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The circuit comprises simply the PWM source, capacitor C, and resistors RD and RW. For CMOS circuits, you calculate the open-circuit output voltage as VCONT=D½§VDD, where VCONT is the control circuit`s output voltage, D is the PWM duty cycle, and VDD is....
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The white-LED flasher in Figure 1 offers an alternative approach to a previously published idea (Reference 1). Targeting use in portable appliances and products powered by a single cell, this circuit flashes an LED to provide a highly visible warning....
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The circuit in Figure 1 allows you to light any type of LED from a single cell whose voltage ranges from 1 to 1.5V. This range accommodates alkaline, carbon-zinc, NiCd, or NiMH single cells. The circuit`s principal application is in LED-based flashlights,....
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Most products use multiple LEDs to provide adequate backlight for a display. Because the LED`s brightness depends on its forward current, these multiple diodes commonly connect in series to ensure that the same current flows through each of them. You need....
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The yellow LEDs are on a small PCB, which are easy to remove. On the PCB there is 3 yellow LEDs and 4 diodes. Pictures of the PCB can be seen here : Top-side - Bottom-side. The schematic is as follows : You now remove the 3 LEDs and the 3 normal diodes....
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You sometimes need to drive a white LED from one 1.5V battery. Unfortunately, the forward voltage of a white LED is 3 to 4V. So, you would need a dc/dc converter to drive the LED from one battery. Using the simple circuit in Figure 1, you can drive one white....
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This circuit was designed on request and can be useful to those whishing to have, say, a red LED illuminated when an appliance is on and a green LED illuminated when the same appliance is off. Any mains operated appliance can be monitored by this circuit,....
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Figure 1 shows a method for driving all the LEDs with a single driver IC from Catalyst Semiconductor (www.catsemi.com), the CAT32. Power comes from a single lithium-ion battery cell. A FET switch can independently turn off the group of six LEDs. The shutdown....
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The circuit of Figure 1 is designed for portable-power applications that require white LEDs with adjustable, logarithmic dimming levels. The circuit drives as many as four white LEDs from a 3.3V source and adjusts the total LED current from 1 to 106 mA in 64....
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This is a practical white LED head mount lamp (flashlight). Recently many white LED flashlights appear on the market. However, most flashlights require three cells because they are regurating output current with only series resister. The odd number of cells....
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Figure 1 illustrates one possible approach that uses external inverter IC1 to drive D1, a red/green bidirectional LED. A logic-high output on the port pin forces current through the green (upper) LED and pulls the inverter`s input high, which drives the....
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This circuit operates a LED in pulsing mode, i.e. the LED goes from off state, lights up gradually, then dims gradually, etc. This operation mode is obtained by a triangular wave generator formed by two op-amps contained in a very cheap 8 pin DIL case IC.....
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* Flashing frequency can be varied by changing R1 value in the 1M - 4M7 range. * This circuit is very efficient when driving a small 3.2V incandescent lamp. In this case omit the LED and R3, connecting the bulb across Q2 Collector and positive supply,....
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Maxim/Dallas > Designer`s Library > App Notes > DISPLAY DRIVERS Keywords: Single FET Controls 2nd LED Array in Switch-Mode LED Backlight Related Parts APP 1871: Feb 03, 2003 Download, PDF FormatDownload, PDF Format (29kB) APPLICATION....
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This deceptively simple sequencer actually pulse width modulates the LEDs as it fades from one LED to the next. Bulbs will last much longer when driven in this gentle manner. Add MOSFETs or transistors to the outputs if you wish to drive bulbs. You can....
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The LED Torch is based on a 7555 timer running in astable mode (do not use an ordinary 555). A white LED (Maplin order code NR73) produces 400 mcd light output, which, when focussed, can illuminate objects at 30 metres. Try Conrad Electronic for what appears....
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High power LEDs are quickly expanding their reach as the lightsource of choice for flat panel computer and TV monitors, TV projection, signage, portable lights and automotive interior, trim and brake lighting. The input voltage and LED voltage....
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The LTC3205 is a highly integrated multidisplay LED controller. The part contains a high efficiency, low noise fractional step-up/step-down charge pump to provide power for both main and sub white LED displays plus an RGB color LED display. The LTC3205....
