Dynomotion

Group: DynoMotion Message: 274 From: dunncl66 Date: 3/29/2010
Subject: Y Axis Woes
Ok we got the X axis behaving. Now the Y is misbehaving. When I command a step move on the step responce screen the table moves one direction the full count move but then moves back less then half the count. The axis screen show the encoder thinks it can back all the way, but the table only comes back half way. Additionally when I try to manually over ride the servo by turning the hand wheel on the x axis the servo drives the axis back to the perfect spot it was. When I manually over ride the y axis, the hand wheel trys to go back to where it was but it moves ~100 counts off where it previously was but the system thinks it returned back to the right spot. Make any sense? Its like its seeing all the counts in one direction but only a portion in the other direction.....

Chris
Group: DynoMotion Message: 275 From: Tom Kerekes Date: 3/29/2010
Subject: Re: Y Axis Woes
Hi Chris,
 
I think your analysis is correct that the encoder is not counting right.  Actually if it moves correctly one direction, but then physically doesn't move all the way back that would actually mean it counted too MANY counts so that it would think it made it all the way back when it really didn't.
 
Possible things that might cause such a thing:
 
#1 bad wiring:  Are all 4 signals A, /A, B, /B connected properly?  Ideally check with a scope for square waves on all 4 going from less than 0.4V to more than 3V.  If you don't have a scope you could use a voltmeter.  Move the encoder to random places and stop.  Sometimes it should be high and sometimes low.  Also if A is high /A should be low, and vise versa.  Same for B.
 
#2 noise:  turn off all motor power and everything except +5V and move the encoder by hand.
 
#3 bad encoder - replace it ;}
 
#4 bad Kanalog - try using a different encoder channel.
good luck
TK

Group: DynoMotion Message: 276 From: dunncl66 Date: 3/29/2010
Subject: Re: Y Axis Woes
Tom,
That's not what I wanted to hear. I wanted to hear "check bit xyz and everything will start working". Anyway I ruled out any KAnalog issues by switching the working X axis on Chan 0 to Chan 1. Everything continued to work. I then put everything back and now both the X and the Y axises are working. I guess chaulk it up to a poor wiring job the first time .....

Tomorrow night I'll start on the Z axis.

Thanks for the troubleshooting help.

Chris




--- In DynoMotion@yahoogroups.com, Tom Kerekes <tk@...> wrote:
>
> Hi Chris,
>
> I think your analysis is correct that the encoder is not counting right.  Actually if it moves correctly one direction, but then physically doesn't move all the way back that would actually mean it counted too MANY counts so that it would think it made it all the way back when it really didn't.
>
> Possible things that might cause such a thing:
>
> #1 bad wiring:  Are all 4 signals A, /A, B, /B connected properly?  Ideally check with a scope for square waves on all 4 going from less than 0.4V to more than 3V.  If you don't have a scope you could use a voltmeter.  Move the encoder to random places and stop.  Sometimes it should be high and sometimes low.  Also if A is high /A should be low, and vise versa.  Same for B.
>
> #2 noise:  turn off all motor power and everything except +5V and move the encoder by hand.
>
> #3 bad encoder - replace it ;}
>
> #4 bad Kanalog - try using a different encoder channel.
>
> good luck
> TK
>
>
>
> ________________________________
> From: dunncl66 <dunncl66@...>
> To: DynoMotion@yahoogroups.com
> Sent: Mon, March 29, 2010 3:47:50 PM
> Subject: [DynoMotion] Y Axis Woes
>
>  
> Ok we got the X axis behaving. Now the Y is misbehaving. When I command a step move on the step responce screen the table moves one direction the full count move but then moves back less then half the count. The axis screen show the encoder thinks it can back all the way, but the table only comes back half way. Additionally when I try to manually over ride the servo by turning the hand wheel on the x axis the servo drives the axis back to the perfect spot it was. When I manually over ride the y axis, the hand wheel trys to go back to where it was but it moves ~100 counts off where it previously was but the system thinks it returned back to the right spot. Make any sense? Its like its seeing all the counts in one direction but only a portion in the other direction... ..
>
> Chris
>