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• 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 LINE TELEPHONE LINE STATUS INDICATOR
  This circuit is similar to the above circuit, but only monitors one phone line.

• 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)

• 12v Lamp Current Indicator
  This circuit turns on a LED indictor light whenever DC current flows into a 12v lamp. (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.

15V Battery Powers White LED Driver:  09/30/04 EDN Design Ideas  /  (added 1/05)  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....

16 Stage Bidirectional LED Sequencer:  (circuit added 7/02)

16x16 LED Matrix and Driver:  (circuit added 9/04)

18 Stage LED Sequencer:  (electronic (schematic / circuit added 11/05)

1a Flash LED Driver :  Sipex Application Note  (app note added 2/06)

1a Low Noise High Current LED Charge Pump with Independent Torch/Flash Current Control:  Linear Technology LT3216 (app note added 02/05)

2 Transistor 2 LED Flasher:  (circuit / schematic design added 6/06)

2 Transistor LED Flasher #1:  (circuit added 7/02)

2 Transistor LED Flasher #2:  (circuit / schematic design added 6/06)

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), so that  contacts are not exposed, but you can still plug and unplug it. Designed by Andrew R. Morris  (added 9/05)

27MHz to 67MHz Low-RF Single-Conversion Superhet Receiver:  Melexis Application Note  (app note added 2/06)

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)

40 LED Bicycle Light (555 Timer 6 Volt):  (circuit added 7/02)

7 by 10 LED Moving Sign ( 27c512 Eprom):  (electronic circuit added 4/05)

7 Segment LED Counter:  (circuit / schematic design added 6/06)

72 LED Clock:  (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. The table below shows  sequence for  LEDs. You can use less than eight LEDs if you wish and  table may help you decide which ones to use for your purpose. (added 6/06)

8 Stage LED VU Meter:  (electronic circuit added 10/05)

9 Second Digital Readout Timer:  (circuit added 7/02)

9 Second LED Relay Timer:  (circuit added 7/02)