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Which to plug in first?

This is a general question about all those plug-in power-supplies/battery-rechargers that we all have so many of. The kind that have a big plug/transformer at one end that plugs into the wall, and a plug that plugs into a low-voltage electronic device at the other end.

The question is (in general): Which is better practice: 1) Plug the big plug into the wall socket, then plug the little plug into the device? 2) The other way around - plug it into the device first, then into the wall?

Or doesn't it matter? I would assume that in the vast majority of cases, it doesn't matter, but that it might matter in some. Incidentally, I have an old USB 1.0 hub from Radio Shack, the instructions to which explicitly said that one should always do it in the way of #2 above.

Reply to
Kenny McCormack
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I'm sure there are exceptions, but I'd expect that it should practically never matter.

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Reply to
Don Bruder

In article , Don Bruder wrote: ...

Agreed. But as I alluded to, the only reason I'm bringing this up at all is because of that one device (an old USB hub) - where they recommended that you plug it into the wall last. I'm confident that this is mostly superstitious learning - I've certainly never blown anything out by doing it one way or the other.

It seems to me that if there's any story here at all, it would be in the opposite direction. That is, that when you first plug it into the wall, there might be a voltage surge on the other end; this would argue for plugging it into the wall first, letting it settle down, then plugging in the device.

But of course, I don't know...

Reply to
Kenny McCormack

Some power supplies need a minimum load to regulate the output voltage properly.

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Reply to
Michael A. Terrell

In article , Michael A. Terrell wrote: ...

Good point.

And this leads into a story about the weirdest power supply I've ever seen. I recently bought a replacement power supply for one of my laptops, from an online dealer. It was advertised as a "universal" power supply, with a series of plugs that would fit any popular type of laptop (with various voltages). It was also cheap ($28). Short story is: it ended up not working and I returned it. But the instructions that came with it read something like this (written in barely-comprehensible pidgen English):

1) Do not "just plug in and go" (like a normal power supply). 2) Plug the power supply into the wall for 10 minutes. 3) Unplug it, then find the right adapter plug for your laptop. Connect that into the power supply. 4) Plug the power supply into the wall for 5 minutes. 5) If everything looks good [???], unplug it from the wall. Plug the adapter plug into your laptop, then plug the power supply into the wall.

Strange. What's going on with the 10 minute and 5 minute delays?

Reply to
Kenny McCormack

Smoke test performed by end user because there's no QC at the factory?

Reply to
IanM

If true, then USB 1.0 Standards was violated. USB must operate with USB powered first, then any or all peripherals connected later. Same for those other power connections.

If 'order of power' makes a difference, then you have a defective component. Some of those directions sound as if written by the language arts major; not by those who knew how the equipment works. Then purchased and imported by a purchasing agent who was just as technically naive.

Reply to
westom1

Eh? The OP had a device which he had to turn on its power unit first. How does this relate to the USB connection?

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Reply to
Peter Hucker

=A0How does this relate to the USB connection?

The OP was discussing how to power on a USB 1.0 interface. Meanwhile, the reply addressed both USB 1.0 and other type interfaces. What were you reading?

Reply to
westom1

does this relate to the USB connection?

This:

Incidentally, I have an old USB 1.0 hub from Radio Shack, the instructions to which explicitly said that one should always do it in the way of #2 above.

He is referring to plugging the USB hub's power supply into the mains first, or the same supply into the hub first.

Whichever way round he does it, the hub will be powered up before he then connects a third thing - a USB device or the computer.

Anyway, if the power is switched off at the mains or there is a powercut, the power supply will be in the hub before the mains is activated, so everything must be able to handle this method, or things would be breaking all the time.

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Reply to
Peter Hucker

I bought an Acer laptop about 8 months ago and could have sworn I'd seen in the owners manual book somewhere about a protocol for plugging the power cord in, just as you describe: either plug it into the wall first; or plug it into the laptop BEFORE plugging it into the wall. When I went back to the book to see which it said, I couldn't find it, and that's always bothered me. So I'm glad you asked that question (although so far I'm still a little confused)! :-))

Reply to
James Goforth

If it's designed properly, it doesn't matter. If it's designed badly, it goes bang then you take it back for a refund.

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Reply to
Peter Hucker

Smoke detector response time.

Reply to
Sjouke Burry

My smoke detectors can detect steam from my steam cleaner in about 0.2 seconds. I wish they'd develop clever ones that could distinguish....

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Reply to
Peter Hucker

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