Safety of electronic equipment?

[John Woodgate]

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog
DOTyou.knowwhat> wrote (in <b8emtvgsov12mi3hkd3tnoic43tbppdm8b@4ax.com&gt
about 'Safety of electronic equipment?', on Sat, 13 Dec 2003:

On Sat, 13 Dec 2003 15:51:47 GMT, the renowned a?n?g?e?l@lovergirl.lrigr
evol.moc.com (The little lost angel) wrote:

After popping in several of the brand names available locally for PSU,
I actually came across one that says the +5v and +12v energy level are
at hazardous levels. Now am I supposed to be concerned if I buy this
thing or am I supposed to be assured that since it passed UL, it's
safe even though they have this warning??

It is NOT unconditionally safe. You could EASILY start a fire with the
power coming from a regular PC PSU. A dead short will trip the
protection and an open won't do anything bad, but a bit of nichrome or
stainless-steel wire..

Yes; the warning is to protect BFs who abuse the product from their own
stupidity.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[Active8]

On Sat, 13 Dec 2003 10:30:02 -0600, jfields@austininstruments.com
said...

On Sat, 13 Dec 2003 15:51:47 GMT, a?n?g?e?l@lovergirl.lrigrevol.moc.com
(The little lost angel) wrote:

Nobody's seem to be active in the compliance NG.

I think it's really quite terrible that regulations and standards
meant to protect consumers... cannot be accessed by consumers to
figure out if what they are being sold is actually safe.
---
That's not quite true. Standards are available to anyone who wants
them. However, in the case of UL and similar organizations where the
standards were developed with private funds, those documents are
proprietary and copyrighted, are not in the public domain, and must be
paid for. The same may even be true for some standards developed with
public funds. It's been a while since I quoted any military equipment
and got the spec's as part of the bid package, so I don't know any more.

According to the bible, UL is a not-for-profit org that provides
listing, classification, certificate, and recognition services and
follow-ups.

So I'm wrong to say that the standards should be public domain.

On second thought, don't they charge money for their services just
like the stinkin' FDA? My mechanic charges for inspecting my
vehicle, but he provides the standards for free. Ok, it's only one
sheet of paper But he didn't charge for 2 muffler clamps when he
put my catalytic converter on. I supplied the converter, he charged
labor. Free clamps! Good rate and low time.

If I write a program, it's copyrighted, and I can give it away and
define the terms of reproduction and distribution.

snip

If there's any question as to the appropriateness of the device for its
intended use or if you're concerned with the interpretation of its
specifications you should contact the manufacturer

for clarification
and/or get copies of the various standards to which it's supposed to
adhere, read them, and put the matter to rest.

Yeah, get paperwork. If the sales dweeb lied to her boss, it's the
only way she can be sure the droid at the manufacturer's office
won't lie.

Mike

 

[Active8]

On Sat, 13 Dec 2003 17:47:43 +0000, jmw@jmwa.demon.contraspam.yuk
said...

I read in sci.electronics.design that Active8 <mTHISREMOVEcolasono@earth
link.net> wrote (in <MPG.1a4516b36a1b077c9896bc@news.west.earthlink.net
) about 'Safety of electronic equipment?', on Sat, 13 Dec 2003:

Did you just misinterpret?

I don't think so.

Who said anything about poorly written standards? I said "spec" and
nothing more. As in, "Hey Mike, this needs to be UL approved for
consumer use." Whatever. and the designer gets to figure it out.

What do you mean by 'spec'? I assumed that you meant whichever UL
standard (such as UL1950) applies. I couldn't see any other
interpretation that made sense.

Assume... Interpret... sorry if I was somewhat ambiguous.

I said:

I suppose even in a large company, a (possibly pointy haired)
manager type who writes the specs would just delegate the
responsibility of meeting them to the designer, but the company
would have the resources to provide that info.


no where does it mention "poorly written specs".

"Hey John. You *did* read the part about the thing needing to be
installed in hospitals, right?"

A spec...

"Yeah boss, I'm looking up the shit now."

Standard...

Say it's for a doctor's office and he asked for it and doesn't know
jack about jargon. He just wants a "thingy" and isn't about to
spend extra time with your boss to help write a "specification"
containing foreign jargon (like "doctor's office" or "load
center" ) OR references to specific "standards." Nor is he going to
understand a completed spec you send him for approval beyond "This
thingy will install in your breaker thingy and make your life
easier."

Mike

 

[Active8]

On Sat, 13 Dec 2003 17:45:37 +0000, jmw@jmwa.demon.contraspam.yuk
said...

