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17 votes

What do system LEDs signify?

Current RPi models have some of the following LEDs: PWR (red) Indicates that power has been provided to the board. On A+ and later models it will flash if the voltage drops below 4.63V ACT (green) ...
Dmitry Grigoryev's user avatar
12 votes
Accepted

Are there other act_led_trigger options besides "mmc" and "heartbeat"?

I have tried describing the values mentioned. none No trigger kbd-scrolllock Keyboard scroll lock kbd-numlock Keyboard num lock kbd-capslock Keyboard caps lock kbd-...
Ameer's user avatar
  • 405
10 votes
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Power LED from 3.3V Power Pin without Resistor

You need to consider that the forward voltage of a white LED is likely in the range of 3.0 V to 3.2 V (according to the linked article). Assuming the best case of 3.0 V and a resistor of 330 Ohms and ...
Ghanima's user avatar
  • 15.8k
10 votes

Is there any built in LED connected with GPIO pin?

Yes, it is possible to control the built-in leds. Green LED is easier. According to here, though it is probably Pi 3 specific, since it didn't work for my Pi 4: In the terminal: sudo echo 1 > ...
Botspot's user avatar
  • 1,759
9 votes

2nd LED not working when connected to different GPIO port

LEDs have different characteristics depending on their color. Of significance is the so called forward voltage. Blue LEDs have a typical forward voltage of 3.3V to 3.4V which is higher than the ...
Ghanima's user avatar
  • 15.8k
9 votes

Is there any built in LED connected with GPIO pin?

though it is probably Pi 3 specific, since it didn't work for my Pi 4 It works on the 4 as well, you just need to set the right trigger. The instructions that you provided are not applicable to the 4 ...
icuwopcui's user avatar
8 votes

How do I control the system LEDs using my software?

I wrote a userspace program which let you control the Ethernet LEDs. The program requires the more recent libusb-1.0 (NOT the older 0.1). It works with LAN9512 (e.g. on the older Raspberry B) as well ...
blip's user avatar
  • 81
8 votes
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Disable LEDs Pi Zero

Add the following to /boot/config.txt and reboot. dtparam=act_led_trigger=none The LED is wired with inverse logic. Write 1 to GPIO 47 to switch it off. Write 0 to GPIO 47 to switch it on.
joan's user avatar
  • 70.9k
8 votes

I can't get three LED lights to turn off and on in an order

You need to set the pin as an output before you use it. To do that add the following line: GPIO.setup(red, GPIO.OUT) below the matching lines for green and yellow: GPIO.setup(yellow, GPIO.OUT) ...
Steve Robillard's user avatar
7 votes
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Using jumper cables to turn on LEDs

Looking at your picture, why not make use of the extra 10 unused rows on your breadboard? I am going to assume that you've figured out that "row 1, holes a-e" are all interconnected, "row 1, holes f-j"...
zmerch's user avatar
  • 206
7 votes
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connecting common anode rgb led

Connect the common anode pin to 3.3 volt and each of the other pins to a GPIO (add a current limiting resistor between the LED and the GPIO pin. To Light one of the colors set the corresponding GPIO ...
Steve Robillard's user avatar
7 votes
Accepted

What is the maximum number of RGB LEDs that can be controlled individually?

Actually, with 17 GPIOs you can drive 72 LEDs using time multiplex (8 groups of 9 LEDs are driven one after another for such a short time that our eyes believes they are on at the same time, just less ...
Philippos's user avatar
  • 230
6 votes

Using jumper cables to turn on LEDs

Using a bread-board is usually a temporary means of allowing you to work out the circuit you want before transferring the design to Veroboard or just for something that you only need for a short while....
SlySven's user avatar
  • 3,621
6 votes
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Help lighting LED via GPIO pins

In your script, you have: GPIO.setup(7, GPIO.OUT) and then you call blink(11), which will lead to calling: GPIO.output(11, GPIO.HIGH) That is, the pin numbers don't match. You want to change both ...
janos's user avatar
  • 561
6 votes
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I need to control 8 LED's but I can only control 3? [helpful pictures attached]

The problem is the breadboard (though some would call it a feature). The breadboard you have has split power rails (Marked by the red and blue lines on the edge of the board). If you look carefully ...
Steve Robillard's user avatar
6 votes
Accepted

