(Ben Nguyen) writes:
Im looking for ideas to do for a school project and came up with
a digital micrometer.

Does anyone know whats involved? I want something challenging, but not
something impossible!

You need a precision screw and a precision nut, probably adjustable to
reduce or eliminate play. You need some sort of rotary encoder to
measure rotation of the shaft to high angular precision, and a computer
of some sort to read the output of the encoder, keep track of position,
and convert that to a displayed measurement. For a practical measuring
device, you also need a ratchet or friction clutch device, like on a
real micrometer, to standardize the measuring force.

The easiest place to obtain the precision screw and nut and the
ratchet/friction device is an old mechanical micrometer, if that's not
considered "cheating". Then you need a rotary encoder, which you might
build yourself (a challenge), or you might find one in the carriage motor of
an old inkjet or dot-matrix printer, or an old tape drive, or even just
buying a surplus encoder.

Then you need to couple the encoder to the spindle (screw). This is
easiest if the encoder has a hollow shaft. Keep in mind that the screw
moves along its length as well as rotating, while the encoder only
wants to rotate, so you'll need a precision sliding coupling between
the two. Alternately, you could use gears to couple the spindle to the
encoder.

Then you need software to take the two sine or square waves coming out
of the encoder, decode transitions into distance and direction info,
keep a running count of where the spindle is, and display the position
in inches or mm (or both). You should also allow for setting zero at an
arbitrary position. The simplest way to write this software might be to
program a PC, using the parallel port for input and the frame buffer for
display. A more professional way is to use a microcontroller like a PIC
or AVR with a LCD or LED display.

What level of school is this for? How long do you have?

Dave

Build A Micrometer

I know it won't be as modern as an electronic mike, but a mechanical mike with
a 40 tpi screw or even 20 tpi would teach them a lot about how things are
really measured. Plus it would be a lot easier to build and get working.

Beginning with v 130 # 3244, March '64 Martin Cleeve has a series in ME on
building a set of micrometers. Won't help with the digital part, but there's
bound to be some good tidbits in there.


"Ben Nguyen" wrote in message
m...
Im looking for ideas to do for a school project and came up with
a digital micrometer.

Does anyone know whats involved? I want something challenging, but not
something impossible!

Thanks!

MichaelWard

Beginning with v 130 # 3244, March '64 Martin Cleeve has a series in ME on
building a set of micrometers. Won't help with the digital part, but there's
bound to be some good tidbits in there.

Michael, at the risk of appearing to be uninformed, would you mind telling us
what the letters "ME" stand for?

Michael Mandaville

"M" == MichaelMandavil writes:

Michael Ward
M Beginning with v 130 # 3244, March '64 Martin Cleeve has a series in ME on
building a set of micrometers. Won't help with the digital part, but there's
bound to be some good tidbits in there.

M Michael, at the risk of appearing to be uninformed, would you mind telling us
M what the letters "ME" stand for?

M Michael Mandaville

Probably Model Engineer

--
This page intentionally left blank

sorry Michael, assumptive on my part. Model Engineer magazine

"MichaelMandavil" wrote in message
...
MichaelWard

Beginning with v 130 # 3244, March '64 Martin Cleeve has a series in ME on
building a set of micrometers. Won't help with the digital part, but
there's
bound to be some good tidbits in there.

Michael, at the risk of appearing to be uninformed, would you mind telling
us
what the letters "ME" stand for?

Michael Mandaville

Thanks for the great ideas! Incidentally, this is for my senior
project in engineering technology at ucsd. I graduate
in June 04, so thats the timeframe Im working with.

I was looking at my computer mouse, and that seems to do something similar.
What if I use the rolling mechanism that the ball turns and its circuit
board to make a digital caliper?

Even better if I could replace the circuit board completely with something
homebrew!

Thanks!

Ben Nguyen wrote:

Thanks for the great ideas! Incidentally, this is for my senior
project in engineering technology at ucsd. I graduate
in June 04, so thats the timeframe Im working with.

I was looking at my computer mouse, and that seems to do something similar.
What if I use the rolling mechanism that the ball turns and its circuit
board to make a digital caliper?

Even better if I could replace the circuit board completely with something
homebrew!

