I'm working on a project that is a mechanical switch of sorts, and it
entails running electrical signals through Phosphor-Bronze contacts.

Now since *all* alloys will oxidize to an extent, I was wondering if I
were to wipe the phosphor-Bronze contacts with the same
material(Phosphor-Bronze), would that be serve to keep the alloy's
surface clean? (The wiping action will be part of the mechanics of the
switch).

Thanks.

Darren Harris
Staten Island, New York.

On Tue, 11 Dec 2012 22:06:24 -0800, Searcher7 wrote:

I'm working on a project that is a mechanical switch of sorts, and it
entails running electrical signals through Phosphor-Bronze contacts.

Now since *all* alloys will oxidize to an extent, I was wondering if I
were to wipe the phosphor-Bronze contacts with the same
material(Phosphor-Bronze), would that be serve to keep the alloy's
surface clean? (The wiping action will be part of the mechanics of the
switch).

Wow. No one who actually knows is answering. Here's my two bits, but
take them with a large grain of salt, 'cause I'm no expert.

I know that "wiping action" is an advertised feature on many switches.

There is probably some minimum normal force that you want to achieve to
make sure that the oxide is wiped off, and probably some minimum wiping
distance to boot. I absolutely couldn't tell you what the necessary
forces and/or distances are, but I'll bet you that there's standards out
there, and probably huge amounts of tribal knowledge at the various
switch manufacturers.

If you can get a good thick silver plating on your contacts then your
required forces will go way down -- silver is a pretty good conductor,
and silver oxide is both mechanically weak and (I understand) not a bad
conductor in its own right.

Finding a switch that has about the same ratings as what you need, taking
it apart, and copying it's actions and forces may not be a bad way to
go. You won't be able to duplicate their metallurgy, but you can't have
everything.

You might try asking this question on sci.electronics.design, since you
don't seem to be getting much info here.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

"Tim Wescott" wrote in message
...
On Tue, 11 Dec 2012 22:06:24 -0800, Searcher7 wrote:

I'm working on a project that is a mechanical switch of sorts, and
it
entails running electrical signals through Phosphor-Bronze
contacts.

Now since *all* alloys will oxidize to an extent, I was wondering
if I
were to wipe the phosphor-Bronze contacts with the same
material(Phosphor-Bronze), would that be serve to keep the alloy's
surface clean? (The wiping action will be part of the mechanics of
the
switch).

Wow. No one who actually knows is answering. Here's my two bits,
but
take them with a large grain of salt, 'cause I'm no expert.

Or no one actually knows. The question is like "How long will this
bearing last" without giving the load, speed, misalignment,
temperature, contamination, etc.

In this case the main electrical conditions that matter are the
voltage and current the switch makes and breaks and how much
resistance increase is too much. Mechanically the contact force and
opening speed affect the life. I've seen contact lifetime ratings
range from 10 to 10 million cycles, and occasionally seen and heard
the number be 1.

Wiping makes the resistance stay low longer and the contacts wear away
faster.

jsw

On Dec 12, 1:15*pm, Tim Wescott wrote:
On Tue, 11 Dec 2012 22:06:24 -0800, Searcher7 wrote:
I'm working on a project that is a mechanical switch of sorts, and it
entails running electrical signals through Phosphor-Bronze contacts.

Now since *all* alloys will oxidize to an extent, I was wondering if I
were to wipe the phosphor-Bronze contacts with the same
material(Phosphor-Bronze), would that be serve to keep the alloy's
surface clean? (The wiping action will be part of the mechanics of the
switch).

Wow. *No one who actually knows is answering. *Here's my two bits, but
take them with a large grain of salt, 'cause I'm no expert.

I know that "wiping action" is an advertised feature on many switches.

There is probably some minimum normal force that you want to achieve to
make sure that the oxide is wiped off, and probably some minimum wiping
distance to boot. *I absolutely couldn't tell you what the necessary
forces and/or distances are, but I'll bet you that there's standards out
there, and probably huge amounts of tribal knowledge at the various
switch manufacturers.

