A LED is a light emitting diode. Lighting a LED is considered the "Hello world" of a circuit design, and it can be as simple as putting a series resistor or can get more complicated, involving PWM and multiplexing.

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35 views

Calculating discharge time of 12V LED light powered by AA batteries

I just want to check up my assumption on power consumption of six 12V LED lights in parallel connection. So I powered it by 6 AA (E91 energizer) batteries. The LED's ideal forward current is 80 mA ...
3
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4answers
88 views

Why do most PWM LED displays and backlights operate at a relatively low frequency?

All around me are a bunch of electronics: digital clocks, my laptop, a refrigerator, a dimmable flashlight, and more. What they all have is perceptible flickering of their displays due to PWM, ...
2
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1answer
142 views

Optimizing LED Project

I'm working on a project the will use 20 white 3mm LEDs that I harvested from a 154 LED Christmas light string. I plan to use a 9 volt battery for power. What's the optimal wiring schematic? Series, ...
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4answers
110 views

Wire for project with 9 volt battery

I'm working on a project that powers 20 LEDs with a 9 volt battery. What gauge of wire should I use? A couple of LEDs are in series with a 180 ohm resistor. Then each pair are in parallel.
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1answer
54 views

Prototype for 8x8 RGB LED display [on hold]

I am planning to build a small, very low-resolution, 8x8 RGB LED display, which would be able to display a video (some kind of colorful visualization, lo-res) or a picture from PC via DVI or HDMI ...
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1answer
47 views

Resistor values and power supply for super bright LED bulb project [on hold]

I want to make an LED bulb with five high power super bright white LEDs. Please tell me about resistors to use, and how do I connect all 5 LEDs (series/parallel)? Also, which power supply (volt and ...
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4answers
171 views

How many LEDs can you chain in serial?

Theoretically, on a 12v with a max of 10w power line, how many LED's could you chain in serial before the LEDs further down the chain begin to dim? Where the LEDs have a forward voltage of 3.2 - 3.5 ...
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1answer
115 views

Why are these LEDs listed as 3W when the forward voltage is 2.4V, and forward current is 700mA?

The title of this listing says 3W: http://www.ebay.com/itm/50PCS-3W-RED-80lm-640nm-LED-Plant-Glow-Light-Emitter-with-20mm-star-base-/221518318191?pt=LH_DefaultDomain_0&hash=item3393854a6f But ...
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3answers
363 views

LED burned on Arduino

I connected a green LED to pin 13 and digital GND on Arduino Uno R3. pinMode was set to ...
9
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5answers
1k views

How is current split with two parallel LED's?

I have two LED's in parallel with different forward voltages, and want to know how much current flows through each of them. They have one series resistor connected before being split. Like so: As ...
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4answers
96 views

Cool White LED bulbs: Are they “full-spectrum”?

I don't have much knowledge on LED lights and find the technology quite fascinating (yes, I know, it is not that knew!) I have read that in order to create "white" light, LEDs actually need to emit ...
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1answer
91 views

LED Polarity: Why does this LED have the anode as the short pin?

Typically the guidance seen is that on LEDs the long pin is the anode and the short pin is the cathode. Often it's also said that if you look inside the LED, the large plate is the cathode while the ...
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2answers
37 views

Replacing a sound module's LCD/EL backlit display with a LCD/LED backlit display

I am attempting to upgrade my Kurzweil K1200 rack sound module's display with a LCD/LED display (it currently has an LCD/EL display). The reasons are numerous; but longer life, brighter display, and ...
2
votes
1answer
67 views

Can I interchange TIP3055 emitter & collector to avoid needing to insulate the heatsinks?

Using three TIP3055 transistors for RGB LED switching. Collectors are tied to cases. They need to be heat sunk and everything's already mounted and assembled and I don't have time to get rubber ...
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2answers
61 views

What is the package name of this Through Hole LED?

Does anyone know the name of this package type for an LED? Does anyone know where I can get one like this in red?
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1answer
111 views

How can I make a POWER-LED Lamp?

What is the best way to light 10 POWER-LEDs with AC mains (220V)? (I want to make an LED lamp.) Here is more info: I have 10 of these POWER-LEDs: Product Chip: 40x40 mil Chip Brand: ...
3
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3answers
702 views

What is the purpose of star pcb?