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The LM317L and resistor act as a current regulator set to 40ma. Current flows from the battery through one pair of LEDs, through the regulator, through the other pair of LEDs, and back to the battery. The capacitor filters out noise on the power supply....
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The circuit`s 90% conversion efficiency offers a distinct power-saving advantage over resistor-limited and linearly regulated designs. It might appear that a series-LED connection is unsuitable for applications in which some (but not all) LEDs must be off. A....
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The LTC3453 is a synchronous buck-boost DC/DC converter optimized for driving up to 4 white LEDs at a combined current of up to 500mA from a single Li-Ion battery input. The regulator operates in either synchronous buck, synchronous boost, or buck-boost....
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The LT®1937 is a step-up DC/DC converter specifically designed to drive white LEDs with a constant current. The device can drive two, three or four LEDs in series from a Li-Ion cell. Series connection of the LEDs provides identical LED currents resulting in....
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This high power led mood light is based on PIC16F628 and the ability of this mcu to produce PWM pulses. Varying pulse width we can produce millions of color combinations using only the three basic colors. So only one RGB (Red-Green-Blue) led is capable....
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A minimum number of parts yields a compact switching converter that can provide sufficient voltage to drive white LEDs. The resulting lamp is much more efficient, in terms of lumen hours per pound of battery, than incandescent bulbs, and because the color of....
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The operating voltage of white LEDs coupled with my emotional need for low cost for a given function, motivates me to make LED drivers suitable for battery operated lanterns that can run from a small number of cells. White and Ultraviolet LEDs available at....
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Finally, white LED`s are bright enough to use in a practical stroboscope. This circuit can operate as a bench-top stroboscope that, in conjunction with an oscilloscope or frequency meter and bench top power supply can accurately measure rotational speeds, or....
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Photo. This is the test circuit -the basic driver is only two transistors, two resistors, the circuit was evaluated using a white LED, but when it was time to button it up and archive it, I replaced the expensive white LED with a cheap green one...
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Each time switch S1 is closed the count on the CD4017 advances by 1 step and the coresponding LED turns on. When the maximium count plus 1 is reached for each circuit the cycle is restarted and repeats...
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These circuits provide a means of altering the YELLOW output of RED / GREEN type two colour light emitting diodes. These circuits use the LM555 timer chip...
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This circuit when used with a 555 timer will cause light emitting diodes to turn on and off more slowly. This will make the LEDs appear similar to incandescent lamps...
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The circuit uses independent timers to flash two light emitting diodes. Any time that light emitting diode D1 is lit__light emitting diode D2 will be switched off. Light emitting diode D3 is on if both D1 and D2 are off. Two versions of the circuit are....
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This may well be the world`s only discreet logic circuit to generate truely random output. It makes an excellent candle flicker light for your haloween pumpkin, and looks much more authentic than a shimmer light wherever a good a simulated flame effect is....
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This is a very simple project using a printed circuit board and 8 components. It will flash an ordinary 3mm or 5mm (1/8" or 1/4") LED at a rate of about one flash per second. This circuit works on the basis of a high-gain amplifier being driven into....
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The circuit consists of two building blocks. The first is a square wave oscillator made up of two transistors in a multivibrator arrangement and the second is a CD 4017 decade counter IC. The multivibrator contains two extra components to speed up the....
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This circuit is usable as a Night Lamp when a wall mains socket is not available to plug-in an ever running small neon lamp device. In order to ensure minimum battery consumption, one 1.5V cell is used, and a simple voltage doubler drives a pulsating....
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Very simple, versatile modular design. The purpose of this circuit was to create a ring in which LEDs or Lamps illuminate sequentially. Its main feature is a high versatility: you can build a loop containing any number of LEDs or Lamps, as each illuminating....
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The heart of the circuit is a string of 10 white LEDs. These are wired in series and connected to a current-regulated step-up switching power supply circuit. DC powered LED lighting circuits can vary from the trivial, with a single LED and a series resistor,....
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This circuit makes a nice lamp that consumes little power, runs cool, and has an incredibly long lifetime. The lamp puts out a warm yellow shade of light, the color may be adjusted by changing the number of red or green LED strings. Operating Voltage: 12V DC....
