Measuring Milling Machine Spindle RPM

Archiver

Hey there,

I'd like to measure the spindle speed of a milling machine and
display on an LCD. The motor specifications: 2.0 KW (2.0Hp), 230V,
50/60Hz Spindle Speed 100 - 7500rpm (Right/Left). I am not interested
in the direction of rotation. I don't want to use any optical sensors
on or near the spindle due to the presence of fluids, chips, etc.

I'm wondering if anybody has used a hall effect sensor to do this
mounted on the side of the motor. The milling machine is German-made,
so I imagine there is some shielding around the motor for EMI
reduction. Not sure if this would cause problems for hall effect
sensors, or even if they are the right solution for the job.

Any tips to save me some time or steer me in the right direction are
truly appreciated.

Thanks,

Ken Gracey
Parallax, Inc.

Archiver

> I'd like to measure the spindle speed of a milling machine and
> display on an LCD. The motor specifications: 2.0 KW (2.0Hp), 230V,
> 50/60Hz Spindle Speed 100 - 7500rpm (Right/Left). I am not interested
> in the direction of rotation. I don't want to use any optical sensors
> on or near the spindle due to the presence of fluids, chips, etc.

You could bounce a laser pointer (LED) off of any part of the rotating shaft
or chuck and use a photo detector to count the pulses.

> I'm wondering if anybody has used a hall effect sensor to do this
> mounted on the side of the motor. The milling machine is German-made,
> so I imagine there is some shielding around the motor for EMI
> reduction. Not sure if this would cause problems for hall effect
> sensors, or even if they are the right solution for the job.

Actually, if there is any stray EMI/EMF coming out of the motor then that
will most likely be periodic enough to base a count on. Bias a transistor or
the FET close to it's trigger point and let the noise push it over the edge.
Use a smitz trigger to clean it up and then count that.

--
Enjoy,
George Warner,
Schizophrenic Optimization Scientists
Apple Developer Technical Support (DTS)

Archiver

--- In basicstamps@yahoogroups.com, "Ken Gracey" <kgracey@p...> wrote:
> Hey there,
>
> I'd like to measure the spindle speed of a milling machine and
> display on an LCD. The motor specifications: 2.0 KW (2.0Hp), 230V,
> 50/60Hz Spindle Speed 100 - 7500rpm (Right/Left). I am not
interested
> in the direction of rotation. I don't want to use any optical
sensors
> on or near the spindle due to the presence of fluids, chips, etc.
>
> I'm wondering if anybody has used a hall effect sensor to do this
> mounted on the side of the motor. The milling machine is German-
made,
> so I imagine there is some shielding around the motor for EMI
> reduction. Not sure if this would cause problems for hall effect
> sensors, or even if they are the right solution for the job.
>
> Any tips to save me some time or steer me in the right direction
are
> truly appreciated.
>
> Thanks,
>
> Ken Gracey
> Parallax, Inc.



Ken,

Overall, if you're doing an industrial type project, use an
inductive proximity sensor on some rotating part of the machine.
We've done this successfully on everything from diesel gen-sets to
conveyor systems.

Depending on what else you've got the stamp doing, you will have
to pay attention to the fastest pulse speed to be expected. For
instance if your prox can see two set-screws on the motor shaft
pulley, you're getting 15000 pulses per min or about 250 Hz which is
pretty fast if the stamp program has much other overhead.PULSIN will
measure it fairly well ( about 4 msec). At the lowest speed, 100 rpm,
2 pulses per rev will give 200 pulse/min or 3.3 Hz. PULSIN should
give a reading of about 300 msec but it overflows at 131 msec.

The other method is to watch gearteeth go by or tie into an
existing tach or encoder signal. This may require some external
circuitry in the form of a high-speed counter which the stamp resets
and samples periodically. We use this technique in lumber tally
systems to measure the width of boards at 1 board per second.

Hope this gives you some options.

Tom Sisk

Archiver

Hi Ken,
I have a couple of questions that may help develop some ideas.

Is the motor 1 phase or 3 phase?
Speed controller different for each.
Does the spindle speed always equal the motor speed?
ie..is there a belt or gear drive between the motor and spindle?
How is the variable speed accomplished?
If a variable frequency drive, the speed could be derived from the
controller AC output. Reduce the voltage to CMOS or TTL levels
and divide the frequency down to something the STAMP can handle
and apply a corresponding factor in the code to get RPM.

Another reply suggested using a dedicated sensor which is no doubt
the most straight forward approach. I have my doubts about being able to
use a hall effect sensor to get the rpm from AC motor EMI.

Dennis

In a message dated 6/1/04 11:46:10 AM Central Daylight Time,
basicstamps@yahoogroups.com writes:
> Date: Tue, 01 Jun 2004 03:33:15 -0000
> From: "Ken Gracey" <kgracey@p...>
> Subject: Measuring Milling Machine Spindle RPM
>
> Hey there,
>
> I'd like to measure the spindle speed of a milling machine and
> display on an LCD. The motor specifications: 2.0 KW (2.0Hp), 230V,
> 50/60Hz Spindle Speed 100 - 7500rpm (Right/Left). I am not interested
> in the direction of rotation. I don't want to use any optical sensors
> on or near the spindle due to the presence of fluids, chips, etc.
>
> I'm wondering if anybody has used a hall effect sensor to do this
> mounted on the side of the motor. The milling machine is German-made,
> so I imagine there is some shielding around the motor for EMI
> reduction. Not sure if this would cause problems for hall effect
> sensors, or even if they are the right solution for the job.
>
> Any tips to save me some time or steer me in the right direction are
> truly appreciated.
>
> Thanks,
>
> Ken Gracey
> Parallax, Inc.
>


[noparse][[/noparse]Non-text portions of this message have been removed]