None of that will be a problem, since I can adjust the wiping force
and number of times.

If you can get a good thick silver plating on your contacts then your
required forces will go way down -- silver is a pretty good conductor,
and silver oxide is both mechanically weak and (I understand) not a bad
conductor in its own right.

Electroplating silver onto Phosphor-Bronze would require redesigning
and and result in an increase in complexity and cost of the project.
The idea is to stick with a material that I wouldn't need to plate. If
it is conductive enough, then wiping would take care of the oxidation.
(The switch of course will be used under "normal" environmental
conditions).

Silver does however have the best conductivity of all metals, but not
the *spring* of Phosphor-Bronze. Copper also has more electrical
conductivity than Phosphor-Bronze, but not it's corrosion resistance.
Gold has excellent electrical conductivity, but is not as wear
resistant.

Finding a switch that has about the same ratings as what you need, taking
it apart, and copying it's actions and forces may not be a bad way to
go. *You won't be able to duplicate their metallurgy, but you can't have
everything.

Nope. This is a switch that doesn't exist in any form yet and will
incorporate unorthodox connections. (One particular version will allow
switching between a dozen 40 pin connections). The wiping will
actually be in the mechanical action of switching from one connection
to the next.

You might try asking this question on sci.electronics.design, since you
don't seem to be getting much info here.

I actually tried a similar question at Sci.Electronics.Basics two or
three years ago, only to have to deal with personal attacks by a group
led by a "John Fields" because I wouldn't give them *detailed* plans
of what I was working on. Specifics that had nothing at all to do with
the question concerning wiping material.

I'd think that lot of the same trolls who hang out at
Sci.Electronics.Basics also frequent Sci.Electronics.Design.

Thanks.

Darren Harris
Staten Island, New York.

On Dec 12, 6:17*pm, "Jim Wilkins" wrote:
"Tim Wescott" wrote in message

...









On Tue, 11 Dec 2012 22:06:24 -0800, Searcher7 wrote:

I'm working on a project that is a mechanical switch of sorts, and
it
entails running electrical signals through Phosphor-Bronze
contacts.

Now since *all* alloys will oxidize to an extent, I was wondering
if I
were to wipe the phosphor-Bronze contacts with the same
material(Phosphor-Bronze), would that be serve to keep the alloy's
surface clean? (The wiping action will be part of the mechanics of
the
switch).

Wow. *No one who actually knows is answering. *Here's my two bits,
but
take them with a large grain of salt, 'cause I'm no expert.

Or no one actually knows. The question is like "How long will this
bearing last" without giving the load, speed, misalignment,
temperature, contamination, etc.

How do you figure?

In this case the main electrical conditions that matter are the
voltage and current the switch makes and breaks and how much
resistance increase is too much. *Mechanically the contact force and
opening speed affect the life. I've seen contact lifetime ratings
range from 10 to 10 million cycles, and occasionally seen and heard
the number be 1.

Wiping makes the resistance stay low longer and the contacts wear away
faster.

None of that matters. I have control over the contact thickness,
number of wipes between connections, length of wipes between
connections, pressure of wipes between connections, and "Break" and
"Make" will only occur when there is no current, so there will be no
arcing.

I was just concerned about using a different material/metal to wipe
the Phosphor-Bronze contacts. If I can just use the same material then
problem solved.

Thanks.

Darren Harris
Staten Island, New York.

On Thu, 13 Dec 2012 11:17:12 -0800, Searcher7 wrote:

On Dec 12, 1:15Â*pm, Tim Wescott wrote:
On Tue, 11 Dec 2012 22:06:24 -0800, Searcher7 wrote:
I'm working on a project that is a mechanical switch of sorts, and it
entails running electrical signals through Phosphor-Bronze contacts.

Now since *all* alloys will oxidize to an extent, I was wondering if
I were to wipe the phosphor-Bronze contacts with the same
material(Phosphor-Bronze), would that be serve to keep the alloy's
surface clean? (The wiping action will be part of the mechanics of
the switch).

Wow. Â*No one who actually knows is answering. Â*Here's my two bits, but
take them with a large grain of salt, 'cause I'm no expert.