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This is a new circuit I just finished. I like the white LED lighting, it is softer and give a better view without being overly bright for the eyes when you just wake up in the middle of the night. This circuit has no transformer to isolate it, so it is a....
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LED's are great display tools. Their prices have decreased to a point where they are replacing more conventional light sources. In one sense their characteristic need for low voltages is an advantage e.g compatibility with I.C drives, but this voltage....
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The circuit comprises two sections: charger power supply and LED driver.The charger power supply section is built around 3-terminal adjustable regulator (IC1) LM317, while the LED driver section is built around transistor BD140(T2). In the charger power....
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This circuit is based around HT?2050 manufactured by HOLTEK semiconductors. It is a low cost, low-power C-MOS LSI designed for lamp andLED flash driver. It requires minimum external components.You can operate it with just two AAA cell or 3v Battery.Circuit....
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This is a novel flasher circuit using a single driver transistor that takes its flash-rate from a flashing LED. The flasher in the photo is 3mm. An ordinary LED will not work. The flash rate cannot be altered by the brightness of the high-bright white LED....
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In this project it was used the ?Piranha Super-flux RGB? Led of common anode, and the PIC18F25K20, in order to generate combinations of colors. It has two function modes, automatic that generate the color sequence that is stored in the ?C memory, and the....
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I needed a pulsating light for a certain signaling. Voltage was 230V. So I decided to make a simple circuit, consisted of a LED diode, two capacitors, two resistors, a diac and a diode. Activity of the circuit is extraordinarily simple. The capacitor charges....
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The parts to the right of T1 form a simple Joule-thief ('Blocking' oscillator) circuit which boosts the 1.2v supply to 3.5v to operate the LED. C1 is used to extend the charge and discharge cycles to increase brightness and efficiency. Components R, C and....
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The device comprises two parts: LED control board and LED display board. The two PCBs are designed to fit together one behind the other using two sets of dual row connectors and 4 spacers. One of this connector is used for the electrical connections, while....
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Here is a schematic of a rechargeable 9-LED flashlight using two Gates SLA cells and nine LEDs. It is as bright as when the single bulb was used, and lasts 3 times longer per charge. That is about 10 hours of bright light, at a lower brightness, is available....
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48 LEDs total, 24 on each side of the board. This gives higher resolution patterns, and they can be seen from both sides of the bike. The LEDs are controlled from a series of 74x373 ICs connected to an 8 bit bus on the microcontroller. As opposed to shift....
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This is a simple, programmable, autonomous and extensible LED matrix with the possibility of being controlled by a computer using a RS232 connection. Its basic modules are the Controller Board, the I/O Port expander boards and the LED matrix cardboard....
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This is a very simple circuit to build, just take note of the control pins on each IC, since both have enable inputs for counting or output, but once set you don't need to worry about them. From left to right, the first IC is a binary counter, 74ls163, that....
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This circuit is built around one of the most popular timer integrated circuits, the 555 timer. It will flash the led on and of at regular intervals. From left to right, the two resistors and the capacitor set the time it takes to turn the led on or off, by....
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The circuit this month is a simple 8 light chaser built around a PIC. This will demonstrate how easy it is to program a PIC and to utilize it in a circuit. The circuit works as follows. When power is supplied to the circuit the PIC resets and starts to....
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The circuit presented this month is a basic configuration of the very versatile 4017 IC Chip. In the most common use of the IC, it will turn on 10 separate outputs sequentially. Typically, the circuit is used to turn on a LED for certain time cycle. In the....
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If you are familiar with LED flashers using transistor, you may know the basic one uses two transistor, one capacitor and three resistors. There is other kind of oscillator called "flip-flop". As I'm starting to develop some basic circuits, I need a simple....
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A LED is defined as "light-emitting diode: diode such that light emitted at a p-n junction is proportional to the bias current; color depends on the material used" [Princeton University]. As the LED is a diode, it doesn't conduct electricity in both ways and....
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The pins RA3 to RA0, are used as outputs driving each column LED. The pins RB0 to RB7 are used as outputs driving signal for each column LED. The 74HC154 (Decoder 4 to 16) is the chip that decodes the signal into a binary digit dekaexapsifio. In the left....
