mmkw43
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Power supply -- new product?

Wed Jul 06, 2016 2:40 pm

Just a thought (can't hurt right?) but rather than a wall wart power supply, some of us like to build into a chassis with an actual line cord.

I've been using this Ebay module --
http://www.ebay.com/itm/231642157662?_t ... EBIDX%3AIT

which powers the PI but concerned about it's performance and current capabilities plus about half of them I get have an audible whine.

Why not, as an accessory the PI foundation designs their own PI approved module with mounts like the one in the link and sells it as an accessory ? I did actually take the guts out of a PI wall wart but that's too much of a hassle.
Last edited by mmkw43 on Wed Jul 06, 2016 3:49 pm, edited 1 time in total.

MarkTF
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Re: Power supply -- new product?

Wed Jul 06, 2016 3:28 pm

Given the target (or anything but a very select) audience, selling a module with unprotected access to mains voltages seems like a spectacularly bad idea.

FlexibleSigmoid
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Re: Power supply -- new product?

Wed Jul 06, 2016 3:29 pm

The power supply is kind of a catch-22. The wall wart style is pretty universal in it's availability and there's not a need for a supplier to stock a different style for each outlet configuration and voltage supply (since mains power configurations differ so widely.) But that also means that quite often the problems that people have with the RasPi is due to an under-performing power supply or a thin USB cable. Do you think the value added would be worth the investment for a Raspberry Pi Official power supply? Personally, I'd like them to stick with they know.

mmkw43
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Re: Power supply -- new product?

Wed Jul 06, 2016 3:53 pm

Well, if they can design the PI -- certainly a power supply is within the realm of what they know.

Anyway, like I say just a thought. Besides, these PCB supplies are from China (wait time) and I'd rather get a PI approved module from MCM or whoever for 10 bucks.

stderr
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Re: Power supply -- new product?

Wed Jul 06, 2016 4:25 pm

mmkw43 wrote:it's performance
FlexibleSigmoid wrote: it's availability
Please, this is a website dedicated in some sense to education and there are impressionable youths potentially reading who could be confused by this. The possessive of it is its and not it's which is the contraction of it is.

Regarding the power supply issue, the pi people shouldn't be selling something that exposes mains to end users, the point made by another poster. This danger is real in North America at 117v but is very great in countries using 230v. If they were to sell a 5 volt supply and covered it with the required protective materials, essentially they'd have a wall wart, so the main argument for that would be that they'd presumably enforce some sort of quality and safety to the devices, which have been often lacking.

I've argued for including the capability of using an unregulated 12 volt supply, which might mean that the power inputs are tolerant to 20 volts. Then various sources of power that could power several or many pi in parallel would be possible and potentially at some distance. Currently at 5 volts, it is difficult to power more than one from one power supply and distances between the supply and the pi or more than one are very limited.

By standardising on 12 volts DC instead of high voltage AC, shock risks are avoided in most normal situations but enough power is made available. This isn't a new idea, cars in general use 12 volts, no one suggests 5v for cars!, and even the ATX power supply standard has moved from trying to provide all the voltages you might need in the power supply to providing mostly the 12 volts and you do what you want with that using DC to DC converters.

Obviously pi that could run off 12 volts would mean that using ATX power supplies with a lot of them wouldn't require support for the massive amperages that otherwise might be required. But if the pi could run from 5v up to 20v, some of them could be used with the 5v rail and some with the 12v, allowing for balanced power supply use. The next trick is to provide 12 volts on USB.

mmkw43
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Re: Power supply -- new product?

Wed Jul 06, 2016 4:45 pm

Whatever.

I guess Heathkit or Eico should have never been in business then. I doubt that anyone not familiar with the electronics of a module would want one anyway. Put a big warning label on it for cryin out loud.

Maybe I'll do it myself and sell them. It IS a good idea regardless.

FlexibleSigmoid
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Re: Power supply -- new product?

Wed Jul 06, 2016 4:52 pm

stderr wrote:
mmkw43 wrote:it's performance
FlexibleSigmoid wrote: it's availability
Please, this is a website dedicated in some sense to education and there are impressionable youths potentially reading who could be confused by this. The possessive of it is its and not it's which is the contraction of it is.
How embarrassing, their must be a way to add a grammar check before people post there work. They're's so much room for blunders as it is now.

