Arduino Stack Exchange
Arduino Stack Exchange

Questions tagged [led]

An LED is a type of light source which is typically fairly small and has low power requirements.

An LED (Light Emitting Diode) is a semiconductor component which emits light (via electro-luminescence) when its forward voltage is sufficiently high.

In Arduino projects, small LEDs are commonly used as indicators. For example, it could be illuminated to show that a system is active/powered-on. LEDs typically operate at around 2-3 volts, requiring a current of 10-20 mA, meaning they can by powered directly from the digital output pins.

For safety, an LED should normally be used with a current-limiting resistor in series.

LEDs can also be used for other purposes, including general illumination, and in opto-isolators.

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What happens to the Arduino if you don't use a resistor with an LED?

Making a blinking light seems to be one of the most common beginner projects with Arduino. A typical approach is to connect an LED + resistor (in series) to an IO pin, and connect the other end to ground. In code, you make the pin an output, and…
Peter Bloomfield
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Can two LEDs attached to different pins share their resistor?

I'm designing an Arduino style board with built-in LEDs for several of the pins. To simplify assembly of the board and save on components, I was wondering whether it would be safe for those LEDs to share a single resistor, as in this…
microtherion
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Pattern library for addressable LED strips

Is there any central place that we can get drawing pattern functions for the addressable LED strips like the once based on the WS2812B component? These are sold on the Adafruit site under the NeoPixel name. For example I know of a few pattern…
Dan McCreary
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Multiple independent LED patterns

I have an problem, which at first thoughts (and being new to Arduino) I though was a perfect application for an Arduino. However, after trying and failing to implement it I am doubting myself! Simply - I need to control many LEDs independently, many…
Nickos
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Use Higher Resistance Than Instructed in a Circuit

I'm following the "Get Started with Arduino" Guidebook, and I'm at the part where pulse width modulation (PWM) is discussed. The instructions say to create a simple circuit with a breadboard, red LED, arduino (connected at pin 9 and ground) and a…
Neuron
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7 segment LEDs on wood face

I'm not sure this is right place for this question, but does anyone have any idea how a 7 segment display is projected or embedded in wood for products like this? Full product info at…
devth
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Digital RGB LED animation

I've been trying to get colours fade into each other for a project I'm working on. I have achieved this with the rainbow effect that some from Adafruit's example code, however I want to be able to choose the colours (eg. dark blue into light…
Rhys Edwards
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How to use a common anode 7-segment, 4-digit display?

Please take this question as an example to (my own) answer below. I've got an 7 segment, 4 digit LED display, but I don't have any idea on how to wire it. I don't understand the difference between common anode/cathode, and I don't have 2 pins per…
aaa
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Using a transistor to get 100mA on a IR led

What i saw is that the led use 1.3V on 100mA with a 1:10 Cycle (100ms). Im currently at 30mA using only a 100 resistor, but the range of the led is 20cm at max, i want to get at least 2 meters. Since i know the max output of the Arduino pin is 40mA…
Luke
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LEDs on TX/RX lines interfering with the programmig of the device

I have recently designed a shield to my Arduino Duemilanove, which has 8 LEDs, on the digital GPIO, from 0 to 7, but it won't program with the shield on because the voltage drop is too much on the RX and TX lines. My question is: can I have a LED on…
Electropepper
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Choosing right Sleep state

I'm planning on building an LED clock, but I want it to be lit only when I press the POWER button on my remote control. Using an IR receiver, which Arduino sleep mode should I use to reduce the current consumption but still be able to receive this…
Paolo Zanchi
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EPS8266 ESP-01: LED manipulation seems to interfere with serial communication

I'm playing around with this udp-example. Both this and the blink-example work perfectly. Now I would like to use the LED to indicate what the ESP is currently doing, as well as reading some data over Serial. My code looks like this: void setup(){ …
user2224350
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Visual clock with millisecond display refresh rate

I need to create a millisecond capable visual clock - I will use the clock for visual frame synchronization of multiple cameras. I found this project but it seems to use a LED display that only has resolution of one 1/100th of a second. Not sure if…
Kozuch
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Why does an RGB LED between VCC and PWM work?

I'm an Arduino beginner and I recently bought a cheap starter kit on eBay. One of the lessons in the starter kit is an RGB LED controlled by 3 PWM output pins. However, the arrangement of the connections seems a bit funny to me: To my surprise, it…
NobRuked
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Why does an LED sometimes flash when increasing brightness?

This is admittedly a cross-post from LED fade malfunction (random flash) but I can't get an answer on the Arduino forum. I was mucking around with some very basic code and I noticed that when repeatedly holding an LED at 0 brightness for 1 second…
Adrian
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