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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.
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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.
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- 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.
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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.
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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.
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- AC Powered White LED Strings
NEW
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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FLASHING LED ADVERTISING BADGE
#1
I have seen numerous Flashing light badges at trade shows and conventions. They are often handed out as gifts to promote some business. The devices often use inefficient circuits, which
cause the battery power source to be quickly depleted. My circuit is simple but efficient enough to provide months of continuous LED Flashing. It also has a tiny push-button switch to turn
on and off the light Flashing, extending battery power.
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- Fake Car Alarm Light
Whenever the car’s ignition is turned off, this circuit activates a
flashing LED, which can be positioned to appear as an active alarm
system.
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High Power LED Flasher
Power LEDs are becoming
more popular these days. The DC input power to these devices ranges from 1
watt to 5 watts. Normal LEDs only receive about 0.05 watts. At this higher
power, these devices can emit a lot of light. You can buy them in just
about any color in the rainbow but white seems to be the most popular. One
application for these devices is a flashing light. If the flash duration
and flash rate is kept low, the average current can be low enough that even
a small battery can last quite a while.....
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- Universal LED Flasher
This low power LED flasher circuit draws about 100ua from any DC power supply ranging from 3 volts to 24 volts. The 1.0Hz
10ms LED pulsed current is held to a constant 10ma.
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Universal 3v LED Flasher
NEW
The circuit below will
flash any LED color with fixed current pulses powered by a 3v battery. It
uses a charge pump approach, which routes a constant current pulse through
the LED, regardless of the LED voltage requirement. Using this approach,
white and blue LEDs, which normally require about 3.6v can be flashed with a
3v battery. With the component values selected, the LED is hit with 15ma
current pulses lasting about 10ms every two seconds. This keeps the average
current draw from a 3v battery to about 200uA. The circuit relies on a
cheap 74HC14 hex Schmitt trigger inverter IC. One inverter forms a pulse
generating oscillator. Other inverters are ganged together to increase the
drive current. A two transistor circuit forms a constant sinking current
controller.
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WHITE LED
NIGHT LIGHT
This simple circuit is designed to plug into a standard AC electrical outlet. It uses four super bright white light emitting diodes (LED) in conjunction with a capacitor coupled full
wave rectifier circuit. The LEDs are mounted in a box and are angled slightly to bounce the light off of a nearby wall. The light should last about 10 years. The circuit draws
less than one half of one watt of power and can therefore run continuously. In spite of the low power, the LEDs provide sufficient illumination for most night light applications.
Circuit component values for both 120vac and 240vac are shown.
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