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davidcoton
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Re: Power supply -- new product?

Wed Jul 06, 2016 4:52 pm

stderr wrote: Regarding the power supply issue, the pi people shouldn't be selling something that exposes mains to end users, the point made by another poster. This danger is real in North America at 117v but is very great in countries using 230v. If they were to sell a 5 volt supply and covered it with the required protective materials, essentially they'd have a wall wart, so the main argument for that would be that they'd presumably enforce some sort of quality and safety to the devices, which have been often lacking.
Correct, so an unenclosed "official" power supply won't happen.
stderr wrote: I've argued for including the capability of using an unregulated 12 volt supply ...
It's a minority requirement, unlikely to happen any time soon.
stderr wrote: The next trick is to provide 12 volts on USB.
The whole reason for using USB connectors was that it uses an established standard of 5V, thus avoiding the problems that arise with barrel connectors (different voltages and polarity on the same connector type, slightly different sizes that are pluggable but make poor contact). I can no longer say what I feel about this suggestion (even if you intended to post with a :lol: or similar) since I would be reported and deleted, see this post.
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HawaiianPi
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Re: Power supply -- new product?

Wed Jul 06, 2016 5:00 pm

FlexibleSigmoid wrote:The power supply is kind of a catch-22. The wall wart style is pretty universal in it's availability and there's not a need for a supplier to stock a different style for each outlet configuration and voltage supply (since mains power configurations differ so widely.) But that also means that quite often the problems that people have with the RasPi is due to an under-performing power supply or a thin USB cable. Do you think the value added would be worth the investment for a Raspberry Pi Official power supply? Personally, I'd like them to stick with they know.
mmkw43 wrote:Well, if they can design the PI -- certainly a power supply is within the realm of what they know.

Anyway, like I say just a thought. Besides, these PCB supplies are from China (wait time) and I'd rather get a PI approved module from MCM or whoever for 10 bucks.
There already is an official Raspberry Pi Foundation power supply.

And as MarkTF said above, a bare PSU board like that is just going to get people killed. The only way that would work would be to build it into a case, and I suspect the market for that would not be large enough to warrant the investment. Wall warts are ubiquitous now, and people are used to them. They also keep the dangerous high voltages well away from the device. This is not only safer for the obvious reasons, but also for less obvious ones, like accidental cord damage.
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gregeric
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Re: Power supply -- new product?

Wed Jul 06, 2016 5:08 pm

That module linked in the first post looks iffy in terms of isolation between mains & the low voltage side. Shouldn't there be wider gaps, and air gaps at that? Bad idea every which way you look at it safety-wise.

FlexibleSigmoid
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Re: Power supply -- new product?

Wed Jul 06, 2016 5:20 pm

HawaiianPi wrote:There already is an official Raspberry Pi Foundation power supply.
Interesting, wonder why there is the note:

Note
The power supply unit for Pi 3 is for use with Pi 3 only.

stderr
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Re: Power supply -- new product?

Wed Jul 06, 2016 5:20 pm

HawaiianPi wrote:Wall warts are ubiquitous now, and people are used to them. They also keep the dangerous high voltages well away from the device.
This is only true if you believe that the wall wart itself has been designed soundly. It has been proved by taking them apart that there are a lot of questionable devices out there, and the source of at least some of them is some ebay sellers and the like.

Wall warts that have been repurposed from UL listed (and the like) products shouldn't be obviously of defective design since looking into that is the business of UL and similar organisations. Now I'm the first to say that UL has passed some things that I think are questionable, although that might be because that's just how that is done, e.g. the relay in the microwave oven I fixed that had a bypass resistor that was of such a low resistance that if the relay stopped working, the resistor would start on fire. That has always seemed dangerous to me although it is inside a metal case and any fire should be contained.

I think though that UL should be capable of checking to see that the design of something keeps the high voltages away from the low voltage parts of the circuit and that is something that people have found questionable in some of the wall warts that weren't submitted for UL certification. People have said, for example, to never put a mobile phone to your head when it is plugged into the wall outlet, especially if you've just bought the lowest priced wall wart available.

