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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ESP32 PWM: How far can it go and how many things can I control per pin?

I am designing lights lights for my fish tank and came up with the idea of using modular pucks of LEDs on small custom PCBs. This modular design would be easily scalable and reusable for future ...
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How to change the wavelength of LEDs in Proteus?

I have a problem in designing a circuit for my project. Can anyone explain how to simulate an LED with 940, 1550, and 1650 nm in Proteus software? Dors the emission coefficient of LEDs in Proteus help ...
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5 votes
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Weird PWM signal if powered by AC/DC source

I've developed a PWM LED strip dimmer equipped with a 230VAC to 5VDC converter and an ESP32 board (schematics below). If I hook up the oscilloscope to the input of the LED, the PWM signal shows weird ...
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To decouple or not to decouple these LEDs/drivers?

I am designing an aluminum PCB for some custom aquarium LEDs. I've done a lot of searching on mouser and read lots of data sheets for drivers that would suit my needs. Most of them have "typical ...
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3 votes
2 answers
917 views

Why is capacitor discharge time higher when an LED is included?

I'm testing the discharge time of a capacitor. I found that the time is higher when an LED is present. Circuit with a capacitance of 100mF, 10k resistance and 5V voltage. By calculating discharge ...
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1 answer
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Possible damage to LED or driver from PWM power source and flickering? [closed]

I recently upgraded my car's headlamps from halogen to LED bulbs with integrated drivers (I believe this is the specific product), and I discovered that they flicker when the lights are on in "...
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3 answers
132 views

Connect different "blinking LEDs" in parallel

I have a simple motor and two LED toy with different color leds: LED D1 is blue blinking listed as 30mA/3V/0.09W (osub5x31a), LED D2 is red blinking listed as 20mA/3V/0.06W (OSHR5X31A). Battery is ...
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Driving multiple strips of LEDs

This might be a very basic question but I am just starting out on my electrical engineering journey, and would like to check something. I have a simple LED design running at 12V, currently I have 12 ...
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1 answer
77 views

How to calculate the total power of a LED using solid angle?

I have a LED with the max power of 130mW/sr and an opening angle of +-10° (so approx. around 20°). I conducted an experiment using this LED, the LED shines light to an un-doped silicon semiconductor ...
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5 votes
3 answers
327 views

Alternative to individally addressable LEDs

I have about 30 small white LEDs tightly packed in a column to together form a value indicator (imagine "virtual mercury thermometer"). I would like to control them as a group with a ...
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Is there a dedicated device for this scenario? [closed]

I'm looking for a logic device or a relay etc. which detects the DC current when it is above a threshold. Basically my system is as follows: I want an LED to turn on when the device sinks more than ...
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LED Current Draw Questions

I need a little help with understanding the current I'm working with. I have these LEDs, and trying to power them with an Arduino type board, a Wemos/Lolin D1 R1, based on an ESP8266. I measured the (...
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30 views

Set brightness of flash lamp/LED with an ESP32

This sketch is to turn on and turn off an LED flash (torch) on board ESP32S camera periodically ...
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3 votes
3 answers
102 views

Driving a LED with a potentiometer in parallel, electronic basics

Today, in class, we were to analyze this circuit: simulate this circuit – Schematic created using CircuitLab And calculate \$\alpha \in [0, 1]\$ associated with R2 a potentiometer. I'm confused ...
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4 votes
6 answers
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LED forward current vs forward voltage

I am trying to make a simple circuit for a nametag for kids to solder at a workshop. The LED I was planning to use is 151033BS03000 it has a graph of forward current vs forward voltage. What is this?...
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2 votes
2 answers
152 views

Two power sources and two outputs with one switch

Hi I'm new to electronics and have little idea how electricity works. I have a motorcycle and wanted to add two LED lights. I want to have one switch in both LED but with different sources. The first ...
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How to wire multiple LED lights to an AC outlet

I am trying to do an arts and crafts project (from this tutorial: https://www.youtube.com/watch?v=D5LjGFkpApw) But instead of using a battery pack like he is in the video I would like to plug the ...
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2 answers
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Keep a 12V led strip on for a few seconds

I connected a 12V led strip to the circuit of the cigarette lighter of my car. Unfortunately, when the car is turned on, the power is cut off for a few seconds (3-4s) and the led strip goes out. I ...
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1 answer
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Power injection LED strip: best method art instalation?

