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LED (Light Emitting Diodes) Circuits   Page 1
LED:   #     A      B      C       D - E       F - H      I - K     L      M - O      P- R      S      T     U - Z
Last Updated on: Friday, March 12, 2010 12:07 PM

Circuits Designed by Dave Johnson, P.E. :
  • 0.5V Negative Supply
    Although not very efficient, this simple circuit, consisting of two LEDs and a photo diode, generates a negative voltage with a current level of a couple milliamps.  It is ideal for supplying a negative rail to low power “rail to rail” op amp circuits, which need to have a true zero volts output.
  • 1.5V LED Flasher VERSION A
    Many published circuits that Flash LEDs need 3 volts or more. This circuit uses only a single inexpensive C-MOS IC and Flashes the LED for a full year on a single 1.5 volt AA alkaline battery cell. The circuit uses a charge pump technique to provide the LED the needed voltage.
  • 1.5V LED Flasher VERSION B
    To 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.
  • 1W White LED Night Light  NEW
    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. The circuit brings together two high power white LEDs made by Cree with a compact AC to DC power supply from Bias Power.....
  • 2 LINE TELEPHONE LINE STATUS INDICATOR
    Many home businesses use multiple phone lines. This circuit gives you a visual indication when a line is in operation. The two AA battery cells should provide enough power for about one year of operation. The circuit is line polarity insensitive.
  • Super Bright 3v Powered LED Flasher
    I have posted several kinds of LED flashers over the years.  This is yet one more flasher, designed to flash any high power LED of any color.  It hits the LED with a 25ms 250ma pulse once every 2 seconds.  This works out to an average current about 3ma.  It is powered by any 3v source.  I suggest two AA cells but a single 3v lithium coin type cell will also work.  With fresh AA cells, the light should flash for about two weeks.  The light flash is very intense and is perfect for any attention getting night time application.....
  • 9v Battery Voltage Monitor
    This circuit turns on a LED whenever the voltage of a standard 9v battery connected to the circuit drops below 7.2 volts.  It uses a LTC1440 comparator, which also contains a 1.18v reference diode.  In standby mode, the circuit draws only 4uA. (added 7/06)
  • 40KHz TV-VCR LIGHT SOURCE REPEATER
    This circuit is designed to be placed directly in front of a standard TV or VCR remote. The exiting light pulses produced by the circuit match the pulses from the remote but are about 10 times more powerful. Using the device, the remote can operate a TV or VCR over three times the normal distance.

