D-Licious
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Raspberry PI 3 "Under Voltage"

Tue Apr 24, 2018 8:41 pm

Hey guys, I'll post this again since my first post seems to have got deleted (unsure why?) but my raspberry pi 3 was working completely fine, now its suddenly coming up with an under voltage warning and not properly booting? Nothing has changed since it worked peripherals wise and I have tried multiple cables/etc. Any advice would be appreciated! (If this is going to get deleted could you pop me a quick message since Im new here and dont know what im doing wrong, sorry!) Thanks in advance!

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mahjongg
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Re: Raspberry PI 3 "Under Voltage"

Tue Apr 24, 2018 11:09 pm

Your first post wasn't deleted, it simply was not yet moderated (let through), also your third post was deleted as a duplicate of your second post (as far I can tell this is the second of three posts) your first I only got to see when I already had let this one through.

Sudden ondervoltage messages means that suddenly the PI receives voltage (dips ) under the 4.65V.

WHY?

I don't know, maybe your local mains developed brownouts, a refrigerator in the next room kicks in and causes brown outs, or a connector isn't making good contact, or you started running more power hungry software, or a hundred other possibilities.

Probably your supply has always been marginal, especially a cheap microUSB cable often causes voltage drops at the receiving end of the cable.
Try a really thick and short one, most cables you get which chargers are trash.

One other possibility is that the polyfuse on your PI has seen a steady current overload, and is on the brink of "blowing".
It might help to give the polyfuse a few days rest, so it can recover.

You should read the boot problem sticky (in trouble shooting).

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Re: Raspberry PI 3 "Under Voltage"

Wed Apr 25, 2018 7:00 am

Thanks for the reply, I only figured out it hadn't been moderated after posting so my bad! Only posted twice though (both about power). Thought I checked that sticky but looking at it now I must have seen something else so will be sure to look through that, sorry for not doing that first. Will read the sticky and if I can't fix it will try here again.

jahboater
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Re: Raspberry PI 3 "Under Voltage"

Wed Apr 25, 2018 7:25 am

The usual recommendation is to get the "official" Raspberry Pi3 PSU.
https://thepihut.com/products/official- ... o_s=gplauk

This has a really thick (18AWG) cable that it is fixed, so the voltage is specified at the end plug.

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Re: Raspberry PI 3 "Under Voltage"

Wed Apr 25, 2018 8:07 am

I have had couple of so-called PSU's go bad anywhere from an hour to a few days. (In other words, built to pass inspection, but not much else...) And as Mahjongg said - most inexpensive cables (even some of the spendy ones) are pure crap (thin wire, poor connectors) My preference is to power my Pi's (And my "other" SBC) via pins 2/6 with a 3A-6A power "brick" using short, heavy gauge wires whenever possible.
You are in a maze of twisty little passages, all alike.
When General Failure and Major Disaster get together, Private Parts usually suffers.

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mahjongg
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Re: Raspberry PI 3 "Under Voltage"

Wed Apr 25, 2018 9:17 am

MaxK1 wrote:
Wed Apr 25, 2018 8:07 am
I have had couple of so-called PSU's go bad anywhere from an hour to a few days. (In other words, built to pass inspection, but not much else...) And as Mahjongg said - most inexpensive cables (even some of the spendy ones) are pure crap (thin wire, poor connectors) My preference is to power my Pi's (And my "other" SBC) via pins 2/6 with a 3A-6A power "brick" using short, heavy gauge wires whenever possible.
Note that if you power through the GPIO header pins you are bypassing all security measures (polyfuse, overvoltage, shorting protection) that powering through the microUSB offers, you also can make costly wiring (polarity) mistakes.

In other words, I cannot recommend powering through the pin-headers.

Its also like shooting with a cannon at a sparrow, no need for such heavy handed measures.

drgeoff
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Re: Raspberry PI 3 "Under Voltage"

Wed Apr 25, 2018 12:13 pm

mahjongg wrote:
Wed Apr 25, 2018 9:17 am
Its also like shooting with a cannon at a sparrow, no need for such heavy handed measures.
The usual English expression is "Using a steamroller to crack a nut".

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Re: Raspberry PI 3 "Under Voltage"

Wed Apr 25, 2018 12:23 pm

I have a number of USB chargers, cables and power banks with uUSB connectors that just don't mate properly with any of my Pi's (Too loose) That's why I gave up using them. I have exactly 1 that does fit well, but it is connected to a 1.5A charger (for a tablet) so only usable on an older Pi . I almost gave up on the pi 6 years ago with my first model B because finding "bad" connectors and cables was a lot easier than finding good ones :D
Since then, I have used pins 2/6 on all my Pi's (15 I think, and my "Other board") with no problems. I know it bypasses a lot of circuitry on the Pi, but I have the ability to measure voltage, count pins,solder and see colored wire. (BTW - if you do this, don't rely on the red/black being the power wires in all USB connectors - I have also encountered a few powered USB supplies that had Red/Green (data) and Black/White (power)!
You are in a maze of twisty little passages, all alike.
When General Failure and Major Disaster get together, Private Parts usually suffers.

