Turn off laser printer with power strip?

[w_tom]

Filter on power cord had no purpose because a better filter is
required inside that power supply. What good is removing a glass of
water from a basement when the basement is flooded? A metaphor that is
answered below.

Do not assume a direct (quantitative) relationship exists between
amount of reduced noise and amount of filtering. Amount of noise is a
non-linear relationship. Add filtering (ie only a capacitor) and hear
no noise reduction. Noise has been reduced, but radio volume does not
indicate such reduction. Increase filtering more, and still no
noticeable reduction - even though filtering has been increased. Then
with a little more filtering, noise is substantially reduced. The
relationship looks more like a hysterisis curve. A little more
filtering suddenly causes a massive reduction in noise volume. Noise
volume reduction does not provide quantitative information; only
suggests a subjective trend.

Even a trivial filter inside a power strip was just enough filtering
to cause noise reduction. That does not for one minute say that filter
is effective because a 'glass of water' filter (inside the power strip)
is made irrelevant by an 'electric pump sized' filter that should have
been inside that power supply.

Of course EMI/RFI filtering that John Smith was touting to protect
appliances is totally irrelevant to the original poster's question.
But John Smith touted it as if it was some major improvement - which
the filter is not. Once numbers were applied, power cord filter does
nothing significant - as demonstrated by the filter that was suppose to
be inside your power supply. Purpose of that filter inside a power
strip protector is for a UL1449 requirement - that is also completely
irrelevant to this thread.

Best way to fix your power supply are filters (which provide both
differential and common mode filtering) just for this purpose such as:
http://www.schurterinc.com/products/usa/pemfilter.asp
http://www.corcom.com/
http://www.cor.com/PDF/Q.pdf
http://www.interpower.com/ic/p30-35list.asp

http://www.interpower.com/scripts/wsisa.dll/WService=ic/p35list2.p?only_filter=YES

Meanwhile power supply creates even more noise when connected to an
antenna. What is the antenna for a power supply missing essential
filters? AC electric wires throughout entire house. If your power
supply is that poorly manufactured, noise may even cause interference
with neighbors - which is why that missing filter inside a power supply
is required by FCC regulations (Part 15 if I remember correctly).

Point remains - the fitler inside a power strip protector does
nothing useful. EMI/RFI filtering is not the purpose of that filter.

 

[w_tom]

FCC has different requirements (classes) for commercial and
residential equipment. Residential equipment must radiate less
interference. So small that filtering inside a power strip is totally
irrelevant. If I remember correctly, those FCC regulations are Part 15.


Meanwhile, that 'filtering' inside a power strip protector is for
UL1449 purposes - human safety. When grossly undersized, some power
strip protectors install a tiny filter to blunt a destructive
transient. This may be enough to obtain UL1449 certification for a
grossly undersized protector. Rememer - a protector can be completely
destroyed - vaporized - in a UL1449 test and yet still be certified.
UL1449 is only concerned that a protector not threaten human life.
Those filtering numbers are trivial as well as incomplete for EMI/RFI.
Those numbers were blindly provided by John Smith becauase he does not
understand what they mean AND was caught claiming that EMI/RFI
filtering was signficant or relevant.

BTW, notice which one puts numbers in perspective AND cited sources
for further investigation. Does that filter inside a power strip
protector claim to make the appliance meet FCC part 15? No, it does
not because, in part, that filter is irrelevant - insufficient - too
small - not intended for a relevant EMI/RFI solution.

 

[w_tom]

FCC has different requirements (classes) for commercial and
residential equipment. Residential equipment must radiate less
interference. So small that filtering inside a power strip is totally
irrelevant. If I remember correctly, those FCC regulations are Part 15.


Meanwhile, that 'filtering' inside a power strip protector is for
UL1449 purposes - human safety. When grossly undersized, some power
strip protectors install a tiny filter to blunt a destructive
transient. This may be enough to obtain UL1449 certification for a
grossly undersized protector. Rememer - a protector can be completely
destroyed - vaporized - in a UL1449 test and yet still be certified.
UL1449 is only concerned that a protector not threaten human life.
Those filtering numbers are trivial as well as incomplete for EMI/RFI.
Those numbers were blindly provided by John Smith becauase he does not
understand what they mean AND was caught claiming that EMI/RFI
filtering was signficant or relevant.

