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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2answers
107 views

wiring leds for car brake lights without throwing warning lights [on hold]

Im working on led tail lights for my vehicle. the standard bulb is a 21w 12v bulb. what i need to try and figure out is whether or not i am able to recreate this same load using leds without a load ...
0
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1answer
54 views

555 timer flashing led circuit

I just have a question about this simple circuit or example: http://www.555-timer-circuits.com/flashing-led.html. I just don't get 1) why do they use 9V battery to power a single red LED light. 2) why ...
0
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2answers
94 views

Turn on an LED when power is lost with a relay

A friend of mine has just finished his race car but is having fan issues. What I want to help him do is setup an LED that turns on when the fans have lost power. Often the fuse blows. I would assume ...
0
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1answer
49 views

Will my 12V power supply ever burn these IR leds blinking at 38kHz even without a resistor?

I'm new to electronics, my background is mostly on the software development side... so go easy on me, as this might be a really stupid question. I just want to be sure what is safe to assume and what ...
0
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1answer
54 views

Alternative LEDs Blinking circuit(Analog) Help

Can someone explain the operation of this circuit, I understand the basics of the BJT and its modes, but most of my confusion arises when there is some-sort of feedback loop in the circuit, my thought ...
0
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2answers
47 views

Powering SMD 5050 strip via LM2596 DC/DC converter

I decided not to order / use the power supply typically sold with SMD 5050 kits. I heard a lot of explosion stories regarding those dodgy stuff. I want to make my own (power supply to drive SMD 5050. ...
1
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1answer
41 views

driving LEDs via a PI a attiny and TLC5940 (validation) and possible powering issues

at the moment I am planning my first real (big) electronics project. I want to build a LED lamp, that can be controlled by a RaspberryPi (for e.g. programming a binary clock or changing the brightness ...
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0answers
28 views

Precise way to compare Color Quality in Monitors [migrated]

I don't know where to publish this question, but here seems like the best place to do it, so here it goes: I couple weeks back I bought a retina-macbook pro and I love it. To go along with it I bought ...
0
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1answer
85 views

What kind of amplifier to use?

I'm driving an LED from the output of an optocoupler. Example, I'm trying to find surface errors on a sheet. When the sheet is flat the average output voltage is around 2.45V (based on the circuitry I ...
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1answer
82 views

3W LED light (15x 3w LED)

I've started to play with LEDs but every time I feel I've come to understand them, I get confused again... I have attached my plan so far, I was wondering if any of you could give me some advice!
2
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5answers
141 views

How does the Brita LED work?

Specifically, I'm talking about this product here... Brita Faucet Filter It has an LED that blinks when the water is running. It blinks red, yellow, or green to indicate filter quality (maybe) - but ...
2
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2answers
63 views

Random flashing on WS2812B LEDs

I'm trying to drive a strip of WS2812B LEDs with a Beaglebone Black(revC). Because the LEDs expect a data signal at 5V and the BBB outputs at 3.3V, some sort of level shifting is required. However, ...
0
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1answer
45 views

12V battery choices (powered LEDs and piezo buzzer)

I need to power two 12 V LED lights (1W - forward current @ 0.083 A) and a small piezo buzzer all in parallel (unsure about the current, tried to measure it with multimeter, but get nothing...). ...
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2answers
54 views

On/Off DC power indicator [duplicate]

I am pretty sure that this should be simple but the answer is eluding me. Basically I would like a simple 12V DC circuit that lights one LED (red) when a power switch to a pump is off and would ...
0
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1answer
112 views

Reducing LED flickering

I am using a PIC18F452 micro-controller to generate PWM with ADC. The PWM output is connected to an LED through a MOSFET. There is some flicker occurring. How can the flickering be reduced?
2
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4answers
262 views

LEDs are burning. Cannot figure out why

I have a lamp that has LED driver producing 35 V (actually lamp driver says 16 - 28 V, but I've measured 35 V). On the lamp I have 7 LEDs (originally 5 + 2 I've added) with heatsinks that have burned ...
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2answers
45 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
103 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
157 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, ...
0
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4answers
141 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
56 views

Prototype for 8x8 RGB LED display [closed]

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 ...
1
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4answers
205 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 ...
0
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1answer
120 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
370 views

LED burned on Arduino

I connected a green LED to pin 13 and digital GND on Arduino Uno R3. pinMode was set to ...
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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 ...
0
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4answers
108 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
95 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 ...
0
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2answers
43 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
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1answer
69 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 ...
0
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2answers
63 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?
0
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1answer
115 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
710 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
92 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
68 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 ...
1
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1answer
87 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
71 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
512 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
128 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 ...
0
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0answers
49 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 ...
0
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1answer
105 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
46 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 ...
0
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1answer
71 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 ...
0
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1answer
106 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
120 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 ...
0
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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
66 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: ...
1
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5answers
155 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
242 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 ...
0
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5answers
119 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 ...