Ernst
Posts: 1231
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Location: Germany

Re: Under-voltage warnings

Tue Sep 03, 2019 3:19 pm

ProDigit wrote:
Tue Sep 03, 2019 3:06 pm
jamesh wrote:
Tue Sep 03, 2019 1:03 pm
Note that if the warning is being reported, you may be more susceptible to SD card corruption, random RAM corruption, USB communication failures etc. All of these may be happening right now but you may not be noticing them. Until one of them hits something critical. Then you will.
Thanks, yes, I read up on that.
So far it passes CPU stress tests, io tests, and glxgears.
I've also done some sdcard writes, installed programs (from wifi), and no errors yet.
I do have an arm and sdram overvoltage setting at +2.

I don't know if this is what prevents errors from happening.
But if it does, perhaps low voltage warnings can be replaced with a bump in overvolting arm and sdram, up to right under where the warranty bit is set?
IMHO you are currently implementing a crude marginal check procedure which will be contra-productive.
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ProDigit
Posts: 374
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Re: Under-voltage warnings

Tue Sep 03, 2019 3:29 pm

PeterO wrote:
Tue Sep 03, 2019 3:14 pm
ProDigit wrote:
Tue Sep 03, 2019 3:00 pm
I'm not confusing any of them. I happen to have an A2 degree in electromechanics, and know what I'm talking about (unlike a certain user (in my block list), who seems to just enjoy ridiculing people. Take a hint, PeterO).
I'm sorry, but when you write
At best, I'd say arm freq 1,2Ghz throttling at 2A, and 600Mhz when voltage drops further (1,5A? I believe I've booted the pi with a 1500mA charger before.
you are mixing up all sorts of things....
" throttling at 2A " is meaningless. Throttling takes place at a particular CPU temperature, not at a particular CPU current. CPU temperature depends on other things besides current draw and has time dependent part due to thermal lag and heat sink efficiency.

"when voltage drops further (1,5A? " Voltage is measured in Volts not Amps, so that is meaningless....

Maybe you know what you are on about, but you're not writing it in a way that is at all understandable.

What is an "A2 degree" ?

PeterO
The CPU gets throttled to idle speed when the undervoltage icon is on.

Like I said above, voltage drop is directly related to what the PSU can provide in amps. U=I*R

People with an A2 electromechanics diploma equal those that have finished the first 2 years of University,
They are certified just under bachelor's degree, and could with 2 additional years get a bachelor's.
I believe in Brittain it's called a GCE Advanced Level, if I'm not mistaken, but I know next to nothing of British certifications.
https://en.m.wikipedia.org/wiki/GCE_Advanced_Level

drgeoff
Posts: 9803
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Re: Under-voltage warnings

Tue Sep 03, 2019 4:03 pm

ProDigit wrote:
Tue Sep 03, 2019 3:29 pm
PeterO wrote:
Tue Sep 03, 2019 3:14 pm
ProDigit wrote:
Tue Sep 03, 2019 3:00 pm
I'm not confusing any of them. I happen to have an A2 degree in electromechanics, and know what I'm talking about (unlike a certain user (in my block list), who seems to just enjoy ridiculing people. Take a hint, PeterO).
I'm sorry, but when you write
At best, I'd say arm freq 1,2Ghz throttling at 2A, and 600Mhz when voltage drops further (1,5A? I believe I've booted the pi with a 1500mA charger before.
you are mixing up all sorts of things....
" throttling at 2A " is meaningless. Throttling takes place at a particular CPU temperature, not at a particular CPU current. CPU temperature depends on other things besides current draw and has time dependent part due to thermal lag and heat sink efficiency.

"when voltage drops further (1,5A? " Voltage is measured in Volts not Amps, so that is meaningless....

Maybe you know what you are on about, but you're not writing it in a way that is at all understandable.

What is an "A2 degree" ?

PeterO
The CPU gets throttled to idle speed when the undervoltage icon is on.

Like I said above, voltage drop is directly related to what the PSU can provide in amps. U=I*R

People with an A2 electromechanics diploma equal those that have finished the first 2 years of University,
They are certified just under bachelor's degree, and could with 2 additional years get a bachelor's.
I believe in Brittain it's called a GCE Advanced Level, if I'm not mistaken, but I know next to nothing of British certifications.
https://en.m.wikipedia.org/wiki/GCE_Advanced_Level
1. "voltage drop is directly related to what the PSU can provide in amps. U=I*R" You are talking techno-babble nonsense.

2. "People with an A2 electromechanics diploma equal those that have finished the first 2 years of University,
They are certified just under bachelor's degree, and could with 2 additional years get a bachelor's.
I believe in Brittain it's called a GCE Advanced Level," More nonsense. GCE A Levels are taken before entering university never mind after two years at university.

3. " I know next to nothing of British certifications." That is certainly not nonsense.

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PeterO
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Re: Under-voltage warnings

Tue Sep 03, 2019 4:25 pm

ProDigit wrote:
Tue Sep 03, 2019 4:03 pm
2. "People with an A2 electromechanics diploma equal those that have finished the first 2 years of University,
I don't normal trade on it, but since you mentioned qualifications, I'll trump your A2 with my Masters Degree in Computing and Communications Engineering .
PeterO
Last edited by PeterO on Tue Sep 03, 2019 6:49 pm, edited 1 time in total.
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bjtheone
Posts: 253
Joined: Mon May 20, 2019 11:28 pm
Location: Kanata, Ontario, Canada

Re: Under-voltage warnings

Tue Sep 03, 2019 5:21 pm

ProDigit wrote:
Tue Sep 03, 2019 3:00 pm
Imperf3kt wrote:
Tue Sep 03, 2019 12:43 pm
You are confusing voltage and current (amperes)
Don't blindly trust the label.
The charger says it supplies 2A doesn't mean it supplies 5v while you're drawing 2A. As you draw more current, the voltage can drop and this is why you are seeing an 'undervolt' warning.

