Dynomotion

Group: DynoMotion Message: 14942 From: cnc_machines Date: 8/10/2017
Subject: Steppers & Encoders
I am running the KStep closed loop with encoders. I am trying to understand the max line count on an encoder that would make sense on a 0.9 step angle motor.

To get the max resolution would I want a 1:1 Gain Ratio? Something like this?

Motor = 400 Counts/Rev X 16 Microsteps 
--------------------------------------------------------- = 1
Encoder = Lines/Rev X 4 State Changes

400 X 16
------------- =1
L X 4

So then L is:

6400
-------- = L
4

So to get the max resolution out of a 0.9 degree motor using the KStep would be with a 1,600 line encoder?

I am currently using a 5,000 line encoder - I figured it was overkill. Is there any downside of using a higher count, use more KFlop resources or something?

Thanks,

Scott
Group: DynoMotion Message: 14943 From: Russ Larson Date: 8/10/2017
Subject: Re: Steppers & Encoders

Scott,

 

The resolution of the encoder has two impacts.  It determine how fine a step you take, but at the same time the higher resolutions require more steps to go the exact same distance.  So what difference does that make?  All pulse systems Dynomotion or any other companies products can only send out so many pulses per second.  So the higher the resolution of the encoder the highest speed is impacted.  Do you follow?  So said simply if you need high precision and speed is not a real concern, then go with high resolution encoders.  If speed is important do some calculations of the max pulse rate and determine you max speed.  It is kind of a balancing act to give you the both of best worlds.

 

Russ

 

 

From: DynoMotion@yahoogroups.com [mailto:DynoMotion@yahoogroups.com]
Sent: Thursday, August 10, 2017 2:05 PM
To: DynoMotion@yahoogroups.com
Subject: [DynoMotion] Steppers & Encoders

 

 

I am running the KStep closed loop with encoders. I am trying to understand the max line count on an encoder that would make sense on a 0.9 step angle motor.

 

To get the max resolution would I want a 1:1 Gain Ratio? Something like this?

 

Motor = 400 Counts/Rev X 16 Microsteps 

--------------------------------------------------------- = 1

Encoder = Lines/Rev X 4 State Changes

 

400 X 16

------------- =1

L X 4

 

So then L is:

 

6400

-------- = L

4

 

So to get the max resolution out of a 0.9 degree motor using the KStep would be with a 1,600 line encoder?

 

I am currently using a 5,000 line encoder - I figured it was overkill. Is there any downside of using a higher count, use more KFlop resources or something?

 

Thanks,

 

Scott


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Group: DynoMotion Message: 14947 From: Tom Kerekes Date: 8/10/2017
Subject: Re: Steppers & Encoders

Hi Scott,

The higher the resolution the better until you exceed the max Encoder count rate of 1 million quadrature counts/sec.

For example if your max speed is 1000RPM at 5000 lines/rev would be:

1000 / 60 * 5000 * 4 = 333,333 counts/sec and would be ok

This assumes your driver, cabling, termination and such can handle that pulse rate.

Regards

TK


On 8/10/2017 11:05 AM, cnc_machines@... [DynoMotion] wrote:
 

I am running the KStep closed loop with encoders. I am trying to understand the max line count on an encoder that would make sense on a 0.9 step angle motor.


To get the max resolution would I want a 1:1 Gain Ratio? Something like this?

Motor = 400 Counts/Rev X 16 Microsteps 
--------------------------------------------------------- = 1
Encoder = Lines/Rev X 4 State Changes

400 X 16
------------- =1
L X 4

So then L is:

6400
-------- = L
4

So to get the max resolution out of a 0.9 degree motor using the KStep would be with a 1,600 line encoder?

I am currently using a 5,000 line encoder - I figured it was overkill. Is there any downside of using a higher count, use more KFlop resources or something?

Thanks,

Scott