kaksi
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All my RPIs 3 are underpowered, all the time

Mon Feb 18, 2019 10:47 pm

Do not tell me to use the original P/S, I am already using it.

I am running Arduino with some Dallas DS18B20 and from time to time, the temperature in the living room drops in 5 seconds from 20 Celsius to -85 Celsius.

About 6 months ago, there were guys from the power company, so I told them about the problem. The measured 228-232-230 [V], 0.46-0.42-0.44 [ I do not know what ] and were very pleased with the results. They did not show much concern for my Arduino.

I believe both problems originate from the wall outlet, but no idea how to prove it to the power supplier.

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Re: All my RPIs 3 are underpowered, all the time

Mon Feb 18, 2019 10:49 pm

Er, what?

You havent said anything about the Pi, and a temperature drop that fast will kill you.

So, you might need to explain in a little more detail what you are talking about.
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kaksi
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Re: All my RPIs 3 are underpowered, all the time

Mon Feb 18, 2019 11:02 pm

Concerning the PIs, there is a yellow flashing bolt on the left top on the screen (I supposed it was clear from the topic). When I power the PI on, the first message is 'undervoltage detected'. I repeat, I use the original P/S.

Concerning the Arduino, this is clearly a measurement error, I bet caused by some electrical irregularity.

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davidcoton
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Re: All my RPIs 3 are underpowered, all the time

Mon Feb 18, 2019 11:06 pm

What OS?
What is connected to each Pi?

You would need severe disruption to the incoming power to affect a Pi, because the PSU will take out most voltage fluctuations. Only a full "brownout" will result in problems on the 5V side.
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kaksi
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Re: All my RPIs 3 are underpowered, all the time

Mon Feb 18, 2019 11:18 pm

davidcoton wrote:
Mon Feb 18, 2019 11:06 pm
What OS?
Two of them are running under Stretch, the third one under Jessie, being now reformatted to Stretch.
davidcoton wrote:
Mon Feb 18, 2019 11:06 pm
What is connected to each Pi?
Camera, keyboard, mouse, eth, monitor.

When it runs with camera only, I log /opt/vc/bin/vcgencmd get_throttled.

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davidcoton
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Re: All my RPIs 3 are underpowered, all the time

Mon Feb 18, 2019 11:31 pm

Are your "original P/S" the official Raspberry Pi PSU, or something else supplied by your retailer?
What is the voltage and current marked on the label?

Is the Raspbian Stretch an upgrade of an older OS, or a new download of the latest version?
It may be that the firmware is not fully updated for the Pi3B (the undervoltage detection GPIO changed on the Pi3B).
You could try

Code: Select all

sudo apt update
sudo apt full-upgrade
then reboot.
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ptimlin
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Re: All my RPIs 3 are underpowered, all the time

Mon Feb 18, 2019 11:38 pm

Just to be sure, you are not running three Pi units off of a single power supply are you?

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HawaiianPi
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Re: All my RPIs 3 are underpowered, all the time

Tue Feb 19, 2019 12:08 am

kaksi wrote:
Mon Feb 18, 2019 10:47 pm
Do not tell me to use the original P/S, I am already using it.
Your quote above tells us nothing, other than it's the PSU you've always been using.

Also, the original "Official" PSU was rated for 2A, but the newer one is 2.5A. So exactly which power supply are you using (brand, model, specs)?

Is the power supply connected directly to the Pi, or are you using anything in between (case, screen, power switch)?
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kaksi
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Re: All my RPIs 3 are underpowered, all the time

Tue Feb 19, 2019 12:15 am

ptimlin wrote:
Mon Feb 18, 2019 11:38 pm
Just to be sure, you are not running three Pi units off of a single power supply are you?
No, each PI has it's own P/S.

kaksi
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Re: All my RPIs 3 are underpowered, all the time

