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Sailing_Nut
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Power issues? How to tell?

Wed Jun 13, 2012 7:34 pm

Hi all,

I know that power issues have been discussed many places, but I am curious how one can tell if improper power is the cause of my problems.

I have been able to use the Debian Squeeze image (seemingly) without problems. I did not push it very hard. I did try playing some MP3 files off of a USB stick and they were very choppy.

I then tried using XBMC (both OpenELEC and Rasbmc) and they do not seem to work at all. I did move everything (keyboard, mouse and USB stick) over to a powered hub, but the USB stick randomly disappeared and I was unable to download any add-ins for XBMC.

I am using a power adapter that is rated ad 1A (I have tried 2 separate adapters and 2 different cables) so I would not think that power is an issue. I have seen that using XBMC is more demanding on the power because of it's heavier use of the video part of the SOC. So that might explain the difference in results between Debian and XBMC (I realize that XBMC is an application not a Linux distro, but just simplifying)

So, at the end of the day, is there any way that I can look at log files, etc. to determine if the board is being starved of power?

TIA!

therealeasterbunny
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Re: Power issues? How to tell?

Wed Jun 13, 2012 7:43 pm

Perhaps buy one of those power meters which sit between mains and your gadget - will these measure down the the small levels of the Pi?

I bought a Silvercrest power meter from Lidl last week for £6.00.

Something similar to this ... http://www.amazon.co.uk/Energy-Monitor/dp/B0039021UU ... but £6 from Lidl at the moment!

Not used it yet (not read instructions yet) ... but getting there slowly.

therealeasterbunny
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Re: Power issues? How to tell?

Wed Jun 13, 2012 8:34 pm

Just tried the gadget and it can report volts, watts and amp usage (down to 0.nnn type scale amps) so maybe worth a punt? Try a Lidl near you! :D

I originally bought it to monitor how many watts by homebrew NAS laptop was using (about 17 watts incidentally) but good for Pi monitoring also now :D

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Sailing_Nut
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Re: Power issues? How to tell?

Wed Jun 13, 2012 8:42 pm

That device won't really tell if it is a power issue with what is being supplied to the Pi. It is only measuring how much the power adapter is drawing from the mains. You need to account for any losses in the conversion from mains AC voltage to the 5V DC for the Pi. The losses can vary widely based on the quality and technology used in the power converter.

I can use my digital volt meter to see what voltage is on the 5V GPIO pin header, but that will not have a quick enough response to tell me if there are "drop outs" in the 5V supply. That would take an oscilloscope and unfortunately, I don't have one :-(

I was wondering if there might be any logging that the Broadcom SOC might be doing through the kernel. Or if this is just a "take a shot in the dark" situation.

Alan Thew
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Re: Power issues? How to tell?

Wed Jun 13, 2012 9:19 pm

When I first got my Pi I too was using a 5V 1A supply (a charger for an HTC Desire in fact) and I also had problems, though not exactly as you describe (poor keyboard response, including missed or randomly repeated keypresses; occasional hangs). Although I thought 1A ought to have been sufficient, I decided to build an all-in-one Pi PSU and powered USB hub using a 4A PSU I had from an old label printer. (I'm going to write a blog post explaining how to do it: it's dead handy to be able to run everything and anything off a single plug.)

Since doing so, all my problems have disappeared. I'm guessing it's maybe voltage-related. The voltage can drop as the current draw increases from some chargers/mains adaptors, so it's possible that a charger delivering 5V unloaded may drop below this when 500mA or more is drawn. This is just a guess; but, as I say, a meatier PSU solved my problems.

I realize this doesn't answer your question about logging but I thought my experience might be useful info anyway...

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Sailing_Nut
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Re: Power issues? How to tell?

Wed Jun 13, 2012 10:11 pm

Thanks for the information.

It looks like power supply "beef" is my issue. The unfortunate thing is that I have a ton of spare very hefty PSUs around, but getting them mated to a micro USB is an issue.

I read somewhere that you can power the Pi by supplying voltage to pins on one of the headers. Unfortunately, I don't recall where I read it. I am guessing that it is the 5V pin (and of course GND) on the GPIO header, but really don't want to risk smoking my Pi by having a go at it. Does anyone have confirmation that you can power a Pi through those pins? If yes were there any little tricks that you had to use?

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mahjongg
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Re: Power issues? How to tell?

Wed Jun 13, 2012 11:27 pm

Sailing_Nut wrote:Thanks for the information.

It looks like power supply "beef" is my issue. The unfortunate thing is that I have a ton of spare very hefty PSUs around, but getting them mated to a micro USB is an issue.

I read somewhere that you can power the Pi by supplying voltage to pins on one of the headers. Unfortunately, I don't recall where I read it. I am guessing that it is the 5V pin (and of course GND) on the GPIO header, but really don't want to risk smoking my Pi by having a go at it. Does anyone have confirmation that you can power a Pi through those pins? If yes were there any little tricks that you had to use?
Yes you can power the PI through the 5V and GND pinheaders, but be very careful, as this route bypasses the main fuse F3, I would strongly suggest adding your own external fuse, certainly if you use a strong external power supply.

You can measure the power on the board by measuring between the two testpoints on the board TP1 (5V after the fuse) and TP2 (GND). The voltage there should be very close to 5.00 Volt, and no lower than 4.75 V (however for the USB ports you would need more to begin with).

The problem could also be the voltage behind the USB polyfuses (F1 and F2), there the voltage could drop as low as 4.4V. But all low current (100mA or less) devices should be able to work with that, but any lower is a problem, and some higher current devices (more than 100mA) want at least 4.75V just like the PI itself.

bredman
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Re: Power issues? How to tell?

