User avatar
abishur
Posts: 4477
Joined: Thu Jul 28, 2011 4:10 am
Location: USA
Contact: Website

FAQ Updated

Wed Nov 27, 2013 4:07 pm

The FAQ Page has gone through a round of revisions.

Feel free to comment here with any questions you think we should have added, broken link reports, and other comments/concerns, but please don't be offended if we don't implement your suggestion ;-)
Dear forum: Play nice ;-)

asPie
Posts: 4
Joined: Wed Nov 20, 2013 6:35 am
Location: Birmingham, UK

Re: FAQ Updated

Fri Nov 29, 2013 5:11 am

Hello & Happy Birthday,

I notice minor typos at -
C#1 final line of text "distro" has "r" missing.
C#6 line #1 recommend > recommended
D#2 line #2 installed> install
D#4 P#2 line#1 than> then
L#3 line#2 pi> Pi
N line#1 hyperlink subform> subforum
O >GPU - .....hardware the> .....hardware that
Last edited by asPie on Sat Nov 30, 2013 2:19 am, edited 6 times in total.

paulie
Posts: 260
Joined: Thu Jan 19, 2012 6:51 pm

Re: FAQ Updated

Fri Nov 29, 2013 10:17 am

Good revision!
Found one typo:
In the TOC, L.3 reads ”W-iFi". Reads correctly in section.
It has been my custom to use Xeyes

klricks
Posts: 5829
Joined: Sat Jan 12, 2013 3:01 am
Location: Grants Pass, OR, USA
Contact: Website

Re: FAQ Updated

Sat Nov 30, 2013 3:40 pm

The following is not accurate:
From section I.1 ...... "Typically, the model B uses between 700-1000mA depending on what peripherals are connected and the model A can use as little as 500mA with no peripherals attached. The maximum power the Raspberry Pi can use is 1 Amp. If you need to connect a USB device that will take the power requirements of the Raspberry Pi above 1 Amp then you must connect it to an externally powered USB hub." .......


The main fuse F3 limits the usable power of the RPi and any connected peripherals to 750mA or so for reliable operation.
If current goes above 750mA then the RPi, and especially USB devices, will become unstable as the resistance of the F3 fuse begins to rise.
If current draw reaches over 1A then the fuse will completely trip and shut down power to the RPi within a few seconds.

The above should be something like this:
Typically, the model B uses up to 750mA depending on what peripherals are connected and the model A can use as little as 500mA * with no peripherals attached. The maximum power the Raspberry Pi can reliably use is 750mA (0.750 Amp). If you need to connect a USB device that will take the power requirements of the Raspberry Pi above 0.750 Amp then you must connect it to an externally powered USB hub.
The RPi is protected by a self resetting type fuse. If current goes above 1A the fuse will trip within a few seconds. If tripped the fuse will self reset after a period of time with no power connected. It can take several minutes to many hours to recover and fully reset.


* The 500mA for model A seems high as my B with nothing attached draws 350-400mA or so...
Last edited by klricks on Sun Dec 01, 2013 12:35 am, edited 1 time in total.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Stretch w/ Desktop OS.

hippy
Posts: 3771
Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: FAQ Updated

Sat Nov 30, 2013 7:15 pm

Excellent work. Under the section on power, while it indicates 4.8V is just enough and 6V may cause damage, there is no explicit statement of what the voltage should be. Would be useful to specify it there.

User avatar
rurwin
Forum Moderator
Forum Moderator
Posts: 4247
Joined: Mon Jan 09, 2012 3:16 pm
Contact: Website

Re: FAQ Updated

Sun Dec 01, 2013 12:42 am

The voltage of the 5V supply should be within 5%: 4.75-5.25V. Those are the official limits. However 5V is not used for much, and most of that is for USB, which has wider limits. In practise there doesn't seem to be a problem until it drops too low for the 3.3V regulator to work, at about 4.6V. Outside the official limits, individual boards may behave differently and as the power draw increases, due to USB or ethernet activity for example, the voltage is likely to drop further, which will cause failures if it is marginal to begin with. The F3 "fuse" will take some voltage, so 4.75V as the lower limit to the input voltage is probably good. For reading the voltage on the board between TP1 and TP2, a somewhat lower voltage should not cause undue worry.

User avatar
blachanc
Posts: 448
Joined: Sat Jan 26, 2013 5:03 am
Location: Quebec,canada(french)

Re: FAQ Updated

Sun Dec 01, 2013 7:24 pm

For Fun,

I took a scope trace of TP1-TP2, in turbo mode, capturing a midori refresh of this forum page.
I am using a 2A Belkin hub to go as a power source. It is illustrating the link between activity and voltage stability.
[email protected] ~ $ vcgencmd get_config int
arm_freq=1000
core_freq=500
sdram_freq=600
over_voltage=6
Attachments
ScreenHunter_61 Dec. 01 14.23.jpg
midori refresh in turbo mode
ScreenHunter_61 Dec. 01 14.23.jpg (60.5 KiB) Viewed 980 times
Autism/Asperger syndrome: what is your score on this quiz?
http://www.raspberrypi.org/forums/viewtopic.php?f=62&t=70191

User avatar
mahjongg
Forum Moderator
Forum Moderator
Posts: 10924
Joined: Sun Mar 11, 2012 12:19 am
Location: South Holland, The Netherlands

Re: FAQ Updated

Sun Dec 01, 2013 9:23 pm

as TP2 is actually GND, against what reference is it measured?
Seems nonsense to do a measurement of GND.
Also it seems just noise picked up by the probe to me.

Peaks (TP1-TP2) of about 50mV (0.05V) seem okay to me.

User avatar
blachanc
Posts: 448
Joined: Sat Jan 26, 2013 5:03 am
Location: Quebec,canada(french)

Re: FAQ Updated

Sun Dec 01, 2013 11:47 pm

mahjongg wrote:as TP2 is actually GND, against what reference is it measured?
Seems nonsense to do a measurement of GND.
Also it seems just noise picked up by the probe to me.

Peaks (TP1-TP2) of about 50mV (0.05V) seem okay to me.
I was too lazy to check the schematics :-), so I took a differential measure from the microusb ground.
I was just having fun with my scope, and fount it cool to see the relation between a midory page refresh & supply.

I work in an ASIC dep., where all I do is digital simulation.
Hardware people try to keep us as far as possible from the equipment (scopes & protocol analyzer),
as they believe we are hopeless, which might be true :lol:

Ben
Autism/Asperger syndrome: what is your score on this quiz?
http://www.raspberrypi.org/forums/viewtopic.php?f=62&t=70191

Return to “General discussion”

Who is online

Users browsing this forum: DarkPlatinum, drgeoff, mikerr, umardastgir and 65 guests