Tue Feb 19, 2019 12:27 am

HawaiianPi wrote:
Tue Feb 19, 2019 12:08 am
kaksi wrote:
Mon Feb 18, 2019 10:47 pm
Do not tell me to use the original P/S, I am already using it.
Your quote above tells us nothing, other than it's the PSU you've always been using.
Sorry, what I meant: "the original Raspberry Pi power supply delivered with the Raspberry Pi."
HawaiianPi wrote:
Tue Feb 19, 2019 12:08 am
Also, the original "Official" PSU was rated for 2A, but the newer one is 2.5A. So exactly which power supply are you using (brand, model, specs)?
HN-5258

BTW, running it only with the camera, w/o anything else, I bet even 2 A should be sufficient. Another hint there is something wrong with the wall outlet. But what?
HawaiianPi wrote:
Tue Feb 19, 2019 12:08 am
Is the power supply connected directly to the Pi, or are you using anything in between (case, screen, power switch)?
Directly, without modifications.

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Re: All my RPIs 3 are underpowered, all the time

Tue Feb 19, 2019 12:31 am

A power supply you got with the Pi doesn't guarantee its the official power supply.
Many vendors like to sell their own supply which in truth, shouldn't be being sold with a Pi3.

What is the brand and model number, will be more useful.people are asking, because it's usually the most common cause of this kind of issue.

Regarding your wall outlet, it is AC, while your Pi is DC. The DC is supplied by the power supply which converts the AC into DC. If you're having problems with it, it's likely nothing to do with the AC.
55:55:44:44:4C
52:4C:52:42:41

kaksi
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Re: All my RPIs 3 are underpowered, all the time

Tue Feb 19, 2019 12:36 am

davidcoton wrote:
Mon Feb 18, 2019 11:31 pm
Are your "original P/S" the official Raspberry Pi PSU, or something else supplied by your retailer?
What is the voltage and current marked on the label?
HN-5258
....
OUTPUT: 5V 2500mA

I even made adapt the charger from ACER able to deliver 3 A.
davidcoton wrote:
Mon Feb 18, 2019 11:31 pm
Is the Raspbian Stretch an upgrade of an older OS, or a new download of the latest version?
fresh dd 2018-11-13-raspbian-stretch.img
davidcoton wrote:
Mon Feb 18, 2019 11:31 pm
It may be that the firmware is not fully updated for the Pi3B (the undervoltage detection GPIO changed on the Pi3B).
You could try

Code: Select all

sudo apt update
sudo apt full-upgrade
then reboot.
Did not help.

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Re: All my RPIs 3 are underpowered, all the time

Tue Feb 19, 2019 12:37 am

kaksi wrote:
Tue Feb 19, 2019 12:27 am
HN-5258
That is NOT the official power supply. :(

It looks like a re-purposed phone charger (not even a real power supply). And it requires a separate micro USB power cable, which can cause additional problems (standard micro USB 2.0 cables aren't designed to deliver much more than 500mA without voltage loss).
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Re: All my RPIs 3 are underpowered, all the time

Tue Feb 19, 2019 12:56 am

Put it on hold for a moment.

You are all seeking for a problem with the RPI. I am sure the RPIs are OK - it is simply not possible to have 3 faulty RPIs or 4 faulty P/S.

To be really, really sure, I will try to borrow a UPS this or next weekend and I will come back.

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HawaiianPi
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Re: All my RPIs 3 are underpowered, all the time

Tue Feb 19, 2019 1:08 am

kaksi wrote:
Tue Feb 19, 2019 12:56 am
it is simply not possible to have 3 faulty RPIs or 4 faulty P/S.
Your P/S isn't a power supply (it's a phone charger). You need a power supply.

To elaborate a bit more on what I posted above, phone charging does not require precise voltage control. Most phones only need a little over 4.2V to charge. Because of that, some phone chargers have poor voltage regulation and can't maintain a stable 5V under load. I have a "5V/2.4A" charger that drops well below 5V at only a 1A load. It charges my phone fine, but it's a lousy Pi PSU.

