Dynomotion

Group: DynoMotion Message: 925 From: loki1725 Date: 2/19/2011
Subject: 5us Pulse using KFLOP
Hello,

I'm trying to use the KFLOP to drive an old foam cutting CNC machine I have and my Stepper Motor Driver board says it wants a 5us pulse input for 'Step'. I have the KFLOP set up to give a 4us (using a divisor of 62 in the FPGA) but my motors aren't working. Is it possible to use something other than the FPGA step driver to output a 5us pulse?

Thank you,
Group: DynoMotion Message: 926 From: Tom Kerekes Date: 2/19/2011
Subject: Re: 5us Pulse using KFLOP
I can't think of a workaround for that unless you only need to step really slow (<1KHz) then you could do it with software.  You might try that as a test to verify that really is the issue.
 
You might also try inverting the pulse polarity (add 0x80 to the word you write to the FPGA pulse time).  Sometimes drivers can handle short low going pulses better than high going pulses.
 
Are the drives not working at all?  Or are they missing some steps?  Are you driving them as open collector or TTL?
 
Regards
TK

Group: DynoMotion Message: 927 From: loki1725 Date: 2/19/2011
Subject: Re: 5us Pulse using KFLOP
TK,

THanks for the quick reply.

I'm currently driving the boards with TTL as they are not opto-isolated, and they accept login inputs from 3 - 5.5 V.

Currently, if I do a 'Step', I will usually get the motor to do a step 'forwards' and then a step 'backwards'. If I do a 'Move' command though I usually don't get anything. I also don't get anything in KMotionCNC when I use the arrow keys to move things. I don't need to run the motors that fast, this is a foam cutting CNC machine and you can't drag a hot wire through foam all that fast. I would like to move about 2kHz though which may be too fast.

I will try inverting the pulse and see what happens. THanks you for the suggestion.

On another note, how do you set the Step frequency? I can't seem to find this anywhere in the setup.

THanks,

--- In DynoMotion@yahoogroups.com, Tom Kerekes <tk@...> wrote:
>
> I can't think of a workaround for that unless you only need to step really slow
> (<1KHz) then you could do it with software.  You might try that as a test to
> verify that really is the issue.
>
> You might also try inverting the pulse polarity (add 0x80 to the word you write
> to the FPGA pulse time).  Sometimes drivers can handle short low going pulses
> better than high going pulses.
>
> Are the drives not working at all?  Or are they missing some steps?  Are you
> driving them as open collector or TTL?
>
> Regards
> TK
>
>
>
>
> ________________________________
> From: loki1725 <loki1725@...>
> To: DynoMotion@yahoogroups.com
> Sent: Sat, February 19, 2011 6:19:56 PM
> Subject: [DynoMotion] 5us Pulse using KFLOP
>
>  
> Hello,
>
> I'm trying to use the KFLOP to drive an old foam cutting CNC machine I have and
> my Stepper Motor Driver board says it wants a 5us pulse input for 'Step'. I have
> the KFLOP set up to give a 4us (using a divisor of 62 in the FPGA) but my motors
> aren't working. Is it possible to use something other than the FPGA step driver
> to output a 5us pulse?
>
>
> Thank you,
>
Group: DynoMotion Message: 928 From: Tom Kerekes Date: 2/19/2011
Subject: Re: 5us Pulse using KFLOP
Are you referring to the "Step" Button on the Step Reponse Screen?  That shouldn't really be used with steppers as it attempts an instant jump to a new destination.  The result is probably a constant burst of full 2.5MHz speed for the size specified which with 4us pulses would all run together and make just one big pulse.  That might explain why you get one step.
 
The Step Frequency varies as the motion accelerates, but the max Step frequency is determined by the Max Velocity Setting (on the Step Response Screen).
 
Good luck.
TK