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Re: Power supply -- new product?

Wed Jul 06, 2016 5:41 pm

stderr,
The possessive of it is its and not it's which is the contraction of it is.
Man that is confusing. Does it make any grammatical sense at all ?

Perhaps it's just me but I can help thinking some quote marks in there would clarify it.
Memory in C++ is a leaky abstraction .

stderr
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Re: Power supply -- new product?

Wed Jul 06, 2016 6:03 pm

davidcoton wrote:
stderr wrote:The next trick is to provide 12 volts on USB.
The whole reason for using USB connectors was that it uses an established standard of 5V, I can no longer say what I feel about this suggestion (even if you intended to post with a :lol: or similar) since I would be reported and deleted.
I'm not sure what your issue is with 12 volts, as I said, ATX has moved that way, some larger SBC boards are using 12 volts.

You are right that there is absolutely no standard in barrel connectors, I've seen various sizes with 5v, 7.5v, 9v and 12v and even 12v with the positive on the outside of the barrel which a long time ago smoked a radio had that I mistakenly plugged the wrong of two exactly the same connectors into, one positive on the outside and the other negative.

But I'm talking about two things here, the first is having the pi zero augmented to allow a pair of wires to be soldered to an additional location that would provide the board with unregulated 12 volts. This would open up a zillion perfectly reasonable to use wall warts and other power supplies that are not now usable with the pi. This would avoid trying to use potentially dodgy stuff from ebay so much, allow use of the 12 volt ATX rail, allow parallel powering of boards, and maybe even allow a poor man's power over ethernet although the voltage is low enough that actually powering it using ethernet cable might be questionable, perhaps with four + and four - lines operating in parallel.

Regarding 12 volt USB, this has got to be a no brainer although it's obviously nothing that the pi people can force into being. They should've added this when they added the connector that can be plugged in either way, although all USB flat connectors could be plugged in either way if the shroud is remove and traces are added to both sides of the connector board. I've got a USB flash drive without a shroud but they didn't add the traces on the other side.

In any case, by adding in 12 volt support, this would immediately mean that hard drives that are currently at their limits would just work. Hubs could provide 5 volts without using a wall wart. I don't know why they haven't done this, I'm sure they'll come up with some reason.

But keep in mind that these are the same people who created a connector that everyone plugs in upside down, turns it the other way, finds out that is wrong too and finally figures out they got it right the first time. All of this occurs because the difference between up and down isn't marked and isn't but a slight difference.

Then these are also the same people who replicated that issue repeatedly with the mini and microusb connectors used on mobile phones and on the pi. And just to make sure they get everything wrong that they can, they *still* can't seem to put the USB plugs far enough apart, or build the USB devices small enough, even flash drives that are obviously mostly just whatever size they want, that you can use all the USB plugs without finding extension cords that were not supposed to even be used at least to end of the 1x spec!

I have a LVM with three USB 32gig flash drives that I can't plug in into my pi2, for example, without putting the drives in diagonally to each other in the four USB slots and one of them in an extension. It's ridiculous, so I'll be assuming it will take a few more decades for 12 volts to make sense to them.

stderr
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Re: Power supply -- new product?

Wed Jul 06, 2016 6:22 pm

Heater wrote:stderr,
The possessive of it is its and not it's which is the contraction of it is.
Man that is confusing. Does it make any grammatical sense at all ?
Are quotes ever required in English to parse it? In Ulysses, Joyce, as I recall, would write dialogue at least some of the time with a form something like this:

--I'm planning to arrive by car at the newspaper said Bobby.

Turns out that 'said' and various other words like that at least often seem to indicate what might otherwise be redundantly expressed using quotes and commas, but in a lighter way, perhaps even Haskellish or more devilishly, in a manner one might call Pythonic. Obviously commas can't be done away with, clearly people who use Insane Texting Mode (ITM) when writing, I see this in Craigslist ads all the time, are impossible to understand.
Perhaps it's just me but I can help thinking some quote marks in there would clarify it.
You are probably correct, although in the instant case there could be some further questions created, even as they might be mitigated by the judicious use of the escape character: \' .

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Re: Power supply -- new product?

