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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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88 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
56 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
152 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
41 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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0answers
52 views

review of various possibilities to drive USART TX/RX leds

I would like to add two leds in my circuit for the TX and RX line in a MCU which run at 3.3V NOTE: the USART is HIGH in idle so the leds should turn on when the signal is LOW To my mind come ...
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0answers
68 views

LED Copper wire string lights Dimming DIY

I am doing a DIY project for a small indoor garden lighting using LED fairy lights, (the ones which use SMD LEDs dipped in a resin and soldered to a laminated copper wire) Since these are laminated ...
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1answer
36 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
29 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 ...
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2answers
58 views

Trying to split the current output of an LED driver

I am currently using an 8 channel LED driver wher I have set the outputs to produce 20mA of constant current. Problem is I have 11 LEDs to drive. So I have decided to connect two LEDs in paralled to ...
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3answers
103 views

how to reduce current to power LEDs

I am replacing a microscope lamp with a motorcycle LED headlight. The light is 20W, 9-85V DC; the driver built in and a complete black box to me. I power it with a 65W power supply (18.5V/3.5A). For ...
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1answer
79 views

Driver Circuit for 10W LED [closed]

I need to understand the 10w led driver circuit shown in image.
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1answer
84 views

Connecting an IR receiver to Transistor for current control

I thought I had a simple circuit ready but I need help finishing it off. I’m using an IR receiver, transistor and a matrix of four 3MM LEDs. Want the LEDs to turn ON only when IR is detected. Using ...
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2answers
72 views

Am I risking damaging this LED backlight?

I have a 12 key matrix keypad with an LED backlight that I am wiring up with an Arduino. The datasheet for it is here; http://www.farnell.com/datasheets/1359150.pdf It states pretty clearly that the ...
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1answer
44 views

18v vs 12v battery question

I have a few 12v LED lights that run off cigarette adapters. I wanted to be able to use my 18v drill batteries so I pulled the guts out of an old charger and added a cigarette socket. The lights work ...
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3answers
96 views

Same LED different voltage drops with different supplied voltage

I have an LED with no specs for it. I decided to mesure what is the voltage drop across the LED, so I connected it to 5 V power supply and 325 ohm resistor. I measured the resistor with multi-meter, ...
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2answers
132 views

Suitable transistors for adaptive motorcycle light project

simulate this circuit – Schematic created using CircuitLab I am working on something very similar to this, Adaptive LED Headlights – Model 8790 Adaptive 2 as a hobby project. I have controller ...
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1answer
39 views

using TTL to drive LED

I have a TTL signal of 1 V, and I need to drive an LED by amplifying the TTL to 3 V. I used the following voltage amplifier circuit with Rc = 10 KOhm and Re = 1 kOhm. The DC input I use is 3 V. ...
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1answer
42 views

Different I/O pins of same PORT of ATMEGA8 not providing exact output [closed]

I have written code to switch ON/OFF some LED light connected different I/O pins of same PORT (i.e PORTD) of atmega8 microcontroller. This process is performed using android app by sending different ...
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0answers
43 views

LEDs driven by GameBoy sound

My circuit does not work as I thought it should and I'm really confused now. What I want? Two LEDs which will pulse to audio LEFT and RIGHT channel separately. And same for display BACKLIGHT, but ...
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2answers
54 views

Let two LEDs blink with Raspberry Pi

I have written a simple Python program which runs on a RPi to make an LED blink. For that I connected my RPi using GPIO 23 with the anode of the LED, and before going back to ground, I added a ...
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1answer
31 views

What is the idle current draw of a charge indicator?

What is the most energy efficient charge indicator for a 12v battery? how many mW does it use for every state of charge?
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3answers
167 views

Making an efficient constant current source

I need help making an efficient constant current driver. I want to power my home with LED light strips for lighting and decorative purposes. I need to be able to turn each strip on and off ...
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0answers
43 views

Minimal components for lighting an LED via wireless power transfer

I understand the basic concept of wireless power transfer. I wanted to make some wireless LEDs (Similar to this concept) and was trying to figure out the minimum component count I required in order ...
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2answers
97 views

Why do different resistors of the same power rating burn out / not burn out?

I have a circuit board for a small LED light, which comes with an annoying strobe mode. To disable this I have found that I can wire a resistor from a pin on a chip to ground and the LED will stay in ...
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1answer
200 views

LED strip without controller

anyone knows if it's possible to use a led strip with 3 pins without a controller? I got this 1,5 meter strip without controller, I don't know if I should've bought it or not... please see attached ...
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3answers
51 views

0402 SMD resistance problems

I've trying make a very simple 3 LED circuit with a red, blue and green LED. I know my 3v battery will take the path of least resistance and only flow through the red, so I've added resisters to the ...
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2answers
68 views

LED light bulbs in low atmospheric pressure

I have these (https://www.amazon.co.uk/gp/product/B01DBOKZVK/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1) LED lightbulbs. Can I use them in a pressure of ~30kPa (21" Hg vacuum)?
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0answers
55 views

NPN / PNP Sound activated LEDs

I have some RGB LEDs (common anode) and I'd like to control them via sound from my stereo (line level). I'd like to be able to switch the two behaviors of the LEDs from flickering off when the input ...
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2answers
86 views

LED's brightness difference in these 2 circuits

I have past exam's problem as follows. Suppose there are circuit A (left image) and B (right image). The question is why LED in circuit A is brighter than in B. The solution states that the Low-level ...
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1answer
118 views

Can someone explain how I turned on a circuit by touching it?