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Re: Raspberry PI 3 "Under Voltage"

Wed Apr 25, 2018 3:36 pm

MaxK1 wrote:
Wed Apr 25, 2018 12:23 pm
I have a number of USB chargers, cables and power banks with uUSB connectors that just don't mate properly with any of my Pi's (Too loose) That's why I gave up using them.
I have the opposite experience. Every charger/power supply/whatever with MicroUSB connectors have had no problems connecting to any of my Raspberrys. (Ok, so a couple were too weak to power them). On the other hand, I have only found a couple that will connect properly to my Samsung mobile phone and actually charge it.

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Re: Raspberry PI 3 "Under Voltage"

Wed Apr 25, 2018 4:15 pm

Interesting ...
You are in a maze of twisty little passages, all alike.
When General Failure and Major Disaster get together, Private Parts usually suffers.

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Re: Raspberry PI 3 "Under Voltage"

Mon Sep 10, 2018 6:47 pm

I also have begun seeing the "Under Voltage" warning, after changing to a larger power supply.

Pi: 3B
PSU: MAA-KU MW (rated [email protected] and [email protected])

Other than the little lightning bolt in the corner, the Pi seems to be functioning normally.

Measurements:
- PSU output = 5.4v
- GPIO output = 4.7v

Can anyone tell me why I'm still getting the warning? :?:
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gordon77
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Re: Raspberry PI 3 "Under Voltage"

Mon Sep 10, 2018 6:50 pm

How good is the usb cable?

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Re: Raspberry PI 3 "Under Voltage"

Mon Sep 10, 2018 7:27 pm

> How good is the usb cable?

High grade stuff... 22 AWG High Gauge Low Impedance wire.
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gordon77
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Re: Raspberry PI 3 "Under Voltage"

Mon Sep 10, 2018 7:46 pm

Is the 5.4v under load?

Brandon92
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Re: Raspberry PI 3 "Under Voltage"

Mon Sep 10, 2018 7:50 pm

What for voltage do you measure at the 5V and ground pin located at the Rpi?

And does you power supply need to have a minimum load? Because that information is missing at they product page.
reverendfuzzy wrote:
Mon Sep 10, 2018 7:27 pm
High grade stuff... 22 AWG High Gauge Low Impedance wire.
Thats sounds like a ebay product description :? 8-)

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Imperf3kt
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Re: Raspberry PI 3 "Under Voltage"

Mon Sep 10, 2018 9:08 pm

Its probably the USB port itself.
Are you able to connect the usb cable directly to the power rails inside?

By that, I mean cut the USB-A end off the USB cable and solder it directly to the internals of the PSU, completely bypassing the port.

I found that this was my issue with a 5A PSU - PSU indeed supplies [email protected] but the USB port was limiting that to around 0.5A
Stop plugging your fan directly into the GPIO 5v
https://www.electronics-tutorials.ws/power/transient-suppression.html

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Re: Raspberry PI 3 "Under Voltage"

Mon Sep 10, 2018 9:24 pm

> Its probably the USB port itself.
> Are you able to connect the usb cable directly to the power rails inside?
> By that, I mean cut the USB-A end off the USB cable and solder it directly to the internals of the PSU, completely bypassing the port.
> I found that this was my issue with a 5A PSU - PSU indeed supplies [email protected] but the USB port was limiting that to around 0.5A

No port... it's already a direct connection.
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Imperf3kt
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Re: Raspberry PI 3 "Under Voltage"

Mon Sep 10, 2018 9:42 pm

Then send it back for a refund, you've been sold something with clearly false specs.
Stop plugging your fan directly into the GPIO 5v
https://www.electronics-tutorials.ws/power/transient-suppression.html

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Re: Raspberry PI 3 "Under Voltage"

Mon Sep 10, 2018 9:49 pm

> Then send it back for a refund, you've been sold something with clearly false specs.

I was just now considering that.

