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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3answers
122 views

LED without resistor

I know Ohms Law, i know leds need resitors. My scenario is this: I need to make a little circuit that controls 2 RGB leds with a 9 Volt battery. This gives an avergare o 5 hours of light before the ...
4
votes
4answers
824 views

Voltage drop across LED in open circuit

I've searched the forums but can't find an answer for my issue. I've got a simple LED circuit powered by 5V DC. When the switch is closed, I've got 2.8V across the resistor, 2.2V across the LED, and ...
0
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5answers
108 views

control multiple leds using only 2 connection wires

i want to control 5 led bulbs using just 2 wires .depending on some condition i want to turn a led with a specific color from 5 led set and only one led should on at a time. here is a small ...
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0answers
13 views

can't change LEDs states using PCA9685

I have a PCA9685 IC connected to i2c of cubieboard like board. Also OE pin is connected to one GPIO pin. I'm using ic2tools to communicate with PCA9685, I can ...
-1
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0answers
47 views

How to learn making LED circuit from the beginning? [on hold]

I have to set up an experiment of Visible Light Communication system in which the transmitter is LED and the receiver is smartphone camera. I just have knowledge about networking and programming. So ...
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1answer
39 views

piezo and 3v LED in series to 3v battery

I'm a complete newbie to electronics. This piezo I have works with a 3v battery, and this green 3v LED works with the 3v battery, but when I combine both the piezo and LED in series on the 3V ...
-4
votes
2answers
93 views

I have a LED problem, please check image [on hold]

I have a problem getting a signal out of a LED circuit, I have written the problem in the image.
0
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2answers
209 views

4 Digit 7 segment display LED missing one light (on all four digits) [on hold]

Hi I ordered online a voltage meter and got this tiny cute little fast refreshing pretty darn precise reliable meter. HOWEVER I am missing on all four digits the left lower vertical light piece. What ...
0
votes
1answer
47 views

need advice with LM317T current limiting circuit ,new alternative

i am using an LM317 as a Current Regulator for series LED similar to protecting LEDs From over current ( in time of short circuiting) for my LEDs and Mosfets, similar to this picture: the problem ...
-1
votes
1answer
40 views

INPUT AND OUTPUT circuit protection for LED [on hold]

I am using a led circuit, and chargeable li-ion battery of 3.7 volt. I want to protect that circuit with a voltage, current, short circuit, and reverse polarity protection, in both the output and ...
0
votes
2answers
122 views

How to plan my LED circuit, voltage, and resistor

The LED emitters in my outdoor lamps blew out and I need to replace them but I have to rebuild the emitter from scratch because replacement parts are not available. The whole lamp was made in China. ...
0
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1answer
52 views

What limits the maximum allowable current of a power LED?

I wonder what it is that limits how much current can flow through a power LED. If the heat removal is managed properly how large can the current get? Why 45x45 mil size LED chips are rated 3W (700mA) ...
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1answer
60 views

BS170 Mosfet equivalent for PWM application

I'm currently using a Mosfet BS170 to drive LEDs from a 3.3V 1Khz PWM output. The problem is I would like to use more current (something around 2A max at 12V Max) than the 500mA allowed by the BS170. ...
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votes
1answer
95 views

All Possible Methods To Reduce The Current Without Reducing LED brightness

Am working on a project where in I had to control 169(13x13) LEDs, I chose ATMEGA 2560 processor for this task but it has absolute maximum Source and sink values as 200ma which was not sufficient. I ...
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vote
7answers
1k views

Transform 8~13V to 12V

I'm trying to build a diving flashlight and now I'm stuck with the electrical part. I have a \$12\$V \$10\$W high brightness LED, and am now trying to decide which is the best option for the ...
0
votes
2answers
53 views

Powering 12V LED strip lights with a 12V deep cycle battery

I would like to run 16.4' of 12V LED strip lighting with a 12v deep cycle battery. The strip lighting says it uses 1.5W per foot so I'm expecting that I'll need to provide about 2A. I was really ...
0
votes
1answer
38 views

IAR STM8 LED Pin On/Off Flash

i tried to flash the LED of this controller: http://www.cnx-software.com/2015/01/18/one-dollar-development-board/ (as you can see, there is a led connected to PD3) with this code: ...
2
votes
1answer
229 views

Where to pull LED: VCC or GND? [duplicate]

I am going to blink with LED from MCU I/O port. Where do I need to connect LED: VCC ot GND? I think it might be a difference whether the current goes into the inside MCU (when the port is low level ...
0
votes
3answers
160 views

Is this PIC micro-controller powerful enough to drive PWM LEDs?

