USB Merge
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- ouroborus
- Posts: 3
- Joined: Sat Jan 19, 2008 4:01 pm
USB Merge
The schematic is of a cable intended such that power is from from one source and data from another. The merge side would be attached to a usb device. The data side would be attached to a laptop. The power side would be attached to a usb charger wall wart. Is this sort of thing feasible? Am I doing it right? Does such a thing already exist?
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- Schematic
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- zener
- Posts: 4567
- Joined: Sat Feb 21, 2009 2:38 am
Re: USB Merge
My concern is that your power be properly regulated. A charger or wall wart may not be.
- dr. au-fait
- Posts: 73
- Joined: Wed Apr 27, 2011 6:17 pm
Re: USB Merge
That should work fine as long as the grounds are at the same potential or one is floating. Most USB ports are fused, but a shift in ground potential can fry something on your PC/laptop main board. I learned that lesson with a USB oscilloscope.
The regulation of the voltage from your secondary source is important for signal quality. Most wall warts are pretty good regulators if they're spec'd for 5V since the typical application for that voltage requires tight regulation.
The regulation of the voltage from your secondary source is important for signal quality. Most wall warts are pretty good regulators if they're spec'd for 5V since the typical application for that voltage requires tight regulation.
- zener
- Posts: 4567
- Joined: Sat Feb 21, 2009 2:38 am
Re: USB Merge
Historically, DC wall warts are unregulated. Only the newer switcher type are typically regulated. The older kind can float very high. Check with a meter before you hook it up.
- ouroborus
- Posts: 3
- Joined: Sat Jan 19, 2008 4:01 pm
Re: USB Merge
I was thinking of those wall warts specifically marketed for USB charging. Like http://www.cobyusa.com/?p=prod&prod_num ... at_id=4002
Please be positive and constructive with your questions and comments.