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1.5V LED Flasher Version A
Many published circuits that Flash LEDs need 3 volts
or more. This circuit uses only a single inexpensive C-MOS IC and Flashes the
LED for a full year on a single 1.5 volt AA alkaline battery cell. The circuit uses
a charge pump technique to provide the LED the needed voltage.
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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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1W White LED Night Light
As many of you know, I have a pet peeve with poorly made LED night lights.
Often, the light from the LED quickly fades, so within months, the light is useless.
I have posted several versions of modified night lights using higher quality
components. This circuit is yet another version, which produces much more light than
those other designs. The circuit brings together two high power white LEDs made by
Cree with a compact AC to DC power supply from Bias Power
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2 Line Telephone Line Status Indicator
Many home businesses use multiple phone lines. This circuit gives you a visual
indication when a line is in operation. The two AA battery cells should provide
enough power for about one year of operation. The circuit is line polarity
insensitive
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24VAC Powered White LEDs
24vac is a popular voltage. It is often used in low voltage lighting systems
and industrial controls. It is much less dangerous than 120vac/240vac line
voltages. The circuit below is one method to efficiently power a cluster of 7
white LEDs from 24vac. It uses a classic bridge rectifier and filter capacitor
to convert the AC to DC
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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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60 Watt Lamp with Auxiliary 14v LED Lamp
This circuit controls power to a standard 60 watt lamp plus generates an auxiliary
14v DC supply which can power an automotive style 12 LED array. (added 7/06)
….
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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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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 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
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Battery Free LED Flasher
LED flashers have been used for a wide variety of applications. Some flasher
units have been used in food and hardware stores, to draw attention to sale items
and are often attached to boxes which dispense product discount coupons. Typically,
as the illustration below depicts, these simple units have a red LED, on each side
of the housing. Inside, is a battery and flasher circuit
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Constant Current LED Driver
Bob Pease from National Semiconductor came up with this circuit and I have used it
many times. It maintains a constant current through one or more LEDs. A
single resistor controls the desired current
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Constant Current LED Driver 5
LEDs are current driven devices. The light they produce is proportional to the
current flowing though them. One way to maintain a fairly steady light output
is to keep the current through the LED fixed, even as the supply voltage may change.
A classic way to do this is shown below. This works fairly well but it has two
weaknesses.
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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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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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Flashing LED Advertising Badge #2
This circuit is similar to schematic Flashing LED Advertising Badge #1. It
uses a CD4013 dual D Flip/Flop IC. The 74HCT74 IC in Flashing LED Advertising
Badge #1 does not always work. As in Flashing LED Advertising Badge #1, a
single lithium battery will provide months of continuous LED flashing. It also
has a tiny push-button switch to turn on and off the light flashing
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High Intensity Line Powered LED Flasher
There are times when you would like to generate an intensely bright flash of light
using electrical power from the AC line. The circuit below can drive a one to
three watt power LED with about 350ma of peak current. Since the circuit
drives the LED with a constant current, any LED color can be used. I have also
shown how you could use an array of 7 LEDs, wired in parallel. This array may not
produce as much light as the single power LED but the array would be cheaper to
build
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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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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. ….
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Line Powered White LED Array
There has been a lot of excitement lately in the lighting industry. Some
companies are beginning to manufacture general lighting fixtures, which replace
incandescent and fluorescent lamps, using LED lights. When proper heat
management is designed into the light fixtures, these LED lights can produce more
light with less electricity and last much longer than other devices. They can
also operate well in cold temperatures. Some of these new lighting fixture
designs use a large number of white LEDs, wired into long series wired string
arrays. The circuit below is designed to provide a regulated DC voltage for
these strings.
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Line Powered White LED Array
There has been a lot of excitement lately in the lighting industry. Some
companies are beginning to manufacture general lighting fixtures, which replace
incandescent and fluorescent lamps, using LED lights. When proper heat
management is designed into the light fixtures, these LED lights can produce more
light with less electricity and last much longer than other devices. They can
also operate well in cold temperatures. Some of these new lighting fixture
designs use a large number of white LEDs, wired into long series wired string
arrays. The circuit below is designed to provide a regulated DC voltage for
these strings. [circuit of the week]
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Pot Controlled Variable LED Intensity Circuit
The circuit below uses power from four rechargeable AA NiMH cells to drive 3 white
LEDs. A potentiometer varies the duty cycle of a pulse width modulator circuit
to vary the intensity of the LEDs from 0% to 100%. The beauty of the circuit
is that when the pot is all the way toward 0%, very little power is drawn from the
battery. Likewise, when the pot slider is moved toward the 100% end, full
power is fed to the LEDs. In effect, the pot becomes the on/off switch
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Pulsed LED Test Circuit
This circuit is designed to test visible and infrared LEDs in pulsed mode
operations. It can drive the LED with peak currents in excess of 10 amps. A light
detector nearby can monitor the response time and intensity of the LED under test.
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Ramping Lamp Driver
This circuit drives any 12v lamp, incandescent or LED type, in a ramping fashion.
Each press of the button toggles the lamp from a fully off mode to a fully on mode.
