Why USB Device is not Working

Quite often encounter questions on a USB device that a single computer is functioning normally and in another makes mistakes, it does not connect. Most common is a 2.5 “external drive, but there are frequent instances of flash drives, difficulty made me even laser mouse? Where is the mistake? In that device, or driver, or wherever? Let’s look at the most common causes and possible solutions to this problem.

When I bought my first external 2.5-inch drive in the manual, I found a strong warning that the drive must be connected to a computer with either a supplied USB cable, or at least cable no longer than 0.5 meters. Shortly thereafter, I had hands another USB drive, which even had a special cable – the one at the end, where it connects to a computer is divided into two USB connectors. In order to drive to work well, you had to be involved in both. If you are into computers involved only one connector, computer disk or not recognized.

USB connection is special in that, in addition to data transfer, the USB port and capable of providing power for the connected equipment. Therefore, your USB drive and runs with no source connected to the outlet. And that power is the cause of a large part of the problems with USB devices from Computergees.

Too many connected devices

Each USB port on the computer should ensure the supply current of 0.5 A at 5 V. If your computer to connect multiple USB devices power-intensive (except 2.5-inch USB drives are, inter alia, hotplates and coffee variety other gadgets – toys, your source may not tighten this all loads. the voltage drops and power sensitive devices start to make mistakes. In practice, this probably reflected so that the disc will pretend disorder, while hotplates go merrily on …

Hub – also too many devices

Insufficient power source in order not to cause trouble among the leaders. Much more likely is the culprit USB hub (sometimes also called the English a USB hub). This allows you to connect to your computer more USB devices, but also thanks to him have the mount points pretty handy.

But when you do not have a separate adapter powered hub, takes the power supply current from the computer, and it usually only up to the amount that is able to provide one USB port – 500mA.

If you connect to a passive (non-powered) hub more devices that are powered via USB, it is likely that the current supplied by the port will not suffice all devices.

Long cable, low voltage

Another typical problem is the voltage drop in long or too thin USB cable. The longer and thinner the wire, the more resistance. Higher resistance means greater voltage drop. With the USB port you measure 5 V, but at the other end of the cable with the device it will be less.

While the data transfer cable is too long mind, has the power to directly influence the length of the cable core. A printer connected 5 m long USB cable will have no problem, the hard drive is powered from the USB port can not handle long cable.

Often you have ports on the back of the computer landlocked and therefore in good faith will help an extension cord, the end of which you are pretty handy, should be on the table. Remember that even the most hubs used by at least one meter connection cable.

When I was in an older computer, a laser mouse connected through a hub, used to have frequent short outages. They stopped at the moment when I plugged it directly into a USB port on the back of the computer.

To make USB devices work well

Based on these findings, we can formulate some practical advice on how to fix any problems.

If using an extension cable or USB hub, try the device that connect directly to the USB port of your computer. Ideally, the port on the back, usually on the power a little better than the front.

If you are angry devices in one port, unplug it and plug in another.

Do not unnecessarily long cables. Especially with external drives, it pays to use the original cable.

Connect to a hub, if possible, only devices that are consuming power – eg. Printers and scanners have their own power supply, so a USB cable to transfer data only. In contrast, mouse, USB headsets, USB external hard drive or USB hotplate coffee usually need a USB port and energy would be better is plugged directly into the computer.

Or use a USB hub with power supply – some hubs have jack adapter, even when sold without it (mostly because of the price). The adapter must have a voltage of 5 V and a four-port hub should deliver a current of 2 A. However meet often weaker (with a current of 1 A), if you do not connect it to the same powered device.