hippy
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Re: Power supply news!

Fri Oct 21, 2011 9:19 am

[quote]Quote from Lob0426 on October 21, 2011, 03:38
I have my doubts about the durability of that connector for extended use outside of a case.[/quote]

That would also be my concern if the micro-USB socket is only held by its solder contacts to the PCB rather than by lugs through the PCB. Lifting and twisting forces can break the connection or lift PCB tracks.

I\'m also wondering if there will be an easy to solder to connection point for those wanting to bring in external power by flying wire or whether it will have to be done through use of a micro-USB plug. I guess we\'ll find out when the final hardware is released.

kme
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Re: Power supply news!

Fri Oct 21, 2011 9:53 am

[quote]Quote from Gert van Loo on October 21, 2011, 08:50
Using linear regulators means the device will use more then the originally promised one watt.[/quote]Sorry, I don\'t get it. Why would the r-pi itself use more energy when fed with clean, predictable power? The power regulator has just moved from the r-pi to the PSU. The mobile phone need clean, predictable power too (and r-pi is basically a smartphone), so the position of the regulator has just changed. Slashing the voltage regulator on r-pi itself should make it more efficient.

WizardOfOZ
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Re: Power supply news!

Fri Oct 21, 2011 10:20 am

My feedback on this decision can be found here, noticed this thread too late to post my commentary here.

tl;dr: Not a good day for hardware experimenters IMO.

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Re: Power supply news!

Fri Oct 21, 2011 10:30 am

[quote]Quote from kme on October 21, 2011, 10:53
[quote]Quote from Gert van Loo on October 21, 2011, 08:50
Using linear regulators means the device will use more then the originally promised one watt.[/quote]Sorry, I don\'t get it. ... so the position of the regulator has just changed.[/quote]
Nope, the type of regulator has changed. Remember, the Pi needs not only 5V, but 3V3, 2V5 and 1V2. Previously 5V and 3V3 were coming off switched regulators, with 2V5 and 1V2 off linear regulators. Now it\'s all linear apart from 1V2 which is coming off the SoC die\'s inbuilt switched supply.

That\'s my reading of the situation, at least.

Also, dammit! I have a pile of 12V supplies lying around doing nothing.

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Re: Power supply news!

Fri Oct 21, 2011 10:32 am

[quote]Quote from WizardOfOZ on October 21, 2011, 11:20
My feedback on this decision can be found here, noticed this thread too late to post my commentary here.

tl;dr: Not a good day for hardware experimenters IMO.[/quote]

See what Gert says in the document he posted:
http://www.scribd.com/doc/69700160/Rasp ... More-Power

[quote]
What if I can\'t afford the higher power?
If you really want to make the design as power efficient as possible you must supply the power yourself. This will require modifications to the board and thus void your warranty.You must remove the linear regulators and feed the board with your own supplies.As we expect a number of users want to do this we will supply more details when the boardscome out
[/quote]

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Re: Power supply news!

Fri Oct 21, 2011 10:51 am

[quote]Quote from asb on October 21, 2011, 11:32
See what Gert says in the document he posted:
http://www.scribd.com/doc/69700160/Rasp ... More-Power[/quote]
He doesn\'t address my concern, which has nothing to do with voltage nor power level. I am happy with a requirement of any reasonable DC voltage. +5.0VDC regulated to use for high speed logic is quite acceptable, and I at least am not worried about power consumption. It is the connector itself I take issue with, and the way it almost lures people into powering the Raspi via a separate AC mains powered \'brick\'.

My hope is that the Raspi team has already taken my concern into consideration somehow, and that they have just not had time to document all the details yet. In this case my posting is just a bit of random forum noise, which can safely be ignored.

But if for some reason they hadn\'t considered the problem I mention, then they might want to be told about it in time to make any changes they feel might be needed.

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Re: Power supply news!

Fri Oct 21, 2011 10:56 am

[quote]Quote from rmike on October 20, 2011, 23:54
what about voltage tolerances? I have seen usb chargers from 4.8V - 5.5V. ... What voltage will do harm? (absolute ratings?)[/quote]

EN 62684:2010 \"Interoperability specifications of common external power supply (EPS) for use with data-enabled mobile telephones\" which is what modern mobile phone chargers with micro-USB connectors should be complying with seem to specify ( I don\'t have an actual copy ) : 5.0V +/-0.25V, with 80 mVp-p ripple, 500-1500mA.