Also, setting the clock to 1510MHz does not mean your Pi is running at 1510MHz.
I'm not confusing any of them. I happen to have an A2 degree in electromechanics, and know what I'm talking about (unlike a certain user (in my block list), who seems to just enjoy ridiculing people. Take a hint, PeterO).
At a higher load, voltage drops. Chargers with low amp rating, drop voltage quickest. Chargers with high amp rating, maintain voltages best.

Although I won't deny that it is possible that this charger triggers the undervolt warning because it provides 5V at low or zero load, instead of full load. They are Chinese products after all, so maintaining a standard might not be priority for some companies.
As Peter pointed out the labels are fairly meaningless, beyond being a guideline to expectations. This is especially true for the more generic ones, from noname supplies in China. Beyond the inability to actually supply the claimed voltage or current, they may have horrible regulation or not be able to supply the claimed current at the claimed voltage. As noted, repeatedly the Pi is rather susceptible to undervoltage conditions and may start doing funky things... hence the under voltage warnings.

There is no relationship between current rating and ability of a power supply to maintain specified output voltage under full load conditions. That is totally dependant on the actual power supply design. Assuming appropriate input power, a good supply will be able to deliver claimed current and claimed voltage. A crappy supply will not. Having said that, buying a P/S with lots of current headroom may result in a having a supply that will supply the required current without voltage sagging. Beyond the regulation abilities of the supply there is the actual delivered power. This is where the lead size, connection method and power jack come into play. Lower quality supplies will also tend to skimp here resulting in significant voltage drop between the supply and the Pi. Obviously add additional adaptors, like a microUSB to USB C, will worsen the situation.

Not sure what an A2 degree in electromechanics is. We don't have those in the colonies. I have a very pretty piece of paper somewhat that grandly claims BaSC in Electrical Engineering from Waterloo and another one that enthusiastically states I an a licensed Professional Engineer in Ontario. Taken together they will hide a fairly large defect in your standard office wall. However, I have spent most of my professional career doing CAD tool stuff and am much more comfortable with client server architecture, and large multi site design environments than wiring bits and bobs. More relevant to most of the discussion here, is that I have been involved with Unix and Linux in both my professional and private life for almost 40 years. I suspect that many folks on these forums also have fancy degrees and titles. Said titles and degrees may be relevant or not, to the discussion at hand. However, waving them about like a magic wand may not have the result you are expecting or looking for.

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PeterO
Posts: 5004
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Re: Under-voltage warnings

Tue Sep 03, 2019 5:37 pm

bjtheone wrote:
Tue Sep 03, 2019 5:21 pm
As Peter pointed out the labels are fairly meaningless, beyond being a guideline to expectations.
It was James that made those points.
PeterO
Discoverer of the PI2 XENON DEATH FLASH!
Interests: C,Python,PIC,Electronics,Ham Radio (G0DZB),1960s British Computers.
"The primary requirement (as we've always seen in your examples) is that the code is readable. " Dougie Lawson

bjtheone
Posts: 253
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Location: Kanata, Ontario, Canada

Re: Under-voltage warnings

Tue Sep 03, 2019 5:53 pm

PeterO wrote:
Tue Sep 03, 2019 5:37 pm
bjtheone wrote:
Tue Sep 03, 2019 5:21 pm
As Peter pointed out the labels are fairly meaningless, beyond being a guideline to expectations.
It was James that made those points.
PeterO
My apologies... More coffee obviously required.

Irregardless it is a very valid and important point. Labels (shockingly) lie. If a company is willing to fake UL/CSA certification they are certainly not particularly bothered about amp and volt ratings. Spending the extra money on a known quality adaptor would solve so many problems.

drgeoff
Posts: 9803
Joined: Wed Jan 25, 2012 6:39 pm

Re: Under-voltage warnings

Tue Sep 03, 2019 6:27 pm

PeterO wrote:
Tue Sep 03, 2019 4:25 pm
drgeoff wrote:
Tue Sep 03, 2019 4:03 pm
2. "People with an A2 electromechanics diploma equal those that have finished the first 2 years of University,
I don't normal trade on it, but since you mentioned qualifications, I'll trump your A2 with my Masters Degree in Computing and Communications Engineering .
PeterO
@PeterO
I am not the original author of that. That is part of a complete paragraph by Prodigit that I quoted and called nonsense.

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PeterO
Posts: 5004
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Re: Under-voltage warnings

Tue Sep 03, 2019 6:50 pm

drgeoff wrote:
Tue Sep 03, 2019 6:27 pm
@PeterO
I am not the original author of that. That is part of a complete paragraph by Prodigit that I quoted and called nonsense.
Sorry, I see that now, but you didn't make the quoting very clear (i.e. no use of quoting tags) , but I've fixed it now.
PeterO
Discoverer of the PI2 XENON DEATH FLASH!
Interests: C,Python,PIC,Electronics,Ham Radio (G0DZB),1960s British Computers.
"The primary requirement (as we've always seen in your examples) is that the code is readable. " Dougie Lawson

jamesh
Raspberry Pi Engineer & Forum Moderator
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Posts: 23632
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Re: Under-voltage warnings

Tue Sep 03, 2019 9:09 pm

Too much sniping.
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