I'm fairly new to electronics, and I was recently looking at some LEDs listed for sale online. Some LEDs were mounted on "star pcb": From the picture, it looks like there are 6 connections. I'm ...
2
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2answers
84 views

Sourcing current with sink LED driver

I'm using an existing keypad with 8 LEDs that source power. I was hoping to use and LED driver of sorts, but all of the ones I find only refer to sinking power. Is it possible to use these drivers to ...
0
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2answers
60 views

How do you perform circuit calculations for the darlington pair

I need to know what formulas or set of calculations would be used to figure out the base resistor and load resistors when hooking up a darlington pair as my datasheet for the ds2003 does not provide a ...
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1answer
80 views

How do I hook up an LED across the tx pin on my Atmega328?

I've built a standalone Arduino and upload sketches via this method From Arduino to a Microcontroller on a Breadboard. I would like to hook up an LED across TX like on the Arduino board, so I simply ...
2
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2answers
65 views

3 LEDs / 1 POT - fade each LED in turn as POT is changed in value ?

I'm looking for a simple (hopefully !) circuit which would allow a variable resistor to control the brightness of three different coloured LED's. As the variable resesistance is changed in value first ...
2
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3answers
495 views

Simple circuit for fading an LED out (no MCU)

What is the simplest circuit you can create which fades an LED in from off to bright, without using any sort of processor or MCU? Would an inductor be of any use here?
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3answers
117 views

How are multi LED flashlights wired to control current w/o resistors or regulator?

I have several cylindrical LED flashlights that have a large number of LEDs in them (the one I'm looking at has 9, which I think is typical.) They take 3 AAA batteries, wired in series, to give ...
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0answers
47 views

Driving LED from two supplies

In my design, I want to drive a LED using two different supplies depending on the control signal for n-mosfet. One of the supply will be disabled at boot-up. P MOS will be used to enable supply for ...
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1answer
100 views

How much power/intensity IR Diode should have to be seen from 30-50 meters

How much power/intensity IR Diode should have to be seen from 30-50 meters by camera with IR pass filter? Must be a good point in a photo. Should be seen in a day light. Preferably with wide angle. ...
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1answer
45 views

circuit with one time flashing LED [closed]

I'm trying to design a DC circuit (1.5v or AA battery as powersource) where the LED turns on for a time less than one second.and it turns off for the rest of the cycle until the power is ...
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1answer
66 views

Constant Current Square Wave through LED

I am running a somewhat powerful LED, on the order of 3.5V 500mA, off of an ~11V battery using a constant current switched mode power supply from Ebay that uses the LM2596. What I need to do now is ...
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1answer
101 views

Simple circuit to fade in / fade out LEDs randomly

I have a group of 8 blue LEDs (Vf 3.2V @ 20 mA) currently powered up in parallel by a resistors (one for LED) and a 4.5V power source (3xAA batteries). I've been playing with fade in/out effects and ...
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1answer
109 views

Why is the LED of my Illuminated rocker switch always on?

I recently purchased a rocker power switch from RadioShack (103-R13-135B-02R-EV) and it works great. However, even when the switch is off, the small red LED stays on. Is this normal? Won't this ...
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0answers
4 views

Computer not detecting my Arduino MEGA 2560 R3 [migrated]

I've tried different USB cables, computers, ports and none of them can detect my possibly bricked Mega 2560 R3. Nothing shows up at all in the Device Manager, not even "Unknown Device". When the ...
0
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2answers
61 views

Efficient way to power 2W LED using 5V Li-Ion battery, with PWM

I am hoping to power a single high power LED with a forward voltage of 1.4V and a forward current of 1.4A using a 5V lithium ion battery. From what I understand, there are several approaches: ...
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5answers
151 views

How to generate Red light from a Blue-Dominated Spectrum

I have a white LED light source, the spectrum of which looks as follows --- want to filter out red light from this white LED source. But as you can see the spectrum dwindles in the red zone. And ...
2
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4answers
240 views

Is there a clever way to prevent a window comparator from oscillating?

