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Motor calibration values
#1
(03-14-2014, 05:48 PM)Airic Lenz Wrote: ...that looks and sounds totally fine to me. Maybe it's the step-based motion that is confusing your ears.

The next step is to find the correct calibration value for your motor (after it is connected to your system and actually moving something).

Then you can increase the max speed of the motor until it stops moving properly. Take this value and reduce it by a decent amount to have your save max speed value. E.g the motor starts jittering at 15cm/sec. Your save setting should be something like 9 to 10 cm/sec.

Have fun!

Can anyone check my Calibration math and tell me if this is right? I think it is, but Airic's example doesn't factor in a geared stepper motor. The number seems too high being that I'll have to turn the calibration knob for a few minutes to get the the number below! Smile

Motor Specs: 1.8° Step Angle with a 27:1 gearbox
Pulley Diameter: 7.97cm
Using the default 1/16 step on Big Easy Driver

360/1.8=200 steps for one revolution before gearbox
200x27=5400 steps for one revolution after gearbox
5400x16=86,400 steps after factoring the 1/16 multi-stepping with BED
86,400/7.97=10,840.65 steps/cm.

Thanks!
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#2
Untill the last calc you are right. But it's
86,400 / (7.97 cm * 3.14159 (PI) ) = steps /cm
86,400 / 25,0385 = 3450,69 steps/cm

Cheers
Sascha
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#3
(03-22-2014, 09:31 AM)rgunnells Wrote: Can anyone check my Calibration math and tell me if this is right? I think it is, but Airic's example doesn't factor in a geared stepper motor. The number seems too high being that I'll have to turn the calibration knob for a few minutes to get the the number below! Smile

Motor Specs: 1.8° Step Angle with a 27:1 gearbox
Pulley Diameter: 7.97cm
Using the default 1/16 step on Big Easy Driver

360/1.8=200 steps for one revolution before gearbox
200x27=5400 steps for one revolution after gearbox
5400x16=86,400 steps after factoring the 1/16 multi-stepping with BED
86,400/7.97=10,840.65 steps/cm.

Thanks!

With a 27:1 Motor these values are in the right ballpark. Anyways, you need to divide by the pulleys circumference and not its diameter. This should reduce the value a bit. If you change to a bigger stepping value (possibly even full steps) you will reduce the calibration value further and also increase the speed with which the motor can move.

If not done, please check the section about how to calibrate the motors in the documentation.

Cheers,
Airic
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#4
(03-22-2014, 09:31 AM)rgunnells Wrote: Can anyone check my Calibration math and tell me if this is right? I think it is, but Airic's example doesn't factor in a geared stepper motor. The number seems too high being that I'll have to turn the calibration knob for a few minutes to get the the number below! Smile

Never forget to push the Menu button while changing the value!
(and using a small cordless-screwdriver works well, too Wink

Greetz
Martin
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#5
Thank you all. I mistakenly wrote diameter instead of circumference. My pulley's circumference is 7.97cm. I like the mini screw driver tip. Smile
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#6
(03-25-2014, 12:59 AM)rgunnells Wrote: Thank you all. I mistakenly wrote diameter instead of circumference. My pulley's circumference is 7.97cm. I like the mini screw driver tip. Smile

I think that incrfeasing the step size will bring the biggest advantages - in terms if reducing the cal-value as well as in increasing the speed. You will loose some resolution but what is your resolution per step right now?

7.97cm movememt per 200 * 16 * 27 steps = 2 240 000 steps for just one rotation !!!

...this results in a step size of 0.00003558 mm. do you really need this resolution? I guess using full steps would really improve your set-up as 0.0005692 mm per step is still plenty of resolution and your motor-speed would increase quite a bit - not to forget that you would need to turn the rotary encoder 16 times less to reach your cal-value.

Cheers,
Airic
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#7
(03-25-2014, 11:11 AM)Airic Lenz Wrote:
(03-25-2014, 12:59 AM)rgunnells Wrote: Thank you all. I mistakenly wrote diameter instead of circumference. My pulley's circumference is 7.97cm. I like the mini screw driver tip. Smile

I think that incrfeasing the step size will bring the biggest advantages - in terms if reducing the cal-value as well as in increasing the speed. You will loose some resolution but what is your resolution per step right now?

7.97cm movememt per 200 * 16 * 27 steps = 2 240 000 steps for just one rotation !!!

...this results in a step size of 0.00003558 mm. do you really need this resolution? I guess using full steps would really improve your set-up as 0.0005692 mm per step is still plenty of resolution and your motor-speed would increase quite a bit - not to forget that you would need to turn the rotary encoder 16 times less to reach your cal-value.

Cheers,
Airic

I'm i totally wrong or did you Airic understand rgunnells not correctly.

With his 7,97 cm circumference pulley he makes with full rotation for what he needs 86400 steps, 7,97 cm way?
Or am I wrong?

How did you calc 2.240.000 steps??

So this should be your parameters:
Toothed Wheel Diameter in cm: 2,53
Toothed Wheel circumference: 7,9482
Motor degrees per full step: 1,8
Full Steps Motor: 200
Dip Settings (Micro stepping): 1/16
Steps per Full Rotation only Motor: 3200
Gear reduction ( if no gear set to 1): 27
Steps per Full Rotation: 86400
Steps per cm/°: 10870,39

Cheers
Sascha

Here is my calibration table SmileSmile


Attached Files
.xls   motor_calibration.xls (Size: 35.5 KB / Downloads: 42)
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#8
(03-25-2014, 09:20 PM)Sascha Wrote: How did you calc 2.240.000 steps??

You are totally right Sascha - I made a mistake somewhere. I guess my calculator app had some old values stored.

Thanks for your Excel sheet as well!
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