If the R-Pi is to work with EN 62684:2010 compliant chargers then it seems it will work with between 4.75V to 5.25V and possibly a higher voltage. It would be nice to know the upper voltage limit as I\'ve also seen USB chargers put out more than 5.25V.

The good news is that it should be possible to regulate other power sources to 5V +/-0.25V with very little effort, either linear regulators or switching supplies. The only challenge is possibly 6V batteries ( 4x1.5V or \"6V\" SLA ); it may be possible directly or with LDO regulators, and rechargeables with up to 1.3V per cell should work directly ( 4x1.3V=5.2V). 4.8V batteries should also be within spec.

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Re: Power supply news!

Fri Oct 21, 2011 11:09 am

[quote]Quote from hippy on October 21, 2011, 11:56
(...) The only challenge is possibly 6V batteries ( 4x1.5V or \"6V\" SLA ); (...)[/quote]
Feeding the +6V from the batteries through an inexpensive 1A rectifier diode, like an 1N4007 or similar, will shave roughly 0.65-0.7V off the supply voltage.

Given the relatively low power consumption of the Raspi, a simple shunt regulator (a resistor, one zener diode plus power bipolar transistor), may also work. It would be less effective though, of course.

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Re: Power supply news!

Fri Oct 21, 2011 11:17 am

[quote]Quote from tufty on October 21, 2011, 11:30
the Pi needs not only 5V, but 3V3, 2V5 and 1V2. Previously 5V and 3V3 were coming off switched regulators, with 2V5 and 1V2 off linear regulators. Now it\'s all linear apart from 1V2 which is coming off the SoC die\'s inbuilt switched supply.[/quote]

My understanding was that there was a 5V regulator allowing a wide range of input voltages, that\'s now been removed requiring a more narrow range of input voltage to be provided.

If the 5V / 3V3 switching regulators have simply been changed for 5V / 3V3 linear regulators I would still expect it to accept a reasonably wide range of input voltages ( limited by current draw and heating of the regulator ). I think we need some clarifications. I suspect a circuit diagram is too much to ask for but that would be ideal.

kme
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Re: Power supply news!

Fri Oct 21, 2011 11:27 am

[quote]Nope, the type of regulator has changed. Remember, the Pi needs not only 5V, but 3V3, 2V5 and 1V2. Previously 5V and 3V3 were coming off switched regulators, with 2V5 and 1V2 off linear regulators. Now it\'s all linear apart from 1V2 which is coming off the SoC die\'s inbuilt switched supply.[/quote]It\'s probably just me being stupid, but I still don\'t get it. On the alpha board you feed some random single DC voltage between 6 and 12 V and need a serious and loss giving regulator to output 5V to the r-pi. Now you feed a nice, clean 5V directly. Whatever you need as 3.3, 2.5 and 1.2V internally is exactly the same as before.

But I\'m just a chemical engineer, what do I know about electronics. I just wonder.

WizardOfOZ
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Re: Power supply news!

Fri Oct 21, 2011 11:28 am

[quote]Quote from hippy on October 21, 2011, 12:17
If the 5V / 3V3 switching regulators have simply been changed for 5V / 3V3 linear regulators I would still expect it to accept a reasonably wide range of input voltages ( limited by current draw and heating of the regulator ). I think we need some clarifications. I suspect a circuit diagram is too much to ask for but that would be ideal.[/quote]
Don\'t need a schematic to answer this question, first principles are adequate:

Power dissipation in linear regulator = V * I, where V is voltage across regulator and I is load+regulator current (usually assumed just being the load current).

If the peak, sustained load current of the Raspi is 500mA, and we assume we power the board from a 12V lab supply/wallwart, then:

P = (12-5) * 0.5 = 3.5W, increasing still further for higher input voltages.

