mcsk
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Micro USB for powering PI is no longer OK

Sat Mar 17, 2018 12:04 pm

Back then when the PI consumed a few hundred milliamps it was a great idea that it was powered by micro USB. Everyone has a few chargers already from the old phones that can power the PI. But now the micro USB port for PI is loosing it's sense. Currently no one has 2.5 Amp adapter and a 22-AWG cable but almost every hobbyist has the general purpose AC adapter. How about to move away from micro USB for power in favor of the standard DC power connector?

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mahjongg
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Re: Micro USB for powering PI is no longer OK

Sat Mar 17, 2018 3:34 pm

If you want to create a situation where you increase the risk of non working pi or even of blowing up your PI then yes go to a barrel jack power input and abandon the perfectly adequate and efficient micro-USB supply.

IMHO what you are proposing is a very-very bad idea.

yes, with each new incarnation the requirements for the PSU have become more strict, but the idea that the fix is to switch to a random barrel jack power supply is completely naive, I'm sorry. Also, it would not decrease the total price of PI+PSU, as the needed 5V regulator (built into all micro-USB supplies) would simply have to move to the PI itself, increasing the price, and putting more heat into the PI.

Also barrel jack supplies come in all kinds of incarnations, there are at least two types of incompatible barrel jacks, one with a 2.1mm and another with 2.5mm opening, both mechanically incompatible with each other, and with poor electrical connectivity and mechanical stability.

Not to mention that barrel jacks are completely non standardised, (your suggestion that they are "standard" does not confirm with reality) not only in output voltage, but also in output polarity, and even in direct or alternating current (DC vs AC) each of them can be different. The likelihood they produce AC means you would be forced to add a rectifier, and a large bulk capacitor (probably as large as the PI itself) after the rectifier, and that would be totally unwieldy. A device with a small current consumption, (like an arduino) can get by with a small capacitor, but NOT a PI, it would need at least a large 10.000uF 16V elco so something like 2cm round and 3cm high, if not larger.

No using a micro-USB is still the very best solution, and old barrel jack supplies, (with their old fashioned low efficiency transformers) should have just one reasonable destination, that is to go into a recycle bin.

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scruss
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Re: Micro USB for powering PI is no longer OK

Sat Mar 17, 2018 3:41 pm

mcsk wrote:
Sat Mar 17, 2018 12:04 pm
… the standard DC power connector?
Which one is the standard? There are at least 52 sizes to choose from. Barrel jacks are also bigger the USB µB, so wouldn't fit in existing cases.

You also get the lovely situation with IEC 60130-10 connectors where a 2.5 mm ID jack will fit into a 2.1 mm socket, but provide no power. And don't get me started on centre negative!
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Re: Micro USB for powering PI is no longer OK

Sat Mar 17, 2018 3:44 pm

mcsk wrote:
Sat Mar 17, 2018 12:04 pm
Currently no one has 2.5 Amp adapter and a 22-AWG cable
Unless you have the good sense to buy the official 5.1V 2.5A PSU with bult-in 18AWG cable, or any of the other supplier's near-equivalents.

In fact the chances of owning a suitable USB PSU are probably greater than the chances of a random barrel connector wall wart being suitable.
(No I don't have evidence to back up that opinion, but I can be certain that standardised USB connectors protect Pis from unsuitable non-standardised barrel connector PSUs.)

Challenge: look at the barrel connector PSUs you own (I assume from your post it is a significant number). What percentage can supply at least 2.5A at between 5V and 5.25V?
Of those, how many different combinations of barrel size and polarity do you have?
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jahboater
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Re: Micro USB for powering PI is no longer OK

Sat Mar 17, 2018 4:49 pm

It does work with the Odroid C2.
That has both a barrel socket and micro usb socket and works fine off either.
I use an Official Raspberry Pi PSU because it appears to be better quality than the Odroid one.

tkaiser
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Re: Micro USB for powering PI is no longer OK

Sat Mar 17, 2018 5:12 pm

scruss wrote:
Sat Mar 17, 2018 3:41 pm
mcsk wrote:
Sat Mar 17, 2018 12:04 pm
… the standard DC power connector?
Which one is the standard? There are at least 52 sizes to choose from.
Me not joining discussions about Micro USB for powering so just providing this bit of information related to somewhat 'popular' SBC:
1) Sony PSP used 4.00/1.70 mm and this connector is also used on Cubieboards, Banana Pi, NanoPi and Orange Pi (or Micro USB)
2) All Minnowboard, Wandboard, Olimex and the larger ODROIDs use 5.50/2.10 mm
3) All older ODROIDs (up to and including C2) use 2.50/0.80 mm
4) All Pine64/Rock64 boards except the first one use 3.50/1.35 mm

Always centre positive. Back at the time when I had +40 different SBC laying around I was totally fine with 5 different PSUs (4 x barrel and Micro USB).

