tadcampagna
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RPi high school lab. B+ issues. B no issues.

Thu Feb 07, 2019 4:36 pm

We have an RPi lab in our high school. We have 18 machines set up. 8 RPi 3 B+ and 10 RPi 3 B models. The issue is with the B+ models. They seem to have very erratic behavior. They will freeze, or the desktop will disappear. Worst case they will become corrupt on some level, not allowing them to boot.

We have tried different OS, update, upgrades. But still nothing.

Any thoughts on why it is only the B+ models with the poor behavior. Any suggestions on what to try or look at.

Thank you.

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B.Goode
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Re: RPi high school lab. B+ issues. B no issues.

Thu Feb 07, 2019 5:17 pm

Welcome to the Raspberry Pi forums.


It sounds as though these problems could be power-related.

The RPi3B+ is known to be more demanding than earlier models: perhaps power supplies that are just adequate for the Model 3 can't cope with the 3B+?
Note that Raspberry Pi 3B+ does consume substantially more power than its predecessor. We strongly encourage you to use a high-quality 2.5A power supply, such as the official Raspberry Pi Universal Power Supply.
From: https://www.raspberrypi.org/blog/raspbe ... le-now-35/

tadcampagna
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Re: RPi high school lab. B+ issues. B no issues.

Thu Feb 07, 2019 7:53 pm

I will check the power supplies on the B+ models. I think they are all 2.5 A, but they are not official RPi. Which means if the school went with the cheaper power supplies (as they sometimes do) we may not be getting what we need.

Thanks

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Re: RPi high school lab. B+ issues. B no issues.

Thu Feb 07, 2019 9:11 pm

tadcampagna wrote:
Thu Feb 07, 2019 7:53 pm
I will check the power supplies on the B+ models. I think they are all 2.5 A, but they are not official RPi. Which means if the school went with the cheaper power supplies (as they sometimes do) we may not be getting what we need.

Thanks
Some of the so-called "power supplies" sold for the Raspberry Pi computers are re-purposed phone chargers, and many of those have poor voltage regulation that can't maintain a stable 5V under load (regardless of what the specs say).

If your PSU requires a separate micro USB cable, then that cable could be trouble as well. Standard micro USB 2.0 cables aren't designed to deliver much more than 500mA without significant voltage loss (you need fast charge rated cables designed for higher current). Longer cables also have more resistance, so shorter is better.
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Re: RPi high school lab. B+ issues. B no issues.

Thu Feb 07, 2019 9:26 pm

Power supplies are one thing I make it a point to buy from reputable retailers. I don't mind paying for peace of mind.
IMHO, 2.5A is getting iffy with a 3B or 3B+. Especially if you have some other power hungry bits plugged into it.

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Re: RPi high school lab. B+ issues. B no issues.

Thu Feb 07, 2019 10:20 pm

alphanumeric wrote:
Thu Feb 07, 2019 9:26 pm
Power supplies are one thing I make it a point to buy from reputable retailers. I don't mind paying for peace of mind.
IMHO, 2.5A is getting iffy with a 3B or 3B+. Especially if you have some other power hungry bits plugged into it.
The internal poly-fuse limits the current at 2.6A, so having a higher amp power supply doesn't increase available power to the Pi itself (much). Using the official Raspberry Pi Universal Power Supply, I have yet to see the low voltage warning, even when using power hungry USB devices, like a 2TB portable hard drive.
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Re: RPi high school lab. B+ issues. B no issues.

Fri Feb 08, 2019 10:15 am

I've seen some reports of it happening with the 3B+ and Pi Foundation 7 inch touch screen. I've taken to using splitters, one cable to my Pi's micro USB power jack, another cable to my displays Micro USB power, another power feed to my speaker amplifier etc. I don't plug anything into my Pi's USB other than my keyboard mouse and the odd thumb drive.

tadcampagna
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Re: RPi high school lab. B+ issues. B no issues.

Fri Feb 08, 2019 11:27 am

Thanks for all the info...

