Isn't using an AC adapter with way higher current ratings ha

[AC/DCdude17]

X-No-Archive: Yes

The common rules for choosing a replacement AC adapter are match the
voltage and amp should be equal or greater than the original AC
adapter. This makes perfect sense in theory, although the small
transformer in AC adapters have a horrible regulation. A 12V AC adapter
often puts out 16 to 20V under no load and is designed to give 12V when
loaded to rated current. Once it's loaded to rated current, I^2R drop
brings the voltage down to 12V.

If you have a walkman that takes a 4.5V @ 250mA and use a 1A
adapter, it will probably send out 6-8V with only 250mA of load. The
walkman most likely has a linear regulator inside, so it should be ok in
a short term, but higher input voltage means higher dissipation which
may cause premature failure.

 

[Mark]

Your answer is wrong and your premise is wrong.
It is completely safe to use an AD-DC adapter with
a higher current rating, provided that the adapters
voltage rating is accurate. If the design of the adapter
requires a load to work correctly, its a poorly designed
product. Such an adapter will not be reliable even at
the rated current and voltage. Most adapters that
put out higher voltage with no load also do not
produce the current they are rated at. So if you
are looking for a replacement adapter look for one
that is a regulated.


"AC/DCdude17" <JerC@prontoREMOVETHISmail.com> wrote in message
news:3F17C447.8B2D9855@prontoREMOVETHISmail.com...

X-No-Archive: Yes

The common rules for choosing a replacement AC adapter are match the
voltage and amp should be equal or greater than the original AC
adapter. This makes perfect sense in theory, although the small
transformer in AC adapters have a horrible regulation. A 12V AC adapter
often puts out 16 to 20V under no load and is designed to give 12V when
loaded to rated current. Once it's loaded to rated current, I^2R drop
brings the voltage down to 12V.

If you have a walkman that takes a 4.5V @ 250mA and use a 1A
adapter, it will probably send out 6-8V with only 250mA of load. The
walkman most likely has a linear regulator inside, so it should be ok in
a short term, but higher input voltage means higher dissipation which
may cause premature failure.

 

[Ben Miller]

"Mark" <md.siegel@sbcglobal.net> wrote in message
news:3RSRa.468$Dc1.265@newssvr24.news.prodigy.com...

Your answer is wrong and your premise is wrong.
It is completely safe to use an AD-DC adapter with
a higher current rating, provided that the adapters
voltage rating is accurate. If the design of the adapter
requires a load to work correctly, its a poorly designed
product. Such an adapter will not be reliable even at
the rated current and voltage. Most adapters that
put out higher voltage with no load also do not
produce the current they are rated at. So if you
are looking for a replacement adapter look for one
that is a regulated.

Not true. Dudes observation is correct. These adapters use "impedance
limiting" to meet the UL class 2 requirements for energy limited
transformers, as opposed to fuse links or other more costly methods. They
will produce approximately rated voltage at rated current, but open circuit
voltage will be higher.

Ben Miller

--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
http://home.att.net/~benmiller

 

[John Popelish]

AC/DCdude17 wrote:

X-No-Archive: Yes

The common rules for choosing a replacement AC adapter are match the
voltage and amp should be equal or greater than the original AC
adapter. This makes perfect sense in theory, although the small
transformer in AC adapters have a horrible regulation. A 12V AC adapter
often puts out 16 to 20V under no load and is designed to give 12V when
loaded to rated current. Once it's loaded to rated current, I^2R drop
brings the voltage down to 12V.

If you have a walkman that takes a 4.5V @ 250mA and use a 1A
adapter, it will probably send out 6-8V with only 250mA of load. The
walkman most likely has a linear regulator inside, so it should be ok in
a short term, but higher input voltage means higher dissipation which
may cause premature failure.

I have had to use a lower voltage rated device when going to a higher
current rated one, to get about the voltage I wanted under load. But
the problem gets less bad with higher current rated devices, as their
regulation gets inherently better, compared to very low current rated
ones.

