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Deeee
Joined: 15 Jun 2007
Posts: 1
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 Posted: Fri Jun 15, 2007 10:53 pm Post subject: IR LEDS, mA, and USB |
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| Soo i went out and bought the 4 IR LEDs and have my little pipe with holes drilled in it and everythings ready to be slapped together but was wondering if the fact that the combined current of the 4 (200mA) will cause any problems with a usb connecter, while technically the spec says that the port only supplies 100mA unless a device asks for it, its capable of supplying 500mA, will it automatically supply enough using magic usb mojo or will i have to get a big honking resister and drop out 2 of the LEDs ? |
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nauht
Joined: 16 Jul 2007
Posts: 4
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| Posted: Mon Jul 16, 2007 5:39 pm Post subject: |
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Unless you can communicate with the USB hub/network that your device wants anything greater than 100mA, you're stuck with 100mA. The hub won't provide anything more than 100mA if you don't communicate on the data lines that you want more than 100mA.
I'm in the process of coming up with a scheme that'll do that and request for 250mA, but this is a tad more complicated and requires a microcontroller. The circuit I drew up works out to require 250mA, but I need someone to verify that it's correct... |
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TDM
Joined: 28 May 2007
Posts: 23
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| Posted: Mon Jul 16, 2007 6:38 pm Post subject: |
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| Technically you shouldn't draw more than 100mA until after requesting it but in reality most usb ports will supply 500mA and beyond without a problem. |
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Oinquer
Joined: 14 Nov 2007
Posts: 44
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| Posted: Tue Dec 25, 2007 11:58 pm Post subject: |
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use 2 USB ports :DDDDDDD
200 Ma...
...if anyone knows anything on asking the Ma from USB PM me i have some experience with microcontrollers i can try to make it. |
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