensityThe circuit below uses power from four rechargeable AA NiMH
cells to drive 3 white LEDs.  A potentiometer varies the duty cycle of a pulse width modulator circuit to vary the intensity of the LEDs from 0% to 100%.  The beauty of the circuit is that when the . . . Hobby Circuit designed by Dave Johnson P.E.-September, 2009

 Controlled Up/Down Ramping LightThere 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 . . . Hobby Circuit designed by David Johnson P.E.-March, 2009

 Convert Solar Powered Light to FlasherThe circuit converts an off-the-shelf solar powered LED path light from producing a steady state light to one that produces a flash.  This circuit includes a tiny dual Schmitt trigger inverter IC which form the pulse generator and the daylight sensor circuit.  The circuit produces a positive pulse, which feeds the constant current LED driver circuit.. . . Circuit by Dave Johnson P.E.-February, 2010

 Current Indicator for Battery ChargersThis circuit was inspired by a company needing a DC current indicator light which was small enough to be molded into a medium size 28v rechargeable battery assembly.  They specified that they wanted the circuit to turn on the LED indicator light with 500ma or more of battery charge current. . . Circuit by David A. Johnson P.E.-January, 2011


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

Caboose Marker Flashing Red LED Light -  A circuit that drives a red LED from a 1.5 volt battery and simulates an incandescent light.  Duty cycle can be changed by selecting resistor values __ Designed by Dick Cappels

Cascaded converter boosts LED-drive capability -  08/16/07 EDN-Design Ideas A two-stage boost converter can drive a string of 20 to 30 LEDs __ Circuit Design by Grant Smith, National Semiconductor, Phoenix, AZ

CFL ballast to drive LEDs -  04/26/07  EDN-Design Ideas A CFL ballast can drive a string of as many as 64 LEDs __ Circuit Design by Christian Rausch, Unterhaching, Germany

Charge Pump & Step Up DC DC Converter Solutions for Powering White LEDs in Series or Parallel Connections -  App Note #1037__ Maxim Integrated

Chipiplexing Efficiently Drives Multiple LEDs using Few Microcontroller Ports -  27-Nov-08 EDN-Design Ideas "Chipiplexing" approach simultaneously drives two LEDs __ Circuit Design by Guillermo Jaquenod, La Plata, Argentina

Christmas Decoration -  This project flashes 18 LEDs at three different rates and you can use these to create a Christmas decoration of your choice.  The circuit is kept simple  (and cheap!) by using the 4060B IC which is a counter and oscillator  (clock) in one package.  The circuit requires a 9V supply, such as a PP3 battery __ Designed by John Hewes

Christmas Star -  Christmas just would not be Christmas if you do not put a flashing star on your Christmas tree.  Here is the circuit of such a flashing star.Fig.1 shows the circuit...__ Electronics Projects for You

Christmas Star -  This project started just before last Christmas when my daughters asked "why don’t we have any flashing Christmas tree lights?" So, while they were out shopping, my son and I grabbed a dozen LEDs, some ribbon cable and a microcontroller.  While my son wired up the LEDs, I wrote some simple software.  It was all installed and running when they came home after spending all my money  (that’s why we didn’t have lights before) ! The smiles on their faces made it all worth while! __ Designed by © Grantronics Pty Ltd

Circuit Controls Two LEDs with One Microcontroller Port Pin -  Microcontroller port pins can typically be driven either high or low, or else be put into an input or high-impedance state.  This circuit uses the three states to drive two separate LEDs with one port pin.  This can be very useful when __ Designed by Spehro Pefhany

Circuit Delivers 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 __ Circuit Design by Wallace Ly, National Semiconductor, Santa Clara, CA

Circuit diagram of 3V LED chaser using 4017 -  There are many 9V chaser circuits that seem to waste about 7V when driving LEDs that are only about 2V.  This project is unique, because it uses only two inexpensive alkaline battery cells totaling 3V for power.  Since most of the waste is eliminated, the cells last a long time.

Circuit drives 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 __ Circuit Design by Roy McCammon, 3M Austin, TX

Circuit drives 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 __ Circuit Design by Mark Pearson, Maxim Integrated Products, Sunnyvale, CA

Circuit Drives White LEDs -  11/23/00 EDN-Design Ideas Newly available white LEDs are replacing CCFLs  (cold-cathode fluorescent lamps] in handheld applications using a back-lit LCD.  These applications include PDAs  (personal digital assistants], digital cameras, and cellular telephones,  __ Circuit Design by Eddy Wells, Texas Instruments

Circuit efficiently switches bipolar LED -  11/22/01  EDN-Design Ideas The circuit in Figure 1 represents one method to switch a bipolar, two-color LED using an SPDT mechanical switch or relay.This circuit wastes power and does not work properly if the power-supply voltage is not substantiallythan t __ Circuit Design by Spehro Pefhany, Trexon Inc, Toronto, ON, Canada

Circuit Indicates Battery Charge Current -  This circuit was inspired by a company needing a DC current indicator light which was small enough to be molded into a medium size 28v rechargeable battery assembly.  They specified that they wanted the circuit to turn on the LED indicator light with 500ma or more of battery charge current . . . Hobby Circuit designed by Dave Johnson P.E.-January, 2011

