USB PORTS POWERED WHEN COMPUTER IS OFF SERIAL

The serial protocol may have been devised long before USB was even on the horizon, but that does not mean that your data communications cannot flow smoothly over both. Rather than abandon serial communications prematurely, the wiser and easier move is to deploy USB-to-serial converters. But, there is still a huge installed base of legacy serial equipment out there and there are numerous new applications for which the serial communications protocol is still the perfect answer. It is hard to find a computer with a serial port these days.

USB PORTS POWERED WHEN COMPUTER IS OFF FULL

Powered USB devices restore the full 500 mA. You will feel better if had installed a powered USB hub or powered USB isolator. After wasting all that time on the problem, you may feel like a donkey. You will try swapping out the USB cables, try reinstalling software, get frustrated, and eventually figure out that the connected device was never receiving full power. It will usually seem as if the connected device or the connection itself is to blame. Perhaps, because so many USB devices are self-powered, some manufacturers cut corners and build boards that do not provide the full 500 mA to the USB ports. Self-powered devices, like printers, typically register as вЂњlow-powerвЂќ devices, requiring only 100 mA. вЂњHigh-powerвЂќ devices should be able to draw the full 500 mA. (A unit load in USB 2.0 is defined as 100mA.) вЂњLow-powerвЂќ devices should be able to draw one unit load or less (under 100 mA). Not every USB port provides the specified 500 mAДЄccording to the USB specification, a device should be able to draw up to 5 unit loads from a USB port. Deploy devices equipped with high retention USB ports like those built by B+B SmartWorx, which require 3.2 lbs of force to dislodge them. So, be wise when using USB off the desktop.

USB PORTS POWERED WHEN COMPUTER IS OFF SOFTWARE

Loose USB cables can also lead to data loss, software hang-ups and blue screens. In the wrong environment, that can lead to fire or explosion. And, when they do, there may be risk of arcing. Over time, the cables can work themselves loose. Standard USB connectors do not grip cables firmly enough to withstand the heavy vibration encountered in industrial applications. That becomes a problem when USB migrates off the desktop and out into the real world. Unfortunately, USB was also designed for quick and easy connections/disconnections. In safe office environments, it is very convenient and normally quite harmless. Connected USB devices can then be powered by the USB cable connection, eliminating the need for an external power supply.

One of USBвЂ™s great advantages is that it provides a 5 V power supply on a single wire. Office-grade USB connections are too weak for real-world applications

Usb ports powered when computer is off