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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 25, 2017 05:10 AM

Circuits Designed by Dave Johnson, P.E. :

  LED Array powered by 24 VA - C24vac is a popular voltage.  It is often used in low voltage lighting systems and industrial controls.  It is much less dangerous than 120vac/240vac line voltages.  This hobby circuit below is one method to efficiently power a cluster of 7 white LEDs from 24vac. . . . Hobby Circuit designed by David Johnson P.E.-December, 2009

 LED Camping Lantern with DimmerA while back I received an email from a Discover Circuits visitor who wanted to build his own LED camping lantern.  He wanted to use a single bright LED powered by 3 large alkaline D cells.  He also wanted to be able to dim the light intensity down to a low night light level, to extend the battery life.  The circuit below performs this task . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2013

 LED Driver using Constant CurrentLEDs 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. . . Circuit by David A. Johnson P.E.-December, 2010

 LED Driver-WirelessThe circuit solves this problem by sending power to the LED through the plastic, using a magnetic coupling technique.  The circuit below can route power through plastic enclosures as thick as ¼ inch.  The circuit will not work through metal boxes . . . Hobby Circuit designed by Dave Johnson P.E.-November, 2008

 LED Flasher needs only 1.5 VOLTSTo squeeze even more energy from a alkaline battery cell, this circuit adds two transistors to a circuit similar to the above design to boost the efficiency.  A small 1.5 volt alkaline N cell should flash the LED for a full year.  It too uses a "charge pump" technique to provide a LED the needed voltage . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

 LED Flasher that is Battery FreeLED flashers have been used for a wide variety of applications.  Some flasher units have been used in food and hardware stores, to draw attention to sale items and are often attached to boxes which dispense product discount coupons . . . Hobby Circuit designed by David Johnson P.E.-December, 2010

 LED Flasher Universal 3vThe electronic 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 . . . Hobby Circuit designed by David Johnson P.E.-June, 2008

 LED Flasher-Wig/WagThis simple circuit will flash two LEDs in an alternating fashion . . . Hobby Circuit designed by David Johnson P.E.-December, 2004

 LED Flasher-Wireless CircuitWhen you would like to flash a LED through a thick plastic case without wires, use this hobby circuit.  It performs this feat.  It draws about 300ua of average current at 5v.  It can be powered from a supply ranging from 3v to 6v . . . Hobby Circuit designed by Dave Johnson P.E.-January, 2011

 LED Flashing Badge #1I have seen numerous flashing light badges at trade shows and conventions.  They are often handed out as gifts to promote some business.  The devices often use inefficient circuits, which cause the battery power source to be quickly depleted. . . Circuit by Dave Johnson P.E.-March, 2002

 LED Flashing Badge #2This circuit uses a CD4013 dual D Flip/Flop IC.  A single lithium battery will provide months of continuous LED flashing.  It also has a tiny push-button switch to turn on and off the light flashing. . . Circuit by David Johnson P.E.-March, 2002

 LED Lighthouse FlasherThis was originally designed for a model in a HO train set.  It simulates the behavior of the light from a lighthouse.  The LED intensity gradually increases, then flashes with a bright light and finally decreases slowly in intensity . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

 LED Lighthouse Flasher for HO Model Train  - HO train sets often have authentic looking scale model homes and buildings.  The hobby circuit below can be mounted inside a model lighthouse.  The electronic circuit drives a single LED lamp in such a way that it produces light which simulates the rotation . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

LED_Light_for_Tool_Shed -  I have a lean-to 8ft by 12ft shed next to my house.  It is full of lawn chemicals and garden supplies.  There were times when I needed to get something from inside the shed during the dead of night.  Early on I had to use a flashlight.  But later, I installed a series of five 12v LED light strips on the ceiling.  Each strip contained 15 3v white LEDs.  The strip had 5 strings of three LEDs, wired in series, with a 150 ohm current limiting resistor. . . . Hobby Circuit by David Johnson P.E.-July, 2017

 LED Pilot Light powered by AC LineThis simple circuit can be used to light a LED indicator lamp, powered from the 120vac line.  I have included component values for 240vac lines as well. . . Circuit by David A. Johnson P.E.-July, 2006

 LED Strings powered by AC LineThis shows 4 different ways to string white LEDs that are powered by a 120vac or 240vac power line.    The circuit was designed by Ken Schultz . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2004