Circuit indicates Battery Charging Current -  Anyone who has ever had a shocking experience on an especially dry day is acutely aware of the kinds of high voltage that can be generated from a simple walk across a carpeted floor.  Those same finger to metal sparks can destroy or disrupt sensitive elect . . . Hobby Circuit designed by David A. Johnson P.E.-January, 2011

Circuit Lets You Measure Zener Voltages & Test LEDs -  10-Jun-10 EDN-Design Ideas To measure a zener diode's breakdown voltage, you need a dc voltage source whose voltage exceeds that of the zener voltage.  In Figure 1, resistor RSER provIdeas voltage drop between VIN and VZEN.  In any case, VIN  should exceed VZEN.  Resistor RSER must provide current, IZEN, that can keep the zener diode in reverse breakdown.  That is, the current must be more than IZEN-IZENMIN  and less than IZEN-IZENMAX.  You also need to consider the current that flows through the load.  Otherwise, VZEN  will be unregulated __ Circuit Design by Vladimir Oleynik, Moscow, Russia

Circuit Provides Visual Verification Of IR Pulses -  09/08/11  EDN-Design Ideas Use a transimpedance amplifier to drive an LED.  You can test an IR  (infrared) link with a circuit that converts an IR-generated photocurrent to an amplified current that drives a standard LED  (Figure 1) .  This approach provIdeas a visual feedback to indicate that the transmitter is working.  The circuit can be enclosed in a small plastic or metal box and requires just a 9V transistor battery for operation.  Diode D1 is a basic Everlight PD333-3C/H0/L2 or equivalent IR photodiode in a T1¾ package.   __ Circuit Design by Michael J Gambuzza, General Electric Measurement and Control Solutions, Billerica, MA; Edited by Paul Rako and Fran Granville

Circuit uses Simple Circuit LED for Near IR Light -  09/01/98 EDN-Design Ideas NOTE :  File has many circuits, scroll down.  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. __ Circuit Design by Lukasz Sliwczynski, Marcin Lipinski, Institute of Electronics, Krakow, Poland

Clap Relay -  Clap sensitive on-off Relay.3V Battery operated, small portable unit,  __ Contact: Flavio Dellepiane, fladello @ tin.it

Classic Linear 5v Supply using 6.3VAC Transformer -  There are times when you wish to control a pulse width modulation  (PWM) signal with a DC voltage, ranging from 0v to 5v.  This voltage is often created by a computer interface.  The circuit below performs this voltage to PWM conversion.  PWM signals are often . . . Hobby Circuit designed by Dave Johnson P.E.-October, 2010

Closet Light with Automatic 3-Minute Timeout -  The circuit below is powered by three 1.5v alkaline AA cells.  With a finger tap to the pushbutton trigger switch, a cluster of 6 wide angle white LEDs is turned on.  The lights remain on for about 3 minutes, then will turn off.  The circuit’s standby current is only a few microamps.  A set of fresh batteries should last at least 200 light applications.  The circuit uses a Schmitt trigger inverter and two transistors.  When the pushbutton switch S1 is pressed, the 10uF capacitor C1 is discharged. . . Circuit by Dave Johnson P.E.-November, 2010

CMOS IC Flashes LED -  Judging from the numerous references I have received, this electronic circuit, hobby circuit seems to be rather popular.  Many published circuits which flash LEDs need 3 or more volts.  This electronic circuit uses only a single inexpensive C-MOS IC and . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000

Color fade -  Let's blink some LEDs again.  Well, fading could be more accurate term.  Meaning of this article is to show you an easy circuit that lets you light up your case with slowly alternating colors or just to make your power led come alive.  Color changing FireWheel could be also cool, what do you think?This is by no means a step by step how to but I think that it will be enough anyway.   __ Designed by Jani Pönkkö

Color-Management LED Drivers Have a Bright Future -  LED lighting designers are challenged with meeting their efficiency and reliability goals faster in advanced LED lighting designs.  LED lighting customers seeking the latest in innovative and affordable LED lighting solutions can benefit from TI's broad product portfolio of LED drivers, AC/DC, DC/DC, power management devices, wireless and wired interface control and embedded processors.  LED designers have the option of not only controlling the power stage, but regulating LED currents as well, eliminating the need for multiple components and reducing system cost.   __ Designed by Texas Instruments App Notes, 20-Jun-07

Compact Inductorless Boost Regulates White LED Bias Current -  App Note #1116__ Maxim Integrated

Computer Controlled PWM Circuit -  There are times when you wish to control a pulse width modulation  (PWM) signal with a DC voltage, ranging from 0v to 5v.  This voltage is often created by a computer interface.  The circuit below performs this voltage to PWM conversion.  PWM signals are often. . . Circuit by Dave Johnson P.E.-October, 2010

Computer, Long Period, Watch Dog Timer -  This circuit uses a simple 4060 IC oscillator/timer that is reset periodically by a computer.  Should the computer fail to send a pulse, the output changes state.  The time can easily be set from seconds to hours . . . Hobby Circuit designed by David A. Johnson P.E.-January, 1998

