Dynomotion

Group: DynoMotion Message: 88 From: roman_road Date: 1/1/2010
Subject: Simple Step/Direction with no Feedback
To Whom It May Concern:

I recently purchased a KFlop motion control board. I have three stepper motor drivers that accept optically isolated differential 5v step and direction input. I have manually tested the drives. I have the drives configured for 1/2 step per pulse. I have followed the instructions for the step and direction example. I am wondering if there is something wrong with my configuration.

Axis Chan0 – Output Chan0 = 0 (using step/dir generator #0)
Axis Chan1 – Output Chan0 = 2 (using step/dir generator #2)
Axis Chan2 – Output Chan0 = 4 (using step/dir generator #4)

The following are the connections that I am using for the JP7-GPIO

Pin 15 Step 0 Output
Pin 16 Dir 0 output
Pin 17 step 1 output
Pin 18 dir 1 output
Pin 19 step 2 output
Pin 20 dir 2 output
Pin 23 +5 volts
Pin 24 +5 volts
Pin 25 digital ground
Pin 26 digital ground



Do you have any insights to what may be wrong?



Is there a way to test each output without it changing states? For example test the step output and verify the step output by measuring the voltage.



Is there additional configuration to tell Kmotion that Channel 0 is x axis, channel 1 is y axis and, channel 2 is z axis? What I am looking for is some way to tell me that the board is connected and configured correctly.



In advance, I appreciate your help.
Group: DynoMotion Message: 89 From: TK Date: 1/1/2010
Subject: Re: Simple Step/Direction with no Feedback

I see one problem with your configuration for axis channels 1 and 2.  But axis channel 0 should work properly.  The issue is that some type of axes modes require 2 output channels to be configured (both Output Chan0 and Output Chan1).  Step/Dir axes are simpler in that they only need one output device to be configured – which Step/Dir generator to use.  So only Output Chan0 is used (Output Chan1 is a don’t care and can be set to any value).  So in the 3 axis channels that you have configured as:

 

Axis Chan0 – Output Chan0 = 0 (use step/dir generator #0)

Axis Chan1 – Output Chan0 = 2 (use step/dir generator #2)

Axis Chan2 – Output Chan0 = 4 (use step/dir generator #4)

 

Should be:

 

Axis Chan0 – Output Chan0 = 0 (use step/dir generator #0)

Axis Chan1 – Output Chan0 = 1 (use step/dir generator #1)

Axis Chan2 – Output Chan0 = 2 (use step/dir generator #2)

 

 

But this doesn’t explain why your axis 0 isn’t working.  What are you commanding and what happens?

 

If you press “Move” on the Step Response Screen:  The screen parameters and configuration settings will be downloaded to the board, the axis will be enabled, and a movement of the specified size should occur.  Do this and watch the Axis Screen.  Does the axis become enabled?  Does the commanded Destination change as if the motion is occurring?  If so but no motor motion, the problem is probably a wiring or compatibility issue with your drives.

 

When you select Step/Dir Output channels 0-7 the Step/Dir generator output pins operate in “Open Collector” mode.  In this mode the output pins basically switch between being shