usb powering? 
Posted: 19 July 2009 05:23 AM   [ Ignore ]
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hello, i need to know what the output of a usb is, how many LED’s will one run efficently? or lazers

the reason im asking is because my my computer has 16 usb ports, and i would like to try it,

also im in new zealand, so costs arnt cheap for importing, anyone in new zealand know any good dealers?

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Posted: 19 July 2009 05:50 AM   [ Ignore ]   [ # 1 ]
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The USB output voltage is ~5V and max current is 500mA. It’s probably easier to use one of the 12V connectors from the power supply in your computer.

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Posted: 19 July 2009 06:21 AM   [ Ignore ]   [ # 2 ]
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hmm i was just thinking about that, i will experiment with both ways and then post my results on the community, thanks for you help and fast reply

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Posted: 20 July 2009 11:25 AM   [ Ignore ]   [ # 3 ]
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If you go to ledcalc.com, you can calculate how you can assemble your LEDs. All you need to make sure is that the Total LED Current Consumption is less than 500mA if you still want to connect it via USB. I’m currently using the 5V molex connector on my computer’s power supply to power four 780nm 25mW lasers, and it works great.

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Posted: 20 July 2009 02:25 PM   [ Ignore ]   [ # 4 ]
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You may run into a problem powering your LEDs with USB, even if you do your caclulations correctly based on the 5V, 500mA output - USB has two power modes, a low-power default and the 5V 500mA ‘high power’ mode - the USB standard defines how to ‘request’ the high-power mode from the USB controller, and without this circuitry you may not get the power you’re requiring from the port.

YMMV however, some USB controllers will simply match the power draw up to the 5V limit.

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Posted: 21 July 2009 12:01 AM   [ Ignore ]   [ # 5 ]
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hmm never knew that, i ran i clock from it last night =]

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