USB Hubs

TTeuer · 04-26-2008, 07:20 PM

I'm a bit confused on how USB Hubs work in a CarPC environment.

Do I need a USB hub that is solely powered with its own power? I'm worried that if it draws power from the computer and switched power (like many sold now do), when I switch the ignition off, it will then draw power from my Mac Mini and possible cause issues that would wake it up from sleep/still draw (more) power when it's asleep.

Do I need a USB hub that I can set to only set to draw power from a separate +5V source? If so, is there a recommended one? I e-mailed both Belkin and D-Link and none of their current offerings have that feature anymore.

Or will just pretty much any USB 2.0 hub work?

Thanks!

Avi · 04-26-2008, 11:06 PM

I am also interested in powered hubs. It would be nice to have it powered by the car battery. Is there anyone who has rigged one up to run off of the battery? I suppose all u would have to do is rig up the power with some sort of resistor to drop the voltage down to 5 v but what about the voltage fluctuating when the alternator kicks in?
is there any discussion on this topic?

blackcobra487 · 04-26-2008, 11:09 PM

From what I've been told by many, the best thing is to use a powered hub and to draw power from your PSU. It already puts out regulated 5v.

rgarjr · 04-26-2008, 11:18 PM

Hubs are normally powered off the psu or a point of load. I run 2 7-port hubs. U simply just cut off the connector off the power brick.

TTeuer · 04-27-2008, 12:38 AM

I'm not worried about where to get power - I'm worried about whether or not my Carnetix P1900 with additional 5V rail is going to keep drawing power for the USB hub when I switch my ignition off. I know a lot of USB hubs are designed to start taking power from the USB port if they lose the "main" power - correct?

blackcobra487 · 04-27-2008, 10:51 AM

If you have your hub power off you PSU with a shutdown controller, your hub will turn off at the same moment the computer does. There won't be any power in the USB port for the hub to draw. The only power that a PSU will supply after the computer if off, is 5v standby power. I know with my M2, that gets cut off after awhile.

TTeuer · 04-28-2008, 12:17 PM

I'll have to verify but for some reason I thought the Mac Mini still sent power to the USB ports when its asleep. I guess I'll just have to verify that when I get a chance. If it doesn't, then I don't think there's anything I have to worry about. Just for reference, what USB hubs are you guys running?

JimmyFitz · 04-28-2008, 01:24 PM

I modified a standard usb cable that feeds my hub by cutting the 5V lead. I use S3 standby which does keep the USB 5V on. My hub is powered separately from a molex plug off my M1-ATX.

Aside from not drawing power when the car is off, my Griffin Powermate now works reliably every time I start back up (out of standy or otherwise). It used to work only sometimes until I connected it through this hub that loses power when the PC goes to standby.

HiJackZX1 · 04-29-2008, 06:34 AM

Quote: Originally Posted by rgarjr

Hubs are normally powered off the psu or a point of load. I run 2 7-port hubs. U simply just cut off the connector off the power brick.

I also do the same, but be very careful and check polarity. You can fry a hub instantly. If you really feel the need to connect to something other then the PSU, you could always get a 5V regulator and connect to the battery, but this will be an issue when start up and shutdown because the hubs would turn on before the PC is on and also the hubs would shut off before the PC is off, not good. The best solution is to stay with connecting to the PSU.

HiJackZX1 · 04-29-2008, 06:39 AM

Quote: Originally Posted by blackcobra487

If you have your hub power off you PSU with a shutdown controller, your hub will turn off at the same moment the computer does. There won't be any power in the USB port for the hub to draw. The only power that a PSU will supply after the computer if off, is 5v standby power. I know with my M2, that gets cut off after awhile.

I think I know what he means....... he's talking about some MoBos that keep power going to the USB ports no matter what. TTeuer hubs do not have this feature. So once the power is off, the hubs are off.

Dave323Ci · 04-29-2008, 07:43 AM

I have a Mac Mini installed, with two 4 port USB hubs - one powered off a P1900 @ 5V, the other @ 12V off the car battery (fused w/relay). The second hub is actually rated for 7V - 24V. When I turn off the ignition the P1900 cuts power to the +5V Hub, the relay cuts power to the 12V hub, and the Mini goes into Standby mode. Unfortunately both hubs are still lit, drawing power from the mini's USB ports. I'm running XP on the mini and so far it doesn't wake up well.

I tried taping over the power and ground contacts in the Hub, but then the Mini doesn't recognize that there's a hub attached, even when it's externally powered.

I just did the install last weekend, so haven't tried all options yet. I'll post back if I can find a solution. In the meantime, I have it set just to shut down.

JimmyFitz · 04-29-2008, 08:14 AM

Quote: Originally Posted by Dave323Ci

...

I tried taping over the power and ground contacts in the Hub, but then the Mini doesn't recognize that there's a hub attached, even when it's externally powered.

I just did the install last weekend, so haven't tried all options yet. I'll post back if I can find a solution. In the meantime, I have it set just to shut down.

The ground wire is still needed for communication. Try interrupting only the +5V wire as it enters the hub via the USB cable. That is exactly what I did in a hacked cable, external to the hub.

Dave323Ci · 04-29-2008, 10:01 AM

Tried taping off only the +5V, but then the device isn't found. The Mac Mini seems to need to be able to connect the power to recognize it, even though it's a self powered hub.

I also tried running Devcon.exe to disable the USB ports, but they still stay lit. I'll mess around with this some more.

I guess the worst case is the USB hubs are drawing some power. Have to do some math to see if it's enough to worry about. Right now I'm more concerned about coming back from standby smoothly.

TTeuer · 04-29-2008, 10:41 PM

Hmm... well I'll just buy a Belkin at Best Buy this weekend and see what ends up happening.

Dave323Ci · 04-30-2008, 06:27 AM

Quote: Originally Posted by TTeuer

I'm a bit confused on how USB Hubs work in a CarPC environment.

Do I need a USB hub that is solely powered with its own power? I'm worried that if it draws power from the computer and switched power (like many sold now do), when I switch the ignition off, it will then draw power from my Mac Mini and possible cause issues that would wake it up from sleep/still draw (more) power when it's asleep.

Do I need a USB hub that I can set to only set to draw power from a separate +5V source? If so, is there a recommended one? I e-mailed both Belkin and D-Link and none of their current offerings have that feature anymore.

Or will just pretty much any USB 2.0 hub work?

Thanks!

Back to one of your original questions. Under XP you can turn off the ability to wake up the machine in the device properties in the control panel. OS X probably has something similar.