BTW, notice which one puts numbers in perspective AND cited sources
for further investigation. Does that filter inside a power strip
protector claim to make the appliance meet FCC part 15? No, it does
not because, in part, that filter is irrelevant - insufficient - too
small - not intended for a relevant EMI/RFI solution.

 

[larry moe 'n curly]

My understanding of the law is that the FCC does not require consumer
equipment to not interferer with other consumer equipment, but that
consumer equipment does not interfere with commercial equipment.

I confess to reading an interpretation of the law and not the law
itself.

All I know is that the manufacturer designed the circuit board of this
PSU for an EMI/RFI filter but never installed the components for it.
Also PC Power & Cooling used to display a higher-power version of it as
an example of what a bad PSU was like:

http://static.flickr.com/24/94444688_70597728f9_o.jpg

And with another cheapo PSU of mine, the manufacturer. Key Mouse
Enterprises (Soyo PSUs, Maxpower, Everpower), outright lied at its
website when it claimed that it contained EMI/RFI filtration..

 

[John Smith]

The screw can create
problems for laser printers when not used - when a rear push-in
connection is used instead.

Using the rhetorical and third-person formats favored by w_tom... Does
w_tom understand how to write so other people can understand him? No, he
does not.

If w_tom used the English language correctly, he would understand such
concepts as sentence subjects, direct objects, and indirect objects. Since
he does not use the language correctly and instead disparages those that do,
w_tom insists on whining about how an unused screw can create problems for
laser printers. It IS possible for a receptacle screw to create a problem;
for example, if it is too long it may short against a metal junction box.
But w_tom said nothing about a screw creating a short circuit, and this
problem would not be limited to affecting only laser printers.

What w_tom may have intended to tell us -- and this is only a guess, since
his constant self-contradictions and tortured spelling and grammar make him
so difficult to understand -- is that a screw connection makes a better
electrical connection than a push-in connection does. If this is what he
intended to say, he should have said something like "Using a push-in
connector instead of a screw terminal may cause a problem." This claim
would be then be open to debate, since it would depend on the skill of the
electrician doing the wiring, the quality of the receptacle, whether the
wire was copper or aluminum, whether the push-in connector had a screw
holding the wire in place, etc. But at least the claim would be feasible.
(An explanation would still be required to explain why this phenomenon only
affects laser printers and electronics.)

But w_tom did not say that, so we can only guess what he meant. If a screw
terminal on a receptacle is unused and it doesn't create a short circuit or
otherwise interfere with the contents of a junction box, it will not create
a problem. Period. For w_tom to claim otherwise is just perpetuating junk
science claims and proves he does not even understand basic electrical
concepts. w_tom should have learned basic science before speculating
wildly, and he deserves this bruising.

Further, w_tom does not even understand the difference between a laser and a
laser printer, since on 2/12/06 he used the two terms interchangeably. This
proves that w_tom does not even have a basic understanding of electrical
components, and he should be asking questions instead of spreading wild
rumors.

We must choose: Either w_tom is a liar spreading myths and half-truths, or
w_tom is a person who cannot express himself clearly. Which selection we
make is immaterial, for in both cases the consequence is that the words of
w_tom cannot be trusted.

Who cares if an engineer has knowledge? If he can't accurately express
himself to others, what good is he? Harsh questions? Yes. Too many people
read a book then think they can explain the book's entire subject accurately
to others. If w_tom explains a concept incorrectly, he should expect to be
challenged vigorously by the rest of us in this forum.

 

[Bob]

Who cares if an engineer has knowledge?

I do.

If he can't accurately express
himself to others, what good is he?

He's likely typical of knowledgable engineers.

Harsh questions? Yes. Too many people
read a book then think they can explain the book's entire subject accurately
to others. >If w_tom explains a concept incorrectly, he should expect to be
challenged vigorously by the rest of us in this forum.

Perhaps. I've learned not to discount people or their knowledge simply
due to a communication gap between us due to language, skills, or
terminology & familiarity with the subject.