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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2
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3answers
178 views

My DIY RGB LED panel powered by 9V battery works but certain colors like blue, white, and purple don't work

I am able to power on my LED unit here with a 9V battery. I'm using a recharble lithium 9V as well. I can't figure out why I can't get blue, purple, and white. The only colors I get are red, orange, ...
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1answer
103 views

What does the collector resistor on this LED driver circuit do?

The resistor in question is R2. The below circuit provides roughly constant current above a certain Vcc. For R2, I arrived at the value by trial and error by checking simulation outputs. I would like ...
8
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4answers
792 views

How to drive 700mA LED cheaply?

I'm new to electronics and am trying to make a night vision circuit. A similar question has been asked before, but with priority on efficiency. I want to control a 700mA-1000mA IR LED using a 5v input ...
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0answers
29 views

Single pulse generator using discrete components

I've a board like this: simulate this circuit – Schematic created using CircuitLab What I want to do is to drive LEDs with OUTPUT pin. This LEDs are used like flash source, so I turn them ON ...
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3answers
910 views

Can an LED be used as a receiver and as an emitter?

I have this idea but I do not know if it makes sense. The idea is to use a red transparent LED connected to an input of a microcontroller. In parallel it is also connected to an output of the same ...
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0answers
35 views

how to select LED protection device?

I have this simple LED configuration: Voltage source is 24VDC so with the 1k resistor and three 2V LED, current is around 20mA. I want to put a PLED device across each LED. how do I select correct ...
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0answers
17 views

Control RF controlled LED panels with a Raspberry Pi 4

I'm trying to "smartify" my LED panels by controlling them without the actual remotes. My goal is to make it possible to control the lamps from an http endpoint. I have an Raspberry Pi 4 as ...
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2answers
53 views

How does the brightness of an LED depend on the average voltage?

I have a circuit where a LED is connected in series through a resistor to a PWM output signal. The pulse width modulation (PWM) signal has two states (ON and OFF) where ON is 5V and OFF is 0V. The LED ...
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0answers
40 views

Remote LED to warn me when a relay in my hot water supply is activated; all wirelessly [closed]

I have installed two electric water heaters in series; the new one is only being used as a preheater that only comes on automatically when my solar panels are producing more than my consumption. All ...
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2answers
68 views

Can I plug in too many LEDs (i.e. 26) on Arduino UNO?

So, I know Ohm's Law and that Arduino UNO R3 pins (digital 2 to 13) have a rated maximum of 40 mA, although it's better to consider that they have a maximum of 20 mA for safety reasons. If I put 2 ...
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3answers
347 views

Is this power supply suitable for powering these chip on board (COB) LEDs?

I have an LED project using 100 Citizen CLU048-1212C4 LEDs. I need to run each LED at 70W, and I want to run every 5 LEDs on 1 power supply. I was thinking of using the MEAN WELL LSR-350-35 (it takes ...
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Why split the resistance on either side of an LED?

In the circuit below, is there any reason why we can't combine R1 and R2 into one 4 kΩ resistor in either location? simulate this circuit – Schematic created using CircuitLab I am reverse ...
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1answer
35 views

Questions about COBs and power supplies from a beginner

I'm planning to use Citizen 1212 COBs, but I don't know how they can be used on 70 watt for each one of them, knowing that each unit will have 5 COBs. So my question is: what is the right power supply ...
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2answers
179 views

LED not outputting square wave signal

I'm working on a sensor similar to an oximeter that measures light attenuation through a medium. I have an LED on one side, and an IC photodiode with on-chip transimpedance amplifier (OPT101) on the ...
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0answers
36 views

display 0-200 on LED or LCD Panel Display using 0-10V signal

I wish to display a number from 33 to 220 on a Panel Display LED or LCD. I have a controller that can output any range from 0-10VDC and I can build a table to output temperature vs Vout in any range ...
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2answers
332 views

LED with built-in resistor and voltage drop

I accidentally bought 12 V LEDs, so an LED with a built-in resistor (you can see it as a black dot on the anode). Now I measured the voltage and get after the LED still a voltage of 11.3 V, when the ...
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1answer
64 views

Max number of LEDs with a given power source and resistors

I had a question about the following problem. I am confused with the number 50. The problems have multiple parts and that's why there are multiple images, and the blue bubble is the answer. Please ...
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2answers
174 views

Is PWM control for LEDs bad?