I read in sci.electronics.design that The little lost angel <a?n?g?e?l@l
overgirl.lrigrevol.moc.com> wrote (in <3fdb34af.45424446@news.pacific.ne
t.sg&gt about 'Safety of electronic equipment?', on Sat, 13 Dec 2003:

Nobody's seem to be active in the compliance NG.

There is less activity at weekends, of course, but there are 10-15
articles a day during the week.

ah. vely good.

<snip>

If you want to delve into this properly, you need to buy, read and
understand UL1950 or whichever safety standard applies. The 'hazard' in
this case is that *if the 5 V or 12 v supply were short-circuited*
through a resistance within critical range of values, there might be
enough energy released to cause overheating. If you use the product
responsibly, there is no problem. But people who don't know this
shouldn't really be buying the product anyway.

I wish she had more info. I'd like for her to know if the sales

puke was blowing smoke up her bosses ass. I hate that. If you don't
have a good AND valid selling point, find another product to sell.

Mike

 

[Active8]

I have a major e-mail attachment downloading, John. Thank you!

Mike

 

[John Woodgate]

I read in sci.electronics.design that Active8 <mTHISREMOVEcolasono@earth
link.net> wrote (in <MPG.1a452b449a7b06df9896c1@news.west.earthlink.net>
) about 'Safety of electronic equipment?', on Sat, 13 Dec 2003:

On Sat, 13 Dec 2003 17:47:43 +0000, jmw@jmwa.demon.contraspam.yuk
said...
I read in sci.electronics.design that Active8 <mTHISREMOVEcolasono@earth
link.net> wrote (in <MPG.1a4516b36a1b077c9896bc@news.west.earthlink.net
) about 'Safety of electronic equipment?', on Sat, 13 Dec 2003:

Did you just misinterpret?

I don't think so.

Who said anything about poorly written standards? I said "spec" and
nothing more. As in, "Hey Mike, this needs to be UL approved for
consumer use." Whatever. and the designer gets to figure it out.

What do you mean by 'spec'? I assumed that you meant whichever UL
standard (such as UL1950) applies. I couldn't see any other
interpretation that made sense.


Assume... Interpret... sorry if I was somewhat ambiguous.

I said:

I suppose even in a large company, a (possibly pointy haired)
manager type who writes the specs would just delegate the
responsibility of meeting them to the designer, but the company
would have the resources to provide that info.


no where does it mention "poorly written specs".

"Hey John. You *did* read the part about the thing needing to be
installed in hospitals, right?"

A spec...

"Yeah boss, I'm looking up the shit now."

Standard...

Say it's for a doctor's office and he asked for it and doesn't know
jack about jargon. He just wants a "thingy" and isn't about to
spend extra time with your boss to help write a "specification"
containing foreign jargon (like "doctor's office" or "load
center" ) OR references to specific "standards." Nor is he going to
understand a completed spec you send him for approval beyond "This
thingy will install in your breaker thingy and make your life
easier."

Mike

I give up. We are not communicating.

--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[Roger Gt]

"John Woodgate" wrote in message

I read in sci.electronics.design that The little lost angel
overgirl.lrigrevol.moc.com> wrote about 'Safety of electronic equipment?',

on Sat, 13 Dec 2003:

<snip>

The MARKING is your assurance that the product is safe.

No, only that it passed their inspection. They are not responsible for any
hazard they miss!

If you want to delve into this properly, you need to buy, read and
understand UL1950 or whichever safety standard applies. The 'hazard' in
this case is that *if the 5 V or 12 v supply were short-circuited*
through a resistance within critical range of values, there might be
enough energy released to cause overheating. If you use the product
responsibly, there is no problem. But people who don't know this
shouldn't really be buying the product anyway.

I have UL1950 and have read and designed produce listed under the
requirements in that "Standard" and I have worked with an entire department
who are responsible for the safety of our consumers. But Not one of us
understand the UL1950 requirements specification! It requires much
interpretation and consultation! IT is poorly written and vague in many
areas!

BTW, 5 to 12 volts are not considered to be critical voltages. But
insulation thickness and spacing for connectors are specified. Under 24
volts is an entire class of circuits.
If you have a Wall wart, the unit may not have been inspected at all. Since
there are no critical voltages. Subject to interpretation and dependant
upon intended use, and other hard to define conditions.
FCC is separate. But can be self certified by many testing labs.

But if you think this one is bad, try to comply with DO160D for aircraft
installation!