...will never trust MAA-KU products, again.
Last edited by reverendfuzzy on Thu Sep 13, 2018 12:31 pm, edited 1 time in total.
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reverendfuzzy
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Re: Raspberry PI 3 "Under Voltage"

Tue Sep 11, 2018 5:25 pm

I believe I will use the refund funds to construct a LINEAR power supply... I've got nearly all the parts to build one right here in the lab, already

...will never trust MAA-KU products, again.
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catalincf
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Re: Raspberry PI 3 "Under Voltage"

Sun Jan 13, 2019 1:52 am

Seems the Power supplied to the PIs is a never ending story and will always be of interest for any newbie/Starter. Apart from the PSUs that do not supply enough power, I realized after several testing, cutting cable, measuring, changing, combining cables that the main reason is the CABLE when you encounter issues with the POWER.
A good PSU2.5/3Amps and cable must never give RED LED blinking even when you hook up a 2.5HDD like the TOSHIBAs rated at1.0Amps. The thing to look at in the cables (built in or not in the PSU) is the AWG. Many cable cheap junk dont even have marked any AWG even though are thick as hell. Cutted one Motorola branded thick cable and found out 5 pieces of ''hair'' in the black and red wires (what a cheap joke). That cable shouldn't even be called a USB cable. Anyone who has the RED LED blinking must do something to make the LED stable even if the rpi works, but will give usb devices restart ''kicks'' changing for example the /dev/numbers. (and no, that trick with the udev to bind some IDs to a certain /dev/sda, does not work). So as stated by others, 22AWG should be minimum. If you hook some hungry devices, use 18AWG on all that is a PwrWire in your project. And stick to short lenght 20-30cm.

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Re: Raspberry PI 3 "Under Voltage"

Sun Jan 13, 2019 9:07 am

TL;DR:
Get the official Raspberry Pi Universal Power Supply (click the green BUY tag at the top of the page).


The more than you ever wanted to know answer:
catalincf wrote:
Sun Jan 13, 2019 1:52 am
Many cable cheap junk dont even have marked any AWG even though are thick as hell. Cutted one Motorola branded thick cable and found out 5 pieces of ''hair'' in the black and red wires (what a cheap joke).
Cables with thin wires are not necessarily cheap junk. The Raspberry Pi uses a USB 2.0 micro USB jack for power, and the USB 2.0 power specification is 5V at up to 500mA (0.5A) of current. Cables don't have to be very thick to transfer 2.5 watts of power. The problem happens when you try to use a standard micro USB cable to power a Pi3 computer that can demand up to 5X that.

When the Pi first came out you could use a phone charger and just about any micro USB cable, and that's still true for the Pi Zero.

However, that is no longer the case with the much more powerful (and power hungry) Pi 3B and 3B+ models, which is why it's recommended to use the official Raspberry Pi Universal Power Supply. It's not just marketing hype from the Raspberry Pi Foundation. That power supply is a proven performer that works very well, and is usually pretty affordable. It outputs 5.1V at up to 2.5A with good voltage regulation and has a built-in power cable with fat 18 AWG power wires.

Q: Can you use a phone charger?
A: Possibly, but not necessarily...

The problem with phone chargers is twofold.
  1. Charging phone batteries does not require precise voltage control (most phones only need a little over 4.2V to charge), and because of that, some phone chargers have poor voltage regulation and won't maintain a stable 5V under load. I have a charger rated for 5V & 2.4A which drops well below 5V at only a 1A load. It charges my phone fine, but it's a lousy Pi PSU.
  2. Phone chargers often use a separate USB cable, and then you run into the problem catalincf found above. Standard micro USB 2.0 cables aren't designed to deliver much more than 500mA without voltage loss. You need a short micro USB cable designed for high current charging (the ones included with smart phones and tablets may work).
So you not only need a phone charger with good voltage regulation, you need a micro USB 2.0 cable designed for high current. Also note that longer cables have more resistance, so you want a micro USB cable with fat power wires that is as short as possible.

This is why phone chargers are not recommended for the Pi 3B(+). You don't really know if it will work unless you can give it a proper load test. It may seem to work fine when you aren't doing anything too heavy, but then you try to play a game or connect a portable hard drive and it crashes, reboots and corrupts your SD card.

Now all that being said, I do have one phone charger that works great, but I did load test it at well over 2A, and I have micro USB cables with fat 21, 20 and even 19 AWG power wires. Unfortunately, that charger has been discontinued.

What about other not-official power supplies advertised for the Raspberry Pi 3B?
They may or may not work. Many so-called power supplies sold for Pi computers are just re-purposed phone chargers.

So yes, powering the much more powerful Raspberry Pi 3B, and especially the even more powerful 3B+ is not as simple as it used to be. But it's hardly a "a never ending story" because there is a proven solution. Click on the green BUY tag at the top of the page, scroll down to the official Raspberry Pi Universal Power Supply and click the BUY NOW button.
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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