Here is my schematic It's basically a crude battery level detector (I am very aware that this isn't the best way to guage battery life, I'm not here for that) it's not crucial that it is super ...
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5answers
115 views

Which resistor to use for this LED

I'm looking to buy resistors for a Raspberry Pi project, but am getting conflicting information on which resistance to use for my LEDs. I will have three LEDs. The voltage from the RPi GPIO pins is ...
15
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3answers
1k views

Are UV LEDs really dangerous?

I just bought some UV LEDs I bought them for testing banknotes and identity papers. I read the documentation and saw some warnings about UV light in which the vendor advises not to look directly at ...
2
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1answer
68 views

Toggle battery powered LEDs

I am helping to build a costume prop that has four LEDs lights on it (1 white and 3 amber). This device is worn on the wrist, so space for power is limited- a 9V battery or something that will fit in ...
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3answers
349 views

Will 74HC595 as LED sink damage LED when pin goes high?

If used as a LED sink, what happens if a 74HC595 pin goes high? Might the LED blow? I expect that when a pin is low, current will sink and the LED will light. What about the opposite condition? ...
2
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1answer
263 views

LEDs flash at the same time and not one at a time

As you can see on the illustration below, I have a voltage supply (a keyboard made of two piezo elements) with two terminals. Each one drives one LED, but since I've added a buzzer in parallel with ...
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1answer
90 views

USB lights up simple circuit but not coin-cell

I have 13 adafruit LED sequins in parallel hooked up to a CR2032 coin cell. This cell is also hooked up to an adafruit Gemma board (Arduino-like board using an Attiny85). Pads D0 & D1 on the Gemma ...
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1answer
61 views

How to choose what a power supply to drive 2 x 10watt RGB LEDS?

I'm trying to figure out how to determine what power supply I should be using for different types of LEDs for this and future projects. I have 2 x RGB LEDS: Forward Current: 350mA Forward Voltage: ...
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1answer
58 views

Controlling various Arduinos with Android

I have an upcoming project which requires me to use about 8 different Arduinos, probably more. They all perform a light show which turns off and on various LEDs at different timings to simulate a ...
0
votes
2answers
103 views

Timed LED circuit with ATX PSU, help

I want to make a circuit that turns on and off the light (LED) of a given time (eg. on 9 pm and off 6 am). I also want it to be adjustable. My idea about the design: I will be using an ATX computer ...
4
votes
3answers
441 views

Extending LED length

Completely new to electronics, I've just begun to play with an Arduino. I was wondering, if I wanted to make an LED sculpture, what is the correct way to extend the legs of each LED so that they stand ...
1
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2answers
70 views

Creating a “virtual” LED display

I have a small project and I would like to have an LED display, just for the sheer fun and look of it. However it would be too expensive for me to make (I would like to use RGB leds) and I would need ...
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votes
2answers
171 views

How to make LED lamp (220V 50Hz input) circuit by using 1 watt LEDs? [closed]

I think to make LED lamp circuit by using 1 watt LEDs (300mA and 3.6V). How to make circuit. But I can not use transformer.Because size and cost of transformer is high). Input single phase, 220V,50Hz ...
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0answers
30 views

Calculating power draw for LEDs and driver (TLC5941)

I am designing a backlit keyboard with 61 white LEDs. These will be individually driven by a TI current limited PWM driver (TLC5941). LEDs: 61 x Osram LCW JNSH.PC (Datasheet) Drivers: 4 x Texas ...
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1answer
79 views

12V LED strips in series with a 24V power supply?

I am purchasing 50x - 1Meter / 12V / 72 LED /Rigid SMD 5730 strips directly from china. I don't know the LED manufacturer, nor the resistor being used. (yes, this is a gamble) The strip is one that ...
1
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1answer
138 views

LED driver circuit help needed

Please help me figure out which inductor to use from this datasheet. Sorry - it's in Chinese as this is an Asian sourced IC and not sold in the US. (Use google translate if necessary - but, the ...
0
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1answer
87 views

Create poolball patterns with LEDs on snooker (pool / billiards) table

I'm building a system which places dots on a snooker (pool/ billiards) table for where the balls should be placed, how can I obtain colours like brown and black from LEDs? Is the best approach to use ...
0
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1answer
45 views

Laser activated switch using a photo-transistor

I would like to make a laser activated switch using a photo-transistor or an LDR, by which I can switch off the lights in a room from a long distance. I just have to point the laser and it will detect ...