Wed Jul 06, 2016 8:45 pm

stderr wrote: I'm not sure what your issue is with 12 volts, as I said, ATX has moved that way, some larger SBC boards are using 12 volts.
The issue with 12V on a USB connector is very clear. The USB spec requires 5V. Designing anything that puts 12V on it will break all the 5V USB equipment out there -- probably in a spectacular, permanent and expensive manner involving the escape of magic smoke.

Standards are standards for a reason. Modifying them requires a lot of thought to avoid compatibility problems.

There is no issue with using 12V in itself. Of course it will need an extra regulator on every Pi, which will cost. Therefore it won't happen any time soon. It would also require a different power connector, one which is used only for 12V, not just by convention but by a defined standard. Defining standards and getting them accepted is hard work, not something a small organisation like RPF would undertake. When others lead, RPF may follow. Don't hold your breath.

POE is a more established method of distributing power at more than 5V. It can be done now, but needs an external adapter. Again, if you have followed the discussion here you would know that most pundits consider it unlikely that POE will go on board a Pi (cost benefit analysis says "No"). The low cost models don't have an ethernet socket anyway. For them, a USB to wired ethernet dongle with POE supplying a 5V back feed would work (protection issues aside), and would be really neat. Of course you couldn't plug in any other USB peripherals. In that case the dongle needs to have a USB hub integrated. Also, back-powering through USB doesn't work on models using an on-board USB hub. Power feed for them would need to be via separate microUSB. So even to solve the POE adapter issue across the range we need three different adapters! Economics rules that out, even if one adapter for all Pi models was viable.
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Re: Power supply -- new product?

Wed Jul 06, 2016 10:43 pm

davidcoton wrote:
stderr wrote: I'm not sure what your issue is with 12 volts, as I said, ATX has moved that way, some larger SBC boards are using 12 volts.
the escape of magic smoke.
Obviously I wasn't advocating putting 12 volts on the 5 volt lines, you are being silly.
Standards are standards for a reason. Modifying them requires a lot of thought to avoid compatibility problems.
USB is a mess that has had major problems that didn't need to happen including, as I mentioned in another post, the bizarre fact that they can't seem to build the devices sized so that they can be actually plugged into each of the ports. You'd think the standard would mention the max size of the device or mention the distance between the ports. I suspect it mentions both but no one involved can add. I can't understand why more people aren't angry about this, don't you want to use all the USB ports on a pi?

In any case, USB is evolving all the time, they are on at least version 3.1. This now includes a connector that can be plugged in one way or the other. I haven't used it yet, it remains to be seen if it is easy to plug in. They also have USB On The Go which they warn not to plug into something that doesn't support it, even though it will evidently fit.

But what 12 volt USB would be isn't USB with no 5 volt line, it would add in a 12 volt line and I think a ground wire for that as well. There is nothing shocking about doing something like this, that exact voltage was added, well, more lines were added, in the ATX spec when it was discovered that a power supply could provide 12 volts and a device could then use now dirt cheap DC to DC converters to make whatever voltage was wanted. Trying to move 5v or 3.3v to the board was just creating trouble; those troubles are true in SBCs although somewhat less so too.
There is no issue with using 12V in itself. Of course it will need an extra regulator on every Pi, which will cost. Therefore it won't happen any time soon.
Of course the pi could just use the USB 5 volt support that would still be there. But I am absolutely advocating putting in support on the pi boards for higher voltages. I want to be able to use the abundant supply of unregulated 12 volt wall warts, or whatever is available, basically 20 volts and below unloaded. And I'd like to be able to use other 12 volt support such as is used to power yard lighting and while potentially more troublesome, automotive power. Having this is on the board means having a consistent expectation of capabilities.
It would also require a different power connector,
In the case of USB, it would be an augmented standard connector that adds in 12 volt and ground wires. It would be backward compatible in that if you don't have the 12 volt support coming in, the hub or whatever falls back to what it used to do or it fails gracefully if this is a new thing that can't be done without 12 volts. There are numerous situations where USB hubs today need their own wall wart, most of those would be not need them barring power need increases from things that previously were impossible.

