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I'm developing for my #iot project with a device, a Raspberry PI, positioned in places without any internet connectivity.

So I'm looking for a really cheap internet connectivity solution; using a cheap 3G USB dongle.

Googling here and there I read about the facts some (or all?) these kind of 3G modem dongles sometime SINK more current than that Raspberry PI circuit can supply... (with usual power-supply say 1.x Amp); and some people suggest to connect the dongle to a separated-powered USB HUB, If I understood that properly.

The point is that I possibly would avoid the hub-connection scenario because of costs (cases + connectors + hub + power supply) and anyway I read about people used successfully 3G dongles connected directly to the Raspberry USB port.

So my question is: Does someone experienced (cheap) 3G Dongles (Europe) that are "compatible" with the current amperage that Raspberry could supply ?

Does exist any list of "compatible" / tested 3G dongles that can be connected directly to the RPi USB port (without an USB hub) ?

BTW, any experience with something similar , or this one ?

  • I use Huawei E220. However, I'm not sure what do you mean by low power. I have never dared myself to connect it without a powered hub... – yo' Aug 18 '14 at 13:12
  • yes, I used a E173 and it seem ok too (I just tryied SMS connectivity until now). I'd like to avoid any external powered hub (see: youtu.be/SJm3KjO6RFU). BTW, I presume the power supply limitation have been overtaken by new Raspebrry Pi model B+ – Giorgio Robino Aug 19 '14 at 13:36
  • Do you NEED 3G? Are you going to be streaming 720p video from it? Or transferring large data? Possibly use a GPRS modem with a rate of 115kb in 2G area. Text is compressed hardware so logs files and stuff can will go quicker thank 115kb – Piotr Kula Sep 17 '14 at 19:09
  • @ppumkin: yes, GPRS/2G modem could be perfect for my bandwidth need. other factors are: cost and availability (of dongle and also of mobile operator SIM...). At the moment i see two "cheap" alternatives: 1. a 3G usb-dongle with a cheap operator M2M SIM. 2. an internal shield (2G/3G) modem. For some reasons I'd preferto avoid any dongle sticking out the Rpi box... – Giorgio Robino Sep 19 '14 at 5:07
  • I just want to warn you that low-power consupmtion = low TX power, and that might lead to signal loss in some places with less GSM masts. – thekiwi5000 Jan 8 '15 at 15:49
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You can try using the Huawei E303FH data card. It works out of the box and does not require additional power too. Here's the link to Ebay UK . It cost's around $20.

Just install Sakis3g and follow this guide to get it working.

  • 1
    but Sakis3g seem now inexistent ... – Giorgio Robino May 17 '14 at 14:30
  • It is listed on the Raspberry Pi compatibility list as of Mar '16 but it doesn't seem to be very available in the U.S. I'd like something I could purchase reliably and use with a service like Ting... – Timothy Lee Russell Mar 8 '16 at 6:39
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Technically the limit is 500millliamps (2.5watts MAX) that the device can draw from any USB port because it must meet USB 2.0 specifications.

The new revision Models and B+ allows for the 500ma to be saturated with out problem. If it used more than 500ma then the devices would not work on half the laptops and computers in the world.

The reason a 1Amp is recommended is because the Model B may use up to 600ma current at full load. The old revisions had a poly fuse that turned off power at a really low rate causing even problems with keyboards and mouse!

Instead of sperate USB Hub, buy a better 2A or 3A Regulated Switching power supply, not the cheap phone USB chargers. The reason is that WiFi needs clean power to generate good signals this may also apply to UMTS (GPRS/EGDE/3G/4G)

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