Pi accessories from Farnell ... USB chargers?

So far have tried a generic one that I had already- not too much use,

Ordered (and in the process of returning) one from Amazon which was sold as a 5V 2A charger..... nice, however, it arrived this morning and it RATTLES (many hours of fun for small children but not a wanted feature for a PSU)

Current thoughts are some sort of 5V mains charger, or running it off of the 300W ATX powersupply that I already have stripped down to being a bench supply- nice stable 5V but it is a little large for me to be perminantly happy with that as a solution.

It would be nice to have some accessories that are guarenteed to work, or at least tested with, the RPi.

Hello All,

The RPi is certainly making a lot of people think about stuff they hadn't thought about before - if not in quite the way that was intended.

There is a slogan on my coffee cup "Good, Cheap, Quick - pick any two".

The RPi is certainly cheap but it looks as if the Good/Quick balance is just a little out on the power supply arrangement.

Based on observations made by contributors to this thread the problem is that the RPi really needs a 5.25 (+/- 0.2V) supply with a nice short thick lead (and hope that connector drop is not too bad) - Farnell could get whoever makes the Multicomp supplies they sell to make a special.

Other than that it's not going to be easy to fix cheaply if you don't want to solder- the obvious hack is to graft a suitable 5V supply (not  a USB charger) to a USB lead or solder it directly to the RPi but

I couldn't see any adjustable supplies in Farnell that cost less than the RPi.

This leaves you with the option of spending a lot or building/modding a supply.

Michael Kellett

Indeed Michael.

Unfortunately with the current generation of board, people will either have to follow the hardware hack articles, or else live with the existing state of affairs.

So far though, only 20k or so boards have been produced, which is a drop in the ocean compared to where the Pi is heading.  That makes it imperative that we help the Foundation and its partners address the issues so that Pi boards beyond v1.0 don't have quite the same level of power supply problems, and so that v2.0 boards eliminate this issue entirely through improved design.

It's an important task.  I'm a bit disappointed though that the Foundation's engineers aren't openly accepting the issue and collaborating with community engineers here to find a range of solutions.  The large amount of engineering experience within the community is a great resource.  It's odd that it's not being harnessed to its fullest extent.

My worst fear is that the Foundation is dragging its feet on recognizing the matter, possibly out of a totally mistaken worry about "egg on face".  No, the egg on face will come when there are millions of units out there, all with the same problem, resulting in many thousands of returns and adverse publicity.  Accepting it now and working openly on fixes would be both strategic and highly responsible of them, and would work very strongly to their advantage.

Morgaine.

http://www.amazon.co.uk/CostMad-Technology-Certified-Approved-Universal/dp/B005NZKTRG/ref=sr_1_16?ie=UTF8&qid=1337636414&sr=8-16

Have checked this at home with a couple of high wattage resistors-

5.24V Open Circuit dropping to

4.74V @ 460mA (10.3 ohms)

4.34V @ 860mA (5.0 ohms)

4.22V @ 1240 mA (3.4 ohms)

Not feeling all too confidant about this, but will give it a go when my SD card decides to make an apperance. Up side is that I now have a new Plan B, before Plan C (the ATX PSU) gets pulled out of retirement

Does seem that there are a couple of teething problems..... A "cheap and available to the masses" bit of kit needing top quality peripherals to function correctly seems to be missing the mark. Also that, so far, I've spent more on the bits to make the RPi function, than I have on the device it's self (and I'm still hedging my bets on a USB hub and case, and I already had the keyboard and mouse.... and the screen).

Jaz

What do you have connecting the power supply to your resistors?  According to my calculations, there's a 1.086 / 1.037 / 0.82 Ohm resistance between an ideal 5.24V voltage source and your test resistor.  It's either in the power supply itself (bad supply! bad supply!) or the wires connecting to your resistor (bad micro USB cable! bad micro USB cable!)

Arggghh!!!!

Please check the things that John has pointed out.  Unless the leads are a complete disaster (easily corrected), that power supply is beneath contempt.  2A USB?  Hahahahahahaha

This Pi experience with alleged "USB-spec" chargers has been amazingly eye-opening.  It points out vividly how manufacturers treat specs with total disdain in the search for profit.

Morgaine.

@ Morgaine,

If it comes to an RPi board change it would seem to me that the best bet was either change over to nominal 12V in (possibly 9)  and use a switcher down to 5V on board or if compatibility is essential stick with the micro USB and nominal 5V in and fit a boost switcher on the RPi to take it up to 5V.

For my money the boost solution is the second best from an engineering point of view but probably the best overall solution since so many people are already locked into the micro USB power connector idea.

It won't be quick - board re-spin, prototype, test (EMC this time ?), feed into production ........ six weeks ?

Short term someone could pick up the pieces with special power supply - talking of which has anyone tried one of the supplies being offered specifically for the RPi ?

Michael Kellett

Will have a looksee over it again tonight when I get home, To be fair to the cable, it was a no-longer-used SE USB data cable, so probably not the biggest bit of cable around, or the best. Just what I happened to have at the time!

Will have a looksee over it again tonight when I get home, To be fair to the cable, it was a no-longer-used SE USB data cable, so probably not the biggest bit of cable around, or the best. Just what I happened to have at the time!