On at least a Pi 3, you can turn the green (SD card activity) LED to be on constantly with the following command (as root):
echo 1 > /sys/class/leds/led0/brightness
Now that Pi will have the green LED on steady, which makes it very easy to identify and label.
To put the LED back to its default state:
echo 0 > /sys/class/leds/led0/brightness
Shut one of them down. There should be recognizable behavior from the green light, which will eventually go out.
Then put a label on that pi with its ipname.
Then you can start that one up again.
Repeat until all are marked.
Or you can shut them all down, and then bring them up one at a time and see what ip number comes up in your router.
Either a ...
For the Raspberry Pi 2 you can add the following lines to /etc/rc.local:
sudo sh -c 'echo none > /sys/class/leds/led0/trigger'
sudo sh -c 'echo none > /sys/class/leds/led1/trigger'
sudo sh -c 'echo 0 > /sys/class/leds/led0/brightness'
sudo sh -c 'echo 0 > /sys/class/leds/led1/brightness'
Maybe it works for RPi3 too?
The latest Raspbian (using kernel 4.9) seems to have restored access to /sys/class/leds/led1 which can be used to control the PWR LED on the Pi3.
NOTE while the LED is now controllable, the circuitry would not allow it to be turned on if the voltage is too low.
The activity of the LEDs is now controlled by Device Tree. See /boot/overlays/README
There is ...
On the B+ (and presumably Pi2) the "PWR" LED was connected to a GPIO pin as was the APX803 voltage monitor chip. This let the LED be controlled, and (presumably) let the Pi detect under-voltage.
The Pi3 "PWR" LED is directly connected to the APX803 but the APX803 is still connected to PWR_LOW_N. Unfortunately this is not documented and the schematic is ...
The activity and power LEDs on the Pi3 are now connected to a GPIO port expander hanging off I2C bus 0 (the bus you must not use on the Pi3).
There is a mailbox interface to the LEDs. An (untested by me) example of using the mailbox interface for the activity LED is given at
I would recommend just pulling the ethernet cable, and pinging each Pi in turn. Which does then not reply? These other solutions are neat, but ping is evergreen. If for some reason you’ve filtered icmp requests on these Pis, you can use nping from the nmap package:
nping —arp 192.168.0.25
If you’re in a hurry, just use Fing (free) from Play/App store to do ...
It sounds like the power supply is failing to regulate and dropping out momentarily. The answer below seems to describe a similar scenario and the rpi wiki also mentions that the blinking PWR LED indicates an issue with the power supply.
From this question:
I have a Raspberry Pi B+ connected to an external USB disk, a Seagate
Portable 1 Tb (no external ...
I haven't figured out how to get the Red LED working but I have figured out (kinda) how to get the Green LED under control.
This is from user pelwell in the post here.
130 is the activity LED, so /opt/vc/bin/vcmailbox 0x00038041 8 8 130 1 will turn it on and /opt/vc/bin/vcmailbox 0x00038041 8 8 130 0 will turn it off. Be aware that any SD card activity ...
Having done some research myself I can't seem to come across any resources that explain how the LEDS work. I suspect the LEDs are something that are hardwired into the Ethernet port and are not controlled through software. For example take a look at this schematic of a RJ-45 Ethernet connector:
You can clearly see the two LEDs labelled YELLOW and GREEN are ...
I found a work around that simply allows me to add a few lines to the boot config file /boot/config.txt
To disable ACT LED, add
To disable PWR LED, add
I would agree with the others on the SD card. Sometimes the cheapo SD cards will give you issues - I'd suggest formatting the card before flashing the image, try this: https://www.sdcard.org/downloads/formatter_4/
You've already indicated that you've tried different power supplies, to no avail, but have you attempted running the board with a different (known working) SD card? If you've ruled that out, I would also look at power load. Are you running any USB devices on this board that aren't on the other boards? If not, it's most likely your board, which does happen, ...
This behavior is typical of an Ethernet interface that detects some signal on a cable, and is trying to establish a link but fails to do so due to either excessive noise, too long of a cable, a broken wire or missing pair, or failure of auto-negotiation (rare) due to hardware incompatibility. It then repeats the process after the timeout as the degraded ...
I have also asked this question Why is the green LED (ACT) blinking without SD card activity also at the Raspberry Pi Forum and received this answer:
by rpdom » Wed Feb 22, 2017 8:02 pm
From what I understand, the Pi sends a "status" request to the card every few seconds to check that it is still there and working. That will cause the LED to flash, ...
From the schematics available at www.raspberrypi.org we learn that the LED's package size is SMD 1611. I assume that is the metric code which corresponds to the imperial size of 0605. Given the resistors of 470 ohms any LED with a forward current of about or a little less than 5 mA should do.