Questions tagged [led]

An LED is a light-emitting diode. Lighting an 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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42 views

list some low voltage(typical voltage as 3.3V) 3 to 8 decoder IC numbers and manufacturer [on hold]

I want to drive 7 LEDs using Attiny85 with different delays, using 3.3V and the light intensity is very important factor that I need to consider. I tried with Charlieplexing, but when more than 1 ...
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Strange LED behavior: Why is there a voltage over the LED with only one wire connected to it?

I am encountering a strange problem when I measure the voltage across an LED. Please see below picture: As you can see, I only connected 1 wire ("-") of adapter and used a multimeter to measure the ...
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48 views

How do pixels in a LCD display are individually controlled by a electrode?

How do tiny subpixels in the Led displays are controlled by those indium tin oxide electrode.How do they provide different voltage for each pixel
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67 views

How to configure PWM on STM32F429I-Discovery Board

Currently I have some difficulties on the Discovery Board STM32F429I to control the on-board LEDs via PWM. According to the data sheet of the Discovery Board the LEDs are located on pin 13 and pin 14 (...
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59 views

How to stop current leakage in LED matrix

I know that this issue has been discussed in this forum, but I am a beginner in electronics and I was unable to come up with a solution to my problem by reading the related threads. I am doing a 3x5 ...
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71 views

Using GPIO to control multiple leds via transistors

I'm trying to control 16 LEDS with the GPIO ports of a Raspberry Pi using transistors. All 16 can potentially be illuminated together. I'm trying to figure out if I can use approach B to save PCB ...
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23 views

RGBW 4 channel LED strips: Do I need externalpower supply or is the LED controller enough?

Not a beginner but still a novice :) Main goal is to find out if the LED controllers I have chosen can drive my LED strips or if I need external power supply. And to understand ofcourse :) ...
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667 views

Edge-lit LED panel best materials?

I'm trying to replicate the effect of this LED panel I found at Home Depot with a different set of LEDs and use a differently sized panel. It's basically just a diffused light that mimics a window or ...
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23 views

Simulating a specific LED on Eagle through NgSpice

I was trying to simulate a current mirror circuit for a parallel set of LEDs in a project that I am undertaking. However, before actually working with real parts, I wanted to simulate the circuit in ...
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44 views

LED Dimmer current source and current sink detection

I'm trying to design an input circuit for a microcontroller that will work with 1-10 V dimmers. There appear to be two standards for dimmers, current source and current sink, and I'm trying to work ...
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17 views

How am I supposed to calculate the half power beamwidth of antenna (HPBW) from radiation intensity?

I know we should set the U equation = 1/2. But am I wondering should we just set the cos^4(theta) = 1/2 or the whole equation including the constant number 200 i.e. 200cos^4(theta)=1/2 to solve for ...
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64 views

Efficient 1 watt Led circuit

I'm new to this forum and glad to be here! I'm building a 1 watt led circuit (planning to...) most of the circuits I found online, make a lot of heat and I wish I could find a better one to get bright ...
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782 views

Simple LED driver, transistor and GPIO

I'm trying to figure out how to create a driver for a led from the GPIO pins of the raspberry and a NPN 2N3904 transistor. I am currently following what seems to be a good sparkfun tutorial. On this ...
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56 views

Effect of changing PWM frequency of a light source on perceived brightness

First and foremost, I'm not entirely sure if this is the proper place to post this question, so I apologize if there's a better section for this. I am looking to determine the effect of changing the ...
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Why are all my yellow 2V/20mA LEDs burning out with 330k Ohm resistor?

I have a very basic circuit on a breadboard using an Arduino's 5V+Gnd to power a few LEDs. All the LEDs are from Sparkfun and rated at 2V/20mA, coming in Red, Green, and Yellow. I'm using 330 Ohm ...
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37 views

Are there cerifications needed to bring 5VDC LED Controller to the US market?

We are producing LED programmable controler, the power supply is 5VDC. Do we need any certification (UL or similar) for the US market?
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Reasons for filament LED bulb failure?

