chrisuk
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Power/Voltage Issues on B+

Fri Feb 06, 2015 10:09 am

Hi guys,

New to the Pi & I wanted one to make into a small, low powered Kodi media center for my kitchen TV.

I've got a 2A mains power supply from a recent Amazon deal (included in the kit) & I keep getting that rainbow square in the top right corner of the screen & flashing red light on the Pi - which I've read is a problem with low voltage.

I've tried both RaspBMC & OpenElec OS & its happening on both & I've experimented with the overclocking & that's not had an affect either.

I've also tried 2 different USB phone charger leads - but again, no joy.

I know the warning can be switched off, but I have found the Pi slows down when it occurs, so want to rectify it.

Does anyone have a recommendation for a different PSU (I'm assuming it is that which is causing the problems - that or a hardware fault ?) - just for reference, the Pi boots up & works fine, although I find it slows down when low on voltage. I've also just tried it with only the wifi USB adapter running (no keyboard/mouse), but with no joy.

Thanks
Chris

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DougieLawson
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Re: Power/Voltage Issues on B+

Fri Feb 06, 2015 11:45 am

Does the rainbow power warning square come on and stay on or does it appear briefly then go away?

My A+ always gets that during boot (as the USB stuff gets woken up), but once booted the square vanishes and the machine runs brilliantly.

If the square stays on then you have a faulty power supply.

My PI2 is using one of these:
http://shop.pimoroni.com/products/raspb ... wer-supply
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chrisuk
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Re: Power/Voltage Issues on B+

Fri Feb 06, 2015 8:45 pm

It comes & goes mate depending on what the Pi is doing.

If streaming a movie for instance it comes on, fades away for 4-5 seconds, then comes back & repeats.

If XBMC is not anything it doesn't pop up, but when navigating menus etc it comes & goes......

I've tried 3 power supplies now with no change, is it just unlucky or something amiss with the hardware ?

Thanks

Chris

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Re: Power/Voltage Issues on B+

Fri Feb 06, 2015 10:45 pm

What peripherals are powered through your Pi? You may be drawing too much in total, which can be solved with a decent powered hub.
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Re: Power/Voltage Issues on B+

Fri Feb 06, 2015 11:23 pm

Use a better microUSB cable, the kernel can pick up very short dips from the brownout detector, often being caused by too much resistance between the bulk capacitance (power) inside the OSU, and the much smaller "reserve" capacitance inside the PI, if a current surge drains the local capacitance empty too fast then it can cause such short power dips.

chrisuk
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Re: Power/Voltage Issues on B+

Fri Feb 06, 2015 11:24 pm

davidcoton wrote:What peripherals are powered through your Pi? You may be drawing too much in total, which can be solved with a decent powered hub.
Just a wifi dongle, nothing else....

chrisuk
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Re: Power/Voltage Issues on B+

Fri Feb 06, 2015 11:26 pm

mahjongg wrote:use a better microUSB cable, the kernel can pick up very short dips from the brownout detector, often being caused by too much resistance between the bulk capacitance (power) inside the OSU, and the much smaller "reserve" capacitance inside the PI, if a current surge drains the local capacitance empty too fast then it can cause such short power dips.
Like I say, I've tried 3 cables so far, so open to suggestions.

Would prefer a USB cable powered by the TV if possible, but have also tried a mains powered adapter (which came with the "ultimate kit").

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Re: Power/Voltage Issues on B+

Fri Feb 06, 2015 11:28 pm

Just a wifi dongle? "just"? These are actually the worst "peak impulse current" users you could plug into the USB port...
Some WiFi dongles will cause exactly these kind of problems, if you have a bad power cable!

Using three equally bad cables doesn't convince me its not a cable problem, cheaply made bad microUSB "charger" cables are very common.

One other alternative culprit is a half blown polyfuse, that has never completely recovered.

rahlquist
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Re: Power/Voltage Issues on B+

Fri Feb 06, 2015 11:32 pm

mahjongg wrote:Just a wifi dongle? "just"? These are actually the worst "peak impulse current" users you could plug into the USB port...
Some WiFi dongles will cause exactly these kind of problems, if you have a bad power cable!
Is there any way for us to get statistical data from the brownout detector? I am being told that some of my issues may be supply related. The cables I use are 24awg/28awg from Monoprice, I know they can move 2A to my phone...

chrisuk
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Re: Power/Voltage Issues on B+

Sat Feb 07, 2015 8:48 am

Looks like best option is to try cable #4 !

