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#1
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Can I fabricate my own USB power cable?
Hi all. Here's the situation:
I bought a Panasonic Toughbook CF-T2 laptop computer recently. It's an awesome small light laptop. But it has no built-in optical drive. The much more expensive W2 does, but I didn't buy one of those because of the cost. What I did buy, however, was a NU-Tech external "slimline" CD-RW/DVD-ROM USB 2.0 combo drive. See, I had this idea that even though the NU-Tech drive is not advertised as being powerable directly from the USB port, that I could make it work with a little bit of work. I want to be able to use the NU-Tech optical drive on the road with no A/C power available, and the drive comes only with an A/C adapter power source. In fact, almost all "portable" external USB 2.0 drives come with an A/C adapter. How is that portable, I ask you? How can you be expected to use such a device in all of the places that notebook computers are used where there is no A/C power source available? Well before buying the drive I did some research and determined that I might be able to power it directly from the USB port, since it takes a 5V power input and USB ports provide 5V power out. It turns out USB power cables are really hard to find. But I discovered that I could buy a mini USB 2.0 hub on eBay that comes with a USB power cable. The dimensions of the power connector are the same. And the hub was only 1 cent on eBay (with $12 shipping of course, which is where they make their money). So I get the laptop, get the drive, and get the hub. I plug the drive's USB data cable into one of the T2's USB ports. I plug the power cable into the other USB port, and into the power in port of the drive. Bingo, the drive fires up and looks like it is working! Only problem is, the bottom of the drive says "1.5 A" and I know that USB ports are only supposed to be able to deliver 500 mA (i.e. .5 A) when designed properly - and some aren't even well-made enought to deliever the full 500 mA. But I'm going to give Panasonic credit, they make an excellent laptop and I believe that I'm getting the full 500 mA out. The problem is that the CD drive really does require more than 500 mA in some situations. First, what works: playing a DVD works. This is awesome, because now I can view DVDs on the road. I think this works because playing a DVD only requires the drive to spin up to a certain low speed, which takes less than 500 mA. Next, what partially works: I can read data off of CD's most of the time but sometimes the drive has problems, I think it's when it spins up too fast and then it kinda spins all the way down for a second like it's lost sync or power or something (probably had a problem driving the laser with all of the power used up spinning the disc at a high speed?). After a few minutes of spin up/spin down cycles, it seems like the drive finally gives up and returns to a low spin speed. Then it continues to work for that disc just fine. But this few minute interval is annoying and can interrupt whatever process is using the CD drive. Finally, what doesn't work at all: burning discs just does not work. Apparently 500 mA is just not enough juice for this. OK, so I'm fine with not being able to burn discs when not near an A/C power source. I don't really ever need to do this anyway. But I really would like the reading of CDs and DVDs to be rock solid. And for this, I think I need to deliver more power to the drive. So my question is, will it help to somehow splice together the USB power cable so that I can plug it into *both* USB ports? Will each deliver the full 500 mA, and will I then be able to give a full 1 A to the drive? Hopefully this will be enough to read any CD/DVD at any speed. I was thinking that I would just take another USB cable (I have zillions), cut it open and untangle the wires. I believe there are 4 wires in there, 2 data and 2 power. I just have to splice the 2 power wires into the 2 power wires of my USB power cable right? I remember embarrasingly little from my college physics classes - will the resulting cable still be 5 V or do the voltages add up (will the resulting cable be 10 V instead?)? Finally, would I be able to take the 2 data wires from the USB cable that I cut up and splice them into a USB hub, so that I would have: * Both USB ports delivering power to 1 power adapter * One USB port connected to an unpowered USB hub into which I would then plug all of my data devices? Is this a crazy/useless idea? Another way to solve my problem, that I actually think would be better in many ways, would be to somehow limit the spin speed of the drive itself. Is there some way under Windows to tell the drive to never spin up to more than, say, 10x (I believe that it is a 24x drive)? How about under Linux? Thanks for any suggestions, and very best wishes, Bryan |
#3
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Maybe a capacitor spliced inline would be the best choice. It will
store the excess power that is not being used by the drive in the low power situations and make it available when the drive demands more. |
#4
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(Aaron) wrote in message . com...
(Bryan Ischo) wrote in message . com... So my question is, will it help to somehow splice together the USB power cable so that I can plug it into *both* USB ports? Will each deliver the full 500 mA, and will I then be able to give a full 1 A to the drive? Hopefully this will be enough to read any CD/DVD at any speed. I was thinking that I would just take another USB cable (I have zillions), cut it open and untangle the wires. I believe there are 4 wires in there, 2 data and 2 power. I just have to splice the 2 power wires into the 2 power wires of my USB power cable right? I remember embarrasingly little from my college physics classes - will the resulting cable still be 5 V or do the voltages add up (will the resulting cable be 10 V instead?)? Finally, would I be able to take the 2 data wires from the USB cable that I cut up and splice them into a USB hub, so that I would have: * Both USB ports delivering power to 1 power adapter * One USB port connected to an unpowered USB hub into which I would then plug all of my data devices? Is this a crazy/useless idea? Yes. Probably all USB ports are sharing 500ma. Another way to solve my problem, that I actually think would be better in many ways, would be to somehow limit the spin speed of the drive itself. Is there some way under Windows to tell the drive to never spin up to more than, say, 10x (I believe that it is a 24x drive)? How about under Linux? Yes, under Windows there is such a program. Search for CD Drive Speed Limiter or something like that, and you should find what you need. http://www.cdspeed2000.com/ Aaron Thank you very much for your response. I guess the program you mention sounds like a better option than messing with the hardware. Thanks again, and best wishes, Bryan |
#5
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#6
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Hi,
Yes you can limmit the speed. As already said, on a notebook, the 500mA will be shared, so more usb ports = same power. Anyway, back to limiting the speed. Nero Drive Speed Download a trial version of Nero, its included in the package. You set the capable speeds and the max speed you would like the drive to spin at. I think you can also download just Drive Speed as a freeware program as part of their utility pack. Good luck. Tarl |
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