HELP!

[scruffy]

i need some help here ...... does anyone know what the exact voltage of a usb port is? i neeed to find out how much juice a usb port will put out

thanks
-mike

 

[dejitaru]

I've measured mine at about 5.48 - 5.8v from different locations
What are you powering?
The voltage needn't be exact. A voltage of 15%- or 30%+ should work (don't quote me) depending on the application.

 

[RossGr]

The voltage says nothing about the amount of current the port can provide. You need to find the specs for your port to get that information. I would expect that all USB devices are designed to use a standard voltage. The current cababilities of the port can vary, this determines how many devices can be driven. This is reason for powered USB hubs, not only do they provide more connections they porvide current to run the devices. But all devices use the same voltage.

 

[CTho9305]

IIRC you aren't supposed to take more than 500mA through USB.

 

[Mark R]

USB is 5V nominal. Range from 4.4-5.25 V depending on load.

Max current is 500 mA per port.