I'm building a modular art installation consisting of multiple 1 meter LED bars. From the power supply / microcontroller there are multiple lines consisting of 2 - 6 bars. The led strips I got need ...
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1 answer
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Dual LED Configuration [closed]

I'm looking for a dual color red/green LED that is not common-anode, not common-cathode, but common anode-cathode (anode of one LED shares a pin with the cathode of the other LED). Can anyone list a ...
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0 votes
1 answer
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Addressable LEDs (WS2815): power and data in a multicore cable

Would it be possible to use a multi-core cable to have power and data in the same wire? I'm using WS2815 LEDs. The total current needed is 9.6A. For a cable of 8 meters, a 2.5mm wire is needed. ...
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1 answer
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Finding replacement LED while measuring power source

I have a scanner which I'm pretty sure has a dead board full of IR LEDs (see image, ignore missing D4) I believe D4 and D7 are defective as I measured the voltage drop across each LED and found the ...
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What are the names of screens used in "Basic calculators"?

I was trying to power a basic calculator that day with a power source and I started from 0V going up to 1.5 v I noticed the calculator screen turning out to show a "0", but I could not do ...
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83 views

Handmade vactrols question concerning ROHS

Handmade vactrols question: If the heatshrink, LDR and LED are ROHS and made with care according to ROHS, and knowing that no other stuff is used, does that mean the vactrol is ROHS?
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Independently control LEDs in series with intermediate point

I bought a bunch of LED bar arrays (DD-12 GWB KINGBRIGHT), with a relatively strange wiring diagram. I would like to control each LED. It's easy for LED A, but B and C for example are wired together. ...
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Best way to LED module depanelling & handling in LED lamp assembly?

Can someone suggest me a better way to handling & depanelling LED modules during LED lamp assembly in mass production? Current process have direct hand contact with module and have pressure on ...
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-1 votes
1 answer
57 views

Is there anything to limit LED output dimming 50% while the wall dimmer controls 50% to 0%?

We got a project for a client but our lights are too bright for the space, we still want to sell the the lights because we have extra inventory and need a way to dim the LED output to 25W instead of ...
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5 votes
1 answer
88 views

Why does this LED have three PCB pads in the data sheet?

Please see this datasheet here for QBLP615 LED. The LED part top and side views are contained on page 3. The recommended PCB footprint is shown on page 9. Why is there a middle pad in the footprint ...
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2 votes
1 answer
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Capacitor discharging after power supply is turned off

I am actually a computer engineer trying to get a feet into the embedded world starting by learning basic circuit stuff using 5 V or 3.3 V provided by Elegoo power supply. I built the following ...
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3 answers
71 views

DC motor as a generator [closed]

I was wondering if I could use a simple DC motor to power a small LED and how fast I would need to spin it to do so. I am making a small air-powered engine in school and I kind of want to connect it ...
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0 votes
1 answer
72 views

How to control a 12V relay from variable voltage source of a LED?

I'm new to electronics and need your help. I have retrofitted a Chromecast to my car and have powered it using a cigarette lighter power adapter to USB. Currently the power adapter is hidden and ...
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1 answer
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Should I continue use daisy chaining or use another Chip Select PIN in MAX7219 8×8 LED matrix module to increase height dimension?

Consider I have 4 daised chaining of MX7219 LED Matrix 8×8. Thats mean i have more width than height (32×8) or (width×height) If i want improve overal width of LED again, thats mean i must continue ...
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0 votes
1 answer
63 views

Ensuring full power from a battery

I'm trying to put together a breadboard solution involving an 18650 cell (routed through a LiPo charging board) that powers both an ATTiny85 and two NeoPixel sticks. Two buttons trigger interrupts ...
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0 answers
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Blocking residual low voltage in a 12V automotive lighting circuit [migrated]

I'm having a problem in my car that I'd like to fix myself. I'm not a skilled electrician, nor an engineer, only someone with some mechanical skills. I apologize in advance, for any mistakes or misuse ...
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10 votes
7 answers
2k views

With a transistor (as a switch), does the order of the parts matter?