Short Question Is a PIC24F16KM202 (Datasheet) powerful enough to vary the brightness of 12 LEDs from 12 PWM outputs without any visible stepping of brightness levels? ...
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1answer
96 views

Need help understanding fast LED driver

I'm trying to drive an LED with a square wave / pulses and look at the output with a photodiode / transimpedance amp detector. The starting frequency is about 1 KHz but I will eventually go up to ...
2
votes
2answers
410 views

Do I Need a Series Resistor in Front of a Blinking LED?

I bought LEDs with a built-in chip which make them blink. The type of the LEDs are Kingbright L-56BSRD-B. The complete spec sheet is here. After reading the spec sheet I do not know if this LED needs ...
1
vote
3answers
260 views

Driving LED with PIC 5V

I have always been taught to driver an LED using an MCP using the following method (Driving the pin high) as shown in the diagram below: However I have recently seen LED's being driven using the ...
2
votes
1answer
40 views

Error in turning ON the LED using UART in PIC32

I have a PIC32 starter Kit & IO Expansion Board. PIC32 Starter Kit has 3 LEDs on baord ...
1
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1answer
53 views

LED Poster configuration

I am helping my sister make a LED poster for a concert she is going to. I am using a foam board with some letters she placed on there. I am then going to add LED's on top of the letters to spell them ...
3
votes
2answers
251 views

Using a microcontroller to make a series of LEDs blink one after the other

This may seem like a nooby question, but I have a cycle light with 5 LEDs: * * * * * And it has a button, which when pressed hase different modes: 1st ...
0
votes
1answer
83 views

Questions about LEDs in a circuit [duplicate]

I read statements like ‘An LED has a fixed voltage drop regardless of the current running through it’, but looking at the following examples (using arbitrary numbers), can someone confirm that the ...
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0answers
36 views

led is getting on but not getting off and gsm sim900A not receiving sms continuously

hello sir i am using the Arduino code below to switch on led by receiving an SMS. Led is getting on but it is not getting off. i am using simcom sim900A gsm modem. please help me in this regard. ...
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0answers
57 views

epoxy resin Opaquing problem [migrated]

I want to put LED lamps in water and up until now i used epoxy glass for it's Isolation, but after one year it becomes Opaquing and lost it clearness. SO what come problem for Opaquing , and what is ...
1
vote
1answer
95 views

Choose the right resistor for your RGB led (calibrate the colors)

Calibrate RGB leds with the correct resistor Playing around with some microcontrollers and multiplexed leds i noticed that i always need to fix the colors of each led rgb output softwareside... thats ...
0
votes
1answer
23 views

WS2812B LED Question

I'm working with a strip of WS2812B LEDs (https://www.adafruit.com/datasheets/WS2812B.pdf), and am seeing something I didnt expect. When I write out my data to the LEDs I'm seeing the last colour I ...
0
votes
3answers
65 views

Accounting for temperature changes in circuit design

In my last post about a simple circuit: +12V -- R1 -- LED1 -- LED2 -- LED3 -- ground A user said: ...you should account for temperature changes and variation between parts. Not all parts (even ...
0
votes
0answers
37 views

why do plug-in LED lights have a special electronic box on the plug? [duplicate]

We purchased LED lights for our kids after having a near fatal carpet burning incident with an incandescent light. We purchased two plug-in LED lights that had a special box around the plug end of the ...
0
votes
2answers
71 views

Where to add a capacitor

So I have a small circuit that I made to flash some led's in sync with my music. It's just a signal from my speaker going into the base of my 2N3903 transistor and the ground of the led is being ...
0
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4answers
222 views

Placing just an LED in a circuit?

