POE / USB - what happens if draw too much power?

I have a Bomebox, powered under POE, I connected a USB hub and to that I connected a keyboard controller, tiny 3 knob controller and RJM controller (small one)… the Bomebox seemed to work for a while but today started to shut down after a while, is this because I was drawing too much from the USB plug?

Is the bomebox shutting off a sign of drawing too much power off the USB bus?

Hi, the USB port can provide up to 1A of power. The USB spec calls for up to 500mA per device, so with PoE power you should be able to handle at least 2 devices. With that said, some vendors do not play fair so you might have a power hungry USB device. Try it with a powered hub and see if that fixes things. With that said, I have never had my BomeBox shut down due to too much USB power draw so maybe your POE converter is faulty.

Steve Caldwell
Bome Customer Care

Also available for paid consulting services: bome@sniz.biz

Thank You

The Cisco POE switch actually keeps a log and there were no overloads or anything, 18watt draw over previous hour and a 65watt budget so no where near the edge there.

I am hoping it was just too much stuff, I would love to know if the BomeBox shutting down/off is a function of this or whether I should replace this BomeBox (we use three of them here). Meanwhile, I am plugging in the keyboard controller and will see if that changes things.

Thank You

As I said, I have not seen BomeBox shutting down from USB current overdraw, however I know the PoE spec calls for a handshake between the PoE source and the PoE device in order to provide power. Once the handshake is complete, power should stay there. What is the status of your leds on the POE connector when the power was dropped? Is the right hand light still on?

Steve Caldwell
Bome Customer Care

Also available for paid consulting services: bome@sniz.biz

Quick correction: USB allows for passive devices to draw up to 500mA, and because the hub also draws some power, 3 USB devices on a hub can already overdraw from the BomeBox. (Steve’s reply above is fixed in that regard, for anyone later stumbling on this forum thread).

Having said that, the BomeBox has multiple safety features to prevent overdraw and also to prevent damage if power is injected into the USB host port (i.e. the wrong direction). Depending where an overdraw occurs, the entire BomeBox might shutdown, or the BomeBox might just switch off power for the USB host connector.

OK, I’ve tried it (just to be sure).

  1. I’ve connected a 4-port USB hub. When I noticed that 4 USB-MIDI controllers worked without problems, I plugged a second USB hub into the first USB hub, and connected MIDI controllers to all ports. They worked fine, 7 MIDI controllers and two hubs, all of them powered by a BomeBox, which is powered via PoE. When trying to measure the current with a USB insert current meter, the setup would not properly initialize the USB devices (but BomeBox does not reboot).

  2. Now I’ve used an artificial fake USB load device. As long as I kept load under 1A, nothing happened. But when exceeding 1A, the BomeBox rebooted.

So it might be that you’ve hit the second case. In that case, your BomeBox is OK, but you’re drawing too much current from it.

Hope that helps! Please keep us posted if you find out anything else. Thanks!

A while back I did an unscientific test of the current draw of my devices using a pluggable USB meter. Here is what I discovered . Notice that the Launchpad MINI (first gen) took most power and this is the one I have most problems with if using an unpowered USB hub. I was not able to figure out why some if these had no power draw or whey the Q88 read so weird. Some devices have their own power so I can understand no power draw on those.

The FCB-1010 was using an iConnectivity MIO1 as a USB to din converter.

FYI only.

APC MINI - 170
Queneo - 319
Conspiracy - 130
APC 40 - 250
Face Cam - 190
Desk Cam - 60
UMC404 -0
Key 24 - 0
Stream Deck - 140
KB Dongle -0
Mouse Dongle -0
Xtouch MINI 110
Launchpad MINI - 500
Launch Control - 80
Vonets - 230
2016 Display - 0
FCB-1010 - 0
Nord S2EX -0
Mini Hub 2 - 7
Korg - 0
Q88 - 70 (subtraction)
Launchpad MK2 - 150
Launch Control XL - 230
MIDI Fighter Twister - 90
APC Key 25 - 80
Launchkey MINI - 0

Edit - My meter does not read less than 10mA so that is probably why some are 0.

Thx very much both of you for all this!

I think the StudioLogic controller is maybe 300 ma, not sure I’m converting the amps to watts correctly, then the RJM thing like 150 )according to their specs), add the 3 knob thing and a usb hub(didn’t measure) and perhaps we are passing the 500 mark as you’ve suggested, So we’ve plugged in the keyboard and so far so good… I think to stay on the safe side I will simply power all my USB Hubs here.