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Questions tagged [led]

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

23
votes
3answers
5k views

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 ...
17
votes
2answers
3k views

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 ...
14
votes
2answers
26k views

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 ...
9
votes
2answers
18k views

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 ...
7
votes
3answers
5k views

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 ...
7
votes
3answers
886 views

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 ...
7
votes
1answer
2k views

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 http://www....
6
votes
2answers
6k views

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 ...
6
votes
2answers
2k views

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 ...
6
votes
1answer
3k views

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 ...
6
votes
1answer
123 views

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 ...
6
votes
1answer
174 views

Working with multiplexers for constant voltage output

I'm working on creating a circuit where I'm trying to have the ability to switch multiple strands of LED rope on and off at a time using an Arduino and a multiplexer. With my current configuration, ...
6
votes
1answer
506 views

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 ...
5
votes
3answers
78 views

How to improve response time of this sound operated LED?

I have written the following code for lighting an LED on a clap ( using sound sensor) that I have connected via a resistance of 330 OHM on pin number 4. However, when I clap once, close to the ...
5
votes
3answers
3k views

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 ...
5
votes
1answer
1k views

No power from Breadboard Power Supply Module

Components Breadboard Power Supply Module IM120525004 1 kOhm resistor Green LED Arduino Nano LiPo 7.4V battery LED Lights Up Fine with USB power from the Arduino LED Does Not Light Up with power ...
5
votes
2answers
931 views

Arduino onboard LED pin number as a constant

To use the onboard LED on an Arduino one usually has to know the pin number (13 in most cases), but is there a constant in the Arduino IDE one can use as well? So is it possible to use something ...
5
votes
5answers
4k views

How can I make a garage door laser sensor?

I would like to make a sensor that detects when my car is clear of a certain point. So, when backing in my car to my garage, I would have a beam and sensor. When the beam is broken, an LED light would ...
5
votes
1answer
764 views

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 ...
5
votes
1answer
955 views

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 ...
4
votes
2answers
1k views

Why are LED 0 and 1 on as well?

I was just playing around a bit and ran into a strange problem. LED 3, 5, 6, 9 and 10 are on, as intended. For some reason LED 0 and 1 are on as well. Can someone explain why this is happening? int ...
4
votes
3answers
170 views

How do I create a 9 bit number based on values from 9 digital inputs?

I have 9 pins that are inputs from 9 IR LEDs. I want to combine all their results into one 9 bit number. example: pin1 = high, pin2 = high, pin3 = high, pin4 = low, pin5 = high, pin6 = low, pin7 = ...
4
votes
2answers
1k views

How to use a Bi-color matrix led 8x8 with 24 pins?

I've just buy this 8x8 LED matrix WLG M20088A/BEG and I'm trying to light all the LEDs in one single color (green) but I don't understand how the 24 pins work for this specific model. I know that ...
4
votes
2answers
8k views

Receiving SMS by Arduino GSM Shield and control the LED with the content of this SMS?

I am using Arduino GSM Shield receiving SMS from an Android app. And the content of this SMS will control a LED. If the content of this SMS is not "off", the LED will be on and the content will be ...
4
votes
3answers
2k views

Are there sensors that can detect the color of an LED?

Are there sensors that can detect the color of an LED? I am working on an Arduino project that needs to detect the color of an LED on an external device. I am trying to identify a light sensor that ...
4
votes
4answers
551 views

Individually control ~200 LEDs

I am planning to build a LED polar clock, so it will need about 181 LEDs (12 Month, 31 Day, 7 Day-of-week, 12 Hour, 60 Minute, 59 Second) and I need to control each one individually. I will be buying ...
4
votes
1answer
754 views

How many Infrared sensor modules can be added to a single Arduino (eg;Uno)

I am looking to add block detection to my model railroad. I need approx. 40 infrared sensors to power 40 LED's on my control panel. No signals or other logic required yet, just the LED indications -...
4
votes
2answers
462 views

Molex power with USB serial Communication from the same PSU

Before I begin I just want to apologize for my mediocre understanding of things electrical and arduino. I know there are a lot of topics similar to this but I'm confused by the term external PSU ...
4
votes
2answers
5k views

Arduino Remote controlled RGB LED strip, having issues with brightness/dimming

I have this sketch: #include <TimerOne.h> #include <IRremote.h> #include <RGBMood.h> int RECV_PIN = 2; // IR-Receiver PIN int led = 13; // Satus-LED PIN int modus; /...
4
votes
1answer
905 views

Reading button presses with the 74HC4067E multiplexer

My project is progressing quite well, but I am having some issues reading button presses through my MUX. The Goal Cycle through twelve buttons and twelve LEDs. When a button is pressed, light up the ...
3
votes
3answers
24k views

Powering up LED strip - How many amps?