We use the RPi's to program our Arduino's. So at times we do use the usb to power the Arduino, but I notice the erratic behaviors with and without the Arduino plugged in.

Can anyone recommend a power supply that has been reliable for you.

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B.Goode
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Re: RPi high school lab. B+ issues. B no issues.

Fri Feb 08, 2019 11:34 am

Can anyone recommend a power supply that has been reliable for you.

As already posted, the Raspberry Pi Foundation recommend this:
https://www.raspberrypi.org/products/ra ... er-supply/

A recommendation from me would be superfluous, but I can say these power supplies have always been reliable for me.

tadcampagna
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Re: RPi high school lab. B+ issues. B no issues.

Wed Apr 24, 2019 1:08 pm

We are back at the same issue as the original post. I have switched the entire lab to the RPi brand power supplies. Since then we have not witnessed any lightning bolts on our screens. However we still have 5 RPi 3 B+ that are constantly acting out on a daily basis. Here is what they are doing at times, but not always:
-won't boot at all
-will start to boot then will loose the hdmi output
-will freeze in the middle of the boot ( usually during the screen with the scrolling commands and checks with the raspberries up top)
-boot to a command prompt instead of the desktop. When the login and password are entered it returns to the same exact command prompt.
-boot to desktop, but no menu bar or cursor

What I have done:
-changed all power supplies
-flashed new sdcards with most up-to-date version of raspbian.
-updated and upgraded everything and anything.
-reinstalled the os from the noobs menu
-unplugged everything, let it sit, and tried again.
-tried the RPi with different sdcard (it worked for a time then went back to its old ways)

please help!!!!!!!!!!!!!

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Re: RPi high school lab. B+ issues. B no issues.

Wed Apr 24, 2019 1:32 pm

tadcampagna wrote:
Wed Apr 24, 2019 1:08 pm
We are back at the same issue as the original post. I have switched the entire lab to the RPi brand power supplies. Since then we have not witnessed any lightning bolts on our screens. However we still have 5 RPi 3 B+ that are constantly acting out on a daily basis. Here is what they are doing at times, but not always:
-won't boot at all
-will start to boot then will loose the hdmi output
-will freeze in the middle of the boot ( usually during the screen with the scrolling commands and checks with the raspberries up top)
-boot to a command prompt instead of the desktop. When the login and password are entered it returns to the same exact command prompt.
-boot to desktop, but no menu bar or cursor

What I have done:
-changed all power supplies
-flashed new sdcards with most up-to-date version of raspbian.
-updated and upgraded everything and anything.
-reinstalled the os from the noobs menu
-unplugged everything, let it sit, and tried again.
-tried the RPi with different sdcard (it worked for a time then went back to its old ways)

please help!!!!!!!!!!!!!
'Tis good to see that there are no low-voltage warnings now. However is there anything else that might be different about the overall setup of the 5 misbehaving P3B+'s eg. cable lengths, what's connected via GPIO or USB. Anything else connected (official display/camera)? What is the HDMI connected to (eg. monitor, TV, HDMI switch, HDMI-to-VGA converter)?
Trev.
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, B2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B+, P3B, B+, A+ and a B2) but Buster on the P4B's. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

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B.Goode
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Re: RPi high school lab. B+ issues. B no issues.

Wed Apr 24, 2019 2:00 pm

We are back at the same issue as the original post. I have switched the entire lab to the RPi brand power supplies. Since then we have not witnessed any lightning bolts on our screens. However we still have 5 RPi 3 B+ that are constantly acting out on a daily basis.


Since the record shows that I was first to point the finger at Power Supply issues I am sorry and puzzled that you still have some residual problems.

But it's not quite the same as the original post, in that you now have 3 RPi3B+ Systems that are now stable? Which is good news in itself, and perhaps invites comparison to see how those 3 differ from the 5 unstable ones? Are they physically grouped together? Are they close to some source of EMI or other radiation? Are they connected to the same network infrastructure?

tadcampagna
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Re: RPi high school lab. B+ issues. B no issues.

