Featured Articles
Announcing Pi
Technical Specifications
Raspberry Pi FAQs
Win a Pi
Raspberry Pi Wishlist
Actions
Forum Thread Details
  • Replies 2 replies
  • Subscribers 663 subscribers
  • Views 293 views
  • Users 0 members are here
Related

USB powered hub to power the Pi

recantha

Hi all.

I know there's a Wiki with a list of peripherals, both working and non-working, but I'm finding it difficult to tell which one has which capabilities.

 

Ideally, what I'd like is to have a powered 7-port USB hub into which I can plug a USB-to-micro-USB cable to power the Pi itself. I'm aiming to get my 'system' so that I do not need yet another mains cable for the Pi itself.

 

Has anyone had any experience or heard of anyone who has managed to get it working?

 

Here's hoping! :-)

 

--

Mike Horne

  • I'm using a 13 port version made by mbeat (http://www.mbeat.com.au/index.php?route=product/product&product_id=89) they do make a 7 port version. There are similar types that don't have switched  ports. I got mine for AU$24.00.

     

    You might have to cut the 5v powed line to the USB PC connector as this will attempt to power the Pi with the Pi power cable disconnected, whichever brand you may buy.

  • I have that working pretty well with a 4-port Inland powered hub, which I got as a US$5 special from Fry's years ago.  My hub has a Schottky diode in the upstream USB cable which makes sure the hub doesn't try to power RasPi through its USB A ports.  Also, my hub just connects all the downstream +5V signals together so there's no current limiting (other than wires and PC board traces).  A smart hub might have slow-start current control and not provide adequate current to RasPi.  I don't know how to tell what a candidate hub is going to do looking at a web page for it.  I found out what my Inland does by taking it apart and playing with an Ohmmeter.

     

    The main problem I have with my set-up is that the Inland hub has a 3.5 mm barrel power jack, and it doesn't always make good contact.  I found out recently that barrel connectors are iffy: the outer conductor has good wiping contact, but the inner pin of the jack has only casual contact with the plug.  You can get a high-current version of a 5.5 mm barrel plug with wiping inner contacts, but I haven't found such a thing for 3.5 mm.

     

    Currently I'm running at 4.65V on my RasPi (if the 3.5 mm jack is conducting well), which happens to work OK with my peripherals but doesn't leave any margin.  My planned solution is to solder power wires directly to my RasPi with a real SMT fuse instead of polyfuse F3.  With that I expect to get 4.8V or more since I'm not getting drops across my 3.5 mm power jack, micro USB cable, and polyfuse F3.