 

[Roger Gt]

"The little lost angel" wrote in message

On Fri, 12 Dec 2003 18:42:27 GMT, Spehro Pefhany wrote:

<snip>

I don't understand the logic to why they demand the finished widget to
be tested but the components in it, while sold in retail doesn't

Not all components require listing. Resistors and most semiconductors are
not required to be listed as they are only inspected in the application.

Connectors for low voltages are not usually component listed, due to the
class of application. But anything rated for over 48 volt service will be
listed. Power levels are specified too, but I do not remember the levels off
hand!

 

[Spehro Pefhany]

On Sat, 13 Dec 2003 21:36:18 GMT, the renowned "Roger Gt"
<Xenot@pacbell.net> wrote:

"The little lost angel" wrote in message
On Fri, 12 Dec 2003 18:42:27 GMT, Spehro Pefhany wrote:

snip

I don't understand the logic to why they demand the finished widget to
be tested but the components in it, while sold in retail doesn't

Not all components require listing. Resistors and most semiconductors are
not required to be listed as they are only inspected in the application.

There are NO components that are *required* to be listed. Using listed
components merely lessens the cost and time to evaluate the end
equipment, and perhaps makes it possible to change suppliers without
re-evaluating the equipment.

Connectors for low voltages are not usually component listed, due to the
class of application. But anything rated for over 48 volt service will be
listed.

No, it just makes life easier to follow rules like that. For example,
I might design a custom molded mains voltage connector that will be
physically part of the housing on my product. The connector will never
be sold separately. It will not be component listed. The same applies
to an unlisted knockoff Tyco connector from the Sum Yung Guy Connector
and Tofu Fty. #9. In both cases I'd have to supply detailed
information and specifications on the materials used (exact resin type
and supplier(s), flammability ratings, and so on).

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[John Fields]

On Sat, 13 Dec 2003 21:29:29 GMT, "Roger Gt" <Xenot@pacbell.net> wrote:

I have UL1950 and have read and designed produce listed under the
requirements in that "Standard" and I have worked with an entire department
who are responsible for the safety of our consumers.

---
Lettuce hope it all works out...

--
John Fields

 

[The little lost angel]

On Sat, 13 Dec 2003 21:29:29 GMT, "Roger Gt" <Xenot@pacbell.net>
wrote:

BTW, 5 to 12 volts are not considered to be critical voltages. But
insulation thickness and spacing for connectors are specified. Under 24
volts is an entire class of circuits.
If you have a Wall wart, the unit may not have been inspected at all. Since
there are no critical voltages. Subject to interpretation and dependant
upon intended use, and other hard to define conditions.

So it would be possible to have a product UL listed but UL never
actually saw or tested the item? Like say virtually everything
involved in a PC since it's all max at +12.

While we're on this issue, new PC casing nowadays like to come with
acrylic windows and even on the PSU. As far as I know, acrylic and
plastics don't block EM radiation, so are these things bluffing their
safety marks wrt EMI? At least one brand I've tried doesn't appear on
the UL listing.


--
L.Angel: I'm looking for web design work.
If you need basic to med complexity webpages at affordable rates, email me
Standard HTML, SHTML, MySQL + PHP or ASP, Javascript.
If you really want, FrontPage & DreamWeaver too.
But keep in mind you pay extra bandwidth for their bloated code

 

[Spehro Pefhany]

On Sun, 14 Dec 2003 04:11:56 GMT, the renowned
a?n?g?e?l@lovergirl.lrigrevol.moc.com (The little lost angel) wrote:

On Sat, 13 Dec 2003 21:29:29 GMT, "Roger Gt" <Xenot@pacbell.net
wrote:
BTW, 5 to 12 volts are not considered to be critical voltages. But
insulation thickness and spacing for connectors are specified. Under 24
volts is an entire class of circuits.
If you have a Wall wart, the unit may not have been inspected at all. Since
there are no critical voltages. Subject to interpretation and dependant
upon intended use, and other hard to define conditions.

So it would be possible to have a product UL listed but UL never
actually saw or tested the item? Like say virtually everything
involved in a PC since it's all max at +12.

No. The wall wart would have the markings but the product would not
have any such markings unless it has been inspected. It's obviously
possible to design dangerous products using listed adapters.

While we're on this issue, new PC casing nowadays like to come with
acrylic windows and even on the PSU. As far as I know, acrylic and
plastics don't block EM radiation, so are these things bluffing their
safety marks wrt EMI? At least one brand I've tried doesn't appear on
the UL listing.

