Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default Anyone with experience with this sensor?

On Sat, 08 Mar 2008 17:55:03 GMT, Mark F wrote:

Tim Wescott wrote:
http://www.murata.com/catalog/r50/r50e15_l0595.pdf

I want to use this in an application where I have this on a PC board,
engaging a shaft. My problem is one of tolerancing: I'd like to have a
tolerance stack-up that just lets me just assemble the whole unit and
have it work, without adjusting and without the shaft binding up on the
pot. But the part doesn't come with any mechanical specifications for
the radial tolerance of the shaft, nor does it come with any guidelines
for using the pot as a bearing (so I assume that's a big no-no).

I got samples and looked at one under a microscope -- it appears that the
rotor can move about 0.005" in any direction before it touches the case.
Using "don't touch" as a guideline, I end up with tolerances that drive
my mechanical assembly costs through the roof. I can't imagine that's
the intended way to use this -- it's for consumer products, so there's
got to be a way to make it happen.

So, how do people make these things work as rotary position sensors? Is
there a mechanical specifications document buried on the MuRata web site
that I'm missing? Is there a cost-effective shaft coupler to be had
that'll couple the angle without coupling off-axis motion?

Comments, advise, brickbats -- all are appreciated.


You need not use assy methods suitable for automated mass production
when making only 50 pcs.

If you must have the pot on the PC board, then mount the board on
standoffs and screws thru oversized holes. Run the shaft thru the pot
hole, tighten mounting screws so everything is lined up. The
precision is in the assembly process, not in the manufacture.

I'd run leads to the pot, assemble the pot, shaft and frame, stick
the pot to the side of the frame with epoxy. The load on the epoxied
joint is negligible and the pot will keep itself properly located
while the epoxy cures. This task could be done by anyone who could
build a model airplane.

I'll bet it would less time (with less skilled help) to do 50 of
these this way than it might take to make detailed dimensioned
toleranced prints and negotiate with fab vendors.



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Default Anyone with experience with this sensor?

Don Foreman wrote:


You need not use assy methods suitable for automated mass production
when making only 50 pcs.

If you must have the pot on the PC board, then mount the board on
standoffs and screws thru oversized holes. Run the shaft thru the pot
hole, tighten mounting screws so everything is lined up. The
precision is in the assembly process, not in the manufacture.

I'd run leads to the pot, assemble the pot, shaft and frame, stick
the pot to the side of the frame with epoxy. The load on the epoxied
joint is negligible and the pot will keep itself properly located
while the epoxy cures. This task could be done by anyone who could
build a model airplane.

I'll bet it would less time (with less skilled help) to do 50 of
these this way than it might take to make detailed dimensioned
toleranced prints and negotiate with fab vendors.




FWIW, I'd take Don's suggestions to the bank.


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Default Anyone with experience with this sensor?

On Sat, 08 Mar 2008 17:03:11 -0600, Don Foreman
wrote:

On Sat, 08 Mar 2008 17:55:03 GMT, Mark F wrote:

Tim Wescott wrote:
http://www.murata.com/catalog/r50/r50e15_l0595.pdf

I want to use this in an application where I have this on a PC board,
engaging a shaft. My problem is one of tolerancing: I'd like to have a
tolerance stack-up that just lets me just assemble the whole unit and
have it work, without adjusting and without the shaft binding up on the
pot. But the part doesn't come with any mechanical specifications for
the radial tolerance of the shaft, nor does it come with any guidelines
for using the pot as a bearing (so I assume that's a big no-no).

I got samples and looked at one under a microscope -- it appears that the
rotor can move about 0.005" in any direction before it touches the case.
Using "don't touch" as a guideline, I end up with tolerances that drive
my mechanical assembly costs through the roof. I can't imagine that's
the intended way to use this -- it's for consumer products, so there's
got to be a way to make it happen.

So, how do people make these things work as rotary position sensors? Is
there a mechanical specifications document buried on the MuRata web site
that I'm missing? Is there a cost-effective shaft coupler to be had
that'll couple the angle without coupling off-axis motion?

Comments, advise, brickbats -- all are appreciated.


You need not use assy methods suitable for automated mass production
when making only 50 pcs.

If you must have the pot on the PC board, then mount the board on
standoffs and screws thru oversized holes. Run the shaft thru the pot
hole, tighten mounting screws so everything is lined up. The
precision is in the assembly process, not in the manufacture.

I'd run leads to the pot, assemble the pot, shaft and frame, stick
the pot to the side of the frame with epoxy. The load on the epoxied
joint is negligible and the pot will keep itself properly located
while the epoxy cures. This task could be done by anyone who could
build a model airplane.

I'll bet it would less time (with less skilled help) to do 50 of
these this way than it might take to make detailed dimensioned
toleranced prints and negotiate with fab vendors.


I concur.

Gunner
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