MP3Car.com - View Single Post

2k1Toaster · 05-15-2007, 05:44 PM

Quote: Originally Posted by gthing

Excellent. I really appreciate your help everyone. I have one last question.

I got a hub that has an independent power supply. I'm going to cut off the transformer and splice into the existing wiring.

The transformer says that it outputs 5V at 2.5A. I guess with 500mA coming off the USB connection, this makes a total of 3A available to the hub. I'm not sure if this assumption is correct.

So if I wire in a 3A connection from my power supply, and hook it up to USB, the hub will have a total of 3.5A available to it, meaning I am pushing ~500mA more than it is designed for.

I don't think this would be a problem, but if I know one thing it is to be careful with USB power as I've fried many-a-expensive electronic item through the USB ports.

So if it IS a problem, maybe I should continue to use that USB extension cable I cut the 5V out of, to bring things back down under control. That might work.... Or do I even need to worry about it?

If it is externally powered, then it wont draw anything off of the usb bus. So will draw 5 ports x 500mA = 2.5A. It will only draw what it needs. So you will draw 2.5A from the power supply, and you will have another 500mA left over to do whatever. Maybe one of those usb nerf rocket launchers or something.

05-15-2007, 05:44 PM	#7
2k1Toaster Fusion Brain Creator Join Date: Mar 2006 Location: Colorado, but Canadian! Posts: 7,623	Quote: Originally Posted by gthing Excellent. I really appreciate your help everyone. I have one last question. I got a hub that has an independent power supply. I'm going to cut off the transformer and splice into the existing wiring. The transformer says that it outputs 5V at 2.5A. I guess with 500mA coming off the USB connection, this makes a total of 3A available to the hub. I'm not sure if this assumption is correct. So if I wire in a 3A connection from my power supply, and hook it up to USB, the hub will have a total of 3.5A available to it, meaning I am pushing ~500mA more than it is designed for. I don't think this would be a problem, but if I know one thing it is to be careful with USB power as I've fried many-a-expensive electronic item through the USB ports. So if it IS a problem, maybe I should continue to use that USB extension cable I cut the 5V out of, to bring things back down under control. That might work.... Or do I even need to worry about it? If it is externally powered, then it wont draw anything off of the usb bus. So will draw 5 ports x 500mA = 2.5A. It will only draw what it needs. So you will draw 2.5A from the power supply, and you will have another 500mA left over to do whatever. Maybe one of those usb nerf rocket launchers or something. __________________ Fusion Brain USB I/O Board with 12 Digital Outputs, 10 Analogue Inputs, 4 Digital Inputs and only 68mm x 68mm! Now Shipping Worldwide!!!