The official USB 2.0 power specification is 5V at 500mA (per port), so that is what most micro USB cables are designed for. There is a higher current charging revision for smart phones and tablets. For the Pi you would need a micro USB cable rated for fast charging, but even those vary in current ratings (you want one rated for 2.4A+). Also, longer cables have more resistance, so you want a short cable with fat power wires.

Your problem could be poor regulation from your non-official charger/PSU, or it could be too much resistance in the micro USB cable delivering the power, or both (if I was a gambling man, my money would be on both).

The genuine, official Raspberry Pi Universal Power Supply is rated for 5.1V at up to 2.5A and has a built-in power cable with fat 18 AWG power wires. It's highly recommended here because it is a proven performer that is usually pretty affordable (of course that depends on where you live and who you buy it from). Try the green BUY tag above.
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rpdom
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Re: All my RPIs 3 are underpowered, all the time

Tue Feb 19, 2019 6:36 am

kaksi wrote:
Mon Feb 18, 2019 10:47 pm
I am running Arduino with some Dallas DS18B20 and from time to time, the temperature in the living room drops in 5 seconds from 20 Celsius to -85 Celsius.
The Dallas sensors usually give +85°C if they have an error, not -85°C. Most times I have encountered this it was because of bad wiring causing power loss to the sensor.

As for the Pi, a proper power supply should be able to power a Pi with the voltage range you listed with no trouble.

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Re: All my RPIs 3 are underpowered, all the time

Tue Feb 19, 2019 3:59 pm

rpdom wrote:
Tue Feb 19, 2019 6:36 am
kaksi wrote:
Mon Feb 18, 2019 10:47 pm
I am running Arduino with some Dallas DS18B20 and from time to time, the temperature in the living room drops in 5 seconds from 20 Celsius to -85 Celsius.
The Dallas sensors usually give +85°C if they have an error, not -85°C. Most times I have encountered this it was because of bad wiring causing power loss to the sensor.
DS18B20 won't report -85C anyway: -55C is the lowest temperature it can report (at least, according to the datasheet - I've never tried measuring that low).

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Re: All my RPIs 3 are underpowered, all the time

Tue Feb 19, 2019 9:31 pm

As repeatedly mentioned:

Get the proper power supply, and not some phone's (phoney) charger.
make sure the USB cable is rated minimum AWG 20 (0.5mm sq ), AWG18 (or 0.75mm sq) is better.

if not, your "underpowered" problem will continue.

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kaksi
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Re: All my RPIs 3 are underpowered, all the time

Tue Feb 19, 2019 10:03 pm

rpdom wrote:
Tue Feb 19, 2019 6:36 am
The Dallas sensors usually give +85°C if they have an error, not -85°C. Most times I have encountered this it was because of bad wiring causing power loss to the sensor.

As for the Pi, a proper power supply should be able to power a Pi with the voltage range you listed with no trouble.
achrn wrote:
Tue Feb 19, 2019 3:59 pm
DS18B20 won't report -85C anyway: -55C is the lowest temperature it can report (at least, according to the datasheet - I've never tried measuring that low).
I checked the code, the most frequent erroneous values are 85 and -127 (but it happens that sensor 2 reports the measure of sensor 7 or continues to report the same value) I wrote it 5 years ago, so I have some excuses not to remember it. );

Treatement of data received from Arduino:

Code: Select all

error=0
old=get_data() // it is a list, but read it as a float here
while 1:
   new=get_data()
   if abs(old-new)>2: //highest observed temp change in 5s=3C; several measures/s
     error=error+1
     new=old
   else
     old=new
 every_5_seconds_save_new_and_error()
It may run for hours w/o error, then a series. Very often, but not always, error is increased by the number of sensors or even a multiple of it. Very often, but not always, error increases when the electricity day/night rate changes. Bad contacts cannot be caused by mini earth quakes, the road is impraticable since 3 months and the next neighbor is 50 meters away.

Do you still suspect bad wiring first or might there be something else?

