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USB power - how much is too much?
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Smeghead:
Whats the limit of USB power? And once exceeded, would adding a PCI USB card give you more?

I am going to have these powered off USB:

Coin slot lights
mouse
Ipac
trackball inputs
trackball power (including light)
Joystick
Sometimes a Memory stick for transferring files

Seems like alot to me. One option is I could use a 9pin serial mouse for the real mouse and power the coinslot lights some other way
But at what point is it going to tell me no more? My other pc I have tells me no more after about 4 devices (ipod/kb/mouse/camera)
MonMotha:
The limit per port (assuming full power to that port is available which it typically will be for ports hosted on the PC itself) is 2.5W or 500mA @ 5V.  It's best to add up all your ratings and figure out what you're working with.

If you coin slot lamps are incandescent, that will probably hit the limit or put you over right there.

Also, power is managed by having devices "request" power.  Most devices will not request less than 100mA since you get that pre-enumeration, anyway.  This means that your mouse, joystick, ipac, flash drive, etc. all will "ask" for at least 100mA.  Given this, you're at or over the 500mA max.

Note that this is PER PORT for things on either root hubs (physically part of the PC) or powered hubs with full power available (good hubs).  If each one of those gets plugged into a separate port, you're probably fine except maybe your coin door lamps.  If you are using an external hub, make sure it is powered and has a brick rated for 500mA (0.5A) times the number of ports you'll be using.
DashRendar:
I have about 6 things running on a powered 7 port USB hub.  They are:

* IPAC4
* Trackball
* 2 U360s
* External Hard Drive
* Spinner

I never have any issues with them.  The key here is that it's a powered USB hub, so it can provide ample juice to everything.
Smeghead:
ok thanks for the replies.
The PC im using has 6 USb ports, a row of 4 and a row of 2 and im using 4 of them right now with no problems.
I do have a nice PCI USB card, from what I just read ^^ sounds like that will help alot
orchidius:
Is there any way to get more out of one port? For example if I would want to power a bunch of LED's from one port using a PCB to wire them on, could I get more then 500ma out of a port so I could wire more LED's to the PCB?

Or could I just use a molex plug out of my computer and tap the red 5v wire and its ground wire to make a circuit for the PCB? How much power does that 5v wire carries?
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