Problems:
1) If you don't realize you need the specific PSU with this barrel plug you end up buying on eBay a 'PSP USB power cable', some of them showing a 'nice' voltage drop under load
2) 12V PSU with the same 5.5/2.1 mm connector exist. A good way to fry your board
3) Same as 1) but getting this specific USB cable with an 2.5/08mm connector at the other end is even harder
4) Same as 3)

Unlike Raspberries not a single other SBC around using Micro USB provides some sort of under-voltage protection and/or signaling. And this (frequency capping when input voltage drops below 4.65V as it's implemented on Raspberries starting with the 2nd generation) is IMO the real reason why Micro USB somewhat works here...

BTW: What is the highest amount of current drawn by a RPi when powered through Micro USB so far? Curious since I've never seen this exceeding 1.8A at the wall (PSU included then of course).

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Re: Micro USB for powering PI is no longer OK

Sat Mar 17, 2018 5:19 pm

jahboater wrote:
Sat Mar 17, 2018 4:49 pm
It does work with the Odroid C2.
That has both a barrel socket and micro usb socket and works fine off either.
What happens when a reversed polarity 24VDC 3A adapter is plugged into the Odroid's barrel connector?
My guess is it releases the magic smoke.

That's the beauty of using the the USB microB standard, there is virtually* no power adapter around that will damage the Pi. The adapter may not allow the Pi to operate correctly due to low voltage but it won't release the magic smoke from the Pi. Not letting out the magic smoke is essential for a device designed to be used in children's education.

* I say virtually because there is probably some bozo somewhere who made a custom unit with more that 5.25V or reversed polarity with a microB connector.

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Re: Micro USB for powering PI is no longer OK

Sat Mar 17, 2018 5:50 pm

mcsk wrote:
Sat Mar 17, 2018 12:04 pm
How about to move away from micro USB for power in favor of the standard DC power connector?
*What* "standard" DC power connector?

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Re: Micro USB for powering PI is no longer OK

Sat Mar 17, 2018 6:02 pm

Paul Hutch wrote:
Sat Mar 17, 2018 5:19 pm
jahboater wrote:
Sat Mar 17, 2018 4:49 pm
It does work with the Odroid C2.
That has both a barrel socket and micro usb socket and works fine off either.
What happens when a reversed polarity 24VDC 3A adapter is plugged into the Odroid's barrel connector?
My guess is it releases the magic smoke.
That's the beauty of using the the USB microB standard, there is virtually* no power adapter around that will damage the Pi. The adapter may not allow the Pi to operate correctly due to low voltage but it won't release the magic smoke from the Pi. Not letting out the magic smoke is essential for a device designed to be used in children's education.
* I say virtually because there is probably some bozo somewhere who made a custom unit with more that 5.25V or reversed polarity with a microB connector.
Well there was at least one "USB-device" barrel power supply with negative polarity: http://www.cpmspectrepi.uk/raspberry_pi ... .0V.22_PSU (Ironically one of the "better" PSU's of its type I've tested w.r.t. "current loading" effects.) Some, now quite old, hubs incorporated their own regulators and were powered, again by barrel jack, from 6V: http://www.cpmspectrepi.uk/raspberry_pi ... ubPSU.html and
http://www.cpmspectrepi.uk/raspberry_pi ... rtHub.html
Trev.
Still running Raspbian Jessie on some older Pi's (an A, B1, B2, B+, P2B, 3xP0, P0W) but Stretch on my 2xP3A+, P3B+, P3B, B+, A+ and a B2. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

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Re: Micro USB for powering PI is no longer OK

Sat Mar 17, 2018 6:03 pm

tkaiser wrote:
Sat Mar 17, 2018 5:12 pm
BTW: What is the highest amount of current drawn by a RPi when powered through Micro USB so far? Curious since I've never seen this exceeding 1.8A at the wall (PSU included then of course).
If you're drawing 1.8A from the wall--in the US that would be 210vA, or just under 150W--something is seriously wrong. (Approximately double those figures for the UK.) The max rating for any Pi is--IIRC--2.4A @ 5.2v, or about 12.5W.

