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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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59 views

Base resistor on transistor

I am new to electronics and creating my first big project but I am stumped on figuring out the value of the base resistor (R2 in diagram) of an NPN 2n3904 transistor. All of the LED are rated for 20mA....
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1answer
40 views

adding a push button on LED string lights

im looking at making a flower in a glass dome with string LED light for a present. the problem is most stings had a on/off switch. Is there a way to attach a push button on/off to it and not have to ...
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2answers
154 views

Is the circuit in this answer wrong?

In the Q/A link below, the circuit in the answer seems to be wrong to me. Answer to "How to gradually light up an LED?" Circuit: simulate this circuit – Schematic created using CircuitLab In ...
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1answer
62 views

Need help understanding PNP Base into NPN Collecter circuit for LED Array

I am a novice in circuitry and I'm trying to make an 8x8x8 LED Cube using an instructables guide for a school project. I have ordered all the parts and was testing the grounding circuit for each layer ...
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1answer
69 views

Should I spread the pads out on the footprint of a THT LED?

I have a 4 pin RGB LED with a common anode. I'm trying to make my first PCB and I am creating the footprint for the LED now. I don't have a datasheet for the LEDs unfortunately. I have a ruler ...
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3answers
54 views

Connecting a single LED to Motherboard CHA Fan Header

I've been reading that it is possible to connect a LED to the motherboards CHA fan controller. The LED I had in mind was this Online people have been saying you would need a resistor as the voltage ...
4
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3answers
139 views

How to stop LEDs from dimming in small circuit

I wired up a simple circuit (below) which was designed using the "Every Circuit" website/app. It's a small LED circuit used inside a costume prop. When the master switch is pressed, the 3 LEDs light ...
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2answers
88 views

What LED driver should I use

I am wiring up a house where the kitchen has multiple LED strips. All I have is a wire hanging out of the light strips. And as the LED lights are built into the cabinets I cannot get inside them to ...
4
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1answer
120 views

Dim 20ma LED in retrofit application

I've done a day of research and haven't found a clear path to my problem. I thank you for taking the time to help! Retrofit application in 1985 VW Jetta (MKII). My instrument cluster lights, the ones ...
2
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1answer
223 views

Can I power this LED circuit from 5V USB powerbank?

I have an old flashlight that says "15W Police Waterproof" on the handle, the battery compartment is normally for 3 type C batteries, unfortunately the bottom battery leaked and is stuck in there. ...
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2answers
126 views

Attaching a 3 mm fiber optic cable to a WS2812 LED

I am wondering how to easily attach a side-glowing fiber optic cable (I have 3 mm here) to a cheap WS2812 LED that is flat and soldered onto a PCB (like these here). I tried with Sugru, hot glue, ...
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3answers
153 views

LEDs in computer case are non-polar?

Normally I think of LEDs being polar and having a definite current direction, the "D" in LED standing for "diode". However, in working with with a computer case recently, the front part of the case ...
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1answer
67 views

LED light cycles on and off - Is it a heat or voltage problem?

I have this LED light that was over the aquarium at my work desk. There's a circuit board (not pictured) that controls when the lights go on and off but, after a power outage a few weeks ago, it seems ...
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2answers
100 views

What happens to the semiconductor in an LED when it is given voltage that it cannot handle?

Let us suppose we have an LED with the allowed voltage range of 1.5V to 4.5V and we gave it somewhat 12V. Now we know that the LED will instantly stop forever. But I want to know what will happen to ...
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4answers
67 views

Does the switching frequency and ON/OFF time duration of LED affect the power consumption of LED?

