Can USB power a LS?

Seeing all those USB LED lights, I was wondering can it power a 1 watt LS? Then I could use my 75watt desk lamp less.

I don't think so, but, I don't know the USB power specs.

I've got two of those Targus USB LED lights...specs on the docs say:

Operation - 2.5 to 5 volts, below 2ma
Sleeping - 2.5 to 5 volts, below .50ua

but those are what the USB LED needs/uses...
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The following info is from Dan's Data:

As you look into a rectangular Type A USB plug, aligned in the usual logo-on-the-top way, the rightmost contact inside is number 1 and the leftmost pin is number 4. Pin 1's the five volt contact, pin 4's ground. The two pins in the middle are the data ones, which you don't care about for mere power supply purposes.

The USB spec only allows for 500 milliamps (mA) of current from each powered port. Root hub ports on your computer are powered ports, and so are ports on a "self powered" hub. That includes standalone hubs with their own plugpack power supply, and ought to include ports built into things like monitors as well. "Bus powered" USB hubs that don't have their own separate power supply can only supply a total of 500mA from all of their ports put together.
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However, don't take anything that I say as fact...I only did a Google search for "USB Port Power Spec"...better verify this data with someone or somewhere else. Someone here must know???

Re: Can USB power a LS? - Yes!

Yes! I already made some prototype and it worked fine! I actually used a step down DC-DC converter and also tried with the constant current driver using ST890 which I posted in this forum before. I checked with many different notebooks and desktop PC's and there was no problem at all. The light output is fantastic! You don't need any other light source at all. No optics required. Flooding light looked better to me..

You can also use the PS2 mouse(or Keyboard) port to power up the LED but it needs a special cable which enables you to connect the mouse(or keyboard) while taking the power from the port.

The easier way is using a resistor. You only need a resistor connected in series to the LED to set the current. As you have to drop around 1.8V and the current thru the resistor is 0.35A, the resistance value should be 5.14ohm and the power consumption is 0.63Watt.

I suggest you use 5ohm, 2 Watt wire wound resistor for that purpose. You need to measure the current and make it sure that the current is below 350mA.

Cheers..

My understanding of USB is that devices can draw 100mA without any communication - just plug in and draw, but are supposed to negotiate to draw up to 500mA. It's been a while since I read this, though. I think this is basically the difference between powered and unpowered USB ports - the unpowered ones will not let the device negotiate the higher currents (besides, of course, not being able to supply more current). Actually, just checked - this is correct, see link below:

usbdeveloper web site

-Ty

Hmmmmmm ... I may have to get another hub just to run some LEDs, eh? /ubbthreads/images/graemlins/grin.gif (I have sixteen USB ports right now, but all are in use).

Actually, I need to find the manufacturer of a backlighted USB keyboard I saw once. Even in zero light there was this neat red glow coming through all the keytops making them findable and readable.

Off to Google ... /ubbthreads/images/graemlins/smile.gif

Could the keyboard you are looking for be something like this?

[ QUOTE ]
JSWrightOC said:
Could the keyboard you are looking for be something like this?

[/ QUOTE ]

I've seen that one on Craig's site, and in person (the local police cars use them) and I really like it's look, but the other one I saw (at a computer show in Portland, OR) was more of a standard sized keyboard with all the bells and whistles I'm more used to (F1 through F15, numeric pad, the extra keys that Apple computers use, etc.).

Thing is, I have NO idea who made it, or where I can find one. /ubbthreads/images/graemlins/confused.gif

(If anyone happens to know where I can find one, could you let me know?)



-= MICROSOFT FREE ZONE =-

[ QUOTE ]
Tomas said:

Actually, I need to find the manufacturer of a backlighted USB keyboard I saw once. Even in zero light there was this neat red glow coming through all the keytops making them findable and readable.

Off to Google ... /ubbthreads/images/graemlins/smile.gif



[/ QUOTE ]

What about a nice blue electroLuminescent keyboard ?



Details Here

Check out Craig's site. /ubbthreads/images/graemlins/wink.gif


LED BACKLIGHTED KEYBOARD

It is an USB powered keyboard, but without the numeric keypad. /ubbthreads/images/graemlins/frown.gif
Availability might be a problem though...
[ QUOTE ]
LED keyboards may eventually become available for sale through this website. Availability at this time is only to OEMs of squad car computers. This may change quite soon, depending on my test results & opinions.

[/ QUOTE ]

Hope this helps,

Reasonably nice looking, xray, but relatively short lived EL panel and Wintel only ... /ubbthreads/images/graemlins/frown.gif

I am extremly weak in the electronics dept. How much would it cost for someone to make one of these things for me? xbrite? /ubbthreads/images/graemlins/grin.gif

x-ray...didn't a friend of a cpf member, or a son or a friend of a son, or a son of a friend come up with that keyboard?

i seem to recall....

Roth, something like that. /ubbthreads/images/graemlins/wink.gif
Check here for the original thread:
BACKLIT KEYBOARD!! /ubbthreads/images/graemlins/grin.gif

IMHO, I think the USB port is more than capable of powering a 1W LS. I just witnessed a pair of desktop speakers powered solely by USB (ie. not outboard batteries) with a rating of 1W RMS (not 1W PMPO) per channel - and this was from one of those new-fangled tablet PCs too, not a desktop PC.

ok, here: "one of my co-workers sons invented"

friend, coworker...same thing. all your co-workers are your friends right? /ubbthreads/images/graemlins/grin.gif