How Good Are Bus Powered USB Devices?
How good are bus powered USB devices? That’s a good question and the answer depends upon the device and the application. To start, let me summarize situations / products you could find problematic. From here we can determine what & when “bus power” is best.
Most problem situations are with USB devices which require a heavy load of power. Products such as USB disc [hard] drives, external USB CD or DVD burners etc. With these products you need a lot of power, if you don’t get it, you have problems. If the power running through the USB cable (the USB bus) to your device is not enough good chance the product will fail. Problems such as drive failures, burning CD coasters or repetitive USB disconnects during operation.
With the larger USB hard drives coming out this is where you need to pay attention. I would recommend against purchasing a “USB hard drive” where the drive itself runs from USB bus power.
But lets say you’ve covered your bases and purchased a USB hard drive with an external power adapter – now we must consider the connection to your computer? Many times I’ve heard users making the connection via their USB port on their keyboard or USB port from a card reader. Simply because those USB ports are most convenient to reach. Well “those USB connections” are not ideal. The weak link comes from the buss powered keyboard or card reader. Instead, the optimal method of connecting is directly to the USB port which is connected to your motherboard. OR if you have a USB controller card running off a PCI slot – that is fine too.
Some other common problems would be:
- A laptop with low power to it’s ports.
- A USB cable longer than two feet.
- Poor quality USB cable or USB cable certified for only USB 1.1 use.
Tags: usb bus power, usb cable
Matt LeBoff
Kicking around in technology since 2002. I like to write about technology products and ideas, but at the consumer level understanding. Some tech, but not too techie.