There is no practical and economical way of dissipating 3.5W on a board the size of the Raspi, which doesn\'t involve frying the linear regulator, meaning killing it. That is why you would need the much more efficient switching regulator if you wanted the 5.0V regulator to be on the board.

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Gert van Loo
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Re: Power supply news!

Fri Oct 21, 2011 11:31 am

To explain it as simple as I can: A linear regulator burns away the excess power. A switch mode regulator takes only the power it needs.

rmike
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Re: Power supply news!

Fri Oct 21, 2011 11:48 am

Hi,

folks, just search for \"car usb\" on ebay or another similar site.
There you can buy automotive usb adapters for less than one british pound incl. shipping.
Types with a small housing are for sure switching regulators.
These adapters will bring 10V - 14V down to 5V without much loss.

Michael

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Re: Power supply news!

Fri Oct 21, 2011 12:22 pm

For those looking to grab power off a (powered) USB hub.
USD$1.80 / EUR 1.44 Short 10.5cm micro USB (to standard USB A) cable.
Also in 15cm translucent blue to add a little color.
Splice in a female USB A jack & you wouldn\'t even loose a port off your hub.

Bet they are even cheaper on ebay.
.

hippy
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Re: Power supply news!

Fri Oct 21, 2011 12:30 pm

[quote]Quote from WizardOfOZ on October 21, 2011, 12:28
That is why you would need the much more efficient switching regulator if you wanted the 5.0V regulator to be on the board.[/quote]

What you suggest here ( and I would agree with you, and kme earlier ) is that there is no 5V regulator on the R-Pi board any more, yet earlier tufty suggested the 5V switching regulator had simply been replaced by a 5V linear regulator.

One of the problems I see on this forum ( not just in this thread ) is people giving apparently authoritative and definitive answers when they are in no position to do so and seem to be simply guessing at best, presuming at worse. Hence why I was suggesting we need clarification, an authoritative answer to cut through potential confusion as a correct answer is important.

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Lob0426
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Re: Power supply news!

Fri Oct 21, 2011 12:31 pm

Well we will just work with what we get as usual. The higher wattage could have a big effect on those that are looking at RasPi for a wearable or battery powered operation. Heat dissipation might now be an issue that looked non existent before. This good news for those that were looking at solar as a lot of the solar outfits that are reasonably cheap are for cell phones.
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Re: Power supply news!

Fri Oct 21, 2011 12:37 pm

[quote]Quote from hippy on October 21, 2011, 13:30
What you suggest here ( and I would agree with you, and kme earlier ) is that there is no 5V regulator on the R-Pi board any more, yet earlier tufty suggested the 5V switching regulator had simply been replaced by a 5V linear regulator.

One of the problems I see on this forum ( not just in this thread ) is people giving apparently authoritative and definitive answers when they are in no position to do so and seem to be simply guessing at best, presuming at worse. Hence why I was suggesting we need clarification, an authoritative answer to cut through potential confusion as a correct answer is important.[/quote]
Simply Ignore any \"answers\" from those who are obviously guessing.
Scan for posts by liz, mods, or known good posters.
[quote]Quote from Johannes on October 20, 2011, 23:18
....will need an external voltage regulator now and flaws in that part will not only lead to fried Raspberry Pis but also fried peripherals as the voltage is passed through. I suppose there won\'t be a polarity protection diode either?[/quote]
[quote]Quote from liz on October 20, 2011, 23:20
There is a polarity protection diode. There\'s a voltage clamp, and there\'s a self-resetting semiconductor fuse. We do think about these things!
[/quote]
Seems clear enough to me.
.

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Re: Power supply news!

Fri Oct 21, 2011 12:45 pm

[quote]Quote from hippy on October 21, 2011, 13:30
earlier tufty suggested the 5V switching regulator had simply been replaced by a 5V linear regulator.[/quote]
I did (and, on a second reading, it appears this is not the case). I apologise for the brainfart, and any confusion it\'s added to the already muddy waters.

I did, however clearly flag that statement as being my reading of the situation. Not my problem if you go round believing what random people say on the internet, is it :)

Simon

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Re: Power supply news!