 Lighthouse LED FlasherThis was originally designed for a model in a HO train set.  It simulates the behavior of the light from a lighthouse.  The LED intensity gradually increases, then flashes with a bright light and finally decreases slowly in intensity. . . Circuit by Dave Johnson P.E.-July, 2006

 Lighthouse_Solar_Powered -  While at a discount store one day, I spotted an interesting tall lighthouse.  It had a tiny solar panel and an equally tiny LED light.  The LED was pointing downward, at the center of a rotating light reflector.  I thought it might be turned into an interesting addition to my wife’s garden. . . . Hobby Circuit by David Johnson P.E.-September, 2017


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

LED Strobe -  with high power led's available, their replacement for a xenon tube is viable! __ Contact: P. Townshend EduTek Ltd

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.   __ Contact: P. Townshend EduTek Ltd

LED Strobe & Contactless Tachometer -  This versatile LED Strobe & Tachometer can be used to observe and measure the RPM of rotating machinery.  It offers three different measurement methods and the readout is via a 2-line LCD module.__ SiliconChip

Led Strobe & Tacho Pt.2 -  Last month, we published the circuit of our new LED Strobe & Tachometer and showed how to build the main unit and the strobe light.  This month, we describe the assembly of the optional Photo-Interruptor and IR Reflector Amplifier boards.  We also describe how the unit is used.__ SiliconChip

LED Strobe Flasher -  This little circuit provides a surprisingly spectacular bright strobe flash which is adjustable with P1, the 200K trimmer potentiometer.  P1, R1, R2, and C1 provide the flashrate.  R1 sets the upper flashrate.  The flashrate for the above circuit was measured at 12Vdc.  If the supply voltage is steady or regulated, the flashrate is very stable. __ Designed by Tony van Roon  VA3AVR

LED Strobe Has Independent Delay & Duration -  11-Jun-09 EDN-Design Ideas High-brightness LEDs, with independent delay and duration, find use in a visual-inspection application __ Circuit Design by Michael C Page, Chelmsford, MA

LED Strobe Light -  Schematic + Info + pictures __ Designed by Lennie Zink

LED Tachometer with Dual Displays, Pt.1 -  A responsive and accurate tachometer is essential for motoring enthusiasts.  This new unit features a bright 4-digit display plus a 32-LED circular bargraph.  The LED bargraph responds rapidly to changes in RPM while the digital display shows accurate RPM readings with a steady throttle.__ SiliconChip

LED Tester -  NOTE : Must register on this site __ Designed by Published in Elecktor July/Aug, 2010

LED Tester -  Schematic + Info + pictures __ Designed by Lennie Zink

LED Thermometer -  This LED thermometer is designed for in home use, to read temperatures between about 60 and 78 degrees Fahrenheit.  It is based around a precision temperature sensor IC, the LM34DZ.  This sensor require no calibration and can measure temperatures of between -50F and +300F.  While the circuit shown here does not use the full range of that sensor, it can be modified to do so by simply changing the voltage reference to U2 at the sacrifice of precision. __ Designed by Aaron Cake

LED Torch -  LEDs are becoming increasingly popular in many lighting applications.  White LEDs are now common in torches.  Here’s a simple and economical LED torch that operates off two 1.5V cells.  For a white...__ Electronics Projects for You

LED Torch -  Based on the MAX660, designed to power three 3mm/5mm white LED's from 3V  (1.5V min) , intended for replacing incandescent bulbs in small torches.   __ Designed by Submitted Andre

LED Torch -  A common problem with small torches is the short life-span both of the batteries and the bulb.  The average incandescent torch, for instance, consumes around 2 Watts.  The LED Torch in Fig.1 consumes just 24 mW, giving it more than80 times longer service from 4 AA alkaline batteries  (that is, up to one month's continuous service)  __ Designed by Rev Thomas Scarborough

LED Torchs -  A LED torch is one of the simplest projects you can build and it's very interesting as it uses a super-bright white LED.  In the history of LED production, red LEDs were the first to be invented and their output was so dim you could barely see if they were illuminated.  You needed a darkened room to see them at all __ Contact: Collin Mitchell

