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| Power adapter advice - Magic smoke from 12V 1.5A portable hard disk |
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| mroguy:
Thanks everyone, Ian... I'd like to say I would do that fix but I'll probably never get around to it. ;) This thread has been a real eye opener. I'm surprised that the devices arn't smart enough to detect the correct polarity. Surely it cant be that difficult to build in some sort of safegard. Anyhow. thanks again for responding. |
| james_s:
It isn't that difficult, but it costs money, isn't foolproof and it adds another potential failure point. The manufacture doesn't really care, they sell you a device that comes with a power adapter and they expect you to use the power adapter they give you. |
| tooki:
--- Quote from: mroguy on July 01, 2021, 08:24:05 pm ---Thanks everyone, Ian... I'd like to say I would do that fix but I'll probably never get around to it. ;) This thread has been a real eye opener. I'm surprised that the devices arn't smart enough to detect the correct polarity. Surely it cant be that difficult to build in some sort of safegard. Anyhow. thanks again for responding. --- End quote --- No, but in addition to the things james_s said, it also adds potential energy losses. The center-negative configuration used to be dominant because it enabled a simple switched contact in the DC socket to switch between batteries and the AC adapter. We didn't always have "smart" electronics with the benefit of cheap but insanely complex ICs to handle every little thing. With smarter electronics came the switch to center-positive, which has some different advantages (namely, that "ground" is what's facing outward). --- Quote from: mroguy on July 01, 2021, 07:08:30 pm ---Now looking for a switchable adapter with interchangable sockets. Loads on amazon but not found one yet where you can switch polarity also. --- End quote --- You mean a universal AC adapter with interchangeable DC plugs? If so, they usually don't bother with a polarity switch, because they simply design the interchangeable plugs to attach in two orientations for the two polarities. |
| amyk:
--- Quote from: tooki on July 03, 2021, 06:38:00 pm ---The center-negative configuration used to be dominant because it enabled a simple switched contact in the DC socket to switch between batteries and the AC adapter. We didn't always have "smart" electronics with the benefit of cheap but insanely complex ICs to handle every little thing. With smarter electronics came the switch to center-positive, which has some different advantages (namely, that "ground" is what's facing outward). --- End quote --- I don't think centre-negative was dominant for anything except audio and some telephony equipment, where it was used for some reasons having to do with shielding, noise reduction, and electrolytic corrosion. A switched contact could just as easily switch the other rail too... |
| james_s:
--- Quote from: tooki on July 03, 2021, 06:38:00 pm ---The center-negative configuration used to be dominant because it enabled a simple switched contact in the DC socket to switch between batteries and the AC adapter. We didn't always have "smart" electronics with the benefit of cheap but insanely complex ICs to handle every little thing. With smarter electronics came the switch to center-positive, which has some different advantages (namely, that "ground" is what's facing outward). --- End quote --- You can do that with center-positive too. It doesn't matter whether you switch the positive or the negative, the batteries are isolated and floating, they don't know what "ground" is. I don't see how it can make any difference either way. |
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