Thu Apr 25, 2019 12:37 pm

The lab is an old PC lab. There are several different circuits in the room, and the troublesome machines are not all on the same one. Of the 5 only 2 are directly beside each other. They are all hooked to the wireless network here at the school. Not sure if there is any interference in the room. All 15 setups in the lab are the same. USB mouse and keyboard, and hdmi to vga to monitor.

I am going to re-install the OS from the Noobs screen and move the machines around the room to see. Change out some of the hdmi adapters and sd cards. There are a lot of variables to change here so it might take me a bit to narrow down the problem. I was curious to see if it was a common issue with the B+. I''ll report back once I get the problem children up and running again.

Thanks.

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Re: RPi high school lab. B+ issues. B no issues.

Thu Apr 25, 2019 1:45 pm

tadcampagna wrote:
Thu Apr 25, 2019 12:37 pm
The lab is an old PC lab. There are several different circuits in the room, and the troublesome machines are not all on the same one. Of the 5 only 2 are directly beside each other. They are all hooked to the wireless network here at the school. Not sure if there is any interference in the room. All 15 setups in the lab are the same. USB mouse and keyboard, and hdmi to vga to monitor.
...
W.r.t. "hdmi to vga to monitor" I'd be suspicious of the (presumably active) HDMI-to-VGA adapters. Whilst I've not used any of the few examples I have with my P3B or P3B+ (they were originally used/tested with older Pi variants than the P2B IIRC) I did notice some "non-detection" issues with a HDMI switch used to share a HDMI display's (TV) input between two Pi's or a Pi and a Gigabyte Brix IIRC. Historically some (older) HDMI-to-VGA adapters, that couldn't be externally powered if needed, have been problematic.
Trev.
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, B2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B+, P3B, B+, A+ and a B2) but Buster on the P4B's. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

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Re: RPi high school lab. B+ issues. B no issues.

Mon Apr 29, 2019 2:35 pm

I have moved two of the problematic B+'s and reinstalled the OS through the NOOBS screen on Thursday. They were running great after that fresh install. Friday one of them worked great, but the other would boot to a blank screen. Today again the same one that did work still runs, now the problem child is freezing during boot up and stops after this message is displayed:

2.407305] --- [end Kernel panic - not syncing: Attempted to kill init! exitcode = 0x00007f00

I also now have a machine that will not shutdown or reboot. I can go to raspberry and try to shutdown or reboot but nothing happens. If I type from command prompt error messges come up.

It seems like the carnage is starting to pile up. I will try to use and hdmi monitor to see if there is any changes.

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Re: RPi high school lab. B+ issues. B no issues.

Mon Apr 29, 2019 10:52 pm

Have you tried swapping the power cables between the good and bad b+'s?

Swapping the power adapters?

Swapping the sd cards between good and bad?

Reducing the sd card lock?

Measuring the 5v and 3v3 rails on the gpio header?
tadcampagna wrote:
Mon Apr 29, 2019 2:35 pm
I have moved two of the problematic B+'s and reinstalled the OS through the NOOBS screen on Thursday. They were running great after that fresh install. Friday one of them worked great, but the other would boot to a blank screen. Today again the same one that did work still runs, now the problem child is freezing during boot up and stops after this message is displayed:

2.407305] --- [end Kernel panic - not syncing: Attempted to kill init! exitcode = 0x00007f00

I also now have a machine that will not shutdown or reboot. I can go to raspberry and try to shutdown or reboot but nothing happens. If I type from command prompt error messges come up.

It seems like the carnage is starting to pile up. I will try to use and hdmi monitor to see if there is any changes.
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Re: RPi high school lab. B+ issues. B no issues.

Tue Apr 30, 2019 12:08 am

tadcampagna wrote:
Mon Apr 29, 2019 2:35 pm
I have moved two of the problematic B+'s and reinstalled the OS through the NOOBS screen on Thursday. They were running great after that fresh install. Friday one of them worked great, but the other would boot to a blank screen. Today again the same one that did work still runs, now the problem child is freezing during boot up and stops after this message is displayed:

2.407305] --- [end Kernel panic - not syncing: Attempted to kill init! exitcode = 0x00007f00

I also now have a machine that will not shutdown or reboot. I can go to raspberry and try to shutdown or reboot but nothing happens. If I type from command prompt error messges come up.