I just read in Phillips led datasheet that led has 200.000 switching cycles. Would that count PWM cycles too? Because it would mean only few minutes of operation. Also - is it ok for all DC led bulbs ...
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0answers
65 views

How to fix low LED light?

I've connected my LED to 1K resistor. When I tested it out on a breadboard it worked fine, the LED was very bright. Now, when I soldered it to the board, the LED light is poor. I did everything the ...
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0answers
16 views

ADG1408+TLC5940 LED matrix leakage

I am controlling a multiplexed LED matrix with a combination of an ADG1408 as power switch and a TLC5940 as current sink. The system works almost perfectly except for some LEDs that do not stay OFF ...
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4answers
131 views

Powering a 1 watt LED using a 3 V coin cell

I was hoping to power a 1 watt LED (would be great if this is capable of powering 2 or 3 watt LEDs) with a 3 volt coin cell. Will the coin cell be able to output voltages and amperages that are ...
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0answers
26 views

How can I at least estimate the optical power that an RGB LED radiates given the typical parameters?

How can I at least estimate the optical power that an RGB LED radiates given the typical parameters - say luminous intensity in Candela or Luminous efficiency - from a data sheet? Assume this is a ...
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4answers
97 views

How to wire LEDs and CR2032 battery to make it work

I've got a problem and it seems that there is an issue with understanding electronic's fundamentals. I've got inspired by Jiri Praus video I am trying to make this Rabbit-shape circuit to work. What ...
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1answer
44 views

Power Supply stopped working after soldering

I am new to electronic circuits. I built a basic led circuit on a breadboard to test everything out.It worked as in pictures,but the connections were not stable because the holes were very large.I ...
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2answers
112 views

What kills my LED lights?

I use an LED installation for night lighting that uses 2 R6, 1.5V batteries. I want to give up buying batteries and for that, I bought a DC power supply that gives an output voltage between 3 and 12V. ...
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0answers
72 views

How to get an old beer sign to work again?

Has anyone tried to upgrade an old beer / cigarette sign before? I'm a total electronics noob, and I got my hands on one of these old Coors signs that has a 45x7 LED display board. The board has what ...
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9answers
2k views

What is the correct supply voltage for LEDs?

I have a 5V supply power, three 5mm red LEDs, and each LED has 47-ohm resistor. Two LEDs are bright but soon as I connect the third one all of them become dim. Where am I going wrong? I'm new so a ...
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2answers
57 views

Can I power a 35 Watt light fixture over a thermostat 5-wire?

I would like to add this light fixture to my ceiling in an area that only has a thermostat 5-wire coming out (something like this). (The other end of the thermostat wire travels about 15 feet, ending ...
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1answer
35 views

Driving series parallel combination of LEDs with a constant current source

I came across some products (fairly reputed) that use a series-parallel combination of LEDs and drive it directly using a CC source. Here is the configuration of LEDs: A series string consisting of 12 ...
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3answers
62 views

Understanding the actual wattage of LED (LM301H)

LED under consideration is LM301H from samsung: Product page link - https://www.samsung.com/led/lighting/mid-power-leds/3030-leds/lm301h/ Datasheet link - https://cdn.samsung.com/led/file/resource/...
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1answer
54 views

1 resistor for all LEDs or 1 for each? [duplicate]

I heard that using a resistor for each LED in parallel is good, and I also watched a video on youtube. The guy said if your LEDs are the same type and color you can use just 1 resistor. Is there a ...
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3answers
63 views

Can an LED “fluorescent replacement” tube be powered without a ballast?

Two high-rep answers seem to have made the same misunderstanding, so to clarify: My LED replacement tubes DO work with an existing, unchanged magnetic ballast. 2 fluorescent tubes out, 2 LED tubes ...
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2answers
92 views

Can I use a resistor with higher resistance?

