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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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21 views

TLC5940 SOUT/SIN signal broken after 4th daisy-chained IC

I have a PCB with 5 TLC5940's daisy-chained. The first 4 work fine, but the fifth doesn't work. The LEDs connected to that one just go on at full brightness and that's it. When I measure the SOUT to ...
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1answer
68 views

Single Cell LED boost Converter

I am planning on powering 10 white LEDs (LUXEON 3014) from a single AA rechargeable battery with Vin min=0.9V, Vin max=1.4v VLed=2.8v @ 23mA so total Vout for 10 LEDs Vout=28v, iout=23mA I found this ...
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13 views

Can I use a single clock line for 6 parallel addressable rgb data lines?

I am making a PCB with the dimensions of about 60 (height) mm by 320 mm (width). The PCB contains 5 Letters and 1 logo. The idea is to have 6 datelines in parallel. This way I can have different ...
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22 views

Low power flashing led with phone battery

I want to make a circuit that flashes a series of leds and that lasts as long as possible from a tablet battery. The battery has a voltage of 4.2 when fully charged and 3.8 when discharged, and has a ...
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2answers
49 views

What happens if LEDs do not get enough current? [duplicate]

I'm building a lighting fixture using big led panels. The LED panel says it requires 7 amps @ 12 volts, but the power supply I have is only rated to 4 amps @12 volts. What will happen? Will it ...
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1answer
165 views

How to clean output from a ubec

I'm bit stuck and at the end of my knowledge. I'm building a light stick that is controlled by a teensy micro controller and using programable rgb led's. (ws2812) the led's run at 5volt and need ...
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1answer
1k views

Flickering LED on BP3106 based LED Driver

I have got a LED fixture with a flickering problem. As I am unable to check the output due to lack of equipment I would like to research and gather some information first. The switch used is not ...
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1answer
32 views

Using Diode As a Solar/Lightbulb Cell

...hi :) a few days back I saw this Instructables.. https://www.instructables.com/id/Using-Diode-As-a-Solar-Cell/ ...so I started to experiment how this can be used to charge a cellphone or a ...
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1answer
102 views

Is this a feasable method for using 12VDC LEDs as power indicators?

I've been looking for the answer, but everything I've found is assuming the LED is of a lesser voltage, or a fixed voltage. More than anything, I'm trying to determine if the concept below is ...
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2answers
88 views

9v & 2 high power LEDs | LEDs dim after time, bright again after being off

fyi, level : newb I'm trying to learn some basics of electronics and electricity with a simple solution to a problem. Problem: I have an African Violet in a terrarium that I want to help bloom due ...
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1answer
39 views

LED lights with a dim light in open circuit

I was installing new LED lamps on my kitchen, which seemed to be functioning well. After turning off the lights, the newly installed lamps still had a dim light, that kept itself for quite long. I've ...
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5answers
143k views

LED bulb still emits light when turned off

I have recently purchased an IKEA LED bulb with G9 fittings, to replace a halogen one. This one. The bulb is installed in a lamp with 3 other halogen G9s in a 3 + 1 configuration with a 3-state ...
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1answer
65 views

Finding the broken cicuit in an Xor Gate

I am new to this particular stack site but I feel that this is the most appropriate place to ask my question. -Background- I've been following an online web course called Nand2Tetris that takes you ...
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0answers
38 views

Arduino pin connection basic

In the Arduino Uno's basic manual, connections for fading led are given. They have connected led on breadboard. The positive of led is connected through a resistor to the pin no 9 (pwm) and negative ...
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1answer
82 views

Why would Discontinuous Conduction Mode be desirable for an LED driver?