I recently purchased a filament LED bulb. However, when installed (AC 220V), it wasn't working well: it had a very low light. But sometimes (~ every 5min) it lights up for a few seconds at its normal ...
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i am using led for a project to flash it for 1ms with the help of ic 555 [duplicate]

LED should have radiation angle of 20 degree and Led intensity=1000microwatt/cm2, Temp range : -40®C to 75®C.,Altitude level=2000 ft above sea level. i am not able to find such led having such ...
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Powering (WS2812B) LED strips through USB 3.1 GEN 1

I bought a new motherboard and it says it has USB 3.1 GEN 1 on the back panel. I did some research and apparently, USB 3.1 GEN 1 has the same power output as a USB 3.0 port which is 5V/1.8A. I thought ...
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41 views

Switch LED with Solid state relay (PhotoMOS)

The SSR is a PhotoMOS AQY211EHAX rated to drive 1 amp. I seem to be shorting the output side of the SSR. Is a pull down resistor normally required on the output side or am I missing something ...
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LED glows slightly during soldering

I recently soldered a number of white LEDs to a PCB using a Weller "standard" soldering station. I noticed some LEDs were glowing slightly during soldering. The PCB was placed on an ESD mat, but I ...
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79 views

Three terminal LED pilot. What's the matter?

Long story short, I've purchased a 24VDC LED pilot and I've got a 12VDC pilot with three terminals instead. I was wondering what are each one of those three terminals for, the terminals have standard ...
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1answer
58 views

Help with wiring OEM LED turn signals that has 2 voltage inputs

The term AFS is used in the 2nd diagram to help differentiate between the bulb type turn signals vs the led type. I'm trying to swap my headlights(without-AFS) to a higher trim version(AFS) on my ...
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28 views

Travel Photography 3.5V 3,6-4,8A LED Lamp powered by power bank

I travel a lot for my work as a photographer. For this I'm building a custom full spectrum lamp. I have no issue running my build with a normal adjustable power supply from my studio. To be able to ...
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1answer
52 views

Arduino RGB spectrum problem

Over the last few days I've been working on an anode RGB LED in Arduino, I've tried getting it to do an RGB spectrum but all I would get is just the colors from red to green, then it would get stuck ...
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33 views

IR Sensor Replacement

I am currently designing a circuit, where output is switched on and off as obstacle passes IR (Infrared) beam, produced by IR LED and received by IR sensor (IR photo-transistor). The problem is that ...
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4answers
81 views

Power supply for multiple parallel LED strings?

My sister is building a display sign, and wants to have several "marquee letters" lit up on it. Like this one: She bought 9 letters like this, and they all run off two AA batteries, and internally ...
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26 views

Convert lumen/m2 to candela/m2

I'm considering a monochromatic Blue LED (is an approximation) with the specs: Luminous flux=6lm, Dominant Wavelength=460nm Surface area= 1,5cm2 How can I calculate the solid angle value? There is ...
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2answers
61 views

LED Circuit - Resistor calculation

If I have an LED such as this It has a forward current of 20mA It has a forward voltage of 2V. If my supply is 3.3v, am I correct in saying I would need a resistor value of 65 Ohms. My calculation ...
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1answer
100 views

Controlling the current through multiple LEDs linearily and efficiently

I have around 100 infrared LEDs, each with an adjacent phototransistor to detect small differences in the distance of several objects (QRE1113). As the objects materials differ, I want to be able to ...
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1answer
83 views

Parallel connected LED and current problem

First of all, I don't have much electronic knowledge. I am having trouble connecting the LEDs in parallel.I have two types of LEDs which have different power.Here are some current measurements: The ...
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1answer
56 views

Driving constant current LEDs with constant voltage?

I have about 6 pieces of bar leds in different colors (all of them are 12V, but different power 18W, 12W, 9W ...) I need to connect them in parallel by regulating 24V, but the problem is that the LED ...
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Calculate Luminance from luminous flux [duplicate]

can you help me? I want to use a RGBw LED (datasheet) and I need to study the BLUE led: Current= 0.350mA; Luminous flux= 13 lm; Efficacy (lumens per Watt) of LED= 12.8 lm/W; Forward voltage of ...
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2answers
37 views

Using serial-input latches from Pi to drive 24V load (LEDs)

TL;DR: LEDs when 'on' are great, however, they're too bright when they should be 'off'. I'm trying to build a custom, large 7-segment LED display driven by a Raspberry Pi. I'm a coder so the bit ...
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1answer
46 views

HDMI/USB Powered Lighting

Alright so a little vague title but here it goes. I'm interested in powering some 5v LED strips with an HDMI cable. I have no idea if this is even possible, I'm lacking knowledge in electronics. My ...
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Thin wall to block LED light from hitting photodiode?