--
John Popelish

 

[jriegle]

Mark, You are one who is wrong. I have numerous "wall warts" and all put out
considerable higher voltage at no load than at rated load. For example all
the 12 volt ones put out 16-19 volts no load and will be higher than 12
volts with lower than rated current.

The exception is the Radio Shack 500ma one with multi voltage selector. It
appears to have a regulator in it.

Also, some of the wall warts are switching supplies with good regulation.
These often have higher current capabilities >1 amp, but are small and
light.
John

"Mark" <md.siegel@sbcglobal.net> wrote in message
news:3RSRa.468$Dc1.265@newssvr24.news.prodigy.com...

Your answer is wrong and your premise is wrong.
It is completely safe to use an AD-DC adapter with
a higher current rating, provided that the adapters
voltage rating is accurate. If the design of the adapter
requires a load to work correctly, its a poorly designed
product. Such an adapter will not be reliable even at
the rated current and voltage. Most adapters that
put out higher voltage with no load also do not
produce the current they are rated at. So if you
are looking for a replacement adapter look for one
that is a regulated.


"AC/DCdude17" <JerC@prontoREMOVETHISmail.com> wrote in message
news:3F17C447.8B2D9855@prontoREMOVETHISmail.com...
X-No-Archive: Yes

The common rules for choosing a replacement AC adapter are match the
voltage and amp should be equal or greater than the original AC
adapter. This makes perfect sense in theory, although the small
transformer in AC adapters have a horrible regulation. A 12V AC adapter
often puts out 16 to 20V under no load and is designed to give 12V when
loaded to rated current. Once it's loaded to rated current, I^2R drop
brings the voltage down to 12V.

If you have a walkman that takes a 4.5V @ 250mA and use a 1A
adapter, it will probably send out 6-8V with only 250mA of load. The
walkman most likely has a linear regulator inside, so it should be ok in
a short term, but higher input voltage means higher dissipation which
may cause premature failure.

 

[Mark]

No, his answer and premise are incorrect. Higher
available current by itself will not harm a device. The
device pulls what it needs. Every answer here that is
a problem relates to voltage not current. A well voltage
regulated supply can have as much available current as it
wants. I will agree there are many AC adapters on the market
that don't meet there rating. Most of those have a UL stamp
on them but have never been UL tested.


<ehsjr@bellatlantic.net> wrote in message
news:3F1978E3.B8FE3900@bellatlantic.net...

Mark wrote:

Your answer is wrong and your premise is wrong.

No, his answer and premise are correct.

It is completely safe to use an AD-DC adapter with
a higher current rating, provided that the adapters
voltage rating is accurate. If the design of the adapter
requires a load to work correctly, its a poorly designed
product. Such an adapter will not be reliable even at
the rated current and voltage. Most adapters that
put out higher voltage with no load also do not
produce the current they are rated at. So if you
are looking for a replacement adapter look for one
that is a regulated.

"AC/DCdude17" <JerC@prontoREMOVETHISmail.com> wrote in message
news:3F17C447.8B2D9855@prontoREMOVETHISmail.com...
X-No-Archive: Yes

The common rules for choosing a replacement AC adapter are match
the
voltage and amp should be equal or greater than the original AC
adapter. This makes perfect sense in theory, although the small
transformer in AC adapters have a horrible regulation. A 12V AC
adapter
often puts out 16 to 20V under no load and is designed to give 12V
when
loaded to rated current. Once it's loaded to rated current, I^2R drop
brings the voltage down to 12V.

If you have a walkman that takes a 4.5V @ 250mA and use a 1A
adapter, it will probably send out 6-8V with only 250mA of load. The
walkman most likely has a linear regulator inside, so it should be ok
in
a short term, but higher input voltage means higher dissipation which
may cause premature failure.