I want to drive the electronics consisting a controller with different peripherals on its I/O pins, one of which is LED, with 3V coin cell battery supply. I want to determine if its switching ...
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0answers
43 views

Isolated vs non-isolated boost converter for LED (12v to 24v)

I have a 12v system in my motorhome and planning on installing 24v LED strips, however, I'm unsure whether I would need an isolated or a non-isolated boost converter. I'll be using roughly 5 meters ...
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0answers
54 views

PSOC 5 turning on a LED with a switch

I'm trying to turn on a LED using a switch and then turn off the LED after 5 seconds with PSOC. With I run the firmware I wrote, the LED is on and then turns off after 5 seconds. What I want is that ...
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2answers
79 views

Using less than 10 LEDs on LM3914

The LM3914 IC has a divider that works over 10 LEDs. Does this IC enable using less than 10 leds and does it automatically adjust the scale based on the number of LEDs (eg 5)?
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2answers
51 views

How to add red led light to my white led lights

What’s the best way to wire the red led to this system? I have it now hooked up to 1 300 ohm resistor & each two white led lights out of 4 hook to 200 ohm resistor. The entry unit is powered by 3 ...
6
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2answers
159 views

LED as light sensor not properly working in circuit

I read some articles about using an LED as a light sensor. I chose an IR LED and checked the voltage levels produced in different light situations resulting in about 200-300mV in full artificial light ...
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3answers
262 views

How can I create voltmeter with Zener diodes?

simulate this circuit – Schematic created using CircuitLab 5 LEDS One LED is to remain always on when current is passed through. One LED will turn on when voltage is between 50 to 90 volts. ...
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2answers
82 views

Control dual color LED without microcontroller

I have a latching, SPDT switch with dual color LEDs (the first page of the datasheet), that can either be Red or Blue depending on the polarity of the voltage. I would like them to be one color when ...
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4answers
1k views

Voltage across LED and source when LED is floating from one end

Refer to these pictures and can you explain why is there 3.335V coming across LED and the LED isn't even turning on. Also to note is that changing the resistor value does not change voltage at D2(A2) ...
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2answers
74 views

How much current will this LED draw?

Sorry if this is a really basic question - software engineer here, so I'm a little out of my element. I'm working on an IoT project, and I'm planning on using this button with a red LED inside of it. ...
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3answers
89 views

Would I get a better lumen output and improved thermal characteristics for the same wattage if I get a higher rated LED? [closed]

I'm planning on building a bright DIY high CRI LED video/photo floodlight out of the following components and considerations: High-power Neutral White (4000K?) LED rated at 95 CRI No add-on lens so I ...
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2answers
101 views

DMX Control - 50W COB LED

I have a DIY project, with the aim of building an (LED-based) stage/theatre light from scratch. One of the challenges I've hit with this is getting DMX control to dim the LED. I spent some time ...
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2answers
149 views

Ohms law and LED driver efficiency? How can this possible be true?

I am having a meltdown with a Chinese supplier at the moment and hope dearly that someone can help. I have an LED driver that is in my mind 28.8W. The output of the driver is 48 V @ 600 mA (48 V x 0....
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1answer
68 views

High Power UV led array for SLA printer

I have a question about a LED array I am designing for a home-made 3D SLA printer. I find the subject of high power led drivers quite confusing but I believe I understand how it works now and I need ...
3
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1answer
63 views

Light-emitting diode luminous intensity at sub-mA currents

I am trying to find a graph or table that relates the light intensity (either relative, absolute, or total luminous flux) of a light-emitting diode at the low range of drive currents - below 1 mA and ...
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4answers
83 views

Reading a Bi-Color LED on Arduino [closed]

I am looking to read the status of a battery charger using an Arduino Board. The battery charger shows red when a battery is being charged and green when a battery is charged. I understand that the ...
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4answers
138 views

Transistor driving LED

I have already asked a question regarding this problem but it was about a different thing, slightly. Here is the drawing of a LED driving circuit. The problem I have encountered with traditional ...
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1answer
173 views

Converting pre-lit Christmas tree with incandescent mini-lights to use LEDs

This might be a dumb question, but has anyone been able to successfully convert a built-in incandescent mini-light string to use LEDs? I have a few of these pre-lit burgundy-colored tinsel Christmas ...
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0answers
53 views

Ultraviolet sensor response curve

I did a search on "ultraviolet sensors" in this forum, and came up with only three results, so, it appears, that this has not been asked before. I have a hand-held ultraviolet light sensor from ...
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2answers
84 views

Will this MOSFET be suitable for driving a 12V 1-2A Load from an Arduino?

