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'[OT] Laptop wall-warts'
2005\09\26@113643 by John Nall

picon face
I thought this might be of passing interest to someone, so thought I
would post it.

I went to a hamfest over the weekend, and picked up an old Toshiba
T1200XE laptop computer for a few bucks.  Only runs MS-DOS, but has a
serial port and a parallel port, and the price was right (when they
begin to close the doors, people want to get rid of their junk).  I
don't know just what I will do with it, but discovered an unexpected
dividend -- the wall-wart that comes with it has an output of 12 volts
at 2.5 amps.  A nice little bench power supply!!!  :-)  So you might
want to keep an eye out for laptop wall-warts on the surplus market, for
powering those target boards.

John

2005\09\26@122155 by William Chops Westfield

face picon face
On Sep 26, 2005, at 8:36 AM, John Nall wrote:

> discovered an unexpected dividend -- the wall-wart that comes with
> it has an output of 12 volts at 2.5 amps.

Are you sure?  My stock of toshiba laptop supplies are all 15V...
(though they're mostly from newer-than-"dos-only" machines.)
Current IBM supplies are 16V, and old Apple supplies are 24V.
There seems to be less variation from model to model from a single
manufacturer than their used to be... (about time!)

> A nice little bench power supply!!!  :-)  So you might want to keep
> an eye out for laptop wall-warts on the surplus market, for powering
> those target boards.
>
Yes, external power supplies tend to multiply like coat hangers, and
increasingly are regulated switchers.  I noticed a while ago,
contemplating
a lab-style power supply, that it was getting to the point where a 24V
3A
regulated switching power supply was smaller, cheaper, and easier to
find
than a 24V 3A 60Hz transformer...  Reasonable selection here:

  http://www.allelectronics.com/cgi-bin/category.cgi?category=480

BillW

2005\09\26@125056 by David Van Horn

picon face


> > discovered an unexpected dividend -- the wall-wart that comes with
> > it has an output of 12 volts at 2.5 amps.
>
> Are you sure?  My stock of toshiba laptop supplies are all 15V...

This is fairly common in newer designs. I use the same trick.
They don't want you to power it directly from the car, because the LT
does not have enough protection built in. So, they set the required
voltage higher than the car will get to, so it won't charge/run with a
direct cable.





2005\09\26@130337 by John Nall

picon face
William Chops Westfield wrote:

>
>> discovered an unexpected dividend -- the wall-wart that comes with
>> it has an output of 12 volts at 2.5 amps.
>
>
> Are you sure?  

I'm sure of what it says, although have not put any instruments on it to
check that it REALLY does that.  :-)

"Toshiba AC Adaptor Model PA7487U    Input 100-240V ~50/60 Hz 45 Watts  
Output 12 V @ 2.5A"

Gosh, that's a lot of variation on that input!  No external switches,
either.

John

2005\09\26@133139 by Spehro Pefhany

picon face
At 01:03 PM 9/26/2005 -0400, you wrote:
>William Chops Westfield wrote:
>
>>
>>>discovered an unexpected dividend -- the wall-wart that comes with
>>>it has an output of 12 volts at 2.5 amps.
>>
>>
>>Are you sure?
>
>I'm sure of what it says, although have not put any instruments on it to
>check that it REALLY does that.  :-)
>
>"Toshiba AC Adaptor Model PA7487U    Input 100-240V ~50/60 Hz 45 Watts
>Output 12 V @ 2.5A"
>
>Gosh, that's a lot of variation on that input!  No external switches, either.
>John

It's probably a flyback power supply with a ~3:1 input range-- the numbers
on the label are nominal line voltage) . Quite possible that it can operate
down
to zero load, BTW, and it's definitely regulated.

The voltage range is to accommodate Japan (100VAC 50/60Hz), North America and
a few other places (120VAC 60Hz) and everywhere else (mostly ~240VAC/50Hz).
Such an adapter can be used pretty much anywhere in the world modulo adapting
the plug.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
spam_OUTspeffTakeThisOuTspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


2005\09\26@143450 by Michael Rigby-Jones

picon face


>-----Original Message-----
>From: .....piclist-bouncesKILLspamspam@spam@mit.edu [piclist-bouncesspamKILLspammit.edu]
>Sent: 26 September 2005 17:51
>To: Microcontroller discussion list - Public.
>Subject: RE: [OT] Laptop wall-warts
>
>
>
>
>> > discovered an unexpected dividend -- the wall-wart that comes with
>> > it has an output of 12 volts at 2.5 amps.
>>
>> Are you sure?  My stock of toshiba laptop supplies are all 15V...
>
>This is fairly common in newer designs. I use the same trick.
>They don't want you to power it directly from the car, because
>the LT does not have enough protection built in. So, they set
>the required voltage higher than the car will get to, so it
>won't charge/run with a direct cable.

Plus the new laptops use a higher voltage battery pack anyway, 4 lithium-ions in series is very common now giving ~16.5volts when charged.  It makes more sense to for the PSU to supply a voltage high enough for charging rather than having to use a step-up switcher on board the laptop.

Regards

Mike

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2005\09\26@163248 by Howard Winter

face
flavicon
picon face
John,

On Mon, 26 Sep 2005 13:03:24 -0400, John Nall wrote:

>...<
> "Toshiba AC Adaptor Model PA7487U    Input 100-240V ~50/60 Hz 45 Watts  
> Output 12 V @ 2.5A"
>
> Gosh, that's a lot of variation on that input!  No external switches,
> either.

That's for Worldwide use - pretty much anywhere with AC power, just by changing the input cable, if it has one
of the three usual-suspect sockets (Kettle, Cloverleaf, Figure-8) or by using a plug-adaptor if not.

Most laptop PSUs have had this input range for some time, and quite a few peripherals' too - I have an Iomega
Peerless drive here that does, along with a powered USB hub, an HP printer and my mobile phone charger!  When
I travel abroad I just take the appropriate leads and a couple of plug-adaptors, and I'm all set - voltage is
pretty-much a non-issue.

Cheers,


Howard Winter
St.Albans, England


2005\09\27@043017 by Alan B. Pearce

face picon face
>Current IBM supplies are 16V, and old Apple
>supplies are 24V. There seems to be less
>variation from model to model from a single
>manufacturer than their used to be... (about time!)

I suspect this is mostly driven by the available battery technology now. You
need a certain voltage level to be able to charge them efficiently, and the
switching technology is now cheap and efficient enough that getting from the
battery voltage to the required internal voltages has resulted in a common
battery voltage.

2005\09\27@183208 by PicDude

flavicon
face
On Monday 26 September 2005 12:03 pm, John Nall scribbled:
> "Toshiba AC Adaptor Model PA7487U    Input 100-240V ~50/60 Hz 45 Watts
> Output 12 V @ 2.5A"
>
> Gosh, that's a lot of variation on that input!  No external switches,
> either.
>
> John


This seems to be the input range on most (?) laptops for many years now.  I'm
checking 4 laptops I have here, some as old as 233Mhz P3, and it too has a
100-240V range.  Makes life really really nice when travelling between US and
Europe.

Cheers,
-Neil.


2005\09\28@020308 by William Chops Westfield

face picon face
>> Input 100-240V ~50/60 Hz 45 Watts
>> Gosh, that's a lot of variation on that input!

The so-called "universal input" power supplies have been very popular
for quite a while now.  I doubt that you can find many current switching
power supplies that don't have that sort of range  (hmm.  Of digikey's
170 "AC to DC converters", only about 20 are limited to the range
85-132V)

BillW

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