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How can I see what's causing my 3G dongle to disconnect from the Internet?

I'm using a Huawei K3565 USB 3G dongle on my Raspberry Pi.

Using wvdial and sakis3g I can connect to my current provider (GiffGaff) - but only for a few seconds.

For example, I can ping 3 - 4 times, or download approx 25,537 bytes.

Then the modem disconnects.

I don't think this is a power issue - I'm using a 1.2A charger with no keyboard or screen attached. I also have sufficient credit :-)

So, any idea what is causing it to disconnect? Which logs can I look at?

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What makes you think it's not a power issue? –  Jivings Jul 5 '12 at 12:34
    
Well, that's a good point. Raspberry Pi recommends 700mA for powering the device. Most 3G dongles need no more than 500mA. 500+700=1200. But I'll try with a 1.8A charger to see if that makes a difference. –  Terence Eden Jul 5 '12 at 15:29
    
Yes, well that's 700mA for powering the Pi alone. You're trying to power things with it as well. –  Jivings Jul 5 '12 at 20:03
    
Interestingly, with a 1.8A charger, it connect for about 3 times as long before suddenly disconnecting. Are there any specific logs I can look at? –  Terence Eden Jul 6 '12 at 10:14
    
Not for this. Look at @AlexChamberlain's answer. The usb port doesn't provide enough power for your dongle. –  Jivings Jul 6 '12 at 10:27

2 Answers 2

up vote 2 down vote accepted

The current on the RPi outputs is limited to 140mA; try it through a powered hub.

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That did the trick. Thanks! –  Terence Eden Jul 13 '12 at 6:58

I found a tutorial in "Cooking Hacks" explaining how to use 3G with the Raspi through GPIO: http://www.cooking-hacks.com/index.php/documentation/tutorials/raspberry-pi-3g-gprs-gsm-gps

They have launched a shield that allows our Raspi to be connected to a server or to make calls through a 3G Module.

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If it is possible to include the important part of the external post in your answer, please do so (since the link you provided may not work tomorrow!) –  Dave Oct 16 '12 at 9:18

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