Kirchhoff's law states that “in any closed loop network, the total voltage around the loop is equal to the sum of all the voltage drops within the same loop” What would happen if you placed a LED ...
0
votes
1answer
60 views

LED array at high current or high voltage?

Is it more efficient to drive LEDs at a high current and low voltage, than a lower current and high voltage? I'm in a situation where I have to design an LED driver for a custom CoB emitter, so can ...
2
votes
5answers
127 views

Inserting Capacitor into CIrcuit causes LED to fade - Why?

My components are 2x 1.5 V batteries 25V 2200uF capacitor 3v Led copper cables My circuit looks like the following. simulate this circuit – Schematic created using CircuitLab My ...
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vote
1answer
59 views

Signal Detector (UHF Field Strength Meter)

after some reading I ended up finding a relatively basic FSM, using a antenna, an LC circuit to tune to a specific frequency, and a RF diode and final a ammeter to measure signal strength. My target ...
0
votes
3answers
68 views

Why wont my 3volt LED light up with two 1.5volt Batteries?

I have two 1.5 Volt batteries, a Red 3V LED, and some cables. The batteries I have connected in series like +- +- From my studying I believe I should now have 3 ...
0
votes
2answers
77 views

Calculating voltage in a simple circuit

If I had a 12V battery and wanted to use an LED that used 2V and 20mA, then I need a resistor that will drop 10V and provide enough resistance to produce a current of 20mA. Therefore I would use R=V/I ...
2
votes
1answer
79 views

What would be the band gap of a white LED?

So I was looking at the graph of the white LED, intensity vs wavelength and I observed two peaks. Which peak would I choose in the formula Eg = 1240 / lambda?
-1
votes
1answer
51 views

dedicated IC for PWM

Is it okay to drive leds through PWM directly from Microcontroller? OR should I use a dedicated PM generator IC like NCP5623? the Microcontroller uses software pwm. what are the pros and cons of both
6
votes
3answers
346 views

Panelization (& Depaneling) a Metal Core PCB

What is preferred way to panelise a Metal Core PCB (MCPCB) - V-scoring or Tab-routing? The engineering challenge I am facing is that the boards are meant for production (1,000 qty in the initial ...
0
votes
1answer
34 views

How to plot I vs V for multiple circuits in one graph? (NgSpice)

I have to see the I-V characteristics for five different LED model files. I'm using ngspice and I want to plot all five I-V characteristics in the same graph. What do you think I should do?
-1
votes
2answers
56 views

Controle Many LEDs with arduino [closed]

Can I control many LEDs with arduino like this project https://www.youtube.com/watch?v=V5kLyt0sv0E ? can the arduino resists with many LEDs ? or should i use a rely or any other technic to keep LEDs ...
1
vote
2answers
67 views

dimming led with photoresistor

I want to dim a led in a circuit if there's less light. However, the Photoresistor I'm working with reduces the resistance when there's more light. How can I achieve the opposite effect on resistance ...
0
votes
1answer
65 views

Most efficient way to drive a low power LED at half brightness

I'm working on a small project where efficiency is very important (every mA counts). I need to drive two red 3528 LED's in series and only have a 9V DC source. I want the LED's to be only around half ...
1
vote
1answer
60 views

looking for a sensor that activates when hit by a certain note [duplicate]

The reason may seem a bit silly, but anyway: I am trying to turn a violin steampunk. I have never done this before and I'm not the best at engineering, so could someone help? The circuitry doesn't ...
1
vote
1answer
48 views

How to drive luxeon Rebel LED

I was working on a project regarding building a high power LED driver as a excitation light to excite the florescence in the plant tissue. I want to turn the LED on and off at around 200Hz~10KHz.I ...
0
votes
3answers
59 views

grounded emitter or common collector circuit or something else?

first of all, I'm sorry if I did not use the technical correct symbols for the circuit diagram, but I think it will do. I've multiple questions. Maybe someone can give me a hint. I'd like to control ...
1
vote
2answers
90 views

Not understanding Forward Voltage and Voltage Drop

I have a simple circuit: +12V -- R1 -- LED1 -- LED2 -- LED3 -- ground Falstad simulation link If the Forward Voltage of an LED is 3V, and the Forward Current is 20mA, I can (I believe) calculate ...