Yeah, I've even seen an entire PC case made of thick clear acrylic. I
didn't notice any FCC markings on it. My favorite so far is the
plastic side "window" that contains a fake aquarium c/w air pump and
CCFL lighting, I think actually filled with water (hopefully it
doesn't leak).

http://www.efrisson.com/main/popup_image.php/pID/2143

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[Roger Gt]

"The little lost angel" <a?n?g?e?l@lovergirl.lrigrevol.moc.com> wrote in
message news:3fdbe1e9.8883623@news.pacific.net.sg...

On Sat, 13 Dec 2003 21:29:29 GMT, "Roger Gt" <Xenot@pacbell.net
wrote:
BTW, 5 to 12 volts are not considered to be critical voltages. But
insulation thickness and spacing for connectors are specified. Under 24
volts is an entire class of circuits.
If you have a Wall wart, the unit may not have been inspected at all.
Since
there are no critical voltages. Subject to interpretation and dependant
upon intended use, and other hard to define conditions.

So it would be possible to have a product UL listed but UL never
actually saw or tested the item? Like say virtually everything
involved in a PC since it's all max at +12.

Possible but not likely if it a volume produce since any insurance company
you do business with will require an inspection. But low volume items might
be shipped before the UL inspection. The Wall wart would be listed though,
it has a higher voltage input and therefore must be listed before sale.

While we're on this issue, new PC casing nowadays like to come with
acrylic windows and even on the PSU. As far as I know, acrylic and
plastics don't block EM radiation, so are these things bluffing their
safety marks wrt EMI? At least one brand I've tried doesn't appear on
the UL listing.

Some plastic cases are sprayed with an anti EMI metallic coating on the
inside. A good design may not require any shielding for EMI, but would
still benefit for ESD.
I've done several designs which didn't require shielding to meet FCC
testing.

 

[The little lost angel]

On Sun, 14 Dec 2003 06:00:39 GMT, "Roger Gt" <Xenot@pacbell.net>
wrote:

Some plastic cases are sprayed with an anti EMI metallic coating on the
inside. A good design may not require any shielding for EMI, but would
still benefit for ESD.
I've done several designs which didn't require shielding to meet FCC
testing.

Is there any way for end users to tell if the plastic's been treated
or not? After all, I know some of these casing and PSU comes from shop
who take the original item and took cutters to them before fitting in
pieces of acrylic from local art & craft shops pPpp

--
L.Angel: I'm looking for web design work.
If you need basic to med complexity webpages at affordable rates, email me
Standard HTML, SHTML, MySQL + PHP or ASP, Javascript.
If you really want, FrontPage & DreamWeaver too.
But keep in mind you pay extra bandwidth for their bloated code

 

[Roger Gt]

"The little lost angel" <a?n?g?e?l@lovergirl.lrigrevol.moc.com> wrote in
message news:3fdc1986.23120215@news.pacific.net.sg...

On Sun, 14 Dec 2003 06:00:39 GMT, "Roger Gt" <Xenot@pacbell.net
wrote:

Some plastic cases are sprayed with an anti EMI metallic coating on the
inside. A good design may not require any shielding for EMI, but would
still benefit for ESD.
I've done several designs which didn't require shielding to meet FCC
testing.

Is there any way for end users to tell if the plastic's been treated
or not? After all, I know some of these casing and PSU comes from shop
who take the original item and took cutters to them before fitting in
pieces of acrylic from local art & craft shops pPpp

The plastic interior will have a metallic cast to it! Usually copper or
dull pot metal colored. It is not thick, and can easily be scratched.

 

[John Woodgate]

I read in sci.electronics.design that The little lost angel <a?n?g?e?l@l
overgirl.lrigrevol.moc.com> wrote (in <3fdbe1e9.8883623@news.pacific.net
..sg&gt about 'Safety of electronic equipment?', on Sun, 14 Dec 2003:

On Sat, 13 Dec 2003 21:29:29 GMT, "Roger Gt" <Xenot@pacbell.net> wrote:
BTW, 5 to 12 volts are not considered to be critical voltages.

I doubt that UL use the term 'critical voltages'. 5 V and 12 V are not
*hazardous* voltages, but there is also a concept of 'hazardous energy
levels', and even a 1 V 50 A supply has hazardous energy.

But
insulation thickness and spacing for connectors are specified. Under 24
volts is an entire class of circuits.

If you have a Wall wart, the unit may not have been inspected at all.

The wall wart will have been inspected. There is no reason to inspect
the unit it feeds if the voltage and energy are bot so low as to present
no hazard. What would be the point?

Since
there are no critical voltages. Subject to interpretation and dependant
upon intended use, and other hard to define conditions.