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

10 LED Chaser - I don't know why, but people like blinking lights. You see LED chasers everywhere, in TV shows (Knight Rider), movies, and store windows. This schematic is my version of a simple 10 LED chaser. There is no 555 timer used because...(electronic design added 09/08)
10 LED Sequencer - in PDF format, text in Finnish (added 4/02)
10 Stage LED Sequencer (Bowden) - The 4017 is a CMOS decade counter with 10 decoded outputs.  Inputs include a clock (pin 14), a reset (pin 15), and a clock inhibit (pin 13)….(design added 5?09)
10 Stage Light Sequencer - schematic only -- flashes 10 low voltage bulbs, operates at10-25-Volt voltage, in PDF format, text in Finnish (added 4/02)
10, 8 & 6 Step LED Circuits CD4017 - (electronic circuit added 05/07)
100ma UltraLow Noise Charge Pump LED Supply with Output Current Adjust - Linear Technology LTC3201 (app note added 02/05)
11 Channel LED Sequencer - based on4017 (added 4/02)
11 to 100 LED Sequencer Using a Matrix  - The circuit above illustrates using a 10x10 matrix to sequence up to 100 LEDs with just three ICs and 20 transistors. The two 4017 decade counters control the 10 rows and 10 columns so that one LED is selected depending on the output of the decade counters. The LED circuit is drawn showing 25 LEDs and 10 transistors but can be expanded up to a 100 by using sucessive stages of the 4017 counters. For example, to expand the circuit to 60 LEDs for displaying minutes or seconds of a clock, the rows counter could be reset from pin 12 (carry out) rather than pin 1 as shown, and the columns..(electronic design added 6/07)
12 Stage Neon Sequencer NE 2/NE 51 - This circuit is similar to the LED clock using 12 neon indicator lamps instead of LEDs. It operates from 2 high capacity ni-cad cells (2.5 volts) which keep it going for a couple weeks. High voltage (70 volts) for the neon lamps is obtained from a small switching power supply using a 74HC14 Schmitt trigger squarewave oscillator, high voltage switching transistor.....(added 4/02)
121 & 240Vac LED Voltage Indicator - Useful for power lines control.  Simple, transformerless circuitry.  (electronic circuit added 6/07)
12v Lamp Current Indicator - This circuit turns on a LED indictor light whenever DC current flows into a 12v lamp. (added 7/06) ….(designed by David A. Johnson)
13 Color LED Rainbow - ….(design added 03/08)
13 Volt Lamp Dimmer (using a pot) - Here is a 12 volt / 2 amp lamp dimmer that can be used to dim a standard 25 watt automobile brake or backup bulb by controlling the duty cycle of a astable 555 timer oscillator. When the wiper of the potentiometer is at the uppermost position, the capacitor will charge quickly through both 1K resistor....(added 05/09)
13 Volt Lamp Fader (LEDs or incandescent) - This circuit is similar to the "Fading Red Eyes" circuit (in the LED section) used to fade a pair of red LEDs. In this version, the lamps are faded by varying the duty cycle so that higher power incandescent lamps can be used without much power loss. The switching waveform is generated by comparing two linear ramps....(electronic schematic / circuit added 05/09)
15V Battery Powers White LED Driver - 09/30/04 EDN-Design Ideas: Although white LEDs are common in a variety of lighting applications, ir 3 to 4V forward-voltage drop makes low-voltage applications challenging. Charge pumps and or ICs are available for driving white LEDs, but y generally don't work with  low supply voltage of 1.5V in single-cell-battery applications.....(design idea added 1/05)
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...(circuit added 7/02)
16x16 LED Matrix & Driver - (circuit added 9/04)
17 LEDs Bar - (circuit / schematic design added 11/06)
18 LED Preset Followers - (electronic circuit added 11/06)
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, pin 11 will move high enabling the AND gate on the right to pass...(electronic schematic / circuit added 11/05)
1a Low Noise High Current LED Charge Pump with Independent Torch/Flash Current Control - Linear Technology LT3216 (app note added 02/05)
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. The circuit brings together two high power white LEDs made by Cree with a compact AC to DC power supply from Bias Power..... ….(designed by David A. Johnson)
2 Line Telephone Line Status Indicator - Many home businesses use multiple phone lines. This circuit gives you a visual indication when a line is in operation. The two AA battery cells should provide enough power for about one year of operation. The circuit is line polarity insensitive. ….(designed by David A. Johnson)
2 Transistor 2 LED Flasher - (Tony van Roon's circuit / schematic design added 6/06)
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(circuit / schematic design added 6/06)
2 Transistor LED Flasher (Bill Bowden) - This circuit will flash a bright LED (500 mcd) as an attention getting device or fack car alarm.  Component values are not cirtical and other transistors may be…...(circuit added 7/02)
20ma LED Ballast - 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 around  female output connector (RS P/N 273-1743), ....Designed by Andrew R. Morris  (added 9/05)
