I need to supply a minimum of 0.5 amps to each port of a number of 10 port USB 2.0 hubs. I have succeeded using 8 amp wall warts so I'm reasonable sure the hubs are capable. I'm powering 8 hubs so that's more wall warts than I want to deal with. I modified a PC PSU, adding a load resistor (10 ohn 10 watt), power led and on/off switch following the many on-line guides.

I have 6 cables off the 5 volt bar, everything is solder and shrink wrap, psu starts as it should. It does supply power to the USB hubs but only a limited amount. I estimate it's about 2.5-3 amps, as all ten of the devices do not work correctly. The measured voltage at each line is 5.01 volts.

I have modified 2 PSU's, one rated at 400 watts with 28 amps for the 3.3 and 5 volt rail combined. The second PSU is rated at 40 amps for the 3.3/5volt rail combined.

I think the problem is because these are "regulated" power supplies, but I'm a noob and I'm totally lost at understanding why I'm not getting even close to the rated current of the PSU's. I would appreciate any advise or constructive criticism.

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    \$\begingroup\$ how much current does each hub need? If you've got 5v on each hub then the problem is not the power supply. \$\endgroup\$ – Andy aka Oct 28 '13 at 13:18
  • \$\begingroup\$ I need 5 amps to each hub, 10 devises per hub each requiring 0.5 amps. The modified psu well power 5 of the devises (ASIC's). I can power several hubs with the pc psu and each well have 4-5 of the devices power up, that's half of the number in the hub. When the hubs are powered by the wall warts all devices power up. When I use a wall wart with a 5 or more amp rating all 10 ASIC's power up. With a 3 amp wall wart, 6 devices power up, and so on depending on the amp rating of the wall wart being used. \$\endgroup\$ – user182165 Oct 28 '13 at 16:31
  • \$\begingroup\$ The pc psu behaves like it is a 2.5 amp power supply, i get this from each of the attached connectors (6). I'm getting the same results from two different psu's, a 28 amp and a 40 amp. I have talked to others doing this same project and they have had the same results, only 2-3 amps per connection from the psu. \$\endgroup\$ – user182165 Oct 28 '13 at 16:37
  • \$\begingroup\$ Do you have a load resistor on the 12v AND 5v rails, or just the 5v rail? Also, have you used an actual ammeter to measure the current, or are you just guestimating? \$\endgroup\$ – Passerby Oct 28 '13 at 17:49
  • \$\begingroup\$ I did the 10 ohm, 10 watt load resister to the 5 volt rail only. Nothing is connected to the 12 volt or the 3.3 volt rails. Do I need to add a load resister to the 12V rail? Yes, just a guesstament on the amps, seeing how other power supplies have preformed. \$\endgroup\$ – user182165 Oct 29 '13 at 19:02

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