I've wired up my project(s) similar to how they're laid out in A to control whether or not an LED is on or off. It works fine (as far as I know), but I've seen lots of examples online of circuits laid ...
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0 votes
1 answer
53 views

Power hundereds of LEDs using shift register

I have 400 LEDs I need to drive with a bank of 75hc595s. My problem is that the controller is a raspberry pi zero and the max input for it is 5 V at 1 A, however my LEDs are 3.0-3.2 V at 20 mA or 8 A. ...
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1 vote
0 answers
62 views

Understanding why Meanwell LDD-350H outputs > 350mA current

I built a LED light for my aquarium. I used 140 various 1 W power LEDs, driven by 14 constant current Meanwell LDD-350H drivers. Each driver is handling between 8 and 11 LEDs. I use 36 V power supply. ...
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1 vote
1 answer
55 views

IR LED current not adding up

I'm trying to power 8 IR LEDs in series with a resistor at 12V. The forward current is 100mA, forward voltage is 1.2V-1.6V. $$R=\dfrac{12V-8\cdot1.2V}{100mA}=8\Omega$$ So my resistor should be around ...
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3 votes
5 answers
1k views

Best way to measure current through LED with oscilloscope

I'm using the following circuit: simulate this circuit – Schematic created using CircuitLab What's the best way to measure the current through the LED with an oscilloscope? Because the ...
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0 votes
3 answers
111 views

Designing driving LED circuit with electricity consumption in mind

I have a question about driving LED in different, inverted way: the LED should light on when the signal/state is LOW (0V) and the same LED should be turned off when the signal is HIGH (5V). I have ...
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0 votes
3 answers
47 views

wire rotary switch with leds that turn one at a time

I have a 9V battery, a rotary switch (one pole, 5 positions), and yellow LEDs (2V drop). How can I wire it so that as I rotate the switch the LEDs turn and stay on until I reach the end of the switch? ...
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2 votes
1 answer
135 views

Selecting transistor base resistor for LED switching application based on datasheet

I have been trying to understand how to read a transistor datasheet properly, and to apply the ratings into my circuit to be able to calculate the needed resistor on the base leg. I have a basic setup ...
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0 votes
1 answer
71 views

How to limit power to LED, efficiently

I am looking to use a 12V, 5 ampere car battery on a small 5V, 2A LED. Typical applications online use a resistor or voltage regulator, but since I am using a battery I would like to conserve power, ...
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1 vote
1 answer
110 views

How to dim an LED with a 10 k potentiometer?

I would like to know how to use a 10 k potentiometer with a small LED. Each time I try, the LED won't turn off completely and also it used only 20% of the potentiometer. I would like to be able to ...
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0 votes
1 answer
64 views

LED flasher circuit: unexpected behaviour

I am a beginner so bear with me. I have attempted to design an LED flasher circuit but it gives unexpected behaviour. Diagram: When I apply the 9V DC voltage, the LED stays on for about half a second ...
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27 votes
2 answers
4k views

Why use two transistors driving LEDs when one would work?

Recently received a small PCB from China with a simple LED driving setup (12v input). I spent some time probing it out and reverse engineered this schematic; I'm trying to understand why they ...
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11 votes
2 answers
716 views

Why do LEDs emit less light as they get hotter?

LEDs get less bright as they heat up. It's in every LED datasheet. Why does that happen? What is the mechanism here? I know the bandgap decreases causing the wavelength shift. I also guess that ...
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0 votes
1 answer
142 views

Control LEDs with 74HC595 shift register through SPI

I'm currently working on a project for which I need to control 16 white LEDs with two shift registers 74HC595 in cascade. I work on a ...
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0 votes
3 answers
76 views

AC LED driving circuit - How to drive low voltage LEDs?

I've been tearing down LED light bulb to see how they were driven and found out that most of them use this very simple circuit: This is my understanding of the circuit: 220V AC Input (I'm un Europe) ...
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2 votes
2 answers
59 views

Custom LED light bulb protection /

I wanted to design a custom LED light bulb, so I bought a couple and tore them down in the hope to reverse engineer them. Most of them implement a circuit with a chip shown as below, with the circuit ...
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