Are there any recommended for both USB & mains powered ?

Thanks for the input guys

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Re: Power/Voltage Issues on B+

Sat Feb 07, 2015 3:02 pm

You can't beat a swag store PSU, no pesky USB leads to get in the way. Its beyond reproach.

http://swag.raspberrypi.org/products/ra ... wer-supply
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TimD
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Re: Power/Voltage Issues on B+

Sat Feb 07, 2015 3:50 pm

12W iPad supplies output 5.2V to allow for cable drop.

edit: Sorry, replied the the wrong thread, should have been for the "Undervolt" thread.

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Seiduna
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pRi 2 and camera board - how much power?

Sun Mar 01, 2015 12:55 am

pRi 2 and camera board - how much power?

oi, i just made my rig to work, and I figured out what that rainbow square means in top right corner of a screen - i got low power.
I have bunch of micro usb cables, I use the shortest one, 50 cm long.
The power supply I have is this: http://www.galagomarket.com/index.php/i ... sb3u-black
it has 5V and up to 2.1 A

It happens as I start some scripts I have for camera board (recording videos or streaming).

vcgencmd measure_volts sums volts to 4.8250 V.

I have not yet tried all apps, but is this to be expected?
I played some short videos with omxplayer, power was ok (no rainbow).

Should I consider another power supply, like official Raspberry Pi Universal Power Supply,
or I need some heavy duty V and A,
or just the right cable?

Any experience or suggestions?
Gnu/Linux,
because I'd rather own a free OS
than steal one that's not worth paying for.

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Re: pRi 2 and camera board - how much power?

Sun Mar 01, 2015 8:03 am

Seiduna wrote:...vcgencmd measure_volts sums volts to 4.8250 V.
I don't think this is helpful. The rainbow square indicates that the 5V supply has dropped below about 4.65V, which does not equate to the sum of these readings.
(see Dom's post: http://www.raspberrypi.org/forums/viewt ... 29&t=82373)
I...Should I consider another power supply, like official Raspberry Pi Universal Power Supply,
or I need some heavy duty V and A,
or just the right cable?...
You can spend a lot of money buying power supplies & cables, and still not get to the bottom of the problem. If you can borrow or buy a cheap multimeter you can measure the voltage on the Pi and determine the problem. (http://captainbodgit.blogspot.co.uk/201 ... rrypi.html).

One of the biggest problems with cheap consumer electronics (like 5V phone chargers & power units, USB to micro cables & so on) is the variability between different samples of the same product (make/model). So in my view, a recommended list for power supplies is often worse than useless.

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Seiduna
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Re: Power/Voltage Issues on B+

Sun Mar 01, 2015 1:31 pm

oi SteveDee, hello there,

But still, I have rPi B that does the same scripts, and it has wireless usb (which consumes even more power) and it is working with no problem, on 5V 1A power supply.

On rPi 2 I have internet cable, mouse and keyboard plugged into it, and it is attached to hdmi monitor, on 5V and 2.1A, and rainbow is going bananas when I run the script...
I made video (it is a bit blury), but the output of vcgencmd measure_volts core; vcgencmd measure_volts sdram_c; vcgencmd measure_volts sdram_i; vcgencmd measure_volts sdram_p is:
volt=1.2000V
volt=1.2000V
volt=1.2000V
volt=1.2250V
DURING the streaming ... ???

my blury video, but you can see rainbow going bananas, and in meanwhile volts are as stated above:
https://www.youtube.com/watch?v=zL-NfczhAJI

So after I read your link and blog, I am kindda dissapointed in rPi,
it is underpovered from the beginning if you add camera board?

I am just a user, i want to plug and play, I do fair amount of research before I buy (right power suply, right components) but than to find out it has flaw from the start...

There shuld definitly be a 5.25 V, and at least3 amps power supply, and yet even official rPi power supply on market is 5.0 V....

What are we to do...? Make one of our own and place it on market?
Gnu/Linux,
because I'd rather own a free OS
than steal one that's not worth paying for.

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SteveDee
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Re: Power/Voltage Issues on B+

Sun Mar 01, 2015 2:16 pm

Seiduna wrote:... I have rPi B that does the same scripts, and it has wireless usb (which consumes even more power) and it is working with no problem, on 5V 1A power supply.

