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)
...
- 27.7k
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-...
- 415
10
votes
Accepted
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 ...
- 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 > ...
- 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 ...
- 15.8k
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 ...
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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.
- 70.6k
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) ...
- 34.6k
8
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 ...
- 81
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"...
- 206
7
votes
Accepted
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 ...
- 34.6k
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 ...
- 230
6
votes
Accepted
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 ...
- 561
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....
- 3,621
6
votes
Accepted
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 ...
- 34.6k
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 ...
- 7,116
5
votes
Turn LED on after a particular time for a particular time period
Let's break this answer in two parts: scheduling a task and turning a led on and off, than wrap together. You can go to the end and just get the script if you prefer!
Scheduling a task
So I would ...
- 172
5
votes
Accepted
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 ...
- 66
5
votes
Accepted
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, ...
- 10.7k
5
votes
Accepted
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 ...
- 76
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.
- 70.6k
5
votes
Accepted
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 ...
- 635
5
votes
Accepted
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 ...
- 2,441
5
votes
Accepted
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 ...
- 66
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 ...
- 4,645
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 ...
- 41
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 ...
- 21.2k
4
votes
Accepted
Is it safe to drive a current between a GPIO output at 0V (LOW) and the 3.3V supply?
Yes. In fact this is normal engineering practice, although for the Pi it probably makes no difference as the outputs are symmetrical. Having said that the amount of current you can supply from 3.3V is ...
- 58.7k
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 &...
- 317
4
votes
Accepted
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 ...
- 5,033
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