I know that "wiping action" is an advertised feature on many switches.

There is probably some minimum normal force that you want to achieve to
make sure that the oxide is wiped off, and probably some minimum wiping
distance to boot. Â*I absolutely couldn't tell you what the necessary
forces and/or distances are, but I'll bet you that there's standards
out there, and probably huge amounts of tribal knowledge at the various
switch manufacturers.

None of that will be a problem, since I can adjust the wiping force and
number of times.

If you can get a good thick silver plating on your contacts then your
required forces will go way down -- silver is a pretty good conductor,
and silver oxide is both mechanically weak and (I understand) not a bad
conductor in its own right.

Electroplating silver onto Phosphor-Bronze would require redesigning and
and result in an increase in complexity and cost of the project. The
idea is to stick with a material that I wouldn't need to plate. If it is
conductive enough, then wiping would take care of the oxidation. (The
switch of course will be used under "normal" environmental conditions).

There are certainly switches that are made of phosphor bronze.

There are no "normal" environmental conditions -- only the environmental
conditions that people of limited imagination assume is normal.

Silver does however have the best conductivity of all metals, but not
the *spring* of Phosphor-Bronze. Copper also has more electrical
conductivity than Phosphor-Bronze, but not it's corrosion resistance.
Gold has excellent electrical conductivity, but is not as wear
resistant.

Yes, I think we all understand that. What we didn't know until this
moment, though, is that you had considered silver plating and decided
against it for cost reasons.

Because, you see, we can't read your mind.

Finding a switch that has about the same ratings as what you need,
taking it apart, and copying it's actions and forces may not be a bad
way to go. Â*You won't be able to duplicate their metallurgy, but you
can't have everything.

Nope. This is a switch that doesn't exist in any form yet and will
incorporate unorthodox connections. (One particular version will allow
switching between a dozen 40 pin connections). The wiping will actually
be in the mechanical action of switching from one connection to the
next.

If you can't replicate _just the forces and actions_ of an existing
switch at the contacts, then you're in a different universe from me, and
no advise that I can give you will help. In fact, no amount of advise
that you get from any of the regulars here will help, because as far as I
know they're all in the same universe as I am, too.

Perhaps this is why you thought that the help you got on s.e.b was all
from trolls? Getting sound engineering advice from the wrong universe
can do that.

Here in this universe, how you _connect_ to a switch is largely
independent of how the _switch's contacts come together_, and with what
forces. This applies in particular if your switch is currently just a
connection diagram, and has not been reduced to practice in a way that
involves any means of making the contacts come together, with or without
any forces.

You might try asking this question on sci.electronics.design, since you
don't seem to be getting much info here.

I actually tried a similar question at Sci.Electronics.Basics two or
three years ago, only to have to deal with personal attacks by a group
led by a "John Fields" because I wouldn't give them *detailed* plans of
what I was working on. Specifics that had nothing at all to do with the
question concerning wiping material.

I'd think that lot of the same trolls who hang out at
Sci.Electronics.Basics also frequent Sci.Electronics.Design.

John Fields is pretty astute, and engineers learn early not to answer
general questions with specifics. "How much paint does it take to paint
a door?" should be immediately replied to with "How big is the door, and
what sort of paint?", because any specific answer is only going to be
correct if the questioner and respondent both share all the same
assumptions.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

On Dec 13, 5:36 pm, Tim Wescott wrote:
On Thu, 13 Dec 2012 11:17:12 -0800, Searcher7 wrote:
On Dec 12, 1:15 pm, Tim Wescott wrote:
On Tue, 11 Dec 2012 22:06:24 -0800, Searcher7 wrote:
I'm working on a project that is a mechanical switch of sorts, and it
entails running electrical signals through Phosphor-Bronze contacts.

Now since *all* alloys will oxidize to an extent, I was wondering if
I were to wipe the phosphor-Bronze contacts with the same
material(Phosphor-Bronze), would that be serve to keep the alloy's
surface clean? (The wiping action will be part of the mechanics of
the switch).