I have an Analog 12V RGB LED strip (which only requires 1-2 amps at most) that I want to control using an Arduino Uno. I looked into how I could go about doing this and saw that i could use several ...
1
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1answer
34 views

Reducing the amount of controller output required - making k of n binary to unary decoder out of 1-of-n decoders

I am a kind of self-taught electronics dabbler and being a selftaught tinkerer has the unfortunate consequence of reinventing the metaphorical wheel quite often. I'd like to avoid this fate again if ...
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3answers
565 views

How to control two separate circuits with one switch? [duplicate]

I have two separate circuits with different types of diodes. One circuit draws 3,5V and the other draws 9V. How can I wire this up so that one switch can turn both circuits on or off? As far as I ...
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2answers
82 views

Attiny45 12V LED Driver

I want a fading effect on a 12V led strip when power is turned on/off. I want to keep it simple and efficient, so I choose an Attiny45. The problem is that for the Attiny to work, I would first need ...
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1answer
67 views

How to calculate maximum amount of bulbs I can connect in parallel to match design specification of 1.5 A?

I'm designing a sensor triggered circuit that involves 220 V passing on a PCB, so I designed the board thickness to withstand a maximum of 1.5 A. The main load on the circuit would be a series of LED ...
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2answers
189 views

Failure of LEDs in the wet — what's going on at the semiconductor level?

Recently I've come across two very different LEDs that have failed due to a soaking, but with interesting and almost identical failure behaviour. I'd like to understand what's going on inside. Once ...
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4answers
111 views

Do I need a relay for my LED bars?

I installed two 4" 18 watt LED light bars on my ATV. It is currently wired to the factory switch on the ATV handlebars and there is no relay being used. I have had to replace the right LED bar twice ...
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1answer
86 views

Doubts in providing power to an LED

I am making a project on water level indicator. I've completed the circuit like this: The circuit is closed through the water. The problem is even before switching on the circuit, and with terminals ...
4
votes
6answers
421 views

Simple LED fade circuit

I've been looking for a simple LED fade in/fade out circuit when power is turned on/off for a 12 V LED. I have tried the following circuits but the problem is that I can't reach the full brightness of ...
0
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1answer
65 views

A simple circuit to turn on door LED when someone visit me

I want a simple circuit do an alarm light that tell me someone visited me. When someone visits me and in the case no one answer the door, I want to know that. So I want a press button switch outside ...
1
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2answers
284 views

LED Circuit design (4 switches, 1 potentiometer)

I need to design an LED circuit that acts as a switching system. It must meet these specifications. Case 1(Press Button 1): LED 1 ON, LED 2 ON, LED 3 OFF Case 2(Press Button 2): LED 1 ON, LED 2 OFF,...
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1answer
117 views

3W infrared LEDs not living up to 500mA-700mA - not even close

Here are the specs: Emitted Color: 850nm Forward Voltage (VF): 1.5-1.7V DC Forward Current (IF): 500-700mA Maximum Pulse Voltage: 2.2V List item But after hooking to power supply (which I first ...
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1answer
68 views

Choosing the right transformer to replace batteries?

I have an idea for a hack I'd like to build, but I need some help figuring out the right transformer. Let me know if there's a better place to post this sort of request. I have some exterior LED path ...
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2answers
184 views

500 watt LED PWM

I'm trying to make a PWM'd floodlight with 6 Cree CXA 2540Ns. My setup is a simple 555 timer set up for PWM, driving a 3904, which in turn drives an FDA59N30 N-channel MOSFET, properly cooled to ...
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1answer
48 views

LED strip power requirement [closed]

I have an approximately 1 meter LED strip in "warm white" running from a 2 amp power supply for some time now with no problems. I want to add another strip, of about 2 meters, to this same power ...
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1answer
37 views

Calculating true output of LED

I'm trying to figure out the true output of the individual LEDs on this panel: https://www.amazon.co.uk/gp/product/B01M10RZ98/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 It's a 96 LED infrared ...
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0answers
37 views

phoresistor vactrol tremolo noise

I made an optocoupler by shrink tubing a generic photo resistor and a cold white led. Then used it in the following setup to be able to control audio level to achieve tremolo effect: simulate this ...