Thu Jun 14, 2012 8:18 am

For a detailed description, please see the wiki.
http://elinux.org/R-Pi_Troubleshooting# ... r_problems

Alan Thew
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Re: Power issues? How to tell?

Thu Jun 14, 2012 2:57 pm

Sailing_Nut wrote:The unfortunate thing is that I have a ton of spare very hefty PSUs around, but getting them mated to a micro USB is an issue.

I read somewhere that you can power the Pi by supplying voltage to pins on one of the headers. <snip>
If you're talking about doing that, it sounds like you're happy to snip off -- or have already snipped off -- the existing plug from your PSU output. So why not just get hold of a USB-to-micro-USB lead, chop off the USB end, and connect the micro USB end to your PSU? Then you can connect the PSU to your Pi via the normal micro USB connector without bypassing the fuses.

Do you live anywhere near a pound shop? My local one has such leads (sold as "USB Blackberry charger") for a pound. I also bought an unpowered USB hub from there, butchered it a bit, and built myself a powered USB hub for a quid.

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Sailing_Nut
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Re: Power issues? How to tell?

Thu Jun 14, 2012 4:10 pm

Alan Thew wrote:
Sailing_Nut wrote:The unfortunate thing is that I have a ton of spare very hefty PSUs around, but getting them mated to a micro USB is an issue.

I read somewhere that you can power the Pi by supplying voltage to pins on one of the headers. <snip>
If you're talking about doing that, it sounds like you're happy to snip off -- or have already snipped off -- the existing plug from your PSU output. So why not just get hold of a USB-to-micro-USB lead, chop off the USB end, and connect the micro USB end to your PSU? Then you can connect the PSU to your Pi via the normal micro USB connector without bypassing the fuses.

Do you live anywhere near a pound shop? My local one has such leads (sold as "USB Blackberry charger") for a pound. I also bought an unpowered USB hub from there, butchered it a bit, and built myself a powered USB hub for a quid.
I've tried things similar to hacking the adapter in the past but have had problems because they all seem to be moulded plastic and it's tough to get a nice clean result. I'll look arouns and see what I can come up with. Thanks!

Unfortunately no pound shops near me, I'm in the USA ;)

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Sailing_Nut
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Re: Power issues? How to tell?

Fri Jun 15, 2012 12:50 pm

Small update.

I took a 5V 2A charger from an old MP3 player, chopped the end off and soldered on a Female USB A connector. I then used a charging cable from my cell phone to apply the power to the Pi. Things seem to be better, but not the performance that others seem to be stating they are getting. I am still seeing a USB stick drive disappearing from the mounted drives during operation which is really odd to me because it is on a powered USB hub. The only USB device attached to the Pi is the powered hub.

Not sure if the charging cable is not capable of supplying enough power or if something else is going on.

I have noticed that my Pi runs quite warm to the touch. Maybe I have a deffective board?

Alan Thew
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Re: Power issues? How to tell?

Fri Jun 15, 2012 2:35 pm

Something as thin as bell wire probably won't do for supplying the current you'll need for a Pi, and I have seen some very thin wires (akin to in-ear headphone wires) being sold with cheapo USB chargers. But I would have thought a charging cable from your phone ought to be OK. The fact that you're seeing the same problems as before even after changing the supply, the connectors and the cable suggests to me that you're right and the root of the problem lies elsewhere.

I obviously don't want to insult your intelligence, but does the USB hub plug fit nice and snugly into the socket on the Pi, are all the contacts clean, and is it all sitting on a reasonably flat surface and not getting joggled about while switched on? Do the solder joints on the board look OK? Both of these types of problem have caught me out in the past and I was very annoyed afterwards to have spent a long time looking for complex solutions when it was all down to loose contacts!

By the way, in your original post you said MP3s were playing back choppily. Is this just if you try to play them directly from the mounted USB stick, or is it the same if you copying them across to the SD card? What software are you using? Even a full-fat media player like VLC ought to have no problems playing MP3s in X with plenty of CPU cycles to spare.

Alan Thew
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Re: Power issues? How to tell?

Sun Jun 17, 2012 2:56 pm

Any progress, Sailing_Nut? In case it's any use, I said above I was going to post how I'd solved my own power problems by building a powered USB hub, and I have now done so, so here's the link:

http://pihub.blogspot.com

No one seems to have found it yet (not even the Google bot) so I thought a bit of publicity might not go amiss. ;)

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Sailing_Nut
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Re: Power issues? How to tell?

Sun Jun 17, 2012 4:28 pm

I did a visual inspection of the board and one of the solder joints on the USB connector does look a bit suspect but it's one of the data lines, so I would not expect that I would be experiencing the problems that I am. Especially because it's not the USB port that I have connected to my hub.

I just loaded up the Debian image again and it is having network issues. It seemed like everything was OK on boot up. I saw it connect to my DHSP server and get an address, but aster I started the x system I was unableto browse to any sites with Midori. :cry: I apsl tries ping from the terminal window and it failed as well (both to a DNS name and a raw IP address on my network)

I also have re imaged raspbmc again and it seems to work perfectly downloading the setup files & etc. but once XBMC is up and running I can't seem to access the network either. (Can't download any plugins.)

So at this point I'm really confused and frustrated. (Wish I had better news to report.)

Any help is appreciated!

therealeasterbunny
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Re: Power issues? How to tell?

Sun Jun 17, 2012 4:32 pm

Alan Thew wrote:[...]

http://pihub.blogspot.com

No one seems to have found it yet (not even the Google bot) so I thought a bit of publicity might not go amiss. ;)
Nice write up and good pics, thanks for sharing :)

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