Quick recommendation for a startup system - UK

Hasn't the polyfuse been dropped in later models? I know /something/ changed. After all, there is the current drawn by the RPi itself, plus

2 x 500 mA from the two USB slots.
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Reply to
David Taylor
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You don't want to be drawing much more than 100mA from the USB sockets

- use a powered hub if you need more.

Reply to
Rob Morley

The two 140mA polyfuses on the USB sockets have been dropped. The main polyfuse on the power input is still there.

It isn't recommended to take more than 200mA total from the USB ports, which is why a powered USB hub is needed.

Reply to
Dom

The problem as I found it was with the wiring. The first cable I used to power the Pi was a plain 6' USB data cable. When I cut it up I found that all the wires, including the Red and Black +5V and Ground wires, were 28 gauge or smaller. When the Pi was drawing heavy power I measured more than

1V lost in the round trip down the +5V wire and back to ground. The processor seems to have kept running, but the resulting 4V power wasn't enough to support ethernet or USB.

Chopping out the middle 5' and splicing the ends together gave me a power cable that worked. Now I'm using the new Adafruit cable with 24 gauge Red and Black wires. It looks better than my splice job, and allows things to run just as well.

There's no harm to having a PSU with more capacity, but it wasn't the PSU's fault that my app was crashing.

Mel.

Reply to
Mel Wilson

I've used a samsung charger without problems

RS-Components sells the pi in a raspberry tinted polypropylene carrier box that will house a raspberry pi with SD card installed. it's large enough to meet two of the ANSI screw holes with empty portions of the box). Kind of ugly though, but who looks at that side ot the telly?

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Reply to
Jasen Betts

On 07/06/2013 19:28, Dom wrote: []

Thankls, I'm running one RPi with a Wi-Fi network adapter and a TV receiver stick, and I'd be very surprised if the current consumption was below 200 mA. Difficult to know for sure, when the data sheets simply say "USB 2.0".

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Do you have a reference for the USB power situation - I couldn't find it on the RPi home page or in their FAQs.

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Reply to
David Taylor

Then why don't you simply key in: lsusb -v

Reply to
Rob

I don't have one to hand, but the Pi is supposed to take up to 500mA (including GPIO) and the polyfuse starts to trip at 700mA (total fail at

1400mA, I think), so 700 - 500 leaves 200 for USB.

The USB polyfuses were removed because they often dropped too much voltage for USB to be stable.

Reply to
Dom

I have an unpowered USB hub on my PI and, although it only has a keyboard and mouse in it, I'm sure they don't draw the 200mA, but I do have a card reader with 1GB SD card in it in the other USB port, so maybe between them all they do. I'll try that '1susb -v' to see exactly what I find out.

Bill Garber

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Reply to
Bill Garber

It's a few months since I set up the card and I'm not certain if I remember now what failed, but I'll be copying a raspbmc image when I get some spare time so I'll note what happens and report. Might be in a few days time, or I might need to order another cheap

32GB card.
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Windmill, TiltNot@Nonetel.com               Use  t m i l l 
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Reply to
Windmill
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Thanks, Rob. I tried the command you suggested (one which is not familiar to me) and got "command not found". So after installing usbutils I see:

Bus 001 Device 004: ID 0bda:2838 Realtek Semiconductor Corp. RTL2838 DVB-T, MaxPower 500mA

Bus 001 Device 005: ID 0846:4260 NetGear, Inc. WG111v3 54 Mbps Wireless [realtek RTL8187B], MaxPower 500mA

which doesn't tell me what power those devices are actually using. Did I miss something?

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David 
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Reply to
David Taylor

It is the power the manufacturers have configured in the USB descriptors to tell the system how much the device requires.

When the manufacturers plug in incorrect information, there is little that can be done. Maybe Realtek are just careless and always put 500mA there. I have tried lsusb -v on some different systems and while I see different power requirements (e.g. 100mA for a mouse or cardreader) I have a RTL8187 Wireless Adapter and it says 500mA as well :-(

OTOH, systems can use this information to allow or disallow a device on the bus, so it would be unwise to overstate the requirements. It could be the wireless device has a settable power level and requires

500mA only on its highest setting (which may not even be available in most versions due to legal regulations).
Reply to
Rob

On 09/06/2013 09:21, Rob wrote: []

The Wi-Fi adapter is quite old, so perhaps Intel just coded 500 mA as the default. The TV receiver dongle is quite recent and could easily be

0.5 A though. Could look up the data sheets for the R820T and RTL2832U, I suppose!

A pity more care isn't taken.

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Reply to
David Taylor

I tried a couple of different wifi dongles - 450mA and 500mA, the latter being one of these

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which is reported to work fine in the RPi without a powered hub. The description of the chip that uses
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says "adaptive transmit power control function to obtain the better performance in the analog portions of the transceiver", I suspect that's true of all of them, so they will report maximum current drain but may not use half of it.

Reply to
Rob Morley

There is a compatibility list. Dunno if it's up to date though.

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I needed a new monitor for the Pi. I'll bet that cost more than your SD card ;-)

FWIW I have two Samsung phone chargers and they both work fine. However it's now normally powered from a USB hub.

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Reply to
Mark

No luck so far in reproducing the problem; I put a raspbmc image on an SD card using my laptop's card slot and it 'just booted'. Wiggling (very gently!) perpendicular to the plane of the card made no difference to the booting process.

(Can't say I like raspbmc's lack of VTs though. I suppose I'll need to use another OS version to edit /etc/inittab, /etc/login.defs, and whatever else is used nowadays, on that card. Right now I can't even adjust the display, which extends off-screen.)

Maybe if I use my spare 32 Gb micro SDHC which currently has some music on it in a micro SD to SD adaptor, then try again, the failure might recur. If so I'll report that.

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Windmill, TiltNot@Nonetel.com               Use  t m i l l 
J.R.R. Tolkien:-                                   @ O n e t e l . c o m 
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Reply to
Windmill

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