Hi,

I'm developing a small appliaction (Win32 for Windows XP). My client wants
to control USB-powered lamp from the application without
connecting/disconnecting it manually. Is it possible?

Thanks,
Jacek

jh wrote:

Without an USB enabled microcontroller you cannot build a valid USB
device. Only valid USB devices are allowed on the bus. Anything else
(USB fans, USB lights etc) are bullshit and can only cause problems.

This has to be a joke posting surely?

If I found a client that wanted a USB powered lamp I'd probably die
laughing!

Don't visit Fry's Electronics, it may be fatal for you.

"fat_boy" <zzebowa@hotmail.com> wrote in message
news:1134997709.273708.131240@g43g2000cwa.googlegr oups.com...

Make a simple HID device. Control the lamp with the HID and limit total
power to <500 mA.

Marc Reinig
System Solutions

"jh" <jh@radio.kielce.com.pl> wrote in message
news:do681n$j23$1@atlantis.news.tpi.pl...

No, but seriously, you can draw, what, 5 volts off a USB bus? What is
the purpose of a lamp as bright as a bicycle light?

fat_boy wrote:
You can try to shove it and see if the light comes out of your mouth.

Well I've just connected my USB lamp (kindly provided by Compuware - thanks
and it is not visible as a device in Device Manager.
So you can't "eject" or disable it by means of SetupDi or CM APIs.
--PA

"jh" <jh@radio.kielce.com.pl> wrote in message news:do681n$j23$1@atlantis.news.tpi.pl...

that's b/c it is a vampire device . it just sucks the power off the bus
w/out actually enumerating itself. great way to kill your battery life on
your laptop ;_

d

--
Please do not send e-mail directly to this alias. this alias is for
newsgroup purposes only.
This posting is provided "AS IS" with no warranties, and confers no rights.


"Pavel A." <pavel_a@NOwritemeNO.com> wrote in message
news:%23YT7aNPBGHA.2568@TK2MSFTNGP10.phx.gbl...

Almost all of these are just sucking juice from USB power and aren't
true USB devices at all. You'd have to somehow turn off the power to the
port.

As far as I know, there's no way to turn the power off to a particular
USB port. Even if there were in the OS, I'm not sure there is
necessarily even hardware capable of doing that in the hub... I'd have
to look at the spec again, but I don't remember any such thing.

If you want to control the lamp you'll need to talk to the device, which
is probably best done using HID. But that would mean that it would
actually have to be a USB device, which I bet it isn't.

jh wrote:

--
Ray

The big limit is that you can only assume 100ma unless you know it is a
powered hub and then your limit is 0.5A. How bright can a light be with 5V
0.5A? Led only? Halogen - doubt it. Is 5V at 0.5A a total of 25w or 2.5w?
I don't pretend to be an EE, so I forget the formula, but I thought it was V
* A = W. Night lights are usually 4w and you can't read with those.

"fat_boy" <zzebowa@hotmail.com> wrote in message
news:1135011868.738553.298490@g44g2000cwa.googlegr oups.com...

David J. Craig wrote:

All the calculation is wrong because the power lines are part of
the bus protocol. Such a device violates the USB spec.

They may, but there are a lot of them on the shelves in the stores.

"Robert Marquardt" <robert_marquardt@gmx.de> wrote in message
news:O4xPWBSBGHA.2692@TK2MSFTNGP10.phx.gbl...

Correct, P = V * I for DC so the power output would be feeble.

Hmm, adding 10 meters of cable isnt going to help the brightness one
little bit, so I doubt your suggestion is really feasible.

On Mon, 19 Dec 2005 16:08:51 -0800, "Doron Holan [MS]"
<doronh@nospam.microsoft.com> wrote:

Ouch. Not so funny as these things are sold to laptop owners for use
on airplanes to provide lighting for the keyboard. I didn't realize
one could do this to a usb bus.
=====================
Mark Roddy DDK MVP
Windows Vista/2003/XP/2000 Consulting
Device and Filesystem Drivers
Hollis Technology Solutions 603-321-1032
www.hollistech.com

Season greetings
http://www.thinkgeek.com/gadgets/lights/6e2c/

--PA

"Mark Roddy" wrote:

David J. Craig wrote:
A big heap of shit is still shit.

Namely? No feedback can go from device to hub via power lines. Also, no
commands can go from the hub to the device via power lines.

They just can have one of 2 states - standby power/full power, that's all.

--
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
maxim@storagecraft.com
http://www.storagecraft.com

I just received a letter from Microsoft Windows Embedded offering a resource
guide and (weird) USB Laptop Computer Light. This is definitely a Twilight
Zone moment.

"Maxim S. Shatskih" <maxim@storagecraft.com> wrote in message
news:upUUs$ZBGHA.2668@TK2MSFTNGP14.phx.gbl...