 

[John Larkin]

On Sat, 19 Jul 2003 17:10:02 GMT, "Mark" <md.siegel@sbcglobal.net>
wrote:

No, his answer and premise are incorrect. Higher
available current by itself will not harm a device. The
device pulls what it needs. Every answer here that is
a problem relates to voltage not current. A well voltage
regulated supply can have as much available current as it
wants. I will agree there are many AC adapters on the market
that don't meet there rating. Most of those have a UL stamp
on them but have never been UL tested.

I cast my vote with the OP. Many warts are not regulated and are
impedance-protected, so are very "soft". Using a high-current "12
volt" unregulated supply in place of a lower-current-rated "12 volt"
one may fry the load.

UL recognizes unfused, impedance-limited transformers as compliant
with safety standards.

John

 

[Ben Miller]

"Mark" <md.siegel@sbcglobal.net> wrote in message
news:KXeSa.23$UL1.30442556@newssvr11.news.prodigy.com...

No, his answer and premise are incorrect. Higher
available current by itself will not harm a device. The
device pulls what it needs. Every answer here that is
a problem relates to voltage not current. A well voltage
regulated supply can have as much available current as it
wants. I will agree there are many AC adapters on the market
that don't meet there rating. Most of those have a UL stamp
on them but have never been UL tested.

Mark

In order to be UL listed as a class 2 transformer, it needs to have limited
short-circuit current. The impedance limiting design accomplishes this
through series reactance & or resistance. In order to deliver the rated
current at rated voltage, the output voltage must be higher under open
circuit condition. There is one anticipated operating condition, at the full
load current rating. The voltage at other loads will be higher or lower.

These devices are operating exactly as designed. How do you know that UL has
not tested the devices that carry the listing mark?

Ben Miller

--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
http://home.att.net/~benmiller

 

[DarkMatter]

On Sat, 19 Jul 2003 20:03:23 GMT, "Ben Miller"
<benmiller@worldnet.att.net> Gave us:

These devices are operating exactly as designed. How do you know that UL has
not tested the devices that carry the listing mark?

If they carry it, they were tested. Period. Almost 100% assured.

Some makers perform in house certification, and are so capable.

UL is big on busting false monikers.

 

[Mark]

The question is " Isn't using an AC adapter with way higher current ratings
harmful?
There is no assumption here that the supply is not regulated to put out
rated voltage. The question is strictly a current rating question.
So are you saying that a AC adapter that has a regulated 3V 500mA
rating would hard a device with a 3V 200mA pull?

"John Larkin" <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote in
message news:fq3jhvcoh97hkuf5pq6khavdc6cmhgdnun@4ax.com...

On Sat, 19 Jul 2003 17:10:02 GMT, "Mark" <md.siegel@sbcglobal.net
wrote:

No, his answer and premise are incorrect. Higher
available current by itself will not harm a device. The
device pulls what it needs. Every answer here that is
a problem relates to voltage not current. A well voltage
regulated supply can have as much available current as it
wants. I will agree there are many AC adapters on the market
that don't meet there rating. Most of those have a UL stamp
on them but have never been UL tested.



I cast my vote with the OP. Many warts are not regulated and are
impedance-protected, so are very "soft". Using a high-current "12
volt" unregulated supply in place of a lower-current-rated "12 volt"
one may fry the load.

UL recognizes unfused, impedance-limited transformers as compliant
with safety standards.

John

 

[Mark]

Over the years I have been involved in hundreds of
products that have AC adapters. In the qualification
of that piece of the product it is tested and then researched.
UL has a nice paper trail. Its been my experience that
a high number of these adapters have ID on them that
don't belong to that product. Hence we rejected them.
However I have purchased products for comparison
qualifications and found these do not have valid numbers
on them either. You would be surprised what comes out
of china. I suspect many companies never qualify products
they bundle. Last year I had a 7.5V 1A adapter from the
orient. Tested with load the device was only 75mA @ 7.5V, now
do you believe that UL would have approved that adapter?


