Which to plug in first?

[Kenny McCormack]

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.

 

[Don Bruder]

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.

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

 

[Kenny McCormack]

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

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...

 

[Kenny McCormack]

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

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?

 

[IanM]

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

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?

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

 

[[email protected]]

Good point.

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.

 

[[email protected]]

Eh?  The OP had a device which he had to turn on its power unit first.  How 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?

 

[James Goforth]

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)! )

 

[Sjouke Burry]

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

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?

Smoke detector response time.