I saw this press release where DCM was listed as a feature for a new Infineon driver chip. Source: led-professional.com I'm involved in LED driver design for Horticulture where DCM is undesirable....
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0answers
22 views

Current leak LCD PCB IT-net vs TN-net

I have a LED with LED PCB mounted on a metalic plate that is connected to earth ground. The driver is a cl.2 driver with no earth wire and it's a constand current driver. The lamp is connected to ...
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3answers
327 views

How to Implement Float Switch On/Off LEDs

I've previously built this circuit to control a submersible pump with a PIR sensor: I'm now going to add a float switch to the circuit to prevent the pump running if the water level gets too low. I ...
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4answers
748 views

Constant Current LED Circuit

In the below circuit, the circuit maintains a constant current on LED. My question is after the LED there is a voltage of 18V, still, need to be dropped. Will the NPN Transistor heat up while ...
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3answers
136 views

How to connect LED strip to be powered by charger and batteries

I plan on using it mostly plugged in, batteries are there just for extra mobility and won't be used most of the time. Don't know lot about batteries so in first scheme I added a switch (pos. 1 ...
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2answers
99 views

can 2 3mm leds fit within a 5mm bi-color led without bending wires?

After creating a circuit calling for a bi-color common-anode LED, I checked places for stock, and to my dismay, all they wanted to sell common-cathode bi-color LED, but the funny thing is I can order ...
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3answers
104 views

How can I indicate that an IR LED is functioning without detecting its emissions?

I have salvaged, non-documented, IR LEDs. Without a datasheet I do not know how much current they can handle. I have run into this before: I confirm the LED is good with by viewing it through a ...
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2answers
91 views

Very low current (<10 microamps) darkness detector circuit that turns off in light

I've made a device that lights an LED at a very low current (<10 microamps) as a very dim indicator for use in the dark. At its simplest, the circuit is a 3V coin battery + resistor (300K-1M ...
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1answer
88 views

Switch module test circuit design

I am doing a project to make a test box that would to test the switch module in the photo below. Please see circuit diagram below for inside of the switch. Please note this switch is not an ordinary ...
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4answers
2k views

Can I use USB data pins as a power source?

I'm trying to build a circuit as seen below, where a sequencer controls the flashing of some LED sections, and an SPDT switch controls power to either the left or the right section of LEDs. However, ...
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0answers
28 views

LED Car Side Dynamic Indicator [closed]

I’m new here so I apologise if this isn’t in the correct location. I have just received a pair of LED Dynamic Union Flag Side Indicators for my car, which are designed to illuminate from the center ...
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1answer
44 views

5V vs 12V addressable LED efficiency

Despite hours of googling, I could not come to clear understanding how efficiency of 5V addressable LEDs compare to their 12V counterparts. If 5V is supplied to WS2812, and the red LED only needs 2....
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1answer
83 views

Proteus fast delay scanning problems 8x8 led

So im practicing shift registers. Im trying to draw a Smiley Image in the 8x8 LED. At first, it was okay because I set the scanning delay to 1 second. but in reality, this must be set to a faster ...
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2answers
63 views

Best way to power LED strip (180 LEDs)

I'm assembling this addressable RGBW LED strip setup that is 3m long and 60 LEDs/m. I have found no answer to my two questions on other sites or youtube. (This is the strip I'm using: https://www....
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1answer
57 views

Unexpectedly high voltage drop in the transistor

I'm driving an LED with a microcontroller through a transistor with a PWM signal. When the gate is grounded, no current flows, as expected. As soon as I start to drive the transistor (1% duty cycle), ...
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6answers
2k views

Highly accurate constant current source

I want a continuous and highly stable light from an LED for around a couple of hours, for which I need a highly constant and highly stable current source. I prefer an opamp-based circuit for the same. ...
2
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1answer
63 views

ADC Selection Pulsed Measurement

I am planning to measure the voltage of an rgb LED pulsed with an ADC. The pulse is around 20ms long. The pulse is necessary so the self-heating is within reason so it won´t affect the any ...
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1answer
45 views

LED selection for my application

I need to select LED/LEDs for a light source in my project. The requirement is that the light source should approximately be able to project light beam of 1.5m diameter on a surface, from a distance ...
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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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3answers
119 views

Off grid LED solar lighting without batteries

I have 2 COB LEDs (12-14V DC, 50W, I think with 3,75 A in data sheet). I need to run them with a solar panel, it should only run when there is sunlight no batteries needed. Using a 270W panel (open ...
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2answers
71 views

Does connecting LEDs in parallel use more current then connecting them in series in my circuit?