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Five pins RA0 to RA4 are used as inputs. The pins are connected to the 5V average resistance 10K (Pull-up). So when no switch is not depressed all the pins have a high potential (HI +5 V). When one of them is pressed then the foot is connected to get a low....
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The circuit is based on the IC1 that is 555, for the creation of alternate flashes from the two led D1-2, that can be also different colour. The frequency of alternation can be regulated from the trimmer R3 and from the C1, if changes his capacity. The....
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IC4, C1, R1 and R2 are used for the clock pulse which is fed to both the counters IC2 and IC3 Pin 14. IC1 is a Flip Flop and is used as a switch to enable ether IC2 or IC3 at pin 13. IC7a detects when ether IC2 or IC3 has reached Q9 of the counter pin 11.....
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Using a PC parallel port to control external devices is a popular approach these days but I certainly couldn’t afford to tie up a PC for the few weeks leading up to Christmas just to flash a few LEDs! Not to mention the power bill! So, why not use a small....
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This is a simple LED flasher using two 2N3904 transistors. Classic astable multivibrator using 2 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....
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This circuit will flash a super-bright LED (5000+ mcd). Good for fake car alarm or other attention getting device. Component values are not critical, try anything else first from your junkbox. Obviously, the 470 ohm resistor (R3) determines the LED's....
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Our circuit is amplifying the current flowing through your finger (when it touches the touch plate) 10,000 times and this is sufficient to illuminate the LED. The current flowing through your finger (when touching the touch plate) is only a few microamps and....
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This circuit will flash a string of LED's, typically 16, with direct connection to the mains and with a period adjustable between 1 and 4 seconds depending on the setting of the 22K/1W pot. Operation at 110V should also be possible but has not been tested.....
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Here is a simple circuit which can be used for decoration purposes or as an indicator. Flashing or dancing speed of LEDs can be adjusted and various dancing patterns of lights can be formed. The circuit consists of two astable multivibrators. One....
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Light emitting diodes are advan- tageous due to their smaller size, low current consumption and catchy colours they emit. Here is a running message display circuit wherein the letters formed by LED arrangement light up progressively. Once all the letters of....
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This circuit can be used to construct an attractive Christmas Star. When we switch on this circuit, the brightness of lamp L1 gradually increases. When it reaches the maximum brightness level, the brightness starts decreasing gradually. And when it reaches....
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I recently purchased 10 SLM1608 (SLM1606) LED matrix display units from Ebay (you might also contact the seller directly at [email protected]). These are 16x16 LED matrix units with a green and a red LED per pixel allowing each pixel to be switched to either....
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Construction LED circuit shown in Figure. It requires manual power, after the circuit is powered, the light will blink to remind people to pay attention to safety. ..
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This unit has a single column of LEDs that are spinning in a left to right motion, as it spins a microcontroller keeps track of the exact position of the board. Words are written in the air by flashing the correct bit pattern in the correct location. The....
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It consists of a 4047 low-power monostable/astable multivibrator, IC1, used in the astable mode to provide the timing pulses to control the flash rate of the LEDs. To accomplish the astable mode, pins 4, 5, 6, and 14 are connected to +12VDC and pins 7, 8,....
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Often the need to control light switch on the instrument. If napájíme LED source of low DC voltage sufficient to classify a series of LED-resistor of appropriate resistance. Another situation occurs, if a small supply available, or to indicate when the....
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White LEDs have a rated current at a voltage drop of about 3.3 to 3.4 V. It is ideal to be powered from the battery voltage which is slightly larger. Then there is the best energy used. In this I used a flashlight battery, Li-ion battery, which lasts the....
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The article describes a simple and very cheap to drive white, blue or UV LEDs, used for example in small lamps and testers. The cost of components shall not exceed CZK 10. Converters for white LED has been on the pages of journals described quite enough.....
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Presented circuit is very simple. With more sampling, I refrained from using the converter and lamp designed for powering three NiCd or NiMH batteries. Because the voltage difference between the battery and the LED is very small, this arrangement is....
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Anyone who has ever dealt with construction of low-voltage-fed inverter realized that this is no easy task. The shrinking supply voltage decreases rapidly transferred power and efficiency. Samokmitající converters fail to provide sufficient power to drive....