On rPi 2 I have internet cable, mouse and keyboard plugged into it, and it is attached to hdmi monitor, on 5V and 2.1A, and rainbow is going bananas when I run the script....
I think the Rainbow Square low voltage indicator was only introduced on the B+ & Pi2. So maybe you have the same issues on the Pi B, but naturally you wont see the Rainbow.

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Re: Power/Voltage Issues on B+

Sun Mar 01, 2015 2:32 pm

I made video (it is a bit blury), but the output of vcgencmd measure_volts core; vcgencmd measure_volts sdram_c; vcgencmd measure_volts sdram_i; vcgencmd measure_volts sdram_p is:
volt=1.2000V
volt=1.2000V
volt=1.2000V
volt=1.2250V
DURING the streaming ... ???
What is the relevance of showing these values? Do you think these are normal or abnormal values?

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Re: Power/Voltage Issues on B+

Sun Mar 01, 2015 2:43 pm

Seiduna wrote:
So after I read your link and blog, I am kindda dissapointed in rPi,
it is underpovered from the beginning if you add camera board?

I am just a user, i want to plug and play, I do fair amount of research before I buy (right power suply, right components) but than to find out it has flaw from the start...

There shuld definitly be a 5.25 V, and at least3 amps power supply, and yet even official rPi power supply on market is 5.0 V....

What are we to do...? Make one of our own and place it on market?
Let me strongly recommend against a 5.25 power supply. The Raspberry Pi is designed to work off 5v with a +/- .25v tolerance. Selling a power supply marketed for the Pi that is at the top of that range is a recipe for disaster. I can take the exact same power supply and depending on where I plug it in, within the same country, I can see wide variation of voltage output based on the quality of power arriving at that location. So if I plug it into somewhere that's running just a bit hotter than other places I'm going to be left with a burned out pi in the worst case scenario, and a pi with a shortened lifespan in the best case scenario.

Beside the problem is not the voltage it's the quality of the power supply. Here's some power usage numbers.

The Camera uses 250 mA
HDMI uses 50 mA
The USB module uses about 200 mA
When you plug in an ethernet cable it uses an additional ~50 mA
Not sure on the keyboard/mouse but lets be generous and say each on only uses 100 mA

So you're using less then 800 mA, even if the the keyboard/mouse were power hogs you're still only coming in at 1.5 A, the problem is not that you need a more powerful power supply, the problem is you need a better quality power supply and possibly a better usb cable (some of them use very, very high AWG wires which limits current draw).
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Re: Power/Voltage Issues on B+

Sun Mar 01, 2015 2:49 pm

hey SteveDee, aha in that case, if rPi B is underpowered, it is doing a good job at running scripts. So in rPi 2 case it should be too ok...

oi DirkS, the relevance is that i am a noob, and before I posted here I searched for rainbow square, found out that it is power related, searshed how can I get my power status from rPi, and I found 2 solutions:
one is to use a device that measure volts, and I need to connect it to rPi,
the other was using that command.
again, i am noob, not a DIY guy, if rPi is for kids, how hard could it be for a over 40 years old kid?

Under line, what is the solution here, what choices do I have to eliminate raibow square?
Turning it off in config.txt does not make the problem go away...
I could stop using Camera board?
Could I, can I get the adequate power for rPi and camera board?

Thank you
Gnu/Linux,
because I'd rather own a free OS
than steal one that's not worth paying for.

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Seiduna
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Re: Power/Voltage Issues on B+

Sun Mar 01, 2015 2:55 pm

hey abishur, you posted while I was writing so I did not include you in my last post,
buy man, those numbers are more than welcome, thank you.

Aha, you made my fuzzy picture sharp, we can not do much but get good power suply, mainly cabels.
So what are those cabel charachteristics that one should be aware of when buying micro usb cabels?
You mentioned AWG, shoud that number be high or low? what value of AWG is good and what is bad?
(I will look it up now also on my own)

Thank you
Gnu/Linux,
because I'd rather own a free OS
than steal one that's not worth paying for.

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Re: Power/Voltage Issues on B+

Sun Mar 01, 2015 2:57 pm

simply get an adequate power supply and cable so that dips below 4.65V no longer occur!

As for measuring the voltage using software, the pi doesn't have the ability to do so, perhaps you may have found a way to measure some low voltage core voltage, but it doesn't tell you anything about the 5V going into the PI.

