Why does my Raspberry Pi reboot when USB devices are plugged into a powered hub?
Question by yuitre_ /

The Pi is non hot-pluggable, meaning whenever a usb device is plugged into it, it reboots itself due to a drop in current. I’ve read that it has something to do with the polyfuse having zero resistance, or something like that.

I did what most forum users recommended–use a powered usb hub. So here’s what I did:
1. Pi only has HDMI, and SD card plugged in. It stares silently at me.
2. I plugged the hub’s usb connector into the the Pi’s usb slot.
3. I switch on the hub.
4. I switch on the Pi.
5. Pi is now fully booted and greeting me is Raspbmc’s main screen.
6. I plug in my external 2.5′ hard disk.
7. POOF! screen goes blank.
8. Pi reboots.

Am I doing anything wrong here? The hub is supposed to supply current to the hard disk, but why does the Pi still reboot?.

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Answers (8)
  • Oron Joffe

    Yuitre, from your reply to Chris, it would seem the hub is not producing enough power. First of all, I have to ask, is this a powered hub (i.e. is it powered by a separate power supply?). If it is, you probably need a better power supply or a stronger power supply! If it isn’t (that’s called “bus powered”) then you need to get a powered hub, and again, make sure it comes with a good power supply (they’re always 5 volt, but should produce at least 700 mA, and preferably 1A or more).

  • Jim Chambers

    What happens if you plug the x-HDD into the hub and then proceed to steps 2-5?

    • yuitre_

      Appreciate your response Jim. Tried it but problem seems to be due to power being supplied by the hub into the Pi. So now the Pi is receiving current from the micro USB where it was meant to receive from AND the USB port.

    • Chris Marcoe

      If you have a source of power that is not the hub, then the Pi will get its power from that source. some people have run it with only the hub as power, though. and that is not recommended. You can fry your Pi.

  • Chris Marcoe

    If you are powering the Pi through the hub, stop. It’s not recommended to power it this way. Get a plug that will power only the Pi. The, you get your power there for the Pi and it won’t die.

    • yuitre_

      Thanks for the info Chris. I didn’t know the hub sending power to the Pi via USB. I think the problem lies there. So here’s what I did:

      First, I booted the Pi with only the SD card, HDMI and power supply. When that was finished I plugged the hard drive into the hub. I then powered on the hub and the hard drive’s LED lights up. No issues so far.

      Finally, the hub is connected to the Pi. No rebooting occurs,
      BUT, the hard disk starts beeping, complaining that it isn’t receiving enough current.

      Is it normal for the hub to send its current to the Pi? I’ve seen a post about cutting the red wire in the usb cable that connects the Pi to the hub to prevent this from happening. Any advice on this?

    • Chris Marcoe

      No. that sounds like the Pi is getting plenty of power from the seperate power source. The HDD blinking and not getting enough power is a problem with the hub not having enough power to get the HDD operative.

      Check the documentation on the HDD and see how much it needs to draw to run right. then check the documentation on the hub to see what it supplies to each port.

      I am thinking you might have to upgrade your hub. This page linked below is the be all/end all for verified peripherals that work. Good luck and jsut ask if you need any more help with it.

      http://elinux.org/RPi_VerifiedPeripherals

    • rekrezreb

      If you want a more robust solution I would recommend rpips.com.
      They power the Pi from the GPIO.
      I run a WD passport drive and a web cam with no issues from the USB port