Wow. No one who actually knows is answering. Here's my two bits, but
take them with a large grain of salt, 'cause I'm no expert.

I know that "wiping action" is an advertised feature on many switches.

There is probably some minimum normal force that you want to achieve to
make sure that the oxide is wiped off, and probably some minimum wiping
distance to boot. I absolutely couldn't tell you what the necessary
forces and/or distances are, but I'll bet you that there's standards
out there, and probably huge amounts of tribal knowledge at the various
switch manufacturers.

None of that will be a problem, since I can adjust the wiping force and
number of times.

If you can get a good thick silver plating on your contacts then your
required forces will go way down -- silver is a pretty good conductor,
and silver oxide is both mechanically weak and (I understand) not a bad
conductor in its own right.

Electroplating silver onto Phosphor-Bronze would require redesigning and
and result in an increase in complexity and cost of the project. The
idea is to stick with a material that I wouldn't need to plate. If it is
conductive enough, then wiping would take care of the oxidation. (The
switch of course will be used under "normal" environmental conditions).

There are certainly switches that are made of phosphor bronze.

There are no "normal" environmental conditions -- only the environmental
conditions that people of limited imagination assume is normal.

So that you will understand what I meant, the switches will not have
to operate in space, under the ocean's surface, immersed in harsh
chemicals or substances, or temperatures below or above what humans
consider comfortable.

Silver does however have the best conductivity of all metals, but not
the *spring* of Phosphor-Bronze. Copper also has more electrical
conductivity than Phosphor-Bronze, but not it's corrosion resistance.
Gold has excellent electrical conductivity, but is not as wear
resistant.

Yes, I think we all understand that. What we didn't know until this
moment, though, is that you had considered silver plating and decided
against it for cost reasons.

Because, you see, we can't read your mind.

You still don't know that. Because it's not true. I decided against
*any* plating of whatever materials I settled on for reasons involving
complexity. Even cost was secondary. But way address it if it had
nothing to do with my original question?

Finding a switch that has about the same ratings as what you need,
taking it apart, and copying it's actions and forces may not be a bad
way to go. You won't be able to duplicate their metallurgy, but you
can't have everything.

Nope. This is a switch that doesn't exist in any form yet and will
incorporate unorthodox connections. (One particular version will allow
switching between a dozen 40 pin connections). The wiping will actually
be in the mechanical action of switching from one connection to the
next.

If you can't replicate _just the forces and actions_ of an existing
switch at the contacts, then you're in a different universe from me, and
no advise that I can give you will help. In fact, no amount of advise
that you get from any of the regulars here will help, because as far as I
know they're all in the same universe as I am, too.

I'm not sure what you meant by "replicate _just the forces and
actions_ of an existing switch at the contacts". Or if you were
referring to general principles or copying exactly. But either way
this has all been addressed in my design and has nothing to do with
the wiping material question.

I set the parameters for the shape, number, and arrangement of
Phosphor-Bronze contacts, as well as the allotted space needed and
supplied by the encasement because it had to be done in order for the
switch to accomplish was is needed.

Perhaps this is why you thought that the help you got on s.e.b was all
from trolls? Getting sound engineering advice from the wrong universe
can do that.

I don't know what this universe stuff is about, but personal attacks
are of a different order. I couldn't tell if there was a genuine
failure to understand my simple question or just immaturity at work.

I asked if Phosphor-Bronze was an acceptable wiping material for
Phosphor-Bronze because I wasn't sure if there would be any problems
with using a different metal as the wiping material even though
contact during wiping is brief.

Here in this universe, how you _connect_ to a switch is largely
independent of how the _switch's contacts come together_, and with what
forces. This applies in particular if your switch is currently just a
connection diagram, and has not been reduced to practice in a way that
involves any means of making the contacts come together, with or without
any forces.

I'm not sure what that meant, or what exactly you are addressing. But
since this is my design, as I mentioned I have control and the option
to change all important variables like "contact thickness, number of
wipes between connections, length of wipes between connections,
pressure of wipes between connections..."