I'm designing a small heart rate sensor using green smd LEDs and a photodiode. The photodiode needs to measure the reflected light, and not direct light from the LEDs. The LEDs are near the perimeter ...
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53 views

Time period of output in relaxation oscillator circuit

I'm an electrical engineering student, and have spent the last 4 hours trying to figure out the time period of the output of the circuit below (in terms of the variables shown in the image). So far, ...
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1answer
142 views

Cannot properly power LEDs

I have two boards from the led headlights. Struggling to power it, I burnt one and now trying to understand how to properly power it. Circuit itself looks quite straightforward: two upper LEDs are ...
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1answer
76 views

Can a LED lights output more light than they are designed to, due to mishandling?

It happens with incandescent lightbulbs sometimes, that they shine brighter due to a mishap by mishandling, and then end up dying earlier. Is the same possible with LEDs? Mishandling can cause parts ...
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2answers
69 views

how to correctly power the LED of a push button?

So I've got a push button and a switch. Both of them have LEDs inside. Both of them seem to have LEDs working at 12V. But according to the specs of the push button, you could also use 6V. My ...
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61 views

LED: Calculate Radiant Power[W] and Luminance[cd/m2] from luminous flux[lm]

I'm thinking of using a LED (Color + Cool White) with the following characteristics: Current= 0.350mA; Luminous flux= 13 lm; Efficacy (lumens per Watt) of LED= 12.8 lm/W; Forward voltage of LED = ...
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2answers
84 views

LED Matrix Light Leakage

I am controlling a 6x6 matrix of LEDs using a PLC with sourcing outputs and sinking outputs (24V). However, there is an issue with current leaking through to other lights. For example, in the ...
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3answers
78 views

Dim LED lamp with constant current power supply using resistors

I own a really bright led lamp that I want to dim. It is powered by a constant current power supply that can supply 37mA between 11V to 17V. If my lamp is connected the voltage settles at 13.58V. ...
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38 views

Over Curent protection for multiple consumers

While designing a light fixture I came across an issue. The fixture is powered by a single ACDC unit that generates 24V. The fixture has around 50 LED elements that are connected to the power source. ...
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4answers
78 views

Driving LED with an N-Channel MOSFET

I am driving a red LED with a forward voltage of approx. 2V as shown in the picture. The driving signal comes from a microcontroller with a logic HIGH of 1.8V. The LED is being sourced from an ...
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1answer
70 views

Using an IR diode as an emitter and receiver?

At the recent Maker Faire Berlin, I was told that LEDs can be repurposed as photo diodes. I assume the same is true in the infrared range. This sounds like a nice solution for building a transmitter. ...
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1answer
49 views

How to harden/prevent ESD in a circuit?

I've designed a simple circuit with three LEDs in series with a matching resistor, all powered by an IC. I want to make my circuit less susceptible to electrostatic discharge since it will be ...
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1answer
69 views

how to lower a power bank USB 5.1v /2.1amps output to 4.5v to power a 150 lumens LED flashlight [closed]

I would like to use a power bank to power a 150 lumens flashlight 3 AAA batteries operated ( https://www.harborfreight.com/ultra-bright-led-portable-worklightflashlight-64005.html ). I already ...
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37 views

Voltage reduction units and LED drivers (lighting)

We have won a tender to supply and install 'upgrade LED lighting' to pole/tower lighting. In order for our business to minimise the risk of premature luminaire failure from poor power quality we have ...
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2answers
61 views

3 to 8 line Decoder Not switching off LEDS

So i'm currently working with a SN74AHCT138N 3-8 line decoder and the whole point of this ciruit is to switch on and switch off a series of LEDS. I connected buttons to the inputs of the IC and LEDS ...