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| Thread ID: 48789 | 2004-09-01 05:14:00 | USB | arjay (1202) | Press F1 |
| Post ID | Timestamp | Content | User | ||
| 267822 | 2004-09-01 10:37:00 | Murray, In regard to this USB powered scanner, your suggestion that the PSU maybe inadequate got me curious. I understood that the current available via the USB connection is 'limited'. Did a search just now, and find that is so. The USB 5 volt power is limited to 500ma. That is 2.5 watts, and within the max power this scanner requires. Accordingly it seems unlikely that a USB powered device will overtax the PSU. Would you agree.. |
Bazza (407) | ||
| 267823 | 2004-09-02 05:01:00 | It depends. :D The standard says each port should be able to supply 500mA. It's allocated in steps of 100 mA. (The devices tell the host how much current it will want in the conversation they have when the device is detected). If you put a non-powered hub on a port, and try to run multiple devices, you'll run out. The 500 mA is all there is. ;-) Some laptops don't provide the full 500 mA. They might assume that it will only be used for mice or keyboards; and anything else can use external power. ;-) I have got one USB scanner -- I forget the brand and type -- but I have run it on a laptop with only the USB connection. So it's possible. If the unit you want has no power connector it will work on a standard USB port. |
Graham L (2) | ||
| 267824 | 2004-09-02 10:34:00 | Thanks everybody, all very helpful. Looks like I'll be ok with a normal USB. | arjay (1202) | ||
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