"Ben Miller" <benmiller@worldnet.att.net> wrote in message
news:fuhSa.99560$Ph3.12278@sccrnsc04...

"Mark" <md.siegel@sbcglobal.net> wrote in message
news:KXeSa.23$UL1.30442556@newssvr11.news.prodigy.com...
No, his answer and premise are incorrect. Higher
available current by itself will not harm a device. The
device pulls what it needs. Every answer here that is
a problem relates to voltage not current. A well voltage
regulated supply can have as much available current as it
wants. I will agree there are many AC adapters on the market
that don't meet there rating. Most of those have a UL stamp
on them but have never been UL tested.

Mark

In order to be UL listed as a class 2 transformer, it needs to have
limited
short-circuit current. The impedance limiting design accomplishes this
through series reactance & or resistance. In order to deliver the rated
current at rated voltage, the output voltage must be higher under open
circuit condition. There is one anticipated operating condition, at the
full
load current rating. The voltage at other loads will be higher or lower.

These devices are operating exactly as designed. How do you know that UL
has
not tested the devices that carry the listing mark?

Ben Miller

--
Benjamin D. Miller, PE
B. MILLER ENGINEERING
http://home.att.net/~benmiller

 

[John Larkin]

On Sat, 19 Jul 2003 20:25:04 GMT, "Mark" <md.siegel@sbcglobal.net>
wrote:

The question is " Isn't using an AC adapter with way higher current ratings
harmful?
There is no assumption here that the supply is not regulated to put out
rated voltage. The question is strictly a current rating question.
So are you saying that a AC adapter that has a regulated 3V 500mA
rating would hard a device with a 3V 200mA pull?

Among other things, I said "many warts are not regulated". The
AC-output ones never are.

John

 

[John Larkin]

On Sat, 19 Jul 2003 20:39:43 GMT, "Mark" <md.siegel@sbcglobal.net>
wrote:

Over the years I have been involved in hundreds of
products that have AC adapters. In the qualification
of that piece of the product it is tested and then researched.
UL has a nice paper trail. Its been my experience that
a high number of these adapters have ID on them that
don't belong to that product. Hence we rejected them.
However I have purchased products for comparison
qualifications and found these do not have valid numbers
on them either. You would be surprised what comes out
of china. I suspect many companies never qualify products
they bundle. Last year I had a 7.5V 1A adapter from the
orient. Tested with load the device was only 75mA @ 7.5V, now
do you believe that UL would have approved that adapter?

UL cares only about safety, not performance.

John

 

[Mark]

But UL still requires that the device meet its rating.

"John Larkin" <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote in
message news:g3djhvs0fm5caai2jip6f9gjgrkef6pain@4ax.com...

On Sat, 19 Jul 2003 20:39:43 GMT, "Mark" <md.siegel@sbcglobal.net
wrote:

Over the years I have been involved in hundreds of
products that have AC adapters. In the qualification
of that piece of the product it is tested and then researched.
UL has a nice paper trail. Its been my experience that
a high number of these adapters have ID on them that
don't belong to that product. Hence we rejected them.
However I have purchased products for comparison
qualifications and found these do not have valid numbers
on them either. You would be surprised what comes out
of china. I suspect many companies never qualify products
they bundle. Last year I had a 7.5V 1A adapter from the
orient. Tested with load the device was only 75mA @ 7.5V, now
do you believe that UL would have approved that adapter?



UL cares only about safety, not performance.

John

 

[John Larkin]

On Sat, 19 Jul 2003 21:48:57 GMT, "Mark" <md.siegel@sbcglobal.net>
wrote:

But UL still requires that the device meet its rating.

Which UL spec are you referring to? I've read and complied with lots
of them, and I've never seen such. For transformer-equipped gadgets,
UL tests ensure that it won't get too hot no matter how improbably the
transformer is loaded.

The only time UL cares about performance is in the specs for
life-safety systems.

