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

Last Updated: December 07, 2017 02:05 PM

Circuits Designed by Dave Johnson, P.E. :
20 LED Night Light -  After 3 years of continuous 24/7 operation I noticed that the 20 LED array I was using as a night light next to my back door was fading.  Some of the LEDs were much dimmer than others.  I figured that over time, the internal heat dissipated from the LED chip was causing the LED light intensity to fade.  I decided it was time to replace the light. . . . Circuit by David Johnson P.E.-July, 2017

4_D-Cell_LED_Lantern_Modified -  While shopping at a sporting goods store one day, I spotted a compact LED lantern.  It looked like the kind of lantern I could modify. The lantern LEDs were grouped into three sections of 7 LEDs each, oriented into 120 degree angles.  The LEDs were standard T 1-3/4 epoxy types.  The lantern had a three mode switch which selected between off, full power and half power modes.  At the half power mode, only half of the 21 LEDs were illuminated.  At full power all LEDs were illuminated. . . . Hobby Circuit by David Johnson P.E.-September, 2017

8 Solar Cell LED Light -  I have been modifying a lot of solar garden and path lights for the last several years.  I buy some units from home improvement stores, then I gut them completely.  I take out the battery, electronic control board, LED and solar panel.  I then replace those components with new units.  I increase the size of the solar panel and battery.  I use a more efficient and brighter LED . . . Circuit by David Johnson P.E.-September, 2017

 

24 Volts AC to 24 Volts DC Power SupplyThe idea for the circuit below came from a company needing to power several 24v DC LED assemblies from an existing 24vac supply.  They did not need a rock solid and regulated 24 volts but a voltage which hovered around that voltage.  Running the AC through . . . Hobby Circuit designed by David Johnson P.E.-February, 2011

 24V DC Powered Beeper with 4 Separate Inputs24vac 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 A. Johnson P.E.-December, 2009


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

16 LED Chaser -  By request, here is a 16 LED sequential chaser.  The LED's light one at a time, sequencing from bottom to top, then back down from top to bottom.  This circuit must be driven from some kind of clock generator.  Each pulse from the clock changes which LED is lit.  This circuit has been prototyped by Tony Hullibarger.  Thanks to Tony, errors were found and corrected! __ Designed by billd @ reprise.com

16 Stage Bidirectional LED Sequencer -  The bi-directional sequencer uses a 4 bit binary up/down counter    (CD4516) and two "1 of 8 line decoders"    (74HC138 or 74HCT138) to generate the popular "Night Rider" display.  A Schmitt Trigger oscillator provides the clock signal for the counter and the rate can be adjusted with the 500K pot.  Two additional Schmitt Trigger inverters are used as a SET/RESET latch to control the counting direction    (up or down) .  Be sure to use the 74HC14 and not the 74HCT14, the 74HCT14 may not work due to the low TTL input trigger level.  When the highest count is reached    (1111) the low output __ Designed by Bill Bowden

16x16 LED Matrix & Driver -  In the early '80s, I read some articles on LED arrays.  They described using arrays of 64 or more LEDs as crude oscilloscopes and other interesting things.  I decided I'd make one myselfa really big array, 256 LEDs arranged as 16 columns by 16 rows.  In 1983, while I was in my final semester of electronics classes at Monterey Peninsula College, I designed my array.  I wanted a high-density array, in part to make the PC board smaller, but mainly to give a better appearance.  So, I used the smallest LEDs I could find, 2mm x 2.5mm.  I was lucky and found that All Electronics was selling them in 200-packs for something like $20.  I bought two packsa fair sum for me at the time __ Designed by John DuBois

18 LED dimmable LED lamp -  This circuit is a dimmable white LED lamp array with 18 LEDs.  The lamp brightness is regulated as long as the input voltage is above 10.5V.  A low-dropout analog voltage regulator is used for a simple and relatively efficient __ Designed by G. Forrest Cook

