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LED (Light Emitting Diodes) Circuits   Page 2
LED:   #     A      B      C       D - E       F - H      I - K     L      M - O      P- R      S      T     U - V     W -Z

Last Updated on:
Tuesday, April 01, 2014 04:29 AM

Circuits Designed by Dave Johnson, P.E. :
  • AC Powered White LED Strings
    A while back a guy by the name of Ken Schultz sent me a simple drawing of how he connected a string of 30 LEDs, to make a nice under the counter accent light, powered by 120vac.  He wired the strings in two series sections of 15 LED each, but wired in opposite directions.  He then used just one capacitor to limit the AC current through the two stings.  I looked at the circuit and decided that it seemed quite reasonable.  The only change I decided to make was to add a metal oxide resistor in series with the capacitor, to act as fuse and to limit the peak current, should there be a voltage spike on the AC line.  With the two strings of 15, the current is first pumped through one series string, then as the AC line polarity changes, it flows through the second string. ...
  • AC Line Powered LED Pilot Light
    This 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.  (added 7/06)
  • AC LINE POWERED LED FLASHER NUMBER 3
    Some of the latest LEDs are amazing.  They can produce a surprising amount of light with very little current.  In the light flasher application shown below I take advantage of a nice surface mounted LED from King Bright.  This flasher circuit draws only about 3ua of average current from the AC power line to flash this green LED.  This flasher might be used as a power indicator light....

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

A Clock Design using the PIC16c54 for LED Displays & Switch Inputs -  Microchip Application Note Published 26-Aug-97.....[App Note]
A low power, long life LED flashlight circuit -  Scouring the Internet for information on LEDs, I accidentally stumbled upon a PDF detailing a flashlight made from PVC.....(project added 6/07)
A Step-Down Conversion Concept for a PWM-Mode Boost Converter -  TI Application Note  (added 2/06)
AC LEDs -  Some useful Circuits with LEDs using the AC voltage. (5/28/2006)
Ac Line Powered LED Pilot Light -  This 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.. [Designed by David A. Johnson]
AC Line Powered LED Strings -  This 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 Corner Circuit by Dave Johnson]
AC Line Powered LEDs -  The circuit above illustrates powering a LED (or two) from the 120 volt AC line using a capacitor to drop the voltage and a small resistor to limit the inrush current. Since the capacitor must pass current in both directions, a small diode is connected in parallel with the LED to provide a path for the negative half cycle..... [Bill Bowden]
Add switch-and-LED I/O to DSP's serial port  -  05/07/98 EDN-Design Ideas.....When you debug an embedded DSP design, it's handy to have a bank of switches and LEDs to simulate inputs or to display intermediate results. You can attach 16 switches and 16 LEDs to the data bus using octal latches and decoded address strobes. However, this connection can be a wiring nightmare.....NOTE  Page includes several designs, scroll to find this one..... [Design Idea by Stan Sasaki, Twenty-First Designs, Lake Oswego, OR Stan Sasaki, Twenty-First Designs, Lake Oswego, OR]
Adjustable flashing LED -  Use a 555 timer IC as the ASCII format  (resistor controlled) frequency source, choose component values to run at 2 x desired flash rate, get the data sheet for this part, it's pretty comprehensive. Use the output to clock a flip flop ASCII format  (e.g. 74HC74). Feed flip-flop Q and /Q outputs to simple transistor stages, vizASCII format  (circuit added 05/06/07)

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