Really...if the connector is to be changed to allow for higher current, the only reasonable change would be to USB-C.

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Re: Micro USB for powering PI is no longer OK

Sat Mar 17, 2018 6:06 pm

Paul Hutch,
* I say virtually because there is probably some bozo somewhere who made a custom unit with more that 5.25V
Ah hemm... that would be me.

I hacked up a micro-usb cable to a black power supply brick that had a slide switch on it to select 5, 6, 12, 18 volts, or whatever.

Why, because I had given up hope of ever finding a USB wall wart and cable that would provide a stable supply. I had tried many.

Sure enough the inevitable happened, one day I powered up a Pi with the slide switch set to 12v.

Smoke came out and I turned it off ASAP!

Amazingly the Pi still worked after that. Even though some protection diode had become unsoldered and "tombstoned" itself.

The second time I made that mistake I was no so lucky. Dead Pi.

I later found that supply would deliver a 20v output if the slide switch was not set exactly right. So it went into the bin.

Now I use a DIN rail mount 5v PSU that has a little adjustment pot to get 5.25v into the cable. The most reliable Pi setup I ever had.

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Re: Micro USB for powering PI is no longer OK

Sat Mar 17, 2018 6:30 pm

mcsk wrote:
Sat Mar 17, 2018 12:04 pm
Currently no one has 2.5 Amp adapter and a 22-AWG cable...
You're right, I don't have 22 AWG micro-USB cables. I have 23, 20 and even 19 AWG micro-USB cables which all work great with Pi Computers.
viewtopic.php?f=63&t=165393
But now that you mention it, I think I might actually have one 22 AWG as well.

My PSU is only 2.4A, but it outputs 5.25V so it has plenty of power.

Something else to keep in mind, the current Raspberry Pi SoC is a 40nm part, and the next generation will almost certainly use a smaller, more cost and power efficient die. So the Pi4B will likely need less power than the Pi3B, which means our micro-USB power supplies will still work fine.
My mind is like a browser. 27 tabs are open, 9 aren't responding,
lots of pop-ups...and where is that annoying music coming from?

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Re: Micro USB for powering PI is no longer OK

Sun Mar 18, 2018 1:29 am

Got my new 3B+ this morning, and it booted right up using the same phone charger and micro-USB cable I have been using on my older 3B. So it seems that "Micro USB for powering PI" is, in fact, still OK.
My mind is like a browser. 27 tabs are open, 9 aren't responding,
lots of pop-ups...and where is that annoying music coming from?

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Re: Micro USB for powering PI is no longer OK

Sun Mar 18, 2018 1:50 am

HawaiianPi wrote:
Sun Mar 18, 2018 1:29 am
Got my new 3B+ this morning, and it booted right up using the same phone charger and micro-USB cable I have been using on my older 3B. So it seems that "Micro USB for powering PI" is, in fact, still OK.
Likewise, this evening. Did an update/dist-upgrade cycle earlier today and simply shutdown, disconnected, swapped in the Pi3B+ (in place of the Pi3B I've been using), reconnected everything and the Pi3B+ booted right up...from a PiDrive. Probably the fastest boot of a new Pi from box opening to running system I've ever done.

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Re: Micro USB for powering PI is no longer OK

Sun Mar 18, 2018 1:53 am

For the censors/moderators: it's stupid to delete my post :)




MOD: Didn't delete it, just removed the offensive comment and banned you for a week. Is that OK?

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Imperf3kt
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Re: Micro USB for powering PI is no longer OK

Sun Mar 18, 2018 8:50 am

I wonder if this fits the bill for a "standard" DC barrel jack? ;)
Image
Its 22AWG OFC with a 2.5mm positive center polarity.

