How to verify the correction of the optical encoder on motor

[Electronic Swear]

I am now designing a DC motor with a optical encoder assembling at the
end of the motor. After I have checked with the specification of the
encoder, there are no problems for me to understand how it function
and how it works.

Now, I would like to assembly the transmissive encoder onto the end of
the motor. Then I have some problems happened:

- For 1 turn motor rotation, encoder will give out 500 signal (because
of 500CPR), I don't know how to verify the signal correct or not. I am
using a 2 channel encoder and hence the 2 signal will be 90 degree
phase shift. However, I really don't know how to use CRO to measure a
contiunous high frequency signal.

- If the assembly between encoder and motor has some problems
(aliasment, eccentricty, perpendicularity, etc...) I would like to
know that can I check the encoder signal to verify the regarding
problems happened in my motor assembly?

- I just have a CRO, no other special equipments. And I would like to
know which extra equipment is needed for me to test the encoder.

Thanks~

 

[Paul Burke]

Electronic Swear wrote:

I am now designing a DC motor with a optical encoder assembling at the
end of the motor. After I have checked with the specification of the
encoder, there are no problems for me to understand how it function
and how it works.

Now, I would like to assembly the transmissive encoder onto the end of
the motor. Then I have some problems happened:

- For 1 turn motor rotation, encoder will give out 500 signal (because
of 500CPR), I don't know how to verify the signal correct or not. I am
using a 2 channel encoder and hence the 2 signal will be 90 degree
phase shift. However, I really don't know how to use CRO to measure a
contiunous high frequency signal.

Not with a CRO. Output the encoder into whatever counter you are using.
Rig up some hard fiducial locator- say a screw you can screw into a
pockmark on the shaft, puulley or whatever. Zero with it screwed in,
rotate the motor, screw in again, and the reading should be a multiple
of the encoder count (probably 500x4xn rotations - a 500 line encoder
usually means 2000 counts/rev). Rotate back to the start, screw in,
should be zero. How near to exact depends on how good your fiducial mark is.

- If the assembly between encoder and motor has some problems
(aliasment, eccentricty, perpendicularity, etc...) I would like to
know that can I check the encoder signal to verify the regarding
problems happened in my motor assembly?

I don't know how you'll get aliasing- or rather, if the frequency
response of your motor/ encoder assembly is higher than about a fifth of
the bandidth of your control circuitry, redesign the whole system.

Eccentricity, etc. will give you cyclical errors, in other words the
'degree' measured by your encoder will vary as you rotate it. You'll
need some means of knowing what the actual angle is to calibrate this out.

Paul Burke

 

[Larry Brasfield]

"Electronic Swear" <swear_terence@hotmail.com> wrote in message
news:910532f6.0503212146.4724d06c@posting.google.com...

I am now designing a DC motor with a optical encoder assembling at the
end of the motor. After I have checked with the specification of the
encoder, there are no problems for me to understand how it function
and how it works.

Now, I would like to assembly the transmissive encoder onto the end of
the motor. Then I have some problems happened:

- For 1 turn motor rotation, encoder will give out 500 signal (because
of 500CPR), I don't know how to verify the signal correct or not. I am
using a 2 channel encoder and hence the 2 signal will be 90 degree
phase shift. However, I really don't know how to use CRO to measure a
contiunous high frequency signal.

- If the assembly between encoder and motor has some problems
(aliasment, eccentricty, perpendicularity, etc...) I would like to
know that can I check the encoder signal to verify the regarding
problems happened in my motor assembly?

If you were to put the two signals into a mixer,
(after suitable limiting and buffering), you would
be able to observe cyclic variations in how well
the inputs conform to quadrature phasing. You
would filter out the mixer output's 2 * f component
and observe what was left. It would be simple to
use a low pass filter after each mixer input to see
what the duty cycle variation looked like.

- I just have a CRO, no other special equipments. And I would like to
know which extra equipment is needed for me to test the encoder.

A frequency counter might be useful, but I would
use the above phase error observation and place
limits on what was allowed in production to ensure
adequate margin in the recovered position/speed.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

 

[Fred Bloggs]

Larry Brasfield wrote:

"Electronic Swear" <swear_terence@hotmail.com> wrote in message
news:910532f6.0503212146.4724d06c@posting.google.com...

I am now designing a DC motor with a optical encoder assembling at the
end of the motor. After I have checked with the specification of the
encoder, there are no problems for me to understand how it function
and how it works.

Now, I would like to assembly the transmissive encoder onto the end of
the motor. Then I have some problems happened:

- For 1 turn motor rotation, encoder will give out 500 signal (because
of 500CPR), I don't know how to verify the signal correct or not. I am
using a 2 channel encoder and hence the 2 signal will be 90 degree
phase shift. However, I really don't know how to use CRO to measure a
contiunous high frequency signal.

- If the assembly between encoder and motor has some problems
(aliasment, eccentricty, perpendicularity, etc...) I would like to
know that can I check the encoder signal to verify the regarding
problems happened in my motor assembly?