Connecting LED to PIC Micro I/O Pins -  So, you’ve got a great idea for a project using a PICmicro microcontroller and you want to use at least one LED in your project as a power indicator.  Or, maybe, you’ve set out to design a bar-graph voltmeter with eight LEDs, __ Sirus MicroSystems

Constant Current Drives LEDs -  LEDs are current driven devices.  The light they produce is proportional to the current flowing though them.  One way to maintain a fairly steady light output is to keep the current through the LED fixed, even as the supply voltage may change.  A classic . . . Hobby Circuit designed by Dave Johnson P.E.-December, 2010

Constant Current LED Driver -  Bob Pease from National Semiconductor came up with this circuit and I have used it many times.  It maintains a constant current through one or more LEDs.  A single resistor controls the desired current. . . . Hobby Circuit designed by Dave Johnson P.E.-November, 2004

Constant current LED driver using an NPN transistor to control an N-channel MOSFET -  Here's a really simple and inexpensive  ($1) LED driver circuit.  The circuit is a "constant current source", which means that it keeps the LED brightness constant no matter what power supply you use or surrounding environmental conditions you subject the LED's to.

Constant current LED driver using LM334 plus a transistor -  Bob Pease from National Semiconductor came up with this circuit and I have used it many times.   It maintains a constant current through one or more LEDs.   A single resistor controls the desired current. __ Designed by David Johnson, Discovercircuits.com

Constant current, constant voltage converter drives white LEDs -  09/02/04  EDN-Design Ideas LEDs usually take their drive from a constant dc-current source to maintain constant luminescence.  Most DC/DC converters, however, deliver a constant voltage by comparing a feedback voltage to an internal reference via an internal error amplifier.  The easiest way to turn a simple DC/DC converter into a constant-current source is to use a sense resistor to convert the output current to a voltage __ Circuit Design by Keith Szolusha, Linear Technology Corp, Milpitas, CA

Constant-Current DC/DC LED Driver in ThinSOT -  LT1932__ Linear Technology/Analog Devices

Control Variable LED Intensity -  The circuit below uses power from four rechargeable AA NiMH
cells to drive 3 white LEDs.  A potentiometer varies the duty cycle of a pulse width modulator circuit to vary the intensity of the LEDs from 0% to 100%.  The beauty of the circuit is that when the . . . Hobby Circuit designed by Dave Johnson P.E.-September, 2009

Controlled Up/Down Ramping Light -  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 . . . Hobby Circuit designed by David Johnson P.E.-March, 2009

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

Controller for Christmas Light Shows, Pt.2 -  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

Convert Solar Powered Light to Flasher -  The circuit converts an off-the-shelf solar powered LED path light from producing a steady state light to one that produces a flash.  This circuit includes a tiny dual Schmitt trigger inverter IC which form the pulse generator and the daylight sensor circuit.  The circuit produces a positive pulse, which feeds the constant current LED driver circuit.. . . Circuit by Dave Johnson P.E.-February, 2010

Count Down Alarm, 3 LED Displays multiplexed & PIC16F84 -  Here I have added two fets for the time-out switch, it is like an electronic relay, just much more reliable it can be used to sound a big horn, or what ever you like. __ Designed by Thomas Scherrer OZ2CPU

Courtesy Light -  Two LED-eyes follow the rhythm of music or speech; 3V Battery-operated device suitable for pins or badges __ Contact: Flavio Dellepiane, fladello @ tin.it

Create LED-Lighting Patterns Without a Controller -  18-Mar-10 EDN-Design Ideas Create hundreds of patterns with a few timers and logic gates __ Circuit Design by Jeff Tregre, www/BuildingUltimateModels/com, Dallas, TX

Create Secondary Colors From Multicolored LEDs -  24-Jul-03 EDN-Design Ideas It is well-known that simultaneously mixing two primary-color light sources, such as red and green, creates a secondary color, such as yellow.  This mixing process commonly occurs in tricolor LEDs.  One disadvantage of this method of generating a yellow color is that the LED must use twice the current because both the red and the green LEDs must be on __ Circuit Design by Claude Haridge, Stittsville, ON, Canada

Cross-coupled gates prevent push-pull-driver overlap -  05/15/08  EDN-Design Ideas Cross-coupled gates in the push-pull drive of a center-tapped transformer's primary prevent overlap __ Circuit Design by Richard Rice, Oconomowoc, WI

Current Indicator for Battery Chargers -  This circuit was inspired by a company needing a DC current indicator light which was small enough to be molded into a medium size 28v rechargeable battery assembly.  They specified that they wanted the circuit to turn on the LED indicator light with 500ma or more of battery charge current. . . Circuit by David A. Johnson P.E.-January, 2011

Current Mirror Drives Multiple LEDs From a Low Supply Voltage -  12/05/08 EDN-Design Ideas A pulsed current mirror comprising discrete transistors drives LEDs from a low voltage, avoiding thermal runaway __ Circuit Design by Rex Niven, Forty Trout Electronics, Eltham, Victoria, Australia

    >>>

LEDs:   #'s - B     C - G      H - L       M - P       Q - T     U - Z 

 


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