But, instead of an instantaneous lamp intensity change, the power is slowly ramped
up and down. With the components shown, the ramping action takes two seconds
to complete. By changing the capacitor C3, you can increase or decrease the
ramping time. The circuit will also operate with supply voltages ranging from
15v to 3v. [Hobby circuit designed by Dave Johnson]
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Ramping LED Driver
The circuit below was designed to drive a LED with an intensity ramping mode.
Two 555 timers generate two different triangle waveforms. The upper device
generates a 10KHz signal while the lower unit produces a 1Hz signal. The two
signals are fed to a voltage comparator. The result is a pulse width
modulation (PWM) signal, which with the aid of the FET, drives the LED in such a way
that its average light output slowly ramps from about zero light to maximum and then
slowly dims back down. The circuit should operate over a supply voltage ranging
from 3v to 12v. You can easily vary the ramping time by changing the value of the 1M
resistor. For an interesting effect, you can place a 1N4148 diode in parallel
with the 1M resistor, with the cathode (banded end) side connected to pin 3
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Reduced Power Sequential LED Flasher
The 74HC4017 is a neat decade counter which has 10 decoded outputs. When
supplied with a low frequency clock and with a LED attached to each of the outputs,
an interesting ten step sequential flasher effect can be produced. The LEDs
can be configured in a wide variety of patterns of loops, lines or arrows.
But, these circuits can often be power hogs. To reduce the average current
needed to produce the same effect, you can strobe the individual LEDs with a short
10mS pulse.
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Remote LED Indicator Light
There are times when you would like to transmit a signal from one LED indicator
light to second LED at another location. The circuit below works well for this
application. It takes advantage of the fact that the internal infrared LED
inside an opto-isolator has a lower voltage drop than the visible LED being tapped
into. Using a darlington type opto-isolator also means very little current
needs to be diverted to the isolator
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Simple 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.
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Super Bright 3v Powered LED Flasher
I have posted several kinds of LED flashers over the years. This is yet one more
flasher, designed to flash any high power LED of any color. It hits the LED
with a 25ms 250ma pulse once every 2 seconds. This works out to an average current
about 3ma. It is powered by any 3v source. I suggest two AA cells but a
single 3v lithium coin type cell will also work. With fresh AA cells, the
light should flash for about two weeks. The light flash is very intense and is
perfect for any attention getting night time application
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Ultra Low Power LED Flasher
The efficiency of some newer LEDs is amazing. Some of the latest green LEDs
can launch blinding light with just one milliamp of current. I take advantage
of one of these newer devices in the circuit below. The flashing circuit uses a
classic multivibrator oscillator, made from a tiny National Semiconductor’s LMC7215
low power voltage comparator. The circuit produces a short 10ms pulse every
two seconds, drawing power from a 3v supply. I suggest using a surface mounted
green LED from Kingbright.
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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
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,
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Voltage to Frequency Converter + 1uS LED Pulse Driver
This circuit receives the signal from the above amplifier and launches powerful 1uS
infrared light pulses from a low cost LED that are frequency modulated by the audio
information. The 10KHz center frequency of the pulse stream is low enough so a
standard infrared LED can emit ten times more light than conventional long pulse
techniques. The circuit is described in more detail in the transmitter section of my
Handbook of Optical Through the Air Communications.
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White LED is Powered by One NiMH Cell
There are a lot of white LED driver circuits floating around. A popular
circuit called the “Joule Thief” can drive one white LED from a single 1.2v or 1.5v
battery cell. Most of these circuits use one or two transistors to form a
voltage boost circuit. Yes, they those circuit do drive a LED but they are not
very efficient and they don’t do a good job of controlling the current to the LED.
The circuit below uses a tiny LT1932 IC made by Linear Technology. This IC can
be configured for a wide variety of LED driver needs. I have shown one simple
application. The circuit takes power from one 1.2v NiMH rechargeable battery
or a 1.5v disposable battery and drives a single white LED with 15ma of current.
With an efficiency of about 70%, the circuit should run for about 40 hours, if a
quality 2500ma-hour battery is used.
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White LED Life Tester
There are lots of white LEDs for sale these days. Many eBay and electronic
component surplus sales claim to sell some very bright devices. Over the years
I have purchased some of them to experiment with. I also have purchased some
products, which contain white LEDs. A major disappointment for me was some LED
night lights I bought from Costco. In just three months of operation, the
night lights I purchased were too dim to be of any use. What I have discovered
is that many of the LEDs
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White LED Night Light
As many of you know, I have a pet peeve with poorly made LED night lights.
Often, the light from the LED quickly fades, so within months, the light is useless.
I have posted several versions of modified night lights using higher quality
components. This circuit is yet another version, which produces much more light than
those other designs. The circuit brings together two high power white LEDs made by
Cree with a compact AC to DC power supply from Bias Power
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Wireless LED Driver
The circuit solves this problem by sending power to the LED through the plastic,
using a magnetic coupling technique. The circuit below can route power through
plastic enclosures as thick as ¼ inch. The circuit will not work through metal
boxes.
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