Safety of USB Passthroughs?

[mctriple]

My knowledge of electronics goes back to my old E&M physics class quite a while ago. All I really remember is V=IR lol. Seems that 5V (USB) and 2.2Ohms (typical atty) would mean 2.27A running through a USB port.

Is that the case? Are people really safely running that much current through a USB port? To my knowledge, they're only rated for 0.5A. Even USB 3.0 is rated for just 900mA.

Or are these not actually designed to be run on a computer? I haven't seen anybody warn against using these on a computer.

Is it safe?

 

[Dave Rickey]

USB standard is 500mA. *However*, the PSU rail feeding it is generally designed to feed 3 others, and is rated for 2.1-1.5A. So direct-drive PST's generally work, but they also probably void your warranty. If it's all you got, you do what you have to, but as a way of avoiding spending the $25 for a real passthrough, or the $5-10 for a strong enough wall wart (which includes those designed for 4-power USB expander hubs), it's bad math to risk a full-on PC.

Yes, you can direct drive an atty off your PC's USB, I've done it. But it's going to cause you problems, probably around the time you're trying to run a USB-power optical drive at the same time, or something else that crowds the edge of the spec.

--Dave

 

[mctriple]

What do you mean avoiding $25 for a real pass through? The PT I'm looking at is more than that. From puresmoker specifically

so a wallwart would be far better?

I appreciate your response!

 

[WillyB]

What do you mean avoiding $25 for a real pass through? The PT I'm looking at is more than that. From puresmoker specifically

so a wallwart would be far better?

I appreciate your response!

Well I doubt that "and 2.2Ohms (typical atty)" is very typical at all. Are you using an authentic Joye 510 atty?

If you are the least bit handy you could build yourself a true, complete 5V scorcher for about $18.

Start with this and then just direct wire it to a switch and atty connector in any enclosure you chose. A cheap 2XAA RS box works well.

5VDC Power Supply 2.4A AC Adapter for D-Link LinkSys 5V - eBay (item 300389514218 end time Jan-28-10 22:54:54 PST)

Here's my first 2A version (smaller than the one I listed), it only runs my Joye 510 at about 4.5V (at about 9watts, that's double what a Joye battery produces), everything else at 5V.

 

[Juan]

do passthroughs ruin ur hubs overtime????????

 

[Craig Patterson]

Been running homemade and store bought passthroughs for 7 months on my PC now. The only problem I had was from when I was using a store bought one... it would overload the USB hub and give windows errors. Turns out it was because the store bought ones are so cheaply made (look at how thin the USB cable is) and there was a break in the wires causing a short.

I got a wall mount AC/DC adapter from a PSP kit that is 5.5V/1A out... and it gives more vapor and stronger hits than off USB, so I don't think that USB is pushing over 1 amp on my system when its connected.

But like I said... 7 months and no problems to Atty's or to my pc.

Craig