18 Stage LED Sequencer -  The question sometimes comes up of how to cascade 4017 decade counters for more than 10 sequencial stages.  The LED sequencer above shows a possible solution using a few extra parts.  When power is applied, the 15K resistor and 10uF cap at pin 15 will reset the counters to the zero count where pin 3 is at +12 and all other outputs are at zero.  The 2 diodes    (1n914) and 15 resistor form a AND gate so the clock pulse will be passed to the right side counter when the sequence starts.  When the right counter reaches the 10th count, .   __ Designed by Bill Bowden

1a Low Noise High Current LED Charge Pump with Independent Torch/Flash Current Control -  LT3216__ Linear Technology/Analog Devices

1-NiMH
Cell powers White LED
-  There are a lot of white LED driver circuits floating around.  A popular circuit called the “Joule Thief” can drive one white LED from a single 1.2v or 1.5v battery cell.  Most of these circuits use one or two transistors to form a voltage boost circuit . . . Hobby Circuit designed by David Johnson P.E.-September, 2009

1us LED Pulse Driver + Voltage to Frequency Converter -  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 . . . Hobby Circuit designed by Dave Johnson P.E.-March, 1999

1W White LED Night Light -  As many of you know, I have a pet peeve with poorly made LED night lights.  Often, the light from the LED quickly fades, so within months, the light is useless.  I have posted several versions of modified night lights using higher quality components.  This circuit is yet another version, which produces much more light than those other designs. . . . Hobby Circuit designed by David A. Johnson P.E.-November, 2008

2 LED trouble light systE - M -  No circuit description, schematic only__ CdS Electronic

2 LEDs Perform Rudimentary Spectral Analysis -  09/01/94 EDN-Design Ideas A pair of LEDs having different wavelengths can supply the stimulus for a rudimentary spectral analysis during quality-control sorting operations.  By measuring the reflectance of each LED, the circuit in Fig 1 can provide information about the spectral response of the object under test.  The circuit's __ Circuit Design by Peter Bojilov, Isomatik Sortex Ltd, Pazardjik, Bulgaria

2 PIC pins drive six LEDs -  06/09/14 EDN-Design Ideas Here’s a take on LED multiplexing with minimal output pins.  This Design Idea demonstrates a new method of driving six LEDs with only two I/O lines from a microcontroller, and so is particularly suitable for any pin-limited chip.  It uses a pair of I/O lines combined with a pair of complementary bipolar transistors.   __ Circuit Design by Benabadji Noureddine

2 Signals Easily Control Tricolor LED -  09/14/95 EDN-Design Ideas Tricolor LEDs come in two- and three-pin packages.  Although the three-pin, or common-cathode, package easily lends itself to 2-bit control, wiring three crowded pins can be mechanically difficult.  Also, fewer manufacturers produce the three-pin types.  The two-pin package is easier to connect to a wiring harness and is readily available.  However, this package requires more control overhead, because, to light the LED yellow, the device must continuously alternate between red and green.   __ Circuit Design by Bob Richards, Digital Audio Corp, Raleigh, NC

2 Transistor Flasher -  The basic two-transistor flasher shown below has found its way into dozens of applications due to its simplicity and versatility.  Applications have included such diverse circuits as a micropower low battery indicator, a lightning detector, a off-line.   __ Contact: Charles Wenzel of Wenzel Associates, Inc.

2 Transistor LED Flasher -  This 1.5 volt led fasher runs more than a year on a single 'd" cell and alternately flashes 2 LEDs at about a 1 second rate.  The circuit employs a 74HC14 CMOS hex inverter that will operate at very low voltages    (less than 1 volt) .  One section is used as a squarewave oscillator    (pins 1 and 2) , while the others are wired to produce a short 10mS pulse on alternate edges of the square wave so the LEDs will alternate back and forth.  The output sections each use a capacitor charge pump to increase the voltage for the LEDs __ Designed by Bill Bowden

2 Transistor LED Flasher -  This circuit will flash a bright red LED as an attention getting device or fake care alarm. __ Designed by Bill Bowden

2 Transistor LED Flasher -  This is a classic 2 transistor astable multivibrator.  Many other NPN small signal or switching transistors can be used, including 2N4401, PN2222 or 2N2222 using the circuit on the left.  The circuit can also be inverted using PNP transistors.   __ Designed by Bill's Electronics Reference Library