You might try asking this question on sci.electronics.design, since you
don't seem to be getting much info here.

I actually tried a similar question at Sci.Electronics.Basics two or
three years ago, only to have to deal with personal attacks by a group
led by a "John Fields" because I wouldn't give them *detailed* plans of
what I was working on. Specifics that had nothing at all to do with the
question concerning wiping material.

I'd think that lot of the same trolls who hang out at
Sci.Electronics.Basics also frequent Sci.Electronics.Design.

John Fields is pretty astute, and engineers learn early not to answer
general questions with specifics. "How much paint does it take to paint
a door?" should be immediately replied to with "How big is the door, and
what sort of paint?", because any specific answer is only going to be
correct if the questioner and respondent both share all the same
assumptions.

I have no idea how "astute" John is. I only know that like several
others on that group, his maturity level needs work.

And if I asked if it was reasonable to make a door knob out of metal,
then I shouldn't expect to be berated because I didn't include
information on the size of the door or what kind of paint I'd be using
on it.

Darren Harris
Staten Island, New York.

Searcher7 wrote:

Tim Wescott wrote:

There are no "normal" environmental conditions -- only the environmental
conditions that people of limited imagination assume is normal.

So that you will understand what I meant, the switches will not have
to operate in space, under the ocean's surface, immersed in harsh
chemicals or substances, or temperatures below or above what humans
consider comfortable.


Will it be in a vacuum? If not, you have a lot of arcing & surface
oxidation that will degrade the contacts. Real switches use some type
of contact lube to keep oxygen away from the contacts. Also, you never
want any silicon based lube on switch contacts. The phone companies
learned that the hard way.


Yes, I think we all understand that. What we didn't know until this
moment, though, is that you had considered silver plating and decided
against it for cost reasons.

Because, you see, we can't read your mind.

You still don't know that. Because it's not true. I decided against
*any* plating of whatever materials I settled on for reasons involving
complexity. Even cost was secondary. But way address it if it had
nothing to do with my original question?


If you can't replicate _just the forces and actions_ of an existing
switch at the contacts, then you're in a different universe from me, and
no advise that I can give you will help. In fact, no amount of advise
that you get from any of the regulars here will help, because as far as I
know they're all in the same universe as I am, too.

I'm not sure what you meant by "replicate _just the forces and
actions_ of an existing switch at the contacts". Or if you were
referring to general principles or copying exactly. But either way
this has all been addressed in my design and has nothing to do with
the wiping material question.

I set the parameters for the shape, number, and arrangement of
Phosphor-Bronze contacts, as well as the allotted space needed and
supplied by the encasement because it had to be done in order for the
switch to accomplish was is needed.

Perhaps this is why you thought that the help you got on s.e.b was all
from trolls? Getting sound engineering advice from the wrong universe
can do that.

I don't know what this universe stuff is about, but personal attacks
are of a different order. I couldn't tell if there was a genuine
failure to understand my simple question or just immaturity at work.


It means that you have to obey the same laws of physics as everyone
else.


I asked if Phosphor-Bronze was an acceptable wiping material for
Phosphor-Bronze because I wasn't sure if there would be any problems
with using a different metal as the wiping material even though
contact during wiping is brief.


Wiping requires force. It sounds like it won't do you any good.


Here in this universe, how you _connect_ to a switch is largely
independent of how the _switch's contacts come together_, and with what
forces. This applies in particular if your switch is currently just a
connection diagram, and has not been reduced to practice in a way that
involves any means of making the contacts come together, with or without
any forces.

I'm not sure what that meant, or what exactly you are addressing. But
since this is my design, as I mentioned I have control and the option
to change all important variables like "contact thickness, number of
wipes between connections, length of wipes between connections,
pressure of wipes between connections..."


Remember mechanical TV tuners? The cheap ones depended only on
'wiping action' and very thin plating. As soon as the plating wore
through they were unrepairable. Contact resistance is important to
proper switch design, in all cases.


John Fields is pretty astute, and engineers learn early not to answer
general questions with specifics. "How much paint does it take to paint
a door?" should be immediately replied to with "How big is the door, and
what sort of paint?", because any specific answer is only going to be
correct if the questioner and respondent both share all the same
assumptions.