Thanks!


Could you make a digital caliper with a digital "voice" that says the
measurement?

Fred

Couple of ideas from outside the box:
1. Put a GPS reciever in the anvil and another one in the screw. Feed the
signals to a PC to compute the diference.
2. Use an ultrasonic transducer coupled to something like a Time Domain
Reflectometer (TDR). Now you can read the thickness without having access to
the other side. Or maybe you can read the thickness of an anodize treatment.
3. Use a scale similar to what is inside a digital caliper and have the
traveling part of the micrometer something like a lever-actuated tailstock
on a lathe.

I also like the "talking micrometer" already mentioned. How about a
micrometer that reads out in braile?

Bruce


"Ben Nguyen" wrote in message
m...
Im looking for ideas to do for a school project and came up with
a digital micrometer.

Does anyone know whats involved? I want something challenging, but not
something impossible!

Thanks!

(Ben Nguyen) wrote in message om...
Thanks for the great ideas! Incidentally, this is for my senior
project in engineering technology at ucsd. I graduate
in June 04, so thats the timeframe Im working with.

I was looking at my computer mouse, and that seems to do something similar.
What if I use the rolling mechanism that the ball turns and its circuit
board to make a digital caliper?

Even better if I could replace the circuit board completely with something
homebrew!

Thanks!

Another thing you might want to do is start building a pile of
subscriptions to the freebie trade magazines, like EDN, Machine
Design, etc. Most are available online now, at least in part. One of
the big publishers is Penton. These are great resources for thing like
new products, technology surveys, etc., and mostly the ads. These are
fairly narrowly targeted (they are free, after all, and the publishers
make their nut on targeted ads), but that is actually an advantage.
Subscribe to the ones that match your field most closely. (I get
several of the welding and fab ones, EDN, machine Design, and a few
others)

e

Use an old mouse for the encoder.

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

"Dave Martindale" wrote in message
...
(Ben Nguyen) writes:
Im looking for ideas to do for a school project and came up with
a digital micrometer.

Does anyone know whats involved? I want something challenging, but not
something impossible!

You need a precision screw and a precision nut, probably adjustable to
reduce or eliminate play. You need some sort of rotary encoder to
measure rotation of the shaft to high angular precision, and a computer
of some sort to read the output of the encoder, keep track of position,
and convert that to a displayed measurement. For a practical measuring
device, you also need a ratchet or friction clutch device, like on a
real micrometer, to standardize the measuring force.

The easiest place to obtain the precision screw and nut and the
ratchet/friction device is an old mechanical micrometer, if that's not
considered "cheating". Then you need a rotary encoder, which you might
build yourself (a challenge), or you might find one in the carriage motor
of
an old inkjet or dot-matrix printer, or an old tape drive, or even just
buying a surplus encoder.

Then you need to couple the encoder to the spindle (screw). This is
easiest if the encoder has a hollow shaft. Keep in mind that the screw
moves along its length as well as rotating, while the encoder only
wants to rotate, so you'll need a precision sliding coupling between
the two. Alternately, you could use gears to couple the spindle to the
encoder.

Then you need software to take the two sine or square waves coming out
of the encoder, decode transitions into distance and direction info,
keep a running count of where the spindle is, and display the position
in inches or mm (or both). You should also allow for setting zero at an
arbitrary position. The simplest way to write this software might be to
program a PC, using the parallel port for input and the frame buffer for
display. A more professional way is to use a microcontroller like a PIC
or AVR with a LCD or LED display.

What level of school is this for? How long do you have?

Dave

On 16 Sep 2003 11:54:21 -0700, (Ben Nguyen) wrote:

Thanks for the great ideas! Incidentally, this is for my senior
project in engineering technology at ucsd. I graduate
in June 04, so thats the timeframe Im working with.

I was looking at my computer mouse, and that seems to do something similar.
What if I use the rolling mechanism that the ball turns and its circuit
board to make a digital caliper?

Even better if I could replace the circuit board completely with something
homebrew!

Thanks!

Ben:

You might take a look at
http://www.capsense.com/capsense-wp.pdf

It will give you several ideas on capacitive sensors for measuring
displacement if you decide to build digital calipers.

