lazybum
Posts: 13
Joined: Sun Jan 22, 2012 12:24 pm

Re: Power consumption (final)

Sun Jan 22, 2012 6:40 pm

I see the FAQ, forums and wiki state different power consumption levels. Got myself two USB-PSUs (800 mA and 1000 mA), will they be enough for RPI feeding a HDMI TV?

Also: is the official statement on power levels reserving any power to connected USB gadgets? What"s the final word on the Raspi power requirements?

Thanks!

stormy1
Posts: 60
Joined: Fri Jan 06, 2012 3:44 am

Re: Power consumption (final)

Sun Jan 22, 2012 7:25 pm

1A auto reset fuse.

typical Max with no usb devices 700ma for B 500ma for A.

Either adapter will work with no usb but I would use the 1000 if using usb devices.

We will have to watch the power usage of attached usb devices.

Some of them can draw more power than will be available.

There should be enough for a wifi adapter but a hard drive/cdrom will have to have its own power or a powered hub.

lazybum
Posts: 13
Joined: Sun Jan 22, 2012 12:24 pm

Re: Power consumption (final)

Sun Jan 22, 2012 7:50 pm

stormy1 said:


1A auto reset fuse.


Thanks. I suppose the fuse is at the PSU side, giving a max of 1 A for the entire system. So no UMTS + WiFi combo without extra PSU. Awww ...

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abishur
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Re: Power consumption (final)

Sun Jan 22, 2012 7:57 pm

Well you could still technically get by on one PSU you'd just have to do one of the following (in order of difficulty )

1) Splice your PSU so it independently powers both the r-pi and the external periphial

2) By-pass the protection circuit by attaching to the 5V rail (there's two pins that are in the GPIO strip that aren't connect to the GPIO but rather to the 5V rail).  You'd need to set up your own little protection circuit board or risk frying the r-pi but I'm sure there will be instructions for doing just that generated by the community sooner or later

3) Replace the 1A self-resetting fuse with a higher amperage one.  I put this as being more difficult than making your own protection circuit because this is a surface mounted component, it's not exactly the easiest thing to replace and at least if you mess up half way through making your own board you can safely keep using the r-pi through the existing circuitry, but if you mess up doing this you are quit simply out of luck.
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jwatte
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Re: Power consumption (final)

Mon Jan 23, 2012 4:26 am

Abishur said:


but if you mess up doing this you are quit simply out of luck.


A bit of wire and a little tape will fix that right up! Steps up from that might include a very steady hand and a soldering iron, and perhaps a replacement PTC/fuse from the vendor of your choice: http://search.digikey.com/us/e.....ND/2639177

I don't know exactly what dimension the part is, but there are several to choose from.

hippy
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Re: Power consumption (final)

Mon Jan 23, 2012 10:05 am

lazybum said:

I suppose the fuse is at the PSU side, giving a max of 1 A for the entire system. 
That is correct, between the micro-USB power inlet socket and the GPIO power pins / rest of the system - hence Abishur's suggestion of it being possible to bypass the 1A fuse by supplying power via the GPIO power pins.

There appears to be two additional fuses on the board ( top right ) which I guess are for each of the USB socket +5V power outs. I'm not aware of that being confirmed nor what their rating is; my gut feeling is 100mA as that keeps board plus USB consumption below 1A.

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Chromatix
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Re: Power consumption (final)

Mon Jan 23, 2012 10:32 am

Or, as occasionally suggested elsewhere, supplying power to a USB hub and powering the R-Pi from one of it's ports.  This is known as the "loopback" method and has already been shown to work with Beagleboard and/or Pandaboard.  It has the advantage of only requiring one power supply.

Bonus points if the hub is built into the monitor.
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jurian89
Posts: 4
Joined: Sat Jan 21, 2012 8:25 pm

Re: Power consumption (final)

Mon Jan 23, 2012 11:25 am

I would recommend the Sony Ericsson EP800 power adapter. It has very high efficiency and up to 850 mA output. Can be found really cheap on ebay.

Also take a look at the EP750 (Dual USB Charger)

richardp
Posts: 117
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Re: Power consumption (final)

Mon Jan 23, 2012 11:40 am

lazybum said:


stormy1 said:


1A auto reset fuse.


Thanks. I suppose the fuse is at the PSU side, giving a max of 1 A for the entire system. So no UMTS + WiFi combo without extra PSU. Awww ...


I was thinking the same... but instead I am going to build the R-Pi in to a 6 port Powered USB hub container... power the Rpi from one of the USB ports (or directly from the regulated power rail within the USB hub

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