I have an optically-couple "supervisory port" on my
devices. A design requirement is that the outer surfaces
of the devices must be "wipe clean" -- no ridges or
grooves.
I mechanically attach the mating "cable" to the port
magnetically (an idea I stole from designing electric
power meters -- but, they aren't "wipe clean"!)
As I can't rely on any significant mechanical structures
to help maintain the attachment's position, that must
be guaranteed solely by the strength of the magnetic
bond.
I have a 1/4" dia glass "jewel" that is just barely convex
to protect the optical port and support light passage.
The slight bump helps locate the port as well as some small
assistance in keeping the mated "cable" positioned properly.
In no case can the needs of the port exceed a concentric
diameter of 1/2". I plan for the magnet to only be present
in the mating cable so its adhesion will be determined by
the metallic ring surrounding the jewel.
I figure I need to specify a magnet strong enough to
"support" (against the force of gravity exerted on the
mass of the cable) the cable in a horizontal position
(i.e., "mated to the ceiling"). And, to support the
cantilevered weight of the cable when mounted
vertically.
I may opt to implement the "cable" as a wireless dongle
if the weight of the cable assembly starts to compromise that
magnetic adherence.
I guess I also need to consider the magnetic force exerted
through the friction between the mating surfaces when
mounted vertically (so the cable doesn't "slide down the wall")
Anything else I should consider? I realize that the cable end
now will have a tendency to want to grab onto metallic objects
so have to factor that into my dongle vs. cable decision
(it's a lot easier to control the position of a dongle in
space than the end of a possibly *dangling* cable!)
I suspect the adhering "metal" piece has to be on the skin
of the device as the magnetic field falls off quickly with
distance -- diluting the ability of the cable to remain
EXACTLY where desired. A "decal" over the surface likely
would be tolerable...
Something like this:
http://www.poppyrecords.co.uk/other/Connector.gif
I suspect the adhering "metal" piece has to be on the skin
of the device as the magnetic field falls off quickly with
distance -- diluting the ability of the cable to remain
EXACTLY where desired. A "decal" over the surface likely
would be tolerable...
Would a rounded bump on the device be acceptable? A matching hollow in
the cable end could then locate over it.
Something like this:
http://www.poppyrecords.co.uk/other/Connector.gif
I have an optically-couple "supervisory port" on my
devices. A design requirement is that the outer surfaces
of the devices must be "wipe clean" -- no ridges or
grooves.
I mechanically attach the mating "cable" to the port
magnetically (an idea I stole from designing electric
power meters -- but, they aren't "wipe clean"!)
As I can't rely on any significant mechanical structures
to help maintain the attachment's position, that must
be guaranteed solely by the strength of the magnetic
bond.
I have a 1/4" dia glass "jewel" that is just barely convex
to protect the optical port and support light passage.
The slight bump helps locate the port as well as some small
assistance in keeping the mated "cable" positioned properly.
In no case can the needs of the port exceed a concentric
diameter of 1/2". I plan for the magnet to only be present
in the mating cable so its adhesion will be determined by
the metallic ring surrounding the jewel.
I figure I need to specify a magnet strong enough to
"support" (against the force of gravity exerted on the
mass of the cable) the cable in a horizontal position
(i.e., "mated to the ceiling"). And, to support the
cantilevered weight of the cable when mounted
vertically.
I may opt to implement the "cable" as a wireless dongle
if the weight of the cable assembly starts to compromise that
magnetic adherence.
I guess I also need to consider the magnetic force exerted
through the friction between the mating surfaces when
mounted vertically (so the cable doesn't "slide down the wall")
Anything else I should consider? I realize that the cable end
now will have a tendency to want to grab onto metallic objects
so have to factor that into my dongle vs. cable decision
(it's a lot easier to control the position of a dongle in
space than the end of a possibly *dangling* cable!)
I suspect the adhering "metal" piece has to be on the skin
of the device as the magnetic field falls off quickly with
distance -- diluting the ability of the cable to remain
EXACTLY where desired. A "decal" over the surface likely
would be tolerable...
On Fri, 20 Sep 2024 00:11:05 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:
I have an optically-couple "supervisory port" on my
devices. A design requirement is that the outer surfaces
of the devices must be "wipe clean" -- no ridges or
grooves.
I mechanically attach the mating "cable" to the port
magnetically (an idea I stole from designing electric
power meters -- but, they aren't "wipe clean"!)
