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Author Topic: Does a 3G USB modem require additional power after network registration?  (Read 2779 times)
kveroneau
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« on: September 25, 2010, 04:40:16 PM »

I have a HUAWEI E182 USB HSPA+ Modem, which works wonders on my Linux laptop, and I am attempting to get it working on the SheevaPlug.  The Plug's kernel detects it fine, however when I enter in my PIN using comgt, the light flashes blue for just a split second confirming registration on the network then goes back to green.

Since I am connecting to the plug using cu, I can see the various kernel output, like it being inserted and detected.  The output is no different than from my laptop.  comgt detects the device with no problems, but then constantly waits for network registration.

I am guessing that it draws additional power from USB when turning on the cellular radio, so when it cannot draw more power, the 3G chip just turns itself back off.  This is very unfortunate, as an external power source is needed in order for the plug to connect to a 3G network to provide remote data.

Keep this in mind when developing remote applications which may just use solar energy for example, you may need to also supply the 3G modem with it's own power source.

Does WiFi act the same way?  When WiFi powers up it's radio, does it also draw more power, and which USB WiFi dongles would work best?
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cjm
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« Reply #1 on: September 26, 2010, 10:57:28 PM »

While the Plug's power supply is known for breaking over time, especially when overloaded by unpowered USB devices, it can power things like an external hard drive even if it takes more than the nominal 500mA to start up. There's no circuit that would limit USB current to 500mA.

Unless your power supply is already half broken, I would not assume that the modem draws enough power to cause the symptoms you're describing.

But I don't have a good explanation about what else could be your problem, either. Maybe you could try hooking up the modem to a powered USB hub, just to rule out power problems?

Thanks,
--Christian
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GuardMoony
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« Reply #2 on: October 06, 2010, 07:50:57 AM »

Most modems have a option to stay connected to a network. Maybe its not enabled for yours. or maybe the signal to connect isnt strong enough?

As said previous the plugs can handle 500mA witch is usb standards. If you truly think its a power issue try a powered usb hub. then you draw power of this instead of the plug
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