Sorry if this is a dumb question, I need a sanity check on this stuff. Is it possible to give LEDs varying current, without sacrificing efficiency? Basically I have 4 LEDs which could all use ...
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4answers
78 views

Will switching a LED on and off at a said frequency reduce or increase heat loss?

In my case, a 50W 34V LED is being used to light a small box. To reduce heat generated by the LED, we are switching it on and off at 50Hz. But I was wondering will this actually help? In the case of ...
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1answer
98 views

Drive LED strip from single LED

I have a USB controlled device (Razer DeathAdder Chroma) that has an RGB LED on it and I would like to use that LED to control a 5050 RGB LED strip about a meter in length. Both the "input" LED and ...
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2answers
56 views

Charging capacitor to power LED with a low current source

I have a 10000uF 6.3V capacitor, and my source is generating 3.3V and 15uA of current. How long will it take to charge it enough so i can pulse a standard 5mm LED for lets say 1 second?.
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2answers
43 views

Powering multiple WS2812B strips from different sources, are all grounds connected?

I'm looking to confirm if I need to connect the ground of 2 LED strips which have different power sources. Adafruit says The key is to have all of the ground pins among the strips connected in ...
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3answers
161 views

Which kind of LED shoud I use for

I'm trying to make a cheap DIY LED nigtstand Lamp. I'm looking for recommendation on which kind of LED I should use to make enough Light to call it a "lamp". Ideally I would use a 9V battery to ...
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1answer
71 views

Calculate the turn-off delay of an LED in parallel with a capacitor

I am trying to create a Custom turn off delay for an LED. For this I take an Capacitor in parallel to an LED My Idea so far was: I have the General Equation for an Capacitor. And the General ...
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2answers
57 views

Brightness when using 3.7v battery for powering 6 LEDs rated at 5v in a series

I am using 6 LEDs in a series (APA102C spec) these specifically powered by some atmega chip, and am having trouble finding a sufficiently small battery that will allow me to run the LEDs at maximum ...
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0answers
22 views

12v Bluetooth Module Bypass Circuit Needed [closed]

GOAL: Retain dimming function of 12V Bluetooth LED Dimmer module when not bypassed from its power source. BACKGROUND: LED strip is usually connected to a portable 12V source containing a small ...
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1answer
74 views

Blue 5mm flashing LED flashes for a while then goes static

This isn't my strong point by far so please bear with me! I have some 5mm blue flashing LEDs 4.5v - 6v operating voltage and my power source is a 12v 1A mains adapter (for CCTV camera) over CAT5e. I ...
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2answers
460 views

LEDs in Parallel; Which Transistor, and do I Need Resistors?

perhaps you can help out. So, I'm making a prop replica and light is a big part of it. To this end, I picked up three cheap LED torches, which have arrays of 9 LEDs in each. Cheaper than I could buy ...
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3answers
99 views

Current Source Output Does Not Become 0

I put a simple current source on a circuit to drive a UV LED with a constant current. According to the LTSpice simulation setting 0 V at the signal input results in 0 A through the LED. But when I ...
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2answers
166 views

Can I add an LED light to an existing device?

I apologize in advance if this question is nontrivially stupid, but I'm not sure how else I would find this out without a theoretical background that I don't posess... What I want to do is add an LED ...
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1answer
65 views

Mosfet: gate voltage 0 but still led strip on

LED strip: DC, 4W Mosfet: IRF740 (datasheet) To Do: Use wall socket (AC) to run DC led strip and also turn it on/off with MOSFET and arduino. AC to DC is done with rectifier and transformer. So ...
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1answer
53 views

How can a circuit cause a PIR sensor to output false positives? (Newbie) [closed]

I want to build a motion-sensor-activated blinking light that will be powered by batteries and should have low power consumption. Unfortunately the motion sensor goes high without a moving heat source ...
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1answer
93 views

regular wall switch on off led dimmer

Is it possible to make a simple dimmer thats operated just with the flick of the regular wall switch on and off? just like what Philips sceneswitch bulb does? My requirement is 100%, 50% and 10% ...