As I can't rely on any significant mechanical structures
to help maintain the attachment's position, that must
be guaranteed solely by the strength of the magnetic
bond.
This approach will attract and hold magnetic debris, like rust and
iron filings. Is that a problem, or is wiping enough? If the magnets
are strong enough, debris removal may be difficult to do in practice.
On 9/20/2024 9:38 AM, Joe Gwinn wrote:
On Fri, 20 Sep 2024 00:11:05 -0700, Don Y
<blockedofcourse@foo.invalid> wrote:
I have an optically-couple "supervisory port" on my
devices. A design requirement is that the outer surfaces
of the devices must be "wipe clean" -- no ridges or
grooves.
I mechanically attach the mating "cable" to the port
magnetically (an idea I stole from designing electric
power meters -- but, they aren't "wipe clean"!)
As I can't rely on any significant mechanical structures
to help maintain the attachment's position, that must
be guaranteed solely by the strength of the magnetic
bond.
This approach will attract and hold magnetic debris, like rust and
iron filings. Is that a problem, or is wiping enough? If the magnets
are strong enough, debris removal may be difficult to do in practice.
Are you expecting the non-magnet surface to assume a
magnetic state, over time?
The actual magnet will be on the cable end so the
"wipe clean" surface will not inherently be magnetized.
And, the cable end should be easier to manipulate, "scrub",
etc (even REPLACE) as it is "portable".
The actual magnet will be on the cable end so the
"wipe clean" surface will not inherently be magnetized.
And, the cable end should be easier to manipulate, "scrub",
etc (even REPLACE) as it is "portable".
That'll work so long as the magnet isn't too strong.
A good way to clean stuff off a magnet pole is adhesive tape.
I'd take a rare earth magnet and roll it around on the floor of the
garage, and see what you catch.
A good way to clean stuff off a magnet pole is adhesive tape.
Joe Gwinn <joegwinn@comcast.net> wrote:
[...]
A good way to clean stuff off a magnet pole is adhesive tape.
If the surface is too convoluted for the tape to work, there is a
product in the UK called "Copydex", which is sold as a carpet glue but
can be used to remove debris from a magnet. It is an emulsified latex solution which doesn't stick well to metal surfaces and can be peeled
off easily.
You apply the Copydex thickly over the surface to be cleaned - and then
wait. Eventually the milky white liquid dries to complete transparency,
then it is strong enough to be peeled off, bringing the debris with it.
On 9/21/2024 12:48 AM, Liz Tuddenham wrote:
Joe Gwinn <joegwinn@comcast.net> wrote:
[...]
A good way to clean stuff off a magnet pole is adhesive tape.
If the surface is too convoluted for the tape to work, there is a
product in the UK called "Copydex", which is sold as a carpet glue but
can be used to remove debris from a magnet. It is an emulsified latex solution which doesn't stick well to metal surfaces and can be peeled
off easily.
You apply the Copydex thickly over the surface to be cleaned - and then wait. Eventually the milky white liquid dries to complete transparency, then it is strong enough to be peeled off, bringing the debris with it.
I would imagine any of the "silicone caulks" would work
equally well.
The downside with any of these is that there is a
"drying time". I don't imagine the folks using
this bit of kit would sit around waiting before
reusing (or retiring) it. <frown> Imagine having
to similarly clean a 'scope probe between uses...
I would imagine any of the "silicone caulks" would work
equally well.
It needs to peel off easily. The silicone caulk I have used has always
stuck very firmly to metal.
The downside with any of these is that there is a
"drying time". I don't imagine the folks using
this bit of kit would sit around waiting before
reusing (or retiring) it. <frown> Imagine having
to similarly clean a 'scope probe between uses...
Yes, this is very much a specialist tool for getting metal debris out of magnet gaps in moving coil meter movements or disc cutterheads, where
time is not a major factor.
Joe Gwinn <joegwinn@comcast.net> wrote:
[...]
A good way to clean stuff off a magnet pole is adhesive tape.
If the surface is too convoluted for the tape to work, there is a
product in the UK called "Copydex", which is sold as a carpet glue but
can be used to remove debris from a magnet. It is an emulsified latex >solution which doesn't stick well to metal surfaces and can be peeled
off easily.
You apply the Copydex thickly over the surface to be cleaned - and then
wait. Eventually the milky white liquid dries to complete transparency,
then it is strong enough to be peeled off, bringing the debris with it.
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