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Farnell power adaptor for the Pi

e14 Contributor

*** EDIT ***

 

In this message, I implied that the PSU supplied by Farnell is inadequate, out of spec etc. it turns out that THIS IS NOT THE CASE - the Farnell PSU apparently works just fine. If you are interested in the details (or if you have similar problems, either with the Farnell PSU or with others) please read on. The short story is, it seems that USB type A -> Micro USB cables are usually the culprits, so check this before discarding/blaming your PSU.

 

*** EDIT ***

 

I was wondering if anyone has used the Farnell "ADAPTOR, USB TO EURO, WHITE " (the last item in page http://export.farnell.com/jsp/bespoke/bespoke7.jsp?bespokepage=farnell/en_UK/promotions/rasp-pi-accessories.jsp - interestingly enough, clicking on the link leads to a page about an unrelated product, but clicking on "buy" from the first page mentioned adds the adaptor to the cart).

 

I got two such adaptors and tried one of them. Tha voltage between tp1 and tp2 on my Pi, after it boots, is 3,88V - way below the nominal 5V. As is to be expected, the Pi is not very stable with this supply. In contrast, using the PSU recommended by another distributor, I get 4.90V and the Pi works like a charm.

 

- Is this a known problem?

- What is the procedure for returning the two PSUs?

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  • in reply to wallarug

    I had trouble with three power supplies.

     

    One was a Toshiba 2.1A version for my tablet, that wouldn't run the Pi, but happily charged the tablet.

    The other supplies seemed to work one day, then wouldn't work at all and I suspect they had too much ripple which was causing the supply to reduce the output voltage.

     

    I now seem to have about 5 mains to usb outlet devices, but I suspect they are designed to charge a 3.6v LiPo battery rather than be a 5v supply, like everyone thinks.

     

    I also had cable suspicions, and was able to measure it at 0.1v. Follow the guide to measure the voltage and check its above 4.8v (which seemed to be the magic screen or no screen).

    Funnily the best one was a cheap one that coiled up.

     

     

    Mark