I was just trying to learn how a transistor actually works by tinkering around myself. I have an Arduino running a flashing light program. I hooked up an NPN transistor to test out how I can make it ...
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4answers
99 views

Open switch that will turn on an LED without power drain

I'm sewing a purse and I would like to put some LEDs inside of the bag that only draw on the battery and turn on when the bag is open. The "switch" that I'm using are the metal snaps on the bag. I ...
46
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10answers
14k views

Why hasn't my LED burned out by now?

I have a 15 year old ReplayTV DVR. I got it used, I'm not sure when, but probably about a decade ago. It's turned on almost all the time, and it has a blue power LED on the front. The LED FAQ says ...
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1answer
48 views

Multisim - How to create a 2-pin red/green LED in one part

I would like to pass the output of an LT1413CN8 op-amp through a 2-pin red/green LED (looks white when off) and back to it's inverted input. In Multisim, there is a red/green LED option but that is ...
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2answers
95 views

Light circuit for RC car

I'm building a small light system for an RC car, this is the schematic: The power source is 5.5 V. These are the LEDs that I am using, KKHMF 100個 3mm LED 発光ダイオード LED電子部品バッグ 5種類 各20個 - two white, ...
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2answers
126 views

Do i need a resistor in this led circuit?

I have made a circuit with two (3v) LEDs in series. Connected to a 5v supply from an adapter with usb. (1.5Amp) I belive in series circuit each led gets around 2.5v which was enough to light them. ...
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0answers
32 views

Control LED panels via a relay and a PIR sensor

I bought 6 x 48W LED panels and a PIR motion sensor to light a shed/workshop area. All 240V rated. I did not appreciate that the LED drivers have a high inrush current. My question is whether I can ...
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3answers
68 views

How would I drive about 440 LED's without breaking the bank?

Alright, I'm trying to create I guess an LED matrix display(?) so that I can make essentially a text display using 8x5 LEDs per letter, to make 11 letters in total. I'm definitely willing to learn a ...
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1answer
136 views

Is electricity saved by switching off the lights when leaving a room? [closed]

Incandescents are very energy inefficient for sure so they have to be turned off whenever you leave the room. But I have tried to find the answer for CFL lights, some say that it's more efficient to ...
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2answers
129 views

TLC5940 - with 200LEDs from car battery

I'm working on project that involves 100 white and 100 RGB leds, controlled with 25 TLC5940. I've managed to connect three TLCs to Arduino MEGAv3 and so far so good. I've found out that I have to ...
3
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2answers
129 views

Powering two 3-LED lamps with battery/Battery pack - Multiple questions

I have seen many questions along these lines but I don't think any is an exact match (if that's incorrect, please just point me to the right match, that would be great and save everyone some time). ...
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1answer
58 views

LED behavior during 24 VAC negative half cycle

I don't understand why the green portion of LED3 is able to conduct. Since the path marked in green represents the negative half-cycle of the 24VAC isn't the green LED reverse biased therefore no ...
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4answers
247 views

What is the RGB value of Edison Light Bulbs? [closed]

I've been doing a little electrical engineering (outside of my lane a bit). I'm trying to get the RGB values for Edison light bulbs. Can anyone provide me with those?
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2answers
105 views

Why is my LED flickering when it is connected to a variable resistor, and it's resistance is at the minimum value

I am doing a simple breadboard circuit, with an LED, 3.3V power supply (a microcontroller connected to the PC will be the voltage source), a potentiometer, and a Voltmeter connected across the LED. ...
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1answer
77 views

Leds in series with buzzer without resistor

So I'm pretty new at this, so I'm sorry for any dumb questions/statements. I'm trying to build a puzzle box where you activate a circuit with a reed switch using a hidden magnet. Activating this ...
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1answer
50 views

PSU for led fixture

My cousin gave me a LED fixture for which the power supply is no longer working. He threw it away so I cannot look at the specs in the PSU. He says he measured 78v out of the PSU before throwing it ...
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2answers
2k views

Why does this simple circuit oscillate? (Ekasi oscillator)

Why does an Ekasi oscillator oscillate? From my research, I learned that when this is first plugged in, the capacitor is charging, so the LED doesn't shine. When the capacitor reaches 12v, then the ...
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3answers
50 views

Convert Battery to AC @ same voltage

I have some LED fair lights that run on 30V @ 0.4A supplied from an AC mains supply. They have been wired to flash using some form of notification to the AC (I'm not interested in them flashing). I ...
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3answers
94 views

How to improve an elegant design for an LED dimmer, low-powered with LDO

I am building a sunrise alarm clock. The LED is supposed to get brighter over the course of 30 minutes, then remain fully lit for another 30 minutes, then switch off. I am using a digital pin on an ...
2
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3answers
182 views

Designing brake light with specific luminous intensity

I am currently designing a brake light for a Formula Student car and I am looking into existing solutions on the market for inspiration. The two specific solutions are this, and this. The LED I found ...
2
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2answers
190 views

Cheap way to power blue LED on coin cell

I need a cheap way to take a 3v nominal coin cell and power a 3.3 forward voltage blue led. It needs to be cheap in production on a large scale, so a rudimentary joule theif won't work. Ideally it ...