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So I managed to diminish my RPi model A power consumption to the impressive mark of 70mA (underclock + replacing the 3v3 regulator). Low current is important because it is a mobile app (robot/car controlled by SSH). Now I want to add Webcam and Edimax WiFi dongle.

Both worked well with a USB hub connected to the RPi. The problem is that the hub, with nothing connected, pushes the total current above 200mA.

Is there any better solution than consuming additional 130mA just for a hub? Is it worth an attempt to buy a model B and reduce consumption by removing ethernet?

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  • Actually, if I use two model A, it is possible to have a Webcam and WiFi and still consume less power than using the USB hub. But they would have to talk to each other.
    – dawid
    Commented Oct 6, 2013 at 3:06

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What about using the RPi Camera Module? I am not sure how much power that consumes compared to your usb camera. If you do wanna check out the RPi Camera Module, then you can have a look at the documentation here to see if its something that fits your needs.

If you still are considering USB hubs, then you can see a list here with RPi-working usb hubs with power ratings.

Additional info:

  • Model A ratings: 300mA. Model B ratings: 700mA. (Reference-A, Reference-B)

  • The RPi + camera draws about 260 mA more current when recording video, than without the camera. The Model B is about 550 mA by itself, so camera use pushes it over 800 mA. (Reference)

  • Nearly 300 mA for the camera module alone (Reference)

  • To save ~2-20 mA on the RPi Camera Module, you can turn off the red led (Reference)

  • If you want a simple way of measuring how much power a USB device is using, you can buy THIS device with free shipping. (5,99USD)

  • A computer's usb port can supply up to 500 mA, unless you have got USB 3.0 which can supply 900mA (Reference)

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I've seen someone disable the LAN chip on the board. Running only 200mA on idle.

Otherwise you'd just have to try out a few hubs, and see which one uses the least amount of current.

Or buy a raspberry camera board, leaving you with only one USB device.

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  • It seems like the LAN chip also controls the second USB port. May be all usb expansions need power for some obscure reason.
    – dawid
    Commented Oct 6, 2013 at 20:09
  • Not sure what you mean. The lan is internally connected through usb, as far as I know. So the single usb the broadcom chip provides is routed through the onboard hub, to the lan and the two usb ports. Both the lan and usb-hub seem to be inside the same chip. But unsoldering this chip will result in both usb ports becoming unusable.
    – Gerben
    Commented Oct 7, 2013 at 15:09
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    I mean that a model B without LAN implies RPi without extra USB. And an extra USB is just what I need.
    – dawid
    Commented Oct 7, 2013 at 16:59
  • That it is, indeed.
    – Gerben
    Commented Oct 7, 2013 at 19:13

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