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Re: All my RPIs 3 are underpowered, all the time

Tue Feb 19, 2019 10:29 pm

You are now describing something different to what you described before, when you gave normal voltage readings. Switching rates and other interruptions count as the "brownouts" I described before. You may indeed need to look for UPS solutions -- but the type of PSU you are using also contribute to the problem.

May I make a suggestion -- when you report a problem here, people will respond based on their experience and the information you give. The amount of experience gathered between the contributors here is vast. If someone gets it wrong, others will offer a correction or an alternative explanation. When there is a consensus here, it is usually not wise to ignore it and insist on your own interpretation, unless you add new information (which you have now done). So when the majority here say that your PSUs may be part of the problem, you would do well to obtain the recommended PSU and test the theory. Your new information shifts the balance somewhat, but does not outweigh the advice already given. The official supply will have better margins to cope with switching transients on your mains supply, and may solve the problem even if it is not exactly what you originally described.
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kaksi
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Re: All my RPIs 3 are underpowered, all the time

Tue Feb 19, 2019 11:41 pm

davidcoton wrote:
Tue Feb 19, 2019 10:29 pm
You are now describing something different to what you described before, when you gave normal voltage readings. Switching rates and other interruptions count as the "brownouts" I described before. You may indeed need to look for UPS solutions -- but the type of PSU you are using also contribute to the problem.
Well, I try to be as short and clear as possible, but having only a poor background in electricity and not your experience, I do not judge elements the same way..

I.e. in this case, I read on the sticker 5V 2500mA - for me, a dogma beyond any need of checking. Only when HawaiianPi explained me the difference between a PSU and a phone charger, I fully understood the answers.

Still, consider the number of messages here style:
Topic: please help
Message: I have got a RPI for Xmas and it does not work what should I do?

And yes, I am thinking about the UPS solution.

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Re: All my RPIs 3 are underpowered, all the time

Wed Feb 20, 2019 12:00 am

Another (minor) assist is to include your locality in your displayed identification for each post. That way, a UPS might've been suggested earlier in the thread...if you're from a country known for poor electrical installations. Plus, someone might be able to suggest specific suppliers of proper components that are relatively local to you. (e.g. Someone in the US might not be well served by being referred to a supplier in the UK.)

kaksi
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Re: All my RPIs 3 are underpowered, all the time

Wed Feb 20, 2019 12:52 am

HawaiianPi wrote:
Tue Feb 19, 2019 1:08 am
Your P/S isn't a power supply (it's a phone charger). You need a power supply.

To elaborate a bit more on what I posted above, phone charging does not require precise voltage control. Most phones only need a little over 4.2V to charge. Because of that, some phone chargers have poor voltage regulation and can't maintain a stable 5V under load."
Cold shower, but I GOT IT NOW!!! Thanks a lot.

From all this, I think the best solution will be to buy a power bank (just the local shop does not have one delivering 2.5A) and closely inspect the PSU when I buy the next RPI.

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Re: All my RPIs 3 are underpowered, all the time

Wed Feb 20, 2019 3:10 am

kaksi wrote:
Wed Feb 20, 2019 12:52 am
HawaiianPi wrote:
Tue Feb 19, 2019 1:08 am
Your P/S isn't a power supply (it's a phone charger). You need a power supply.

To elaborate a bit more on what I posted above, phone charging does not require precise voltage control. Most phones only need a little over 4.2V to charge. Because of that, some phone chargers have poor voltage regulation and can't maintain a stable 5V under load."
Cold shower, but I GOT IT NOW!!! Thanks a lot.

From all this, I think the best solution will be to buy a power bank (just the local shop does not have one delivering 2.5A) and closely inspect the PSU when I buy the next RPI.
I have yet to see a powerbank (== Li Ion battery pack with charging and voltage regulation) that is rated for 2.5A. I have some that are rated at 2.4A and I use them with a Pi2Bv1.1 and RPF 7" display.

Your *best* course of action is to get an official RPF PSU, and once tested to your satisfaction, get enough more for the rest of your Pis.

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