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LED (Light Emitting Diodes) Circuits   Page 1
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Last Updated on: Thursday, October 30, 2014 09:22 AM

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.
  • 3V BATTERY POWERED WHITE LED DRIVER
    The circuit below will drive any LED color, including white LEDs, using a DC power supply ranging from 2v to 3.3v.  White and blue LEDs normally require over 3v, so the circuit below uses a charge pump scheme to deliver a constant LED light intensity from a voltage less than 3v.  The LED is rapidly pulsed with 3ma peak current, which remains fairly constant, even as the battery voltage changes.  The circuit is designed only for low LED current applications.  A common CR2032 lithium coin battery should run the light for two days.  A pair of 2.5 amp-hour AA NiMH cells should operate the circuit for nearly a month.

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

“Chipiplexing” efficiently drives multiple LEDs using few microcontroller ports -  27-Nov-08 Issue of EDN  "Chipiplexing" approach simultaneously drives two LEDs..... [Design Idea by Guillermo Jaquenod, La Plata, Argentina]
µP Displays 10 Bit Data on Three LEDs -  11/07/96 EDN-Design Ideas.....circuit in Figure 1 uses a PIC16C55 µP to read 10-bit binary data and directly display  data in decimal format on three common-cathode LED displays. If value of  data exceeds 999,  displays show three hyphens (---) to represent overflow.  PIC16C55 has high drive..... [Design Idea by Yongping Xia, Philips Lighting Electronics, Torrance, CA]
0.3-1.5V LED Flashlight -  It's a little wisp of a circuit that allows you to drive a blue or white LED from a low voltage. Normally, if you want to light up a blue or white LED you need to provide it with 3, 3.5 V, like from a 3 V lithium coin cell. But a 1.5 V battery like a AA cell simply will not work. But using the Joule Thief, it works like a charm. Not only does it work with a brand new battery, but it works until the battery is nearly dead-- down to 0.3 V. ....
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.  (added 12/04). …. [Designed by David A. Johnson]
0.6/1.6 MHz Boost Converters with 22V Inrternal FET Wsitch in SOT-32 -  National Semiconductor Application Note LM2731 July 2003.....[App Note]
1 Line Telephone Line Status Indicator -  This circuit is similar to the above circuit, but only monitors one phone line..... [Designed by David A. Johnson]
1.2MHz White LED Step-Up Converters with Built-In Schottky in ThinSOT -  Linear Technology LT3465 Switching Regulator (app note added 6/06)
3V BATTERY POWERED WHITE LED DRIVER - The circuit below will drive any LED color, including white LEDs, using a DC power supply ranging from 2v to 3.3v.  White and blue LEDs normally require over 3v, so the circuit below uses a charge pump scheme to deliver a constant LED light intensity from a voltage less than 3v.  The LED is rapidly pulsed with 3ma peak current, which remains fairly constant, even as the battery voltage changes.  The circuit is designed only for low LED current applications.  A common CR2032 lithium coin battery should run the light for two days.  A pair of 2.5 amp-hour AA NiMH cells should operate the circuit for nearly a month. [Dircuit designed by David A. Johnson, P.E.]

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