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 __ Designed by Bill Bowden

LED used 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

LED Volt Meter -  Here is a Simple LED Volt meter to Monitor the charge level in Lead Acid Battery or Tubular battery.  The terminal voltage of the battery is indicated through a four level LED indicators.  The nominal terminal voltage of a Lead Acid battery is 13.8 volts and that of a Tubular battery is 14.8 volts when

LED Voltage Indicator -  This teensy little board is only 1 inch  (25mm) square, and is handy as a combined power on and low battery voltage indicator.  The two colour LED changes from green to red when the battery voltage drops below the adjustable trigger voltage.  It's usable between about 6V and 30VDC, and uses a precision LM336Z-2.5 voltage reference.  The LED can be reversed so it changes from green to red if the preset voltage is exceeded, if required.   __ Designed by Bob Barker, not the TV Host

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

LED Voltmeters 20 & 30 LED's -  These are Basic Expanded Voltmeters based on the National LM3914 chip.  They can be Switched to either Bar or Dot Mode.  The 20 LED one has a Minimum 2.5 volt range for Full Scale and it can be adjusted to Much Higher voltage ranges with the input potentiometer. __ Designed by G.L. Chemelec

LED white light bulb -  mains powered, no loss power supply, ultra green  __ Designed by Thomas Scherrer OZ2CPU

LED Wink Tester for 1.5 Volt Cells -  This page contains a collection of circuits that wink when the power switch is thrown to indicated whether the 1.5 volt  (and other voltages near 1.5 volts) cell still has a significant charge left.  Choose the best one for your application.   __ Designed by Dick Cappels

LED Zeppelin -  The name of our game, LED Zeppelin, is a play on words.  It comes not from the pop group of the same name but from Graf Von Zeppelin, a German who invented the first rigid air ship in 1900.  The association fits perfectly.  The game consists of six LEDs and an indicator LED that flashes at a rate of about 2 cycles per second.  A push button is the "Operations Control" and by carefully pushing the button in synchronisation with the flashing LED, the row of LEDs will gradually light up __ Contact: Collin Mitchell

LED Blinker uses 4 parts -  EDN-Design Ideas March 26, 1998    [ NOTE : File has multiple design, scroll for this one.]   The circuit in Figure 1 is an easy-to-make attention-getter and runs for a week or longer on two AA cells. In September, I used this circuit for a school fundraiser, and it helped me generate more than $100. My dad showed me a circuit in EDN that did the same thing, but it uses more parts  (see "Alternating LED flasher uses minimal parts," EDN, Nov 20, 1997, pg 104) . __ Circuit Design by Andy Meng, Cincinnati, OH

Led Strobe 2 -  this version has been built and tested and is very simple indeedbased on alien project astable! __ Contact: P. Townshend EduTek Ltd

LED2 LED Sensor Relay Tracker -  Circuit 1 tends to chatter the relays under certain lighting conditions as there is no built in hysteresis.  This version uses a Schmitt trigger hex inverter circuit to eliminate the chatter.  It works better but is more complex __ Contact: Duane C. Johnson

LED3X LED Sensor Electronic Tracker with H-Bridge Drive -  The LED3 using surface technics was just to hard to assemble in a timly manor as sales were increasing.  I needed a circuit that could be built with mostly through hole components.  At the same time, there were other features and enhansments that I thought were needed.  This was the impetus for the LED3X series of solar trackers __ Contact: Duane C. Johnson

LED7 Solar Tracker -  Schematic only, no circuit description __ Contact: Duane C. Johnson

LED-Based Message Display -  This LED-based message display is built around readily available, low cost components.  It is easy to fabricate and makes use of 3mm red LEDs.  A total of 172 LEDs have been...__ Electronics Projects for You

LED-Based Reading Lamp -  This lamp circuit using ultra-bright white LEDs provides sufficient light for reading purposes while consuming approximately 3 watts of power.  In the case of AC mains failure, the battery backup circuit...__ Electronics Projects for You

LED-Based Running Display -  Here is a circuit that creates an eye-catching running display effect using LEDs.  It can be used to light up borders of animations, pictures, etc, and also for short word displays.__ Electronics Projects for You