It seems like the carnage is starting to pile up. I will try to use and hdmi monitor to see if there is any changes.
I've been reading this thread since it started and wondering, too, what the problems could be.

In my experience, the 1200 MHz clock speeds of the Pi 3B and the 1400 MHz for the 3B+ can sometimes be too high for fully consistent and reliable operation. While power supply issues are often to blame, I have at least one 3B that has never run reliably at the default clock speed. Over time, system crashes can further lead to SD card corruption in which case a full reformat of the card or replacement may be needed.

As a test, I would suggest underclocking the problematic Pi computers to 900 MHz by adding

arm_freq=900

in /boot/config.txt as a temporary measure to see if it makes a difference.

In addition to increasing reliability, setting the clock slower uses less power and generates less heat. This in turn can mitigate the effects of insufficient cooling, power supplies and USB power cables.

tadcampagna
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Re: RPi high school lab. B+ issues. B no issues.

Mon May 06, 2019 12:52 pm

Could our problem be the quality of SD card?

Almost every machine is using Patriot 16GB Class 10 cards.

Could our issue be the number of power cycles we go through per day?

We start up/ shut down 2 times per day.

I have tried switching cables, monitors, keyboards, mice.... Same issues

tadcampagna
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Re: RPi high school lab. B+ issues. B no issues.

Thu May 09, 2019 1:02 pm

Could this also be a power consumption issue while using Arduino UNO? We are using the RPi's to code and run Arduino Programs. Could the Arduino cause these types of behaviors? For the most part our programs are simple and only powering a few LEDs or buzzers, but we do get some students programming servos, dc motors...

There is also the great possibility that some students are mis-wiring their boards...

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Re: RPi high school lab. B+ issues. B no issues.

Tue May 14, 2019 3:12 pm

I am still stuck with 5 erratic machines. I had them all working Friday of last week. New OS from NOOBS, no Arduino. They are all back down today.

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Re: RPi high school lab. B+ issues. B no issues.

Tue May 14, 2019 9:56 pm

Very frustrating. I am beginning to suspect those Pi's may have been zapped.

Given the amount of time you have invested so far, perhaps get one or more new 3b+'s? Fortunately they are cheap.

Or, break out the test gear... I would suspect an issue with the 3v3 regulation, or poor connection in the sd card socket.

Software wise, try underclocking the cpu and also sd card by 50% initially, and if that works, go back up in 10% steps.
tadcampagna wrote:
Tue May 14, 2019 3:12 pm
I am still stuck with 5 erratic machines. I had them all working Friday of last week. New OS from NOOBS, no Arduino. They are all back down today.
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Re: RPi high school lab. B+ issues. B no issues.

Wed May 15, 2019 4:46 am

tadcampagna wrote:
Tue May 14, 2019 3:12 pm
I am still stuck with 5 erratic machines. I had them all working Friday of last week. New OS from NOOBS, no Arduino. They are all back down today.
Have you tried underclocking them as described in my post above?

tadcampagna
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Re: RPi high school lab. B+ issues. B no issues.

Wed May 15, 2019 11:08 am

I will try to under-clock.

I also posted somewhere else about going read-only with the sd cards and having students save all work to usb storage. This was suggested to reduce the impact of so many power cycles. Any thoughts?

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Re: RPi high school lab. B+ issues. B no issues.

Wed May 15, 2019 11:16 am

Paranoia raising its head ... do you keep a note of which students use which machines?

tadcampagna
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Re: RPi high school lab. B+ issues. B no issues.

Wed May 15, 2019 11:24 am

Yes. I thought for sure that would narrow it down, but with the crashing I have had some students jump to different machines. They have not yet turned those other machines to corruption.

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