John

 

[Mark]

That's not been my experience with UL, they expect the
unit to perform to the ratings you intend to sell the unit at.
You can tell them what that rating is. Then they will make sure
the unit is safe. They go a lot father then heat. They test plug
life, shorting and what ever the hell they feel the unit needs.
And I have never found them to be very reasonable about
what they do for testing. I have always made sure what I
submitted to UL would pass.

However I have seen a lot of china made adapters that are
UL marked and not even safe. I don't know what UL would
do if they got one of those as a real submission. I have seen
adapters from china with UL markings on what could not possibly
be UL approved material. So I know they were never submitted.

When you get an adapter, unless you bought it yourself from
the real manufacturer. You have no idea if the information on the
unit is valid. I have seen units that had UL numbers for a component
on the adapter itself as if that makes it UL listed as an adapter.

"John Larkin" <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote in
message news:c0gjhvolrn5sgvcturo43n7vfvdd1tefnf@4ax.com...

On Sat, 19 Jul 2003 21:48:57 GMT, "Mark" <md.siegel@sbcglobal.net
wrote:

But UL still requires that the device meet its rating.


Which UL spec are you referring to? I've read and complied with lots
of them, and I've never seen such. For transformer-equipped gadgets,
UL tests ensure that it won't get too hot no matter how improbably the
transformer is loaded.

The only time UL cares about performance is in the specs for
life-safety systems.

John

 

[meirman]

A 12V AC adapter often puts out 16 to 20V under no load
and is designed to give 12V whenloaded to rated current.
Once it's loaded to rated current, I^2R drop brings the
voltage down to 12V.

Where R in the formula above is the internal resistance of the
adaptor. It was a transformer winding and maybe a diode, or other
parts in the output, so of course those parts have resistance, which
doesn't show when there is no output current.

In sci.electronics.basics on Fri, 18 Jul 2003 15:01:05 GMT "Ben
Miller" <benmiller@worldnet.att.net> posted:

Even if what Ben said below had never been said, or in other cases
where there were no equivalent answer to Ben's, let me add this:

"Mark" <md.siegel@sbcglobal.net> wrote in message
news:3RSRa.468$Dc1.265@newssvr24.news.prodigy.com...
Your answer is wrong and your premise is wrong.
It is completely safe to use an AD-DC adapter with
a higher current rating, provided that the adapters
voltage rating is accurate. If the design of the adapter
requires a load to work correctly, its a poorly designed
product.

So those must be the products that AC/DC is talking about. Let's talk
about them. Why is it necessary to say his premise is wrong**, when
there are such adaptors, when he said "although the small transformer
in AC adapters have a horrible regulation." So he's talking about
small tranformers with horrible regulation, even if better adaptors
exist. Lots of products are not worth buying a better adaptor for if
there is another way to keep them from burning out, or if it turns out
they won't burn out anyhow.

**As if his premise is totally wrong. His premise is partially right,
just as your premise that he is wrong is only partially right.

Such an adapter will not be reliable even at
the rated current and voltage. Most adapters that
put out higher voltage with no load also do not
produce the current they are rated at. So if you
are looking for a replacement adapter look for one
that is a regulated.

But in fact, loads of cheap appliances work pretty well with cheap
adaptors. When I get a device that doesn't have a spec written on it.
I start with a universal adaptor and work my way up in voltage until
it works well. Then often I look through my box of scrap adaptors,
almost all of them cheap, and if I find one that matches, I use that.
Some things I give away after that. I'm not going to go out and buy a
good adaptor for a cheap appliance that I'm going to give away, or use
once every 6 months.

Not true. Dudes observation is correct. These adapters use "impedance
limiting" to meet the UL class 2 requirements for energy limited
transformers, as opposed to fuse links or other more costly methods. They
will produce approximately rated voltage at rated current, but open circuit
voltage will be higher.

Ben Miller

Meirman

If emailing, please let me know whether
or not you are posting the same letter.

Change domain to erols.com, if necessary.

