Power Requirements for Elan USB Adapters
General Information
Normally no additional power adapter is required, as a USB port should (according to the USB specification) supply 0.5V, and this should be enough to power the USB adapter and the 3G card. Occasionally a computer's USB port (most often a laptop) does not supply 0.5V, i.e. it breaks the USB specification, and this can mean that a card plugged into the adapter doesn't work.
Most installations do not need extra power; the DC jack on the back of the adapter is provided 'just in case' for those customers who do need to supply more power.
Power Problems
In cases where insuffient power is supplied by the USB port, typical symptoms include :
- the USB adapter appears in Device Manager only briefly and then disappears
- the connection drops for no reason (particularly if you are moving around physically)
Problems are most likely to occur when the card needs an extra surge of power for some reason. This can be when it is first plugged in, or if it switches from one connection type to another (for example from HSDPA to UMTS, which can happen if the HSDPA signal becomes weak.)
This type of problem can be very 'intermittent' because it depends on the strength of your 3G signal, and that can change with your location, according to the weather, if your operator has problems and as more people log onto your local 3G cell.
Known Bad Systems
The following PCs are known to be prone to power problems :
- Dell Latitude C840 Laptop
Solutions
There are two ways to supply more power to your USB adapter:
Solution 1 : Y-Cable
This is a USB cable with two USB connectors. One is used as normal to connect the U111/U132/U142 to the computer via a USB slot. The other is a 'power only' interface, which you plug into another USB port. It doesn't make any 'connection' via that port, but can scavenge extra power from it to make up the shortfall.
These cables require you to have a second USB port available, but they are more portable than the external option.
Several companies make these, one of them is Addonics and their part number is AA2USBPC.
Solution 2 : External Power Adapter
These are widely available adapters which can be used for many appliances which plug into a normal electricity socket and into the USB adapter. Here are some models which are suitable for use with the USB adapter models; you would need to buy one appropriate to your adapter and also to your local electricity supply. Variable adapters can be used with many different appliances.
Adapters suitable for use with U111
if you do need a power adapter, the simplest choice is a variable one. The following adapters are widely available and suitable for the U111, if you can't obtain one of these an equivalent should be easy to come by from a computer accessories catalogue :
- Farnell 426-5373 (fixed 7.5V)
- Farnell 488-800 (Variable)
- RS 423-9224 (Variable)
- RS 431-7302 (Variable)
Adapters suitable for use with U132 and U142
- The specification for the supply is 6Vdc, 1A. The absolute maximum input voltage to be applied to the dc jack input is 7.5Vdc.
- Farnell 488-800 (Variable)
- RS 423-9224 (Variable)
- RS 431-7302 (Variable)
- 3-12VDC/1000mA Regulated AC-to-DC Adapter, Model 273-1680 from Radioshack. (Because this is a variable power supply, it is also suitable for use with the U111-530/630.)
- 3-12VDC/800mA Regulated AC-to-DC Adapter, Model 273-1667 from Radioshack
- Model DMS0601050-PC-IC from Digikey. The P7 is the suitable connector for use with the U132