In this vision, the pi higher voltage support would be via solder connection which should avoid thoughtless plugging in of who knows what. I suppose there's always thoughtless soldering but this has always been possible with the pi, it has some lines that are not 5 volt tolerant yet it runs on 5 volts. This reality seems at least as dangerous to hardware as what I'm talking about.
unlikely that POE will go on board a Pi (cost benefit analysis says "No"). The low cost models don't have an ethernet socket anyway.
Real PoE is beyond the scope of what I was talking about. By real I mean standards compliant. All the pi needs is a poor man's version that uses cheap to free 12 volt wall warts or whatever.
For them, a USB to wired ethernet dongle with POE supplying a 5V back feed would work (protection issues aside), and would be really neat.
The pi needs 5 volts, especially if you are going to use the USB devices. The reason for 12 volt support is so that at a distance, you still have more than 5 volts. And the reduced current requirements.

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davidcoton
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Re: Power supply -- new product?

Wed Jul 06, 2016 11:33 pm

OK, you have an almost coherent case for a new USB standard with a new USB connector. You need to start with whoever is the USB standard authority, not with the Pi. As I said before, where others lead RPF may follow, but they can't and won't lead the change. And it is still in the category of "I want...", not a good cost-effective case for putting 12V (or 5-20V) inputs on every Pi. (Yes I do understand your Use Case, but a standards compliant 48V POE would be technically a better solution. More power through thinner cables for starters.)

You have one point of inconsistency. You argue for a 12V USB standard, but 5-20V on the Pi input. You can't (sensibly) have both. You might end up having to generate a 12V line to support GenerationX USB and 5v for legacy USB, when the unregulated supply could be above or below 12V. Not impossible but not a minimum cost solution. Remember the RPF's aims.

Do you really want to have to sort out people's power problems when the source can be not just 5V, but anything up to 20V? Even supplies nominally conforming to 5V USB specs cause enough issues, how do you tell people that they need 2.4A at 5V, or 1A at 12V, or ... ? And what are you going to say to the first punter after they confuse a 28V supply with the 18V one they thought they were using? Or the one whose cheapo PSU emits enough RF to block Bluetooth?

Of course, if you think there is a good market for a 5-20V power input, you could Kickstart a regulator HAT. I look forward to being able to save money by not investing.
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HawaiianPi
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Re: Power supply -- new product?

Wed Jul 06, 2016 11:59 pm

davidcoton wrote:OK, you have an almost coherent case for a new USB standard with a new USB connector.
Yes, because the one thing USB really needs is yet another "standard" added to the mess.

Image

And there already is a "standard" for 12V over USB. It's called Qualcomm Quick Charge, which bumps the USB output from 5V to 9-12V with compatible devices to help deliver more power through USB cables (and micro-USB in particular, which tends to be rather poor at power delivery). The nice thing about Qualcomm QC is that it does NOT require a special cable. Just a compatible charger and device (it uses a data handshake to authenticate QC compatibility before bumping up the voltage, so you can charge non-QC devices on a QC charger and they will only receive 5V).

My Samsung Galaxy Note 4 is a QC compatible phone (most recent devices with a Snapdragon processor are), and when I plug it into a QC charger it charges at around 9.5V @ 1.7A, compared to 5V at around the same current on a non-CQ charger. Needless to say, this results in significantly faster charging. Oh, and I've also use the same charger to power my Pi computers (including my Pi3).
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Re: Power supply -- new product?