I have no idea how "astute" John is. I only know that like several
others on that group, his maturity level needs work.


You should talk. John has designed and built custom electronics for
decades. OTOH, he doesn't like to waste time on people who ask
questions and ignore the answers.


And if I asked if it was reasonable to make a door knob out of metal,
then I shouldn't expect to be berated because I didn't include
information on the size of the door or what kind of paint I'd be using
on it.


If you asked that on an electronics group you would deserve to be
treated like a troll. You asked a question and gave no information.
Engineers want to know what you really need, not what you think you
want. Your doorknob statement proves that. Even doorknobs aren't 'one
size fits all'.

"Searcher7" wrote
...
Nope. This is a switch that doesn't exist in any form yet and will
incorporate unorthodox connections. (One particular version will
allow
switching between a dozen 40 pin connections). The wiping will
actually be in the mechanical action of switching from one connection
to the next.

Darren Harris
Staten Island, New York.

http://www.technology.niagarac.on.ca...oneSwitch.html
http://www.moog.com/products/slip-rings/

"Searcher7" wrote in message
news:fe1a23c1-9b49-49c9-856c-
On Dec 13, 5:36 pm, Tim Wescott wrote:
There are no "normal" environmental conditions -- only the
environmental
conditions that people of limited imagination assume is normal.

So that you will understand what I meant, the switches will not have
to operate in space, under the ocean's surface, immersed in harsh
chemicals or substances, or temperatures below or above what humans
consider comfortable.

Harsh chemicals include ammonia from cleaners and sulphur from eggs.
Silicones can cause some strange problems when they break down in
electric arcs too.

"Michael A. Terrell" on Fri, 14 Dec 2012
03:47:08 -0500 typed in rec.crafts.metalworking the following:

So that you will understand what I meant, the switches will not have
to operate in space, under the ocean's surface, immersed in harsh
chemicals or substances, or temperatures below or above what humans
consider comfortable.


Will it be in a vacuum? If not, you have a lot of arcing & surface
oxidation that will degrade the contacts. Real switches use some type
of contact lube to keep oxygen away from the contacts. Also, you never
want any silicon based lube on switch contacts. The phone companies
learned that the hard way.

What, other than "don't" was the lesson?
--
pyotr
Go not to the Net for answers, for it will tell you Yes and no. And
you are a bloody fool, only an ignorant cretin would even ask the
question, forty two, 47, the second door, and how many blonde lawyers
does it take to change a lightbulb.

"Michael A. Terrell" on Fri, 14 Dec 2012
03:47:08 -0500 typed in rec.crafts.metalworking the following:

John Fields is pretty astute, and engineers learn early not to answer
general questions with specifics. "How much paint does it take to paint
a door?" should be immediately replied to with "How big is the door, and
what sort of paint?", because any specific answer is only going to be
correct if the questioner and respondent both share all the same
assumptions.

Oh shoot, that's easy. "A cup" - you may have to thin it a bit to
cover the whole door, but a cup will paint it.
For a more precise answer: If you are going to paint just one
side, then half as much as to paint both sides. Conversely, twice as
much to paint both sides as you'd need for one side.
For more precision, you can mark out a scale representation on the
wall of the door, paint it, and the scale up the quantity needed.
Of course, all this presupposes that the inquirer wants to apply
paint to the entire door, and not just put some paint on the door.

It is like determining how long is a piece of string: Hold by both
ends, flip it up in the air, guess how high up the mid-point is, and
then double it.

(Similar as to hear how Frislanders weigh pigs.]


tschus
pyotr
--
pyotr
Go not to the Net for answers, for it will tell you Yes and no. And
you are a bloody fool, only an ignorant cretin would even ask the
question, forty two, 47, the second door, and how many blonde lawyers
does it take to change a lightbulb.