I want my Arduino to drive a LED strip. The LED strip in particular is the 3528 non-waterproof type. To power this up, I need a 12V power supply. My LED strip is going to be 5 meters. Now my ...
3
votes
2answers
769 views

Need help with 2X3 matrix for braille

I'm an intermediate Arduino progammer, and I'm making an electronic braille display for my friend. You can think of this display as an array of 28x3 LEDs(one braille character contains a maximum of ...
3
votes
3answers
2k views

Uno pin 13 LED mysteriously always ON at 0.14V unless pinMode OUTPUT

I upload a blank sketch: pin 13 LED is on. Why? I connect pin 13 to GND: it turns off until I remove the connection I connect multimeter between pin 13 and GND: measures 0.14V and LED turns off until ...
3
votes
1answer
1k views

Use LED on pin 13 again after using the SD library

The question in short: On an Arduino UNO or Nano using the SD library, is it somehow possible to use the LED on pin 13 (or any other pin that is used by the library) again after finishing all SD ...
3
votes
3answers
7k views

7-Segment Common Anode

I accidently bought a "Common Anode" 7-segment display instead of a "Common Cathode". I understand that the polarity of the leds within the display is 'reversed'. So instead of putting the common pin ...
3
votes
2answers
2k views

Why all blink tutorials use 330 ohm resistor

When I do the led calculation I found 150 ohm resistor is enough for 3mm red led. If so why all arduino tutorials, like this one, are suggesting 330 ohm resistor? I assume V = 5 Volt, diode forward ...
3
votes
3answers
12k views

Using external power supply to power leds on multiple pins (A0-A5)

I'm totally new to Arduino, and microcontrollers for that matter, so I'm having a hard time figuring out how to connect LEDs to multiple pins, but using a common external power supply... I've created ...
3
votes
3answers
2k views

Arduino PWM fading led

I am trying to blink an LED with PWM on Arduino. I don't know what is wrong but my LED is not fading as expected. What is wrong? I think that I have bad registers settings, but I am not sure. LED ...
3
votes
3answers
8k views

How many LED Strips can we connect to an Arduino Uno? Is there a way to connect 1-3 meters worth without needing extra parts (relays)?

I am looking at Adafruit to purchase some LED strips for a mod for my computer case, and want to power it with an Arduino. I am looking at the Uno, but the Mega looks good too. I hear the Uno is ...
3
votes
1answer
414 views

Why LED light delay is 5 second in arduino?

My code : int pin = 8; int pout = 12; int result=0; void setup() { pinMode(pin, INPUT); pinMode(pout, OUTPUT); } void loop() { result = digitalRead(pin); if(result == 1) { ...
3
votes
4answers
11k views

LEDs: difference between common anode and common cathode?

What is the difference in using a common anode and common cathode of the 7 Segment in interfacing with the Arduino? How can you change the code if we need to add another 7 Segment display? How can ...
3
votes
5answers
579 views

Emergency Vehicle - Make two LEDs flash with buttons and a passive buzzer change sound

My Dad and I are just learning how to use my new UNO. We have learned how to make leds flash at the touch of a button. We have also learned how to make a passive buzzer sound at the touch of a ...
3
votes
2answers
84 views

just a silly doubt about glowing an LED

what will happen if i insert the anode of a LED to pin 12 and cathode of the LED to pin 11 and set pin 12 to high and pin 11 to low,will the led glow??
3
votes
2answers
268 views

How can I connect nearly 450 LEDs to an arduino without drawing too much current?

The question seems simple, but there's more to it: I'm connecting 4 74HC595 shift-registers to an arduino pro micro. 28 of the 32 outputs will be used to control LED segments of numbers. Each segment ...
3
votes
4answers
3k views

Hex to binary, LED blinking

I need to write a program that takes a user inputted HEX value and converts it to binary, then an LED blinks according to the number of 1's in the binary. For instance, if the value is 0xABC then ...
3
votes
3answers
206 views

Unexpected Delay Between For Loops

I made some arduino code for leds that blink down a row and then back again, but when the program is run, there is an approximately 2 second delay in between the first for loop and the second. This is ...
3
votes
2answers
23k views

How to control 19 RGB LED strips with one arduino?

I need to light up 19 RGB LED strips, which it seems would require 19*3=57 PWM outs and 57 transistors. The transistors aren't an issue, but of course the 57 PWM's is. Even if I hacked the digital ...
3
votes
2answers
11k views

Fading from color to color using for-loop FastLEDs

I'm attempting to fade a strip of ws2812 7 pixels in length. Below I am using a for loop to increment the color red. I can fade it to red (from blue) but it will do it one pixel at a time or it just ...
3
votes
1answer
320 views

Overheating Shift-Register(74HC595)

I am working on a project where I need to use around 50 LED's connected to an Arduino UNO board. To begin with i worked on the tutorial provided by Arduino (https://www.arduino.cc/en/Tutorial/ShiftOut)...
3
votes
1answer
279 views

Arduino leave PWM on

I am doing an aquarium light sunrise/sunset. Till now programming wise I only did the sunrise. After running the code the light starts to rise up fine, than at full brightness, it turns off. I want ...