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Re: Power/Voltage Issues on B+

Sun Mar 01, 2015 3:04 pm

Seiduna wrote:hey abishur, you posted while I was writing so I did not include you in my last post,
buy man, those numbers are more than welcome, thank you.

Aha, you made my fuzzy picture sharp, we can not do much but get good power suply, mainly cabels.
So what are those cabel charachteristics that one should be aware of when buying micro usb cabels?
You mentioned AWG, shoud that number be high or low? what value of AWG is good and what is bad?
(I will look it up now also on my own)

Thank you
for an experiment, open up one of the microUSB cables you used while having the rainbow square, to have a look at what was used as conductor. For a good cable you would need a copper conductors with a diameter of something like 0.3mm, most of these cheap microUSB charger cables use either nylon wire interwoven with 0.005mm or thinner strands, or even worse thin strips of plastic foil with some spurious metal deposited on them. this makes them thin and supple, but above everything very cheap to make!
Thus these are very lousy for powering a PI!

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Re: Power/Voltage Issues on B+

Sun Mar 01, 2015 4:36 pm

Same answer as I gave earlier :

http://swag.raspberrypi.org/products/ra ... wer-supply

Sold by the foundation especially for the Pi. Fixed thick cable, slightly over voltage (5.15 V) to allow for voltage drop. Bags of current.

Probably the only power supply that is absolutely beyond reproach. I've successfully had it powering 3 Raspberry Pi's at the same time all with Wifi adaptors. A Pi2 powered from the supply, an A+ plugged into one of the Pi2's USB's and an old B powered from the Pi 2's GPIO.

Yeah, I know.....
Don't judge Linux by the Pi.......
I must not tread on too many sacred cows......

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Seiduna
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Re: Power/Voltage Issues on B+

Sun Mar 01, 2015 5:43 pm

hey pluggy, hello,

yes, but I do not think I have bad power supply, just cable, and what if I but rPi Power supply and i have the same problem...
users here reported that have same rig on different places and it shows different cuttent, so... wel I do not know, khehe



ok, i gathered all my micro usb, i got 5 of them:

first one: 4mm 80cm, on it it says:
5216131 AWM 2725 80C 30V VW-1 Eternal Well

I have 2 of 4mm 100cm USB 2.0 Cable Fully Rated 80C 30V

next one is 4mm 180cm USB Shielded highh speed cable 2.0 Revision 28AWG/1P+28AWG/2C

last one is 5mm 180cm AMW Style 2725 80C 30V VW-1 28AWG/1PR+24AWG/2C High speed USB 2.0 Revision Genbird

All of them give rainbow... Are any of those good cables?

So this is where I am now, I will continue to use it as it is since there is not much more I can do.
I could buy official power supply, but if problem persists...?

Thank you all for your input and time to clear this out for yours noob.
Gnu/Linux,
because I'd rather own a free OS
than steal one that's not worth paying for.

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Re: Power/Voltage Issues on B+

Sun Mar 01, 2015 7:32 pm

Seiduna wrote:...There shuld definitly be a 5.25 V, and at least 3 amps power supply, and yet even official rPi power supply on market is 5.0 V....

What are we to do...? Make one of our own and place it on market?
Hi Seiduna,
I hope you have picked out the useful feedback, and that this will lead to a solution to your power quality problem.

The reference to 5.25V on my blog post refers to the rated upper limit for the Pi, and the final comments were slightly tongue-in-cheek.

5.25V won't fry your Pi, and even voltages slightly above this limit are not disasterous due to the 5V clamp and fuse arrangement which has been included in the circuit in an attempt to protect the Pi from destruction.

Using a power supply with a nominal output voltage above 5V would just be an attempt to overcome the resistive losses caused by cables, connectors and other series components such as the Pi fuse. But I certainly don't want to take responsibility for the effectiveness of either line regulation or load regulation for any make/model of cheap black-blob power supply.

As I've already pointed out, the quality (and repeatability) of cheap consumer electronics is very poor. If we could rely on good quality power supplies and capable, low resistance cables, we wouldn't be having this conversation.

For demanding Pi applications, it may be worth considering a dedicated supply such as Nick's Pi Power module: https://www.tindie.com/products/nsayer/pi-power/

Supplies like these are directly connected to the PI, minimising resistive losses, and also providing good line & load regulation.

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