Hi all, I've been looking at the system of connecting wirelessly on 3G using a USB dongle. When looking at them most places say it requires an external power source due to the high currents required. Most show an external power supply like an ac adaptor breadboard. Does any one know if it can be powered from the microcrontroller? And if not, is there a suitable battery set up that would power it so its completely wireless? Thanks Rob

Do you know what the current draw of the dongle is? As the mbed draws its own power from a USB port I doubt that UBS port would have enough power to power the dongle as well. As far as the batteries go some of the LiPo batteries have good power densities an might be suitable but would need a voltage regulator to drop them down to the correct voltage.

The only 5V source the mbed has is the USB port, it doesnt have its own 5V regulators. So if you already use an USB port for your mbed, you might as well use a second USB port for the dongles power.

If you really want it to be mobile I would do what Martin suggested, a LiPo battery + DC-DC converter.

Thanks for that. Looking at that range of battery's it appears they are rechargeable. I am looking at incorporating a photovoltaic cell in the project so I assume this could recharge the battery? Thanks again. Rob

Be careful recharging LiPo batteries! If they are not charged correctly they can be a bit of a fire hazard. Maybe try NiCad or NiMH and search for some recharge circuits on line before you decide

Ok thanks very much for the info. Rob :)