One design mentioned can yield 0.0002 accuracy over 6" with standard
PCB fabrication of the sensor.


Jack

Bruce C. wrote:
Couple of ideas from outside the box:
1. Put a GPS reciever in the anvil and another one in the screw. Feed the
signals to a PC to compute the diference.

Uh, not the easiest approach. Although you could do differential
decoding to find the distance between the two points accurately despite
GPS not giving you *absolute* positions very accurately, it still
wouldn't be *very* accurate, and it'd be bloody complex!

2. Use an ultrasonic transducer coupled to something like a Time Domain
Reflectometer (TDR). Now you can read the thickness without having access to
the other side. Or maybe you can read the thickness of an anodize treatment.

Might be interesting to develop a micro-radar or micro-sonar where the
sensor head transmits pulses and then you use an oscilloscope to view
the reflected signal as it comes in - the further down it's looking the
longer the echo took so the further along the scale the point has moved.
Once it was calibrated, you could put it on a surface and see things
like the actual far surface, but also things like the layer of solder
within a braze joint, etc.

I also like the "talking micrometer" already mentioned. How about a
micrometer that reads out in braile?

Erm... yes, but how many blind machinists are there? It doesn't sound
like an easy profession for the partially sighted to me. Having to put
your fingers into the lathe to see where the tool was doesn't sound very
safe. Although you could doodle on things with an automatic centre punch
- braille graffiti!


Bruce


ABS

"Ben Nguyen" wrote in message
m...
Im looking for ideas to do for a school project and came up with
a digital micrometer.

Does anyone know whats involved? I want something challenging, but not
something impossible!

Hmm... for something hacked, you could take a bit of threaded rod and
tap a hole in a piece of stock for it, then pull the encoder circuitry
out of a mouse (as I mentioned above) and setup the computer software
to read the X or Y axis of the mouse and scale it to revolutions.
Then based on TPI of the thread, you've got your measurement. Give or
take 1/16".

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

I was not aware that braille micrometers existed. I just wanted to
contribute a few "idea seeds". None of them would be easy and maybe not
doable with current technology - but one of the input criteria was a
challenge. And if you are going to go to all that trouble, then stretch and
do something new and maybe useful to the world. I think the TDR idea might
be especially useful for some specialized tasks (hell, they might already
exist too).

As a side note I wasn't suggesting that anyone put themselves in a dangerous
situation. I didn't even consider blind machinists - machinists are not the
only ones that use micrometers.

Bruce

"Mike" * wrote in message
...
Blind machinists are out there. Although I have never seen or heard a
talking micrometer, there are braille micrometers available. This I
know because I am blind. Although I do not currently do any machine
work, I want to. I rebuild car engines and just now have started
looking in to model engines.

Mike




On Wed, 17 Sep 2003 16:25:01 +0100, Alaric B Snell
wrote:

Bruce C. wrote:
Couple of ideas from outside the box:
1. Put a GPS reciever in the anvil and another one in the screw. Feed
the
signals to a PC to compute the diference.

Uh, not the easiest approach. Although you could do differential
decoding to find the distance between the two points accurately despite
GPS not giving you *absolute* positions very accurately, it still
wouldn't be *very* accurate, and it'd be bloody complex!

2. Use an ultrasonic transducer coupled to something like a Time Domain
Reflectometer (TDR). Now you can read the thickness without having
access to
the other side. Or maybe you can read the thickness of an anodize
treatment.

Might be interesting to develop a micro-radar or micro-sonar where the
sensor head transmits pulses and then you use an oscilloscope to view
the reflected signal as it comes in - the further down it's looking the
longer the echo took so the further along the scale the point has moved.
Once it was calibrated, you could put it on a surface and see things
like the actual far surface, but also things like the layer of solder
within a braze joint, etc.

I also like the "talking micrometer" already mentioned. How about a
micrometer that reads out in braile?

Erm... yes, but how many blind machinists are there? It doesn't sound
like an easy profession for the partially sighted to me. Having to put
your fingers into the lathe to see where the tool was doesn't sound very
safe. Although you could doodle on things with an automatic centre punch
- braille graffiti!


Bruce


ABS