Or perhaps it's this one, which is 3.5mm center positive polarity with 20AWG 2 core wire. The supply is [email protected](+/-0.25v)
Image
Or is it one of these?
https://i.imgur.com/ycXoHHf.jpg
2.5mm center positive with [email protected] 22AWG
3.5mm center positive with [email protected] 20AWG

Or is it my PSP-100 AC adaptor which though stated to give [email protected], only gives me [email protected]

Or maybe the one connected to my modem which is 15v and AC not DC

If someone could please instruct me on which is the "standard", I'll start using it right away!
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Re: Micro USB for powering PI is no longer OK

Sun Mar 18, 2018 9:15 am

Imperf3kt wrote: If someone could please instruct me on which is the "standard", I'll start using it right away!
That's good. None of them are standard, don't use any of them :lol:
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Re: Micro USB for powering PI is no longer OK

Sun Mar 18, 2018 9:35 am

tkaiser wrote:
Sun Mar 18, 2018 1:53 am
I know of one specific Pi fanboy who ran a 48 node RPi 3 cluster. 9 of his nodes were able to run at 1200 MHz while all the other where frequency capped and limited to 600 MHz. That's the realitiy out there.
Got so wrapped up asking which of my (small selection) of barrel connections was standard that I forgot to ask if this person you speak of was using an adequate power supply?

I mean, personally I've had little trouble powering a Pi3B with [email protected] - well below the recommended 2.5A - and pushing my Pi to it's knees (stress testing the poor thing past it's limit)

The reality is out there: The Pi foundation told people the power requirements and even went so far as to provide an official power supply. If people fail to listen, you cannot blame the Raspberry Pi Foundation. That'd be like blaming Tesla for your electric car that catches fire because you didn't read the instructions and poured petroleum over the batteries.


Oh yeah, and for the record: I'm not a "fanboi" - a simple check of my history with this forum can prove that I am quite the troublemaker normally.
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Re: Micro USB for powering PI is no longer OK

Sun Mar 18, 2018 9:44 am

Got my 3B+ on Friday. Started setting it up. Finished on Saturday morning. Boots fine from USB HD (which my Pi 3B wouldn't do from the same disk) using the official PSU. No warnings. Runs at 1.4GHz when needed. Not overheating (60°C currently when fairly busy). I'm happy. Ignoring troll-like person. :-)

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Re: Micro USB for powering PI is no longer OK

Sun Mar 18, 2018 10:04 am

W. H. Heydt wrote:
Sat Mar 17, 2018 6:03 pm
If you're drawing 1.8A from the wall
My bad, misunderstanding. I was translating to the current drawn at 5V. I've never seen any of my Pi 3 exceeding 9W at the wall (5V @ 1.8A) since all the time then frequency capping occured.

Quoting from https://libre.computer/2017/12/03/perfo ... 3-model-b/
While running these benchmarks, we noticed significant deficiencies of the Raspberry Pi 3 Model B. At first we thought it was our specific board but it was repeatable on every Raspberry Pi 3 Model B we purchased. Using a programmable DC power supply set for 5.1V was not sufficient to prevent the nasty rainbow square issue at full load. The polyfuse on the Raspberry Pi 3 experienced unexpectedly high voltage drop at just 1.5A. This caused huge inconsistencies in its benchmark results until we determined the cause. We had to drive the MicroUSB plug at 5.55V in order for it to achieve the necessary voltage levels on the 5V rails to prevent firmware clock throttling at full load.
Seems this got better with the new board but still... Micro USB is rated for 1.8A max anyway. And why do people focus on amperage ratings (or are told to do so) when the problem usually is the voltage drop?

The official RPi power supply is great since it provides stable +5V even in higher load situations but the 2.5A rating seems irrelevant to me. And yes, I also agree on USB-C.

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Re: Micro USB for powering PI is no longer OK

Sun Mar 18, 2018 11:05 am

tkaiser,
For the censors/moderators: it's stupid to delete my post
Excellent. Your muddle headedness is preserved for all to see, forever. And you have brought it to our attention :)

Well done.

I have here dozens of SBC's, dev boards and other gadgets that get their power from barrel jacks. To go with them I have a box full of power bricks with barrel connectors. They have been collected over many years. I'm pretty sure they are all different. The connectors are different diameters and various lengths. Very similar looking barrel connectors do not fit into the same jack. And of course they are all different voltages. 5, 6, 12, 15, 24 etc, etc.

This chaos has been driving me nuts for years. And here you are suggesting the Pi adopt the same chaos!
I know of one specific Pi fanboy who ran a 48 node RPi 3 cluster. 9 of his nodes were able to run at 1200 MHz while all the other where frequency capped and limited to 600 MHz.
Do you have a link to this project. Surely anyone building such a thing would write it up some place. Especially if they are a "fanboy". In fact, with such a high failure rate I would expect that they popped up here to complain in person. Where are they? I'm sure whatever issue that they had getting power to those Pi could be addressed.