2 Transistor LED Flasher -  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

2 Transistor LED Flasher 1 -  Circuit Only __ Designed by Tony van Roon  VA3AVR

2 Transistor LED Flasher 2 -  This circuit will flash a super-bright LED  (5000+ mcd) .  Good for fake car alarm or other attention getting device.  Component values are not critical, try anything else first from your junkbox.  Obviously, the 470 ohm resistor  (R3) determines the LED's brightness and limits the current flow to about 20mA.390 ohm can also be used as a save value.  If you decide to go with a green or yellow led, which draw more current, you may want to replace the 470 ohm with an appropriate value.  Flash rate is determined by R2 and C1 __ Designed by Tony van Roon  VA3AVR

2 transistor lights LEDs -  04/09/09  EDN-Design Ideas A previous Design Ideasdescribes a circuit that uses an astable multivibrator to drive an LED    (Reference 1].  The circuit in Figure 1 uses a simpler alternative approach.  The circuit uses a 2N3904 NPN transistor and a 2N3906 PNP trans __ Circuit Design by Barry A Tigner, Michigan State University, East Lansing, MI

20mA LED Ballast -     (corrected text) I use this circuit for general use to power white LEDs, like a headset light I use on my desk and a keyboard light for my computer.  I built it into a tiny Radio Shack project box    (270-288) , which y no longer sell.  I put heat-shrink tubing  __ Designed by Andrew R. Morris

20 LED Night Light -  After 3 years of continuous 24/7 operation I noticed that the 20 LED array I was using as a night light next to my back door was fading.  Some of the LEDs were much dimmer than others.  I figured that over time, the internal heat dissipated from the LED chip was causing the LED light intensity to fade.  I decided it was time to replace the light. . . . Circuit by David Johnson P.E.-July, 2017

220v AC Powered Blinking Led -  I needed a pulsating light for a certain signaling.  Voltage was 230V.  So I decided to make a simple circuit, consisted of a LED diode, two capacitors, two resistors, a diac and a diode.  Activity of the circuit is extraordinarily simple.  The capacitor charges by the diode and the resistor.  When the voltage on the

220V Blinking LED -  This is a simple blinking led circuit powered from 220V that can be used to mark special places or as voltage indicator.  The voltage from the mains charges the capacitor through R1 resistor and D1 diode.  

230V Rotating & Blinking LED -  This design can be of some interest for those wanting striking light signs, as it can drive up to three 230V lamp strings in three operating modes.  The 15V dc supply is obtained from a nominal 230/24V center tapped ac transformer    (T1) and a full wave rectifier __ Contact: Flavio Dellepiane, fladello @ tin.it

24 Volts AC to 24 Volts DC Power Supply -  The idea for the circuit below came from a company needing to power several 24v DC LED assemblies from an existing 24vac supply.  They did not need a rock solid and regulated 24 volts but a voltage which hovered around that voltage.  Running the AC through . . . Hobby Circuit designed by David Johnson P.E.-February, 2011

24V DC Powered Beeper with 4 Separate Inputs -  24vac 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 A. Johnson P.E.-December, 2009

25 LED Chaser (Sequencer) -  A Fairly Simple C-Mos Circuit.   __ Designed by G.L. Chemelec

25 Light Sequencer using Xmas Lamps -  This circuit above can drive 25 small Xmas lights.  The lights operate at about 200mA and 3 volts.  The supply voltage is set to 5 volts and the 4017 counter output will drop about a volt using the 2N3053 transistors.  The voltage on the emitters of the rows transistors will be about 0.7 volts less than the base so the lamp voltage will be about 3 volts.  You can __ Designed by Bill Bowden

28 LED Clock -  This is a programmable clock timer circuit that uses individual LEDs to indicate hours and minutes.12 LEDs can be arranged in a circle to represent the 12 hours of a clock face and an additional 12 LEDs can be arranged in an outer circle to indicate 5 minute intervals within the hour.4 additional LEDs are used to indicate 1 to 4 minutes of time within each 5 minute interval.   __ Designed by Bill Bowden

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


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