Fri Oct 21, 2011 1:37 pm

[quote]Quote from tufty on October 21, 2011, 13:45
[quote]Quote from hippy on October 21, 2011, 13:30
earlier tufty suggested the 5V switching regulator had simply been replaced by a 5V linear regulator.[/quote]
I did (and, on a second reading, it appears this is not the case). I apologise for the brainfart, and any confusion it\'s added to the already muddy waters.

I did, however clearly flag that statement as being my reading of the situation. Not my problem if you go round believing what random people say on the internet, is it :)

Simon[/quote]

I didn\'t mean to pick on you and I had seen your statement as being simply an interpretation - so please put it down as a leak of exasperation on my part which wasn\'t really your fault.

My main concern is that we now have people saying \"just use this\" when we don\'t know exactly what the spec of those devices are or what the spec of the input is. Choose a USB adapter that happens to put out 5.5V or more when the R-Pi only accepts up to 5.25V and you\'ve possibly destroyed your R-Pi from the off.

Perhaps all those adaptors will be okay but I\'d like to be confident to say they are okay. With the regulator on-board, and a wide input voltage tolerance, there was much less risk in getting it wrong. With no 5V regulator we may have to be more careful in recommending choices. As it is currently, we just don\'t know.

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Re: Power supply news!

Fri Oct 21, 2011 2:06 pm

[quote]Quote from hippy on October 21, 2011, 14:37
I didn\'t mean to pick on you[/quote]
Oh, the days when I worried about people on the internet \"picking on me\" (or, indeed, about \"being wrong\") are long since gone.

I\'ve got the same worries as you regarding power, and \"being able to hook it up to a car battery\" was a potential win for me, too.

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Re: Power supply news!

Fri Oct 21, 2011 4:04 pm

[quote]Quote from hippy on October 21, 2011, 13:30
.....
What you suggest here ( and I would agree with you, and kme earlier ) is that there is no 5V regulator on the R-Pi board any more, yet earlier tufty suggested the 5V switching regulator had simply been replaced by a 5V linear regulator.

One of the problems I see on this forum ( not just in this thread ) is people giving apparently authoritative and definitive answers when they are in no position to do so and seem to be simply guessing at best, presuming at worse. Hence why I was suggesting we need clarification, an authoritative answer to cut through potential confusion as a correct answer is important.[/quote]
Probably. Another problem is that some things are self evident for \"those in the know\" and they don\' even realize it. I am an electronics engineer so for me it was \"self evident\" that an external 5V supply means there is no longer a 5V regulator. In this case you can accept it from this authoritative figure that: there is no 5V regulator on the board. (I have the schematics...)

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Re: Power supply news!

Fri Oct 21, 2011 8:45 pm

I know it is abit late in the day for this but is it possible that the board could have headers (pined or unpined) for external regulated supplies without the wattage overhead.
Gee The Rabid Inventor :)

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Re: Power supply news!

Fri Oct 21, 2011 8:50 pm

Not at present, afaik - but Gert\'s your man for a definitive answer on this question. Gert?
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Re: Power supply news!

Fri Oct 21, 2011 9:36 pm

I suggest that if you are not sure what power supply you need for these, Raspberry Pi, then buy one from them. When the specs come out, I will make sure the one that I intend to use, will meet those specifications. Hopefully we will get a working range from them that we can use to find other power supplies that will work as well.

This fuss is why I liked the original concept. The onboard regulator removed all of this fuss. Find a power supply that was 6v to 20v and you were in the money. If the model C ever comes true maybe it will return to being self regulated. I hope so. The 7805 that I intend to use needs 7.5 volts minimum to put out 5v. The changes needed for the new design appear to rule out replacing the linear with a switching regulator (edit) 3.3v no regulator on 5v at all).
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Re: Power supply news!

Fri Oct 21, 2011 10:28 pm

Micro USB for power and Standard Type A socket for... well... USB?

At least the vast majority of people will be able to see the difference and avoid plugging the power supply into the USB data socket. Though if the USB socket isn\'t powered and the supply pins aren\'t wired into the circuit then accidentally applying power into the data USB socket shouldn\'t cause any problems at all. Might be a problem if there\'s tracks leading into circuitry when there\'s no protection there?

Just an idle thought I had while reading ;-)
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