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Power off a USB device


per carles

I wanted to power off a USB device. Searching in Google for “power off usb” returns different results but I didn’t succeed in any of the suggestions (Linux version 3.2.0).

I asked on the linux-usb mailing list (question, see one of the relevant answers (from Alan Stern). In short: not possible. When using a USB hub it’s then maybe possible -some models only-. The answer includes a link to a small program to try to disable the port. I could disable the port, but the device had still power.

I still didn’t want to give up. I remembered that I bought, 2 years ago, a USB relay. Actually that one could be used, as it says, with 220VAC/10A, so I could power on a heating or some big device.

I did a bit of very bad-done hardware work: I “broke” a USB cable, got the red inner-cable to pass through the relay. Then using one USB port I control the relay and I can switch on and off the other USB device like I initially wanted.

As you can see in the photo I broke the shield too much -because a confusion that wasn’t directly related to the project-. Still, it works well with my dumb device and other devices.

Aquesta entrada fou publicada el dissabte, 12/05/2012 (10:11) i està arxivada dins English, Programari Lliure, Tecnologia. Per a seguir els comentaris subscriu-te al fil RSS 2.0. Pots deixar un comentari o fer un retroenllaç des del teu web.

7 comentaris a l'entrada “Power off a USB device”

  1. xavi ha dit:
    14 de maig, 2012 - 11:22

    Why do you want to power off that?

  2. carles ha dit:
    14 de maig, 2012 - 13:27

    Xavi: because it’s off and I can turn it on when something happens. For example, I have a Python script that when I receive an email of a some people I turn it on. It’s a aroma notificaton instead of visual or audio notification.

  3. fsafsa ha dit:
    24 de maig, 2012 - 03:45

    fasgad

  4. pintant… » Arxiu » Olfactory notifications: presentation, code ha dit:
    2 de juny, 2012 - 10:44

    [...] Previously I talked about how to power off a USB device. [...]

  5. Al_ ha dit:
    9 de desembre, 2012 - 15:12

    Aroma notification? An amazing idea! Another, slightly more common example, why it makes sense to power off an USB device: to save energy and wear and tear of external harddisks connected to a mediaserver. As for the aroma notification, the harddisks can be restarted (and mounted) by a script if someone accesses a song or movie on it.

  6. Rick ha dit:
    13 de desembre, 2012 - 21:00

    I found a relay exactly the same as yours for sale. Can you tell me how to hook it up and make it work? Can you provide more details about the red inner-cable, etc.

  7. carles ha dit:
    13 de desembre, 2012 - 23:15

    Hi Rick,

    Could you read this other entry: http://pintant.cat/2012/06/02/olfactory-notifications-presentation-code/ ? There are some slides that should have the schema.

    Actually here a LibreOffice presentation: http://git.pinux.info/?p=misc.git;a=blob;f=smell/presentation.odp

    There is one slide that may help, but a small description:
    a) with one USB Port you need to control (on and off) the USB relay. You need to start with this.
    b) then you need to buy a new USB cable, cut the plastic cover, cut the red cable. The USB has 3 connectors: you need to put one side of the red cable in the center, other side in one of the sides (I can take a photo if this is not clear).

    Then with the port from a) you can control if your device is on or off.

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