I'm very new to electronics and wanted to use a couple of led diodes, I used an online calculator and it says I need a 40-ohm resistor, my question is can I use a 100-ohm resistor instead of 50? what ...
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1answer
57 views

Using a UA741 IC as sensor for an existing AA LED

I am trying to know if an air conditioning is ON/OFF (Daikin with only Wired Remote Control). I want to read its LED. The circuit is fed by a simple 17.8 V two wires from the machine. I've read the ...
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2answers
103 views

LED open and short detection

Can someone tell me on what how to detect a short circuit and LED open circuit for the below circuit? Is it possible to detect which LED? Could someone provide a circuit which would help to detect an ...
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4answers
307 views

Right way of wiring discrete LEDs to make a high power LED panel

I want to make an LED panel as shown below: I need some help understanding the wiring of discrete LEDs. Typically discrete LEDs are rated for 185 mA at 2.7 V. Calculated wattage will be roughly 0.5 ...
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1answer
71 views

Trailing edge dimmer circuit limitations

I just came across this circuit meant for trailing edge dimming of LED bulbs but I was wondering what else could it be used for and what its limitations are during general use. To my understanding by ...
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2answers
205 views

What is the “collector light current” of a phototransistor and how does it relate to the collector current?

I found the "collector light current" term in this datasheet (Vishay TEFT4300) but I can't find a definition for it on the internet nor figure out how it relates to the collector current. I ...
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2answers
46 views

LED driver operation vs boost converter operation

I am having this A80604 - LED Driver IC for driving a string of 9 LEDs. Each LED has a forward voltage drop of 3.1V and a forward current of 300mA through each LED. So, I need to generate a maximum of ...
0
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1answer
85 views

Simplest circuit to light an LED in parallel or series to a Li-ion battery being charged

I have a very small TP4056 based li-ion battery charging circuit board. It has integral LED charging status lights, but I would like to add a remote LED to indicate when a battery is inserted and ...
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4answers
61 views

Recycling a flashlight

I am "another one of those" :) with some understanding but lacking knowledge. I can identify components, know what they are for and even change them when they are visually burn or broken. So ...
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1answer
56 views

Continued illumination of LED after removing voltage

I am designing high-speed flash for my microscopy project and as I know from my practical experience when you stop applying voltage on the LED it needs some time to fully stop illuminating, because of ...
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1answer
41 views

What do these forward currents at specified wattages mean?

An LED I'm looking at has various specs listed that I can't make heads nor tails of. It is listed as a "3W LED" supporting a 2.5V minimum and 3.6V voltage. However, "Forward voltage&...
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1answer
56 views

LED specs: difference between nominal power and power consumption?

I have have a question regarding the technical specs of a LED. In the specs are two values given: Nominal power: 30W Power consumption: 6,6W What is the difference between these two values? The ...
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4answers
113 views

Synchronising self-blinking LEDs (for fun)

I think most here are familiar with Big Clive's super computer, or one of the many variations. This effect 'works' because the timing of the LEDs isn't super precise of course. But this got me ...
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1answer
77 views

Why is the light emitted by the LED not of a single wavelength but consists of a narrow range of wavelength instead? Spectral linewidth change?

I do understand that the wavelength of the lights depends on the energy gap of the semiconductor, but why does it consist of a narrow range instead of a fixed value? is it because during recombination ...
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0answers
14 views

Trailer Light Conversion Module Not Working

I have a module with the attached schematic that I'm testing. On the left is the "vehicle" and the right is the "trailer" I don't have a load on the left side just inputting ...
0
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1answer
18 views

VCSEL to project a 2D array of dots [closed]

Background Apple iPhone Face ID uses VCSEL inside its dot projector to project infrared dots into a person face. Then an infrared camera captures the pattern to be used in a structured light algorithm ...
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1answer
32 views

Flywheel/Dynamo behavior under variable load

I have a special effects project in mind where I simulate a bellows and coal fire without, you know, actual fire. My vision thusfar involves rigging a flywheel to a short-stroke lever (the upper arm ...
1
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1answer
98 views

How can I sync an LED with a camera shutter? [closed]

For an academic research project I need to visualise a fast movement. To do so, I need to sync a small (< 6 cm on the longest side) LED light source with the shutter of a high-FPS camera. The FPS ...

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