Current draw from USB port

RatLabGuy

RatLabGuy

You look like a monkey and smell like one too
Joined
May 18, 2005
Location
Churchville, MD
I know we have some engineers/computer geeks here.

What the max current you can draw from a typical PC usb port? It's 2.0 spec, if that will make a difference.
There are 4 bazillion devices that run "self powered" off 'em so I figrue it's got to be more than a couple mA....
 
Most of our Dell Laptops are rated approx 500ma's. You may find an externally powered hub will get you more, but... WHY?

Jonesing for one of those USB powered vacuum cleaners, aren't you? :flipoff2:

awww.coolest_gadgets.com_wp_content_uploads_k7046b.jpg
 
LOL!!!
 
If I recall correctly it's a maximum of 500 mA per port unless it's an externally powered hub
 
Green ford said:
Anyone seen the USB beer cooler they had for sale at Tiger? Yet plug it in a set your beer on it to keep it cool.....lol
Click to expand...

Was that the white one? I saw one of those in a magazine a while back and thought about picking it up, but it looked too small for your standard beer. Looked like it was made for Pepsi Bawls or whatever that is.
 
OK jackasses.

Well I gues I should say thanks.

I'm building a circuit to control an LED board. I knew it was more than enough, but just wanted to be sure. Technically it's designed for a parallel port, but those can only supply like 80mA (easy to kill by overdraw...) and don't always havet he juice to flip several relays simulaneously... I found a cool parallel "port" device that plugs in through the USB, Windows sees it as parallel so the communication is the same... but now should have sufficient juice.
 
Yeah, 500ma per port rating. Which is actually pretty impressive when you consider the size of the trace that carries that...
 
Hm.
So you think if you pulled across 4 ports, you could really draw 2 amps? That's actually quite a bit of power.
But I doubt they really are that independent.
 
Another techy question.

Need some BNC cables, for carrying misc analog signals (generally of the 5v type).
Why is a 25" cable rated at 75 Ohm more expensive than one rated at 50 Ohm? Former listed as for "video", latter "usable for 10 mbit ethernet" (why you'd do that these days IDK).
Wouldn't lower resistance (Ohms) alway be better?
 
25' BNC cables should be under $6....
It could always depend on the brand.
Of course if you were ultra cheap 25'QSRG6 and 2x.70 on ends and viola
 
RatLabGuy said:
OK jackasses.
Well I gues I should say thanks.
I'm building a circuit to control an LED board. I knew it was more than enough, but just wanted to be sure. Technically it's designed for a parallel port, but those can only supply like 80mA (easy to kill by overdraw...) and don't always havet he juice to flip several relays simulaneously... I found a cool parallel "port" device that plugs in through the USB, Windows sees it as parallel so the communication is the same... but now should have sufficient juice.
Click to expand...

I built a circuit using a Basic STAMP micro controller that will control several relays and LEDs. It's connected via serial port to the PC. The STAMP uses a 9V battery. It's handy to be able to program some logic into the micro controller.
 
I need to put you in touch with our Russian electro-phys guy... he has the knowledge (both electronics & machining) to make dang near anything. He's "assembled" 3 - 42U racks FULL of various electronic gizmo's for that lab
 
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