 

[Mark]

I don't know about you but I cant remember the last
device I saw that used an AC-AC adapter. And since
the example was a sony walkman AC-DC must be assumed
since we are talking about replacement adapters.

The question related to current not voltage. Had he stated
that a regulated adapter was not a problem his premises is fine.
However he leaves the reader with the assumption that all adapters
are created equal.

His further assumption that any two adapters with the same
voltage and current rating will produce the same result under
the same load. This again is a poor assumption unless both adapters
are regulated. His premises is that no adapters are regulated.

<ehsjr@bellatlantic.net> wrote in message
news:3F1A06A9.9D0001CF@bellatlantic.net...

Mark wrote:

No, his answer and premise are incorrect.

Again, you are wrong. Go back and re-read his
original. Nowhere does he say AC-DC adapter.
Your original answer specified an AC-DC adapter.

Higher
available current by itself will not harm a device. The
device pulls what it needs. Every answer here that is
a problem relates to voltage not current.

The voltage problem relates to current. The adapter
has an internal impedance that reduces the voltage
when current is drawn. The amount of voltage drop is
the product of the current times the impedance. Draw
less current and the voltage drop is lower, so the output
voltage is higher.

A well voltage
regulated supply can have as much available current as it
wants.

That's true, but is not what the OP was talking about.
He specifically addressed badly regulated supplies - here's
what he said: "... the small transformer in AC adapters have
a horrible regulation."

I will agree there are many AC adapters on the market
that don't meet there rating. Most of those have a UL stamp
on them but have never been UL tested.

They meet their ratings at the specified current.

What you apparently do not realize is that many AC adapters
rated at say 12 volts at say .5 amp will put out much higher
voltage when loaded well below their current rating. The OP
said some of the adapters he is talking about put out between
16 and 20 volts with no load, and 12 volts when loaded at
their current rating. I'll use 12 volts at .5 amps as the
transformer specs and pick 17 volts - on the lower side of
the OPs range - as the no load output voltage, in the
following. How could that be? Our 12 volt transformer puts
out 17 volts with no load and 12 volts with a .5 amp load.
That means it has an internal impedance of 10 ohms.

Say your device uses 50 ma at 12 volts. The device impedance
is 12/.05 or 240 ohms, and it will dissipate .6 watts when
supplied by 12 volts. Suppose it is connected to the 12V
transformer whose internal impedance is 10 ohms. The total
circuit impedance is 250 ohms, so .068 amps will be
drawn. (17/250) The total dissipation is I^2R, or 1.156
watts. .04624 watts are dissipated in the transformer,
and 1.10976 watts are dissipated in the device - almost
twice what it would dissipate with a proper adapter.

 

[DarkMatter]

On Sat, 19 Jul 2003 15:07:07 -0700, John Larkin
<jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> Gave us:

The only time UL cares about performance is in the specs for
life-safety systems.

This is true. We make a product for GE Medical that we had to send
an Engineer up to UL in order to train them on the equipment. They
are very stringent on manufacturing conformance, and that to the
original approved spec. No changes without a re-cert.

 

[DarkMatter]

On Sat, 19 Jul 2003 22:43:58 GMT, "Mark" <md.siegel@sbcglobal.net>
Gave us:

When you get an adapter, unless you bought it yourself from
the real manufacturer. You have no idea if the information on the
unit is valid.

We sell several, and we have them made in china, by a standard
contract manufacturer. The best way is to simply research the
manufacturer of an item you may wish to purchase. Chances are, if you
cannot even find information on the maker of the product online, it's
a hokey product. Current limited, overdesigned products work well,
because they are hard to "blow up". Don't find many out there,
though. Some fudge on ripple specs too. Watch out particularly if
you re powering devices meant for communicating with computers, or
that have microcontrollers in them. A good, clean power supply is
what proper circuit operation is all about. Low ripple figures at
rated loads are what good, clean power supplies are all about. (Well,
it actually does get much deeper than that... )
By the way... have I said fuck you to you lately?