On Fri, 14 Dec 2012 14:22:26 -0800, pyotr filipivich wrote:

"Michael A. Terrell" on Fri, 14 Dec 2012
03:47:08 -0500 typed in rec.crafts.metalworking the following:

John Fields is pretty astute, and engineers learn early not to
answer general questions with specifics. "How much paint does it
take to paint a door?" should be immediately replied to with "How
big is the door, and what sort of paint?", because any specific
answer is only going to be correct if the questioner and respondent
both share all the same assumptions.

Oh shoot, that's easy. "A cup" - you may have to thin it a bit to
cover the whole door, but a cup will paint it.

Alternately, "a bucket". Just be sure to size the bucket differently if
it's the front door of a doll house, or the door to the hanger where you
keep your 747.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

"Searcher7" wrote in message
...
On Dec 12, 6:17 pm, "Jim Wilkins" wrote:

Or no one actually knows. The question is like "How long will this
bearing last" without giving the load, speed, misalignment,
temperature, contamination, etc.

-How do you figure?

Long experience building prototypes, switching signals from microVolts
to 40KV, from picoAmps to 1000 Amps, both AC (locomotives) and DC (48V
telephone batteries), and a few RF diode switches. Much of it was
custom test equipment that didn't permit sloppy design.

I trained for but never practiced teletype repair. They use a voltage
high enough to blast through minor contact oxidation:
http://ed-thelen.org/Teletype-28/index.html
http://www.navy-radio.com/manuals-ttycorp.htm

Whatever you are thinking of, if you haven't seen it done you either
didn't look hard enough or it had been tried and discarded by 1930, or
disappeared into crypto machines:
http://en.wikipedia.org/wiki/Enigma_rotor_details

These switch hundreds of contacts manually:
http://www.digikey.com/product-highl...dl-series/1174
If your alignment tolerances are good enough they can be used on the
inaccessible rear of plug-in modules.

jsw

Tim Wescott on Fri, 14 Dec 2012 17:14:41 -0600
typed in rec.crafts.metalworking the following:
On Fri, 14 Dec 2012 14:22:26 -0800, pyotr filipivich wrote:

"Michael A. Terrell" on Fri, 14 Dec 2012
03:47:08 -0500 typed in rec.crafts.metalworking the following:

John Fields is pretty astute, and engineers learn early not to
answer general questions with specifics. "How much paint does it
take to paint a door?" should be immediately replied to with "How
big is the door, and what sort of paint?", because any specific
answer is only going to be correct if the questioner and respondent
both share all the same assumptions.

Oh shoot, that's easy. "A cup" - you may have to thin it a bit to
cover the whole door, but a cup will paint it.

Alternately, "a bucket". Just be sure to size the bucket differently if
it's the front door of a doll house, or the door to the hanger where you
keep your 747.

True that.
--
pyotr
Go not to the Net for answers, for it will tell you Yes and no. And
you are a bloody fool, only an ignorant cretin would even ask the
question, forty two, 47, the second door, and how many blonde lawyers
does it take to change a lightbulb.

I know that I am jumping in late, but unless you tell us what voltages and
currents you will be connecting, you won't really get any useful solutions.
Do you know what a "dry circuit" is?

Pete Stanaitis
----------------


On Tue, 11 Dec 2012 22:06:24 -0800, Searcher7 wrote:
I'm working on a project that is a mechanical switch of sorts, and it
entails running electrical signals through Phosphor-Bronze contacts.

On Dec 15, 11:12*am, "Pete S" wrote:
I know that I am jumping in late, but unless you tell us what voltages and
currents you will be connecting, you won't really get any useful solutions.
Do you know what a "dry circuit" is?

I've concluded that I wouldn't get any useful solutions here anyway
since it was implied that I posted this in the wrong group.

But since you asked, when the circuits are closed and power applied
the voltages can be +3.3, +5, +7, +9, +12, and -5v, not to mention
data lines.

However I have no idea why it would make a difference, because as I
mentioned there would be no current during "make" or "break" of the
connections.

And yes, I know what a dry circuit is. Why do you ask?

Thanks.

Darren Harris
Staten Island, New York.

In article ,
says...