LED-Current Limiter Accepts AC or Dc -  07/14/11  EDN-Design Ideas Prevent excessive current from overdriving your LEDs.  LED drivers have lots of features and require plenty of external components.  When your application requires no PWM  (pulse-width-modulated) dimming or controlled frequency operation, your primary concern may be that too much current could damage or destroy your LEDs.  In this case, you can make a simple LED-current limiter from a common low-dropout linear regulator.  The circuit in Figure 1 is an LED light bulb for a landscape-lighting system.  Landscape lighting typically operates from 12V ac, and peak voltage is approximately 17V.  Because the regulator is in series with the LED string, the LED-string current equals the regulator’s output current.   __ Circuit Design by Roger Griswold, Micrel, San Jose, CA

LED-flashlight works at voltages as low as 0.5V -  09/23/10 EDN-Design Ideas Extend the life of alkaline batteries.    __ Circuit Design by GY Xu, XuMicro, Houston, TX

LEDMATRIX, a 80x32 pixel DIY LED matrix display -  The LEDMATRIX additionally includes a simple speaker allowing to e.g.  notify the user of a new message being displayed.  Furthermore a TSOP1736 IR receiver can optionally be connected.  This device receives and decodes the IR signals used by ordinary TV remote controls.  By returning informtion about received IR signals to the controlling PC, the displays contents may e.g.  be remotely changed using a simple spare IR remote control. __ Designed by Till Harbaum <Till @ Harbaum.org>

LEDs Flasher Alternately -  Classic astable multivibrator using 2 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.   __ Designed by Tony van Roon  VA3AVR

LEDs Indicate Sound Level -  08/25/11  EDN-Design Ideas Build a battery-operated portable meter to measure sound-pressure levels.   This Design Idea describes a battery-operated, portable soundlevel meter  (Figure 1) .  Its portability makes it useful for detecting the source of noise in automotive engines and power trains, factory machinery, and residential HVAC  (heating/ventilation/air-conditioning) systems __ Circuit Design by Stephen Kamichik, Ile Bizard, PQ, Canada

LED_Light_for_Tool_Shed -  I have a lean-to 8ft by 12ft shed next to my house.  It is full of lawn chemicals and garden supplies.  There were times when I needed to get something from inside the shed during the dead of night.  Early on I had to use a flashlight.  But later, I installed a series of five 12v LED light strips on the ceiling.  Each strip contained 15 3v white LEDs.  The strip had 5 strings of three LEDs, wired in series, with a 150 ohm current limiting resistor. . . . Hobby Circuit by David Johnson P.E.-July, 2017

LEDs Light LAN-Cable Tester -  12/02/10 EDN-Design Ideas A series of LEDs indicate the health of an Ethernet cable.  [Design Ideas by Noureddine Benabadji, University of Sciences and Technology, Oran, Algeria __ Circuit Design by Noureddine Benabadji, University of Sciences and Technology, Oran, Algeria

LEDs Light Up Digital POV Clock -  1-Apr-11 -Design News:   Steve RavetThis gadget, created with a dead hard drive, flashes softly glowing green digits. __ Gadget Freak

LEDs or Lamps Sequencer -  Very simple, versatile modular design No limits to the number of modules used in the ring __ Contact: Flavio Dellepiane, fladello @ tin.it

LEDs used as Photodiodes -  11/18/10 EDN-Design Ideas Ambient light changes an LED's resistance, making it act like a photodiode.  [Design Idea   by Raju R Baddi, Raman Research Institute, Bangalore, India __ Circuit Design by Raju R Baddi, Raman Research Institute, Bangalore, India

Left-Right Right-Left Running Lights -  Our ROCKERUD6 has many applications; fill your party with running, blinking ROCKERS.  Mount the ROCKER on your bicycle so you'll be more visible and have a safer ride when signaling.  Use as a sign on room door as an indicator of how way "cool" you are.  Place ROCKER anywhere you’d like to draw attention and a smile.  The unique small design will allow you to mount it almost anywhere.  Operate it with 9V battery, 12V car battery, four 1.5V batteries, or via one of our battery simulator kits.   __ Contact: Kit from Elich Industrial Development, Corp

 Lighthouse_Solar_Powered -  While at a discount store one day, I spotted an interesting tall lighthouse.  It had a tiny solar panel and an equally tiny LED light.  The LED was pointing downward, at the center of a rotating light reflector.  I thought it might be turned into an interesting addition to my wife’s garden. . . . Hobby Circuit by David Johnson P.E.-September, 2017

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

 


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