So it would be possible to have a product UL listed but UL never
actually saw or tested the item? Like say virtually everything involved
in a PC since it's all max at +12.

Absolutely not. See above for the explanation why listing is
*unnecessary*.

While we're on this issue, new PC casing nowadays like to come with
acrylic windows and even on the PSU. As far as I know, acrylic and
plastics don't block EM radiation, so are these things bluffing their
safety marks wrt EMI? At least one brand I've tried doesn't appear on
the UL listing.

There are no known safety issues with non-ionising EM emissions at the
levels produced by PCs and similar electronic equipment. There are well-
known and understood physiological effects due to tissue heating at far
higher power densities, e.g. in the vicinity of high-power transmitters.

What is more mysterious is how these products meet FCC requirements for
emissions, which are set at really low levels, intended to prevent
interference with radio communication, not biological effects.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

 

[Roger Gt]

"John Fields" <jfields@austininstruments.com> wrote in message
news:cj5ntvs2hegjoi9p8rigebdcntjdkbgb15@4ax.com...

On Sat, 13 Dec 2003 21:29:29 GMT, "Roger Gt" <Xenot@pacbell.net> wrote:


I have UL1950 and have read and designed products listed under the
requirements in that "Standard" and I have worked with an entire
department
who are responsible for the safety of our consumers.

---
Lettuce hope it all works out...
--
John Fields

Spelling checkers can screw up things to. No plural for "Product!"

 

[Keith R. Williams]

In article <Ik7Db.71538$4A5.50557@newssvr25.news.prodigy.com>,
Xenot@pacbell.net says...

"John Fields" <jfields@austininstruments.com> wrote in message
news:cj5ntvs2hegjoi9p8rigebdcntjdkbgb15@4ax.com...
On Sat, 13 Dec 2003 21:29:29 GMT, "Roger Gt" <Xenot@pacbell.net> wrote:


I have UL1950 and have read and designed products listed under the
requirements in that "Standard" and I have worked with an entire
department
who are responsible for the safety of our consumers.

---
Lettuce hope it all works out...
--
John Fields

Spelling checkers can screw up things to. No plural for "Product!"

Sure there is ("produce" and "products"). I suppose you don't
think there is a plural for "fish" either. Good grief!

--
Keith

 

[Spehro Pefhany]

On Sun, 14 Dec 2003 20:45:07 -0500, the renowned Keith R. Williams
<krw@attglobal.net> wrote:

In article <Ik7Db.71538$4A5.50557@newssvr25.news.prodigy.com>,
Xenot@pacbell.net says...

"John Fields" <jfields@austininstruments.com> wrote in message
news:cj5ntvs2hegjoi9p8rigebdcntjdkbgb15@4ax.com...
On Sat, 13 Dec 2003 21:29:29 GMT, "Roger Gt" <Xenot@pacbell.net> wrote:


I have UL1950 and have read and designed products listed under the
requirements in that "Standard" and I have worked with an entire
department
who are responsible for the safety of our consumers.

---
Lettuce hope it all works out...
--
John Fields

Spelling checkers can screw up things to. No plural for "Product!"

Sure there is ("produce" and "products"). I suppose you don't
think there is a plural for "fish" either. Good grief!

Or people. But, Eggs Benedict has no plural.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[Keith R. Williams]

In article <9t8qtv8v725bvp0o8805bv29176d3osp8o@4ax.com>,
speffSNIP@interlogDOTyou.knowwhat says...

On Sun, 14 Dec 2003 20:45:07 -0500, the renowned Keith R. Williams
krw@attglobal.net> wrote:

In article <Ik7Db.71538$4A5.50557@newssvr25.news.prodigy.com>,
Xenot@pacbell.net says...

"John Fields" <jfields@austininstruments.com> wrote in message
news:cj5ntvs2hegjoi9p8rigebdcntjdkbgb15@4ax.com...
On Sat, 13 Dec 2003 21:29:29 GMT, "Roger Gt" <Xenot@pacbell.net> wrote:


I have UL1950 and have read and designed products listed under the
requirements in that "Standard" and I have worked with an entire
department
who are responsible for the safety of our consumers.

---
Lettuce hope it all works out...
--
John Fields

Spelling checkers can screw up things to. No plural for "Product!"

Sure there is ("produce" and "products"). I suppose you don't
think there is a plural for "fish" either. Good grief!

Or people. But, Eggs Benedict has no plural.

Wrong! Egg*S* Benedict. ...rather like Atournys General.

--
Keith