If you were to put the two signals into a mixer,
(after suitable limiting and buffering), you would
be able to observe cyclic variations in how well
the inputs conform to quadrature phasing. You
would filter out the mixer output's 2 * f component
and observe what was left. It would be simple to
use a low pass filter after each mixer input to see
what the duty cycle variation looked like.


- I just have a CRO, no other special equipments. And I would like to
know which extra equipment is needed for me to test the encoder.


A frequency counter might be useful, but I would
use the above phase error observation and place
limits on what was allowed in production to ensure
adequate margin in the recovered position/speed.

hahahahaaaaaaaaaaaaaaaaaaaa! ONE FAKE TROLL TAKEN IN BY ANOTHER- TOO
GODDAMMED FUNNY!!!!!!!!!!!!

 

[Electronic Swear]

I would like to know that is there any equipments can count the input
signal and capture out 2 channel waveform for compare~

For TekXXXonix, there are some equipments call Logic anaylizer. And I
want to know that the regarding equipment is suitable for checking
encoder signal or for verifying the assemblied motor with encoder.

------------------------------------------------
If you were to put the two signals into a mixer,
(after suitable limiting and buffering), you would
be able to observe cyclic variations in how well
the inputs conform to quadrature phasing. You
would filter out the mixer output's 2 * f component
and observe what was left. It would be simple to
use a low pass filter after each mixer input to see
what the duty cycle variation looked like.
------------------------------------------------

For the quoted procedures, I am sorry I cannot understand.
The mixer is a equipment or using a self-made circuit to do so?
Would you please describle more detail or in a simple way.

Thanks~


"Larry Brasfield" <donotspam_larry_brasfield@hotmail.com> wrote in message news:<OJR%d.58$Hp3.1579@news.uswest.net>...

"Electronic Swear" <swear_terence@hotmail.com> wrote in message
news:910532f6.0503212146.4724d06c@posting.google.com...
I am now designing a DC motor with a optical encoder assembling at the
end of the motor. After I have checked with the specification of the
encoder, there are no problems for me to understand how it function
and how it works.

Now, I would like to assembly the transmissive encoder onto the end of
the motor. Then I have some problems happened:

- For 1 turn motor rotation, encoder will give out 500 signal (because
of 500CPR), I don't know how to verify the signal correct or not. I am
using a 2 channel encoder and hence the 2 signal will be 90 degree
phase shift. However, I really don't know how to use CRO to measure a
contiunous high frequency signal.

- If the assembly between encoder and motor has some problems
(aliasment, eccentricty, perpendicularity, etc...) I would like to
know that can I check the encoder signal to verify the regarding
problems happened in my motor assembly?

If you were to put the two signals into a mixer,
(after suitable limiting and buffering), you would
be able to observe cyclic variations in how well
the inputs conform to quadrature phasing. You
would filter out the mixer output's 2 * f component
and observe what was left. It would be simple to
use a low pass filter after each mixer input to see
what the duty cycle variation looked like.

- I just have a CRO, no other special equipments. And I would like to
know which extra equipment is needed for me to test the encoder.

A frequency counter might be useful, but I would
use the above phase error observation and place
limits on what was allowed in production to ensure
adequate margin in the recovered position/speed.

 

[James Meyer]

On 23 Mar 2005 23:39:27 -0800, swear_terence@hotmail.com (Electronic Swear)
wroth:

I would like to know that is there any equipments can count the input
signal and capture out 2 channel waveform for compare~

Save one motor/encoder for use as a "standard". Make sure that it works
well in the system.

When you want to test and/or adjust another motor, connect the shaft of
the test motor to the standard motor with a rigid coupling. Power up the
standard motor and run it at some convenient speed.

Use a two channel oscilloscope to view each of the encoder signal phases
on the test and standard motors. Any deviation will be readily visible. Make
your adjustments to the test motor to minimize the deviations.

Jim

 

[James Meyer]

On 30 Mar 2005 17:58:05 -0800, swear_terence@hotmail.com (Electronic Swear)
wroth:

Thank you for your suggestion.

May I know that can I use some equipment to measure the output signal?
For example: logic analysier, frequency counter?

If there are some all-in-one solutions, it will be better to purchase
for measurement.


James Meyer <jmeyer@nowhere.net> wrote in message..........

When you want to test and/or adjust another motor, connect the shaft of
the test motor to the standard motor with a rigid coupling. Power up the
standard motor and run it at some convenient speed.

Use a two channel oscilloscope to view each of the encoder signal phases
on the test and standard motors. Any deviation will be readily visible. Make
your adjustments to the test motor to minimize the deviations.

Jim

The best instrument I can think of would be a digital oscilloscope with
at least two channels, a sampling speed compatable with the motor's speed, and
the ability to store the input waveforms for later analysis.

Such an oscilloscope would be a valuable general purpose test instrument
for many different uses. It would function as a logic analyzer as well as a
frequency counter. You may find that additional instruments would make the
measurements easier, but a good oscilloscope should be your first investment.

Jim