Reccomendation on a cheap externally powered USB hub/adapter - Page 1
Forum section: electronics / general

author: XOIIO
author_rank: Super Contributor
timestamp: August 05, 2014, 01:26:12 pm
content: Hey all, for my tech work I use the zalman ve 300 usb drive enclosure since it can emulate any ISO, and its dead simple to use, I'm in love with it.Bought a second one since my first one appeared to have stopped working, I have to test it but it may have been due to the really long cable I have, though usually the drive at least tries to spin up.Anyways, on quite a few computers the USB ports can't give enough current, the short lead it comes with usually helps, but that also makes it harder to use and also increases the chance of the port on the drive getting damaged, since it is the mini usb 3.0 connector.Anyways there are basically two options, three if I want to do the DIY approach.I could get an SSD to put in the case, it would be even faster, however that would cost roughly $80 for the same sized drive and I already need more space on this. I can get a 32gb one for $54 but I have an ISO that would take up that entire amount, and I wouldn't have much for other stuff anyways (yes, a 32gb iso, it's ophcrack with all the libraries included)The other option is just to get an externally powered USB hub, however most of them are fairly large, I am looking for something that would even just have one port to power the drive. Using a little USB current meter I have seen it draw up to 700ma when it starts the drive up, with the long cable it sits at around 200 and the drive can't spin up properly.I was also thinking I could either make my own with an external power adapter, I am guessing the way they do it is just hook ground ground together and don't connect VCC to the computer, though I've never looked into it.So, any suggestions on a product that would fit my needs? I might grab a cheap hub off ebay but I'd like something fairly compact. I could also maybe try making a split cable adapter like the USB 2.0 hard drives had but I'm not sure that would work.

author: jolshefsky
author_rank: Regular Contributor
timestamp: August 05, 2014, 02:03:19 pm
content: I went ahead with the DIY solution for my "mega hub". I basically used cheap USB hubs to handle the data transfer, and a PC power supply to provide the 5V at the output and to the USB hub circuitry. The 5V power from the CPU to the hub input is disconnected.What I was finding is the cheap USB hubs tended to tie their external power port to a common 5V bus. That meant the 5V would back-feed into the CPU when it was turned off. Also, the traces for the 5V power at the hub output ports were pretty weak, and the design permitted a substantial sag in the 5V rail when a high-current device was connected. This resulted in hub errors and such.The "mega hub" I made seems to have improved the reliability of the cheap hubs quite a bit, although a few ports are kind of wonky and relegated to being additional charging ports.So long way around: I have had success in wiring an external 5V supply to a USB port to give extra current to a device, with only ground, D+, and D- connected to the CPU.

author: XOIIO
author_rank: Super Contributor
timestamp: August 05, 2014, 02:20:38 pm
content: Alright. I do have an older usb only hub laying around, fairly compact and I could modify it easily I think, though there is not much space inside of it to add a power jack. Interesting that they tie the 5v bus together

author: Bassman59
author_rank: Super Contributor
timestamp: August 05, 2014, 07:49:31 pm
content: Quote from: XOIIO on August 05, 2014, 01:26:12 pmThat's BY SPEC and BY DESIGN. A compliant USB 2.0 host (or powered-hub downstream) port can provide a maximum of 500 mA after a device which requests that much current enumerates.A lot of disk drive mechanisms draw more than 500 mA. That they work on some hubs indicates that the hub doesn't do much power management.The use of the second Type A cable connector to syphon power from a second port is a hack, and sometimes the hack doesn't work.

author: nctnico
author_rank: Super Contributor
timestamp: August 05, 2014, 08:37:27 pm
content: I recently got a Belkin and a V7 USB hub in aluminum casing. The V7 has the ports in oriented so I can stick 6 SD adapters in them and duplicate 6 SD cards in parallel. The Belkin in more general purpuse. Both seem to work but are probably not really cheap.

author: XOIIO
author_rank: Super Contributor
timestamp: August 06, 2014, 01:03:16 pm
content: Quote from: Bassman59 on August 05, 2014, 07:49:31 pmYes, I am aware of that. I believe that counts for the entire hub as well, at least for some setups, which is why the split cable doesn't work sometimes.

author: Jeroen3
author_rank: Super Contributor
timestamp: August 06, 2014, 01:32:42 pm
content: Spec says a USB 2.0 port should not deliver more then 1 power unit (100 mA) when not asked for.Also a device should not draw more than 1 unit when not allowed.USB Suspend current (for a device in sleep) is 2.5 mA, and 12.5 ma for a hub. Initially this was 500 uA and something.With an interval exception for peak usage, read the standard.Standard also explicitly states that current may never feed back into the host.But a lot of devices do not comply. Thats why Y cablesdon'tshouldn't work.iPhones do comply, that why they do not charge until the driver is installed.