How to indicate read / write disk operiation via LEDs connected to GPIO

Have a look at /proc/diskstats. It shows a lot of details per partition. Monitor for changes and light up an LED connected to the GPIO. You could even whip up a script and monitor multiple individual ...
Aloha's user avatar
  • 7,126
5 votes
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GPIO stuck in High Mode

The cable is connected wrong. The end on the cobbler is Ok but the end on the RPi needs to be reversed so that the white stripe is next to the RPi's onboard led's. I had this same issue many months ...
pxgator's user avatar
  • 66
5 votes
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Powering up a WS2812 led strip with different power supplies

I'm presuming that WS2818 is a typo. For the most part your setup sounds fine. The only thing I'd change would be the connection between the LED strip and the Pi. WS281[x] chips, strictly speaking, ...
goobering's user avatar
  • 10.7k
5 votes
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Light a led without GPIO board

Yes, You can connect LEDs directly to Pi's pins. The Pi has many GPIOs on the header and you can use any one of them and connect an LED on a breadboard. Here is one very well explained tutorial for ...
HallMark's user avatar
5 votes
Accepted

RPI GPIO Ports default on?

Yes, it is normal. GPIO 0-8 have their internal pulls to 3V3 enabled at boot. That will allow enough current to flow to dimly light a LED.
joan's user avatar
  • 70.9k
5 votes
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Pi Zero W - Switching camera LED from program or command line

After much searching I attempted to use an overlay as detailed here https://github.com/raspberrypi/linux/issues/1332 however on checking the source dts file it appears that the camera led for the pi ...
Charemer's user avatar
  • 635
5 votes
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Turn on a Led with Raspberry Pi

The Raspberry Pi GPIO header has 40 pins. There are two 5V pins, two 3V3 pins, some ground pins, and the rest are general purpose - you can use them as input or output pins. These general pins are ...
ben_nuttall's user avatar
  • 2,451
5 votes
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Dimming a 0-10v dimmable light

For 0-10V DC Dimming, 0V does not equate to 0 light output. The dimming ballast or drivers are rated for a 10-100% or 1-100% dimming range. To turn the fixture completely off, you also need a relay ...
Adam Geron's user avatar
5 votes
Accepted

How can Rpi Python PWM GPIO pins control PT4115 to dim LED strips of 1W 350mA?

Question How can Rpi Thonny Python PWM GPIO pins control brightness of white LED strips of 3 to 4 1W 350mA power LEDs? It would be nice to start easy with a cheap module, and later do a DIY project ...
tlfong01's user avatar
  • 4,665
4 votes

How to blink LEDs on/off continually, while continuing execution of a script?

I'm relatively new to Python, but I have been able to flash the LEDs while continuing execution by using Pulse Width Modulation(PWM) which is built into the RPi.GPIO module. This in my opinion was a ...
josxou15's user avatar
4 votes
Accepted

How do you connect 81 LEDs to as few pins as possible?

81 makes a nice 9x9 grid; if you wire them across 18 outputs such that each has a unique combination of X & Y: Resistors are needed on one set of 9 only. To light an LED, bring the anode low &...
Mark Williams's user avatar
4 votes

Why is a resistor needed for LEDs?

The Question: Why is a resistor even needed, and how would you know what ohms it should be? The Short Answer: A resistor is not needed. The parameter of primary importance is the current to be ...
Seamus's user avatar
  • 21.7k
4 votes
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How to calculate how many watts a resistor need?

Watts(P) are the product of Voltage(V) and Amperage/Current(I). So if this is hooked up to the GPIO of the RPi, you know V=3.3V (assuming you didn't wire this up to the 5V pin). Assuming the LED has a ...
Phil B.'s user avatar
  • 5,043
4 votes
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Powering WS2812B LED strip from Pi brownouts

Powering the Pi using the pins at the GPIO connector and connecting the LEDs at the other pins of the same connector bypasses the Pi's protective circuitry that could not handle that much current. ...
Ghanima's user avatar
  • 15.8k
4 votes

What is the maximum number of RGB LEDs that can be controlled individually?

Yes and no. If you are talking about discrete LEDs then yes each one will need 3 pins and a common power or ground connection. However, they also make individually addressable RGB LED strips, rings ...
Steve Robillard's user avatar

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