Thu Jul 07, 2016 3:44 am

davidcoton wrote: not a good cost-effective case for putting 12V (or 5-20V) inputs on every Pi.
Support for this might cost less than a dollar. I saw some ebay dc to dc converters that purport to do this and they were two for a dollar with free shipping from the Moon or something. The conversion needs to occur somewhere, might as well have it at least partly on the pi itself.
You have one point of inconsistency. You argue for a 12V USB standard, but 5-20V on the Pi input. You can't (sensibly) have both.
These are two different issues, one is adding in support for 12 volts to USB, something that the USB standards body would need to do. The other is adding in support for a broader choice of power voltages for pi boards, which would open up a lot of different power sources currently unavailable, potentially allowing powering boards in parallel which reduces the number of power supplies, and allowing powering from at least some reasonable distance. These are all good things. If USB supported 12 volts, that would be available in the above scenario on the pi, so I'm not clear why you think one precludes the other.
Do you really want to have to sort out people's power problems when the source can be not just 5V, but anything up to 20V? Even supplies nominally conforming to 5V USB specs cause enough issues, how do you tell people that they need 2.4A at 5V, or 1A at 12V, or ... ?
The reason that there are so many problems with power is exactly the reason I'm suggesting looking at more options. The main problem seems to be that it takes a beefy 5 volt power supply to power the pi2 and pi3, especially the pi3 with its wifi. A lot of wall warts will plug in but won't work, a lot of USB ports will plug in but won't work, a lot of USB cables will plug in but won't carry the current well. So this use of the usb plug has not meant side stepping a lot of problems, although it has got around polarity issues and ensured that the power is likely a nominal 5 volts. This problem largely goes away if the pi supports higher voltages and is less critical about what the voltages actually are, because voltage drops, caused by too thin wire, are reduced or matter less.
And what are you going to say to the first punter after they confuse a 28V supply with the 18V one they thought they were using? Or the one whose cheapo PSU emits enough RF to block Bluetooth?
What happens right now when they put 5 volts on a 3.3 volt io line? I'd test this idea out on the pi zero whenever it gets its next redesign. Using the support would require soldering to the board, which should mean that the person either thinks a bit about what they are doing or should be thinking about it. I really can't see how this is more of a threat to anything than any pi hardware hacking is.

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Re: Power supply -- new product?

Thu Jul 07, 2016 8:54 am

stderr wrote: Support for this might cost less than a dollar.
On a $5 Pi Zero? Not viable.
stderr wrote:These are two different issues,
Clearly. So why did you mix them up and present them together? For the reasons of economy I stated they are not compatible on a single Pi.
stderr wrote:The reason that there are so many problems with power is exactly the reason I'm suggesting looking at more options.
and
stderr wrote:What happens right now when they put 5 volts on a 3.3 volt io line?
So you solve a problem by making it bigger?
stderr wrote: two for a dollar with free shipping
As I said, make a Hat. Kickstart it. When you have a major sales success other people will listen.

I will just reiterate finally, there is a sensible use case for remote powering at low voltage (<50V) DC. An on-board regulator works technically but not economically. 12V over USB is a standards nightmare. POE is a suitable, standard, available solution -- but does not sell widely. If you can do better, stop talking and do something. I've said all I can about the technical and economic problems. I'm going to stop now before I get rude.
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Re: Power supply -- new product?

Thu Jul 07, 2016 9:50 am

Having a barrel connector and a decent 5V regulator on board isn't a particularly radical idea. It's been there on Arduinio Uno boards and the like in parallel with a USB connection for years with no problem. The circuit could have polarity protection.

The argument for adding one has become far stronger with the increased power requirements of the Pi3 coupled with the large number of micro USB socket-compatible 5V chargers and PSUs which simply don't have the grunt to power the board. This gives rise to the posts we see here with "I have a problem"....which mostly turn out to be supply related.

I've ended up just throwing a 50p buck converter into the mix and wiring it to GPIOs on the 5v side and a barrel connector salvaged from my junk box and powering from a 12v supply.

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Re: Power supply -- new product?

Thu Jul 07, 2016 2:57 pm

piglet wrote:I've ended up just throwing a 50p buck converter into the mix and wiring it to GPIOs on the 5v side and a barrel connector salvaged from my junk box and powering from a 12v supply.
That's OK as long as you realise that you are bypassing the polyfuse.
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Re: Power supply -- new product?

Thu Jul 07, 2016 3:04 pm

How is the buck converter in your link working out? pretty reliable? So the input requirements would be a standard 12vdc supply -- what would the transformer current requirements be?

I may try that instead of the AC input module I've been getting -- have a bunch of 12v transformers and some LM317 regulators.
Because it's step down how big of a transformer would I need for the PI 3? -- thank you

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Re: Power supply -- new product?

Thu Jul 07, 2016 3:10 pm

Is this what you're using ?

http://www.ebay.com/itm/LM2596-DC-DC-Bu ... ZoPthiq-Vw

What input voltage will get you 5V? I may get some and then I can use a better quality transformer. -- thanks

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