I for one am very glad the Pi does not use barrel connectors.

On occasion I don't want to use the USB connection, so I just power from the 5v pin on the GPIO header.

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Re: Micro USB for powering PI is no longer OK

Sun Mar 18, 2018 11:08 am

It's quite simple.

Use a power supply that is up to the job.

Ours are specially designed for the job, so are therefor up to the job.

uUSB is also up to the job, and ALL Pi models use uUSB, so everything is backwards compatible. ie latest power supply will power all models of Pi.

What's so difficult to understand?
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tkaiser
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Re: Micro USB for powering PI is no longer OK

Sun Mar 18, 2018 11:23 am

Heater wrote:
Sun Mar 18, 2018 11:05 am
And here you are suggesting the Pi adopt the same chaos!
Nope, I tried to explain the problems associated with the various barrel plugs that are used and already said that I would be happy getting USB-C since this standard unlike Micro USB has been designed thoughtfully.

The problem is especially headless users not even noticing that they run frequency capped since they trust in 'Linux standards':

Code: Select all

/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
Also a lot of people are not aware that under-voltage will result in your Pi being limited to 600 MHz while scaling_cur_freq provides still some fantasy value of 900 (Pi 2), 1200 (Pi 3) or even 1400 now (Pi 3 B+). It's a pretty common problem BTW: see Dougie Lawson executing a rather harmless OpenSSL benchmark: viewtopic.php?f=63&t=207888#p1285414

USB-C is the way to go for the next gen Pi (most probably then also allowing for DisplayPort through USB-C so any somewhat recent display then will power the Pi) but it would've been great if the Pi people would have defined a rather exoting barrel plug providing also an appropriate PSU to stop this under-voltage drama (e.g. connected disks corrupting the filesystem when voltage at the USB ports drops below a certain amount. Some disks tolerate 4.5V, some only 4.75 as minimum)

Seriously: What is the highest consumption you've seen with a Pi so far? Me not more than 9W drawn from the wall.

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Re: Micro USB for powering PI is no longer OK

Sun Mar 18, 2018 11:24 am

tkaiser wrote:
Sun Mar 18, 2018 10:04 am
W. H. Heydt wrote:
Sat Mar 17, 2018 6:03 pm
If you're drawing 1.8A from the wall
Micro USB is rated for 1.8A max anyway. And why do people focus on amperage ratings (or are told to do so) when the problem usually is the voltage drop?
People focus on the current and not the voltage, because the current matters, not the voltage. the only thing you need to worry about with voltage is not exceeding 5.25v at the power input and not dipping below ~3.4v at the GPIO 5v header.

1.8A is not correct. The standard calls for 2.4A maximum from a Micro B USB receptacle.
I believe you pulled your information from here?
https://en.wikipedia.org/wiki/USB#USB_2.0
Battery Charging Specification 1.1: Released in March 2007 and updated on 15 April 2009.
Adds support for dedicated chargers (power supplies with USB connectors), host chargers (USB hosts that can act as chargers) and the No Dead Battery provision, which allows devices to temporarily draw 100 mA current after they have been attached. If a USB device is connected to a dedicated charger, maximum current drawn by the device may be as high as 1.8 A. (This document is distributed with the USB 3.0 and USB On-The-Go. specification packages)
Unfortunately this is related to battery charging and not the maximum currrent the port/receptacle can carry - as can be proven just a few lines later:
Battery Charging Specification 1.2:[29] Released in December 2010.
Several changes and increasing limits including allowing 1.5 A on charging ports for unconfigured devices, allowing High Speed communication while having a current up to 1.5 A and allowing a maximum current of 5 A.
It is also talking about USB A, not Micro B.


Unfortunately I cannot find the official specifications which claimed the 2.4A as I understand it, but this should help somewhat:
http://www.usb.org/developers/docs/devc ... Conn20.pdf
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tkaiser
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Re: Micro USB for powering PI is no longer OK

Sun Mar 18, 2018 11:32 am

Imperf3kt wrote:
Sun Mar 18, 2018 11:24 am
People focus on the current and not the voltage, because the current matters, not the voltage.
Funny. What was the maximum consumption you've ever seen when using an RPi? More than 9W?

For Micro USB maximum current rating do a simple web search for Micro-USB_1_01.pdf.

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