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This Is a capacitor power supply. This is a very small currents of energy-effective, because it has very little loss, much smaller than the miniature transformer. Capacitor impedance is inversely proportional to frequency. This is a great disadvantage when....
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There have described the involvement benefited LM3909 circuit, which is quite expensive. That's why I prefer to use a much cheaper known timer 555th.Involvement of the tree is a very simple scheme is to figure 2 . It is based on several multivibrator used as....
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The circuit is a 0-60 second timer using timer 555 and two 4017 for LED driving...
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The clock circuit above uses seven ICs and 19 LEDs to indicate binary coded decimal time. The LEDs can be arranged (as shown in example above) so that each horizontal group of 3 or 4 LEDs represents a decimal digit between 0 and 9 and each individual LED....
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The LED flasher circuits below operate on a single 1.5 volt battery. The circuit on the upper right uses the popular LM3909 LED flasher IC and requires only a timing capacitor and LED. The top left circuit, designed by Andre De-Guerin illustrates using a....
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This circuit is used to slowly illuminate and fade a pair of red LEDs (light emitting diodes). The fading LEDs could be installed as 'eyes' in a small pumpkin or skull as a Halloween attraction, or mounted in a Christmas tree ornament. Or, they might be used....
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General There are many 9V chaser circuits that seem to waste about 7V when driving LEDs that are only about 2V. This project is unique, because it uses only two inexpensive alkaline battery cells totaling 3V for power. Since most of the waste is eliminated,....
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A constant-current power LED driver circuit is shown in Fig. 1. Q1 is turned on by R1 and acts as a variable resistor. Q2 is an “over-current” switch and R2 sets the maximum current. For the power LEDs that I use, the 1W circuit draws about 440mA from the DC....
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Explanation The circuit is nothing more than two light emitting diodes (D1 and D2), its position is controlled by the temperature of the surrounding environment. Here the tempe..
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Driving series white LED, flowing through the same song in each white LED current, it is possible to obtain a uniform brightness. The disadvantage of the tandem drive is the dr..
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Drive the light emitting diode is shown in the digital display circuit, the count signal to ICM7217 feet in the chip by the count and after the coding process to drive the digi..
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A voltage ranging from 6 V to 15 V is supplied if only one LED per module is used. The increase in the number of LEDs also corresponds to the increase of voltage supply and the connection of additional LEDs should be in series. The maximum allowed voltage is....
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With the relaxation oscillator, we basically achieved a fairly regular square wave. Let's change the duty cycle (and visualize the effect with LEDs). Wire up the following variation on the relaxation oscillator circuit..
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Configure National Semiconductors DS8877 drive circuit as shown, when the 6 digit calculator and digital current conjunction, the current range is 5 to 50mA. Drive does not req..
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Merry Company (Micrellnc) introduced the industry's smallest and most powerful of the most used in portable electronic devices each LED driver MIC2298...
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Using MAX1576Y charge pump white LED driver circuit as shown, the circuit is capable of driving up to 480mA total current two groups (n = 4 white LED) white LED...
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White LED can be used in series or parallel connection, both solutions have advantages and disadvantages. The disadvantage is that parallel the LED current and brightness do not automatically match...
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LT3755 in the LED string high side sensing output current, high-side current sensing is used to drive the LED's most flexible program, PWM input provides up to 3000: 1 dimming ratio,..
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Due to the lack of speed in the entire series TTL monostable multivibrator, and because of the requirements of ECL voltage swing wide range of small and power, which drives us to use F series circuit having a fast transition..
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Powerint's DER322 reference design uses LinkSwitch-PL family LNK460VG devices, the industry's first alternative 100W A19 incandescent LED driver using a single-layer PCB, a low-cost low component count and small size characteristics, efficiency of....
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LTC3202 is Linear TECHNOLOGY company does not need a charge pump gated oscillator Pictured LTC3202 charge pump using a lithium-ion battery-powered white LED driver circuit...
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LB140 is shown in Figure Five-digit LED level indicator typical driver IC circuit, BL1405 widely used tape recorders and tape recorders do with level indication...
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Have you ever in the dark watching time from the mobile phone In this case the bright and dark backlit strong contrast will make the eyes uncomfortable, which requires the use of "ICON" model "that is in standby mode with a slight current time,..