Tim Wescott on Fri, 14 Dec 2012 17:14:41 -0600
typed in rec.crafts.metalworking the following:
On Fri, 14 Dec 2012 14:22:26 -0800, pyotr filipivich wrote:

"Michael A. Terrell" on Fri, 14 Dec 2012
03:47:08 -0500 typed in rec.crafts.metalworking the following:

John Fields is pretty astute, and engineers learn early not to
answer general questions with specifics. "How much paint does it
take to paint a door?" should be immediately replied to with "How
big is the door, and what sort of paint?", because any specific
answer is only going to be correct if the questioner and respondent
both share all the same assumptions.

Oh shoot, that's easy. "A cup" - you may have to thin it a bit to
cover the whole door, but a cup will paint it.

Alternately, "a bucket". Just be sure to size the bucket differently if
it's the front door of a doll house, or the door to the hanger where you
keep your 747.

True that.

Then there's the VAB, where each door is roughly an acre in area.

--
pyotr
Go not to the Net for answers, for it will tell you Yes and no. And
you are a bloody fool, only an ignorant cretin would even ask the
question, forty two, 47, the second door, and how many blonde lawyers
does it take to change a lightbulb.

"Searcher7" wrote
-However I have no idea why it would make a difference, because as I
-mentioned there would be no current during "make" or "break" of the
-connections.
-Darren Harris

Even after we told you the reason.

BTW, if the ground connection fails or is made after the others, the
+3.3 supply line (for example) could disastrously become the return
for the +12V.

http://en.wikipedia.org/wiki/Hot_swapping

On Dec 11, 11:06*pm, Searcher7 wrote:
I'm working on a project that is a mechanical switch of sorts, and it
entails running electrical signals through Phosphor-Bronze contacts.

Now since *all* alloys will oxidize to an extent, I was wondering if I
were to wipe the phosphor-Bronze contacts with the same
material(Phosphor-Bronze), would that be serve to keep the alloy's
surface clean? (The wiping action will be part of the mechanics of the
switch).

Thanks.

Darren Harris
Staten Island, New York.

That's the approach Ford took with their relays they use for low-
voltage and current switching in their cars. Took one apart and it had
a pretty elegant method for wiping the contacts. Relay lived in the
rear of the van and was exposed to salt spray vapor a lot of the
time. Not sure of the material, the contacts themselves consisted of
wire welded onto the springs, when in contact, they made an "X" with
each other rather than being parallel and wiped each other the length
of the contacts. It all worked until the non-conformal-coated circuit
board got eaten up.

Stan

In article
,
Stanley Schaefer wrote:

On Dec 11, 11:06*pm, Searcher7 wrote:
I'm working on a project that is a mechanical switch of sorts, and it
entails running electrical signals through Phosphor-Bronze contacts.

Now since *all* alloys will oxidize to an extent, I was wondering if I
were to wipe the phosphor-Bronze contacts with the same
material(Phosphor-Bronze), would that be serve to keep the alloy's
surface clean? (The wiping action will be part of the mechanics of the
switch).

Thanks.

Darren Harris
Staten Island, New York.

That's the approach Ford took with their relays they use for low-
voltage and current switching in their cars. Took one apart and it had
a pretty elegant method for wiping the contacts. Relay lived in the
rear of the van and was exposed to salt spray vapor a lot of the
time. Not sure of the material, the contacts themselves consisted of
wire welded onto the springs, when in contact, they made an "X" with
each other rather than being parallel and wiped each other the length
of the contacts. It all worked until the non-conformal-coated circuit
board got eaten up.

This crossed-bars design was developed by Western Electric for the
relays in the telephone switching systems of the 1950s or so, for
exactly the same reason - making the relays self-cleaning in the
presence of (slightly) corrosive environments. These relays were
expected to last 40 years.

Joe Gwinn

Joseph Gwinn wrote:

This crossed-bars design was developed by Western Electric for the
relays in the telephone switching systems of the 1950s or so, for
exactly the same reason - making the relays self-cleaning in the
presence of (slightly) corrosive environments. These relays were
expected to last 40 years.


At very low current.