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....(electronic design added 09/08)
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 ....(schematic added 02/09)
28 LED Clock Timer 72 LED Clock - programmable clock Timer circuit that uses individual LEDs to indicate hours and minutes (added 4/02)
3-Colour Display using Bicolour LEDs - (electronic Circuit / Schematic added 10/04)
3V LED Chaser - ….(electronic schematic added 03/08)
40 LED Bicycle Light 555 Timer 6 Volt - The 555 circuit below is a flashing bicycle light powered with four C,D or AA cells (6 volts). Two sets of 20 LEDs will alternately flash at approximately 4.7 cycles per second using RC values shown (4.7K for R1, 150K for R2 and a 1uF capacitor). Time intervals for the two lamps are about 107 milliseconds (T1, upper LEDs) and 104 milliseconds (T2 lower LEDs)....(circuit added 7/02)
40kHz TV-VCR Light Source Repeater - This circuit is designed to be placed directly in front of a standard TV or VCR remote. The exiting light pulses produced by the circuit match the pulses from the remote but are about 10 times more powerful. Using the device, the remote can operate a TV or VCR over three times the normal distance. ….(designed by David A. Johnson)
5 Lamp/ LED Flash Driver - (schematic added 09/08)
555 timer drives multiple LEDs from one NiMH cell - 10/02/08 EDN-Design Ideas: ,  Using a CMOS 555 timer, you can drive seven high-brightness LEDs from a single 1.25V cell.....(design idea added 08/09)
5x7 Display - Sit back and take a big breath. You are about to take part in one of the best microcomputer (microprocessor) projects you have seen. It uses a PIC16F84 micro and you will be shown how to program the chip to create quite amazing effects. It's a simple project and you will be starting at the beginning of programming, so don't worry if you have never worked with a microprocessor before....(added circuit 05/07)
60 LED Clock - As you can see see we have changed the circuit a little. For example, the 4093 NAND gate is now set to exactly 1 second clock pulses. The clock rate is determined by the resistor and capacitor combination on the 4093. If the resistor is 220k ohms and the capacitor is 4.7uf then ….(added 08/08/08)
60 LED Clock (Bowden) - 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....(added 6/07)
60 Watt Lamp with Auxiliary 14v LED Lamp - This circuit controls power to a standard 60 watt lamp plus generates an auxiliary 14v DC supply which can power an automotive style 12 LED array.  (added 7/06) ….(designed by David A. Johnson)
7 by 10 LED Moving Sign 27c512 Eprom - This sign I designed uses no microprocessor. It has an eprom and multiple counters. As in most electric signs, the LEDs are matrixed, and strobed very quickly….(electronic circuit added 4/05)
7 Segment LED Counter (Aaron Cake) - This simple counter can be used to count pulses, as the basis for a customer counter (like you see at the doors of some stores), or for anything else that may be counted. The circuit accepts any TTL compatible logic signal, and can be expanded easily (see Notes).....(circuit / schematic design added 7/02)
72 LED Clock (bowden) - In the circuit above, 60 individual LEDs are used to indicate the minutes of a clock and 12 LEDs indicate hours. The power supply and time base circuitry is the same as described in the 28 LED clock circuit above. The minutes section of the clock is comprised of eight 74HCT164 shift registers cascaded so that a single bit can be recirculated through the 60 stages i....(circuit added 7/02)
8 Random Flashing LEDs - This project flashes eight LEDs in an apparently random manner. It uses a 4060 combined counter and display driver IC which is designed for driving 7-segment LED displays. The sequence is not really random because seven of  LEDs would normally be  display segments,  eighth LED is driven by an output that is normally used for driving furr counters.... (added 9/05)
8 Stage LED VU Meter - The circuit below uses two quad voltage comparators (LM339) to illuminate a series of 8 LEDs indicating volume level. Each of the 8 comparators is biased at increasing voltages set by the voltage divider so that the lower right LED comes on first when the input is about 400 millivolts or about 22 milliwatts peak in an 8 ohm system. The divider voltages are set so that each LED....(electronic circuit added 10/05)
9 Second LED Relay Timer - This circuit provides a visual 9 second delay using a 7 segment digital readout LED. When the switch is closed, the CD4010 up/down counter is preset to 9 and the 555 timer is disabled with the output held high. When the switch is opened,....(circuit / schematic design added 6/06)
9v Battery Voltage Monitor - This circuit turns on a LED whenever the voltage of a standard 9v battery connected to the circuit drops below 7.2 volts.  It uses a LTC1440 comparator, which also contains a 1.18v reference diode.  In standby mode, the circuit draws only 4uA. (added 7/06) ….(designed by David A. Johnson)

 
LED:   #     A      B      C       D - E       F - H      I - K     L      M - O      P- R      S      T     U - Z
 
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