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LED (Light
Emitting Diodes) Circuits Page 2
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Last Updated on:
Monday, October 03, 2011 06:07 PM |
| Circuits Designed by
Dave Johnson, P.E. : |
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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. ...
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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)
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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....
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Links to electronic circuits,
electronic schematics, designs for engineers, hobbyists, students & inventors:
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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] |
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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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