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LED Voltage Indicator - This teensy little board is only 1 inch (25mm) square, and
is handy as a combined power on and low battery voltage indicator. The two colour LED
changes from green to red when the battery voltage drops below the adjustable trigger
voltage. It's usable between about 6V and 30VDC, and uses a precision LM336Z-2.5
voltage reference. The LED can be reversed so it changes from green to red if the
preset voltage is exceeded, if required. (circuits added 09/05) |
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LED Voltmeter - Measures voltages up to 199.9V with 0.1V resolution.
(circuit added 8/06) |
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LED Voltmeter Expanded Scale (ideal for your car) - Its Useful to see the charge
voltage. This Helps in detecting a Bad Alternator before it creates a dead
battery....(electronic schematic added 12/08) |
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LED VU Meter - The circuit is completely conventional, and is based on the
application notes from National Semiconductor. The circuit is shown in Figure 1 and as
you can see it uses a single IC and a few discrete components. The extra diode (D3) is
included to ensure that the DC to the LEDs is almost unfiltered..... (schematic added
6/07) |
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LED Zeppelin - The name of our game, LED Zeppelin, is a play on words. It comes
not from the pop group of the same name but from Graf Von Zeppelin, a German who
invented the first rigid air ship in 1900. The association fits perfectly. The
game consists of six LEDs and an indicator LED that flashes at a rate of about 2
cycles per second. A push button is the "Operations Control" and by carefully pushing
the button in synchronisation with the flashing LED, the row of LEDs will gradually
light up....(electronic circuit added 2/07) |
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LED7 Solar Tracker - (electronic circuit added 7/03) |
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LED-Based Message Display - (electronic Circuit / Schematic added 10/04) |
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LEDs Flasher Alternately - Classic astable multivibrator using2 transistors.
Transistor is not critical. Try these:2N4401,2N2222, NTE123A, NTE123AP, NTE159, TUP/TUN
and those in your junk box, you may find that most of them will work. (added 4/02) |
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LEDs or Lamps Sequencer - Very simple, versatile modular design No limits to the
number of modules used in the ring (added 9/04) |
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Light a White LED from Half a Cell - 06/12/03 EDN Design Ideas /
(added 1/05) Whether you use them as indicators or to provide illumination, LEDs
are hard to beat in efficiency, reliability, and cost. White LEDs are rapidly gaining
popularity as sources of illumination, as in LCD backlights, but with forward voltages
typically ranging from 3 to 5V, operating them from a single cell presents obvious
difficulties.... |
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Light Pollution Meter - LED brightness control circuit and a millimeter to compare
light levels to LED level. (added 6/07) |
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Lighthouse LED Flasher - This was originally designed for a model in a HO train
set. It simulates the behavior of the light from a lighthouse. The LED
intensity gradually increases, then flashes with a bright light and finally decreases
slowly in intensity. ….(designed by David A. Johnson) |
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Lighting Management System for Six White LEDs and One RGB or Flash LEDs - National
Semiconductor Application Note LP3936 June 2004 (app note added 02/05) |
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Lighting Management System for Six White LEDs and Two RGB or Flash LEDs - National
Semiconductor Application Note LP3933 March 2004 (app note added 02/05) |
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Line Powered White LEDs - The LED circuit above is an example of using 25 white
LEDs in series connected to the 120VAC line. It can be modified for more or less LEDs
by changing the R value. The exact resistance value will depend on the particular LEDs
used. In operation, a DC voltage of around 170 is produced from the bridge rectifier
and 50uF capacitor. The capacitor value is not critical ...(electronic circuit added
1/06) |
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Linear Constant Current LED Lamp Dimmer - This circuits drives24 white light LEDs
with an adjustable constant current. (added 4/02) |
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Linear-brightness controller for LEDs has 64 taps - (Design Ideas - EDN, 3/15/2007
Digital potentiometer controls the brightness of LEDs. (electronic design idea added
9/2008) |
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Line-powered driver lights up high-power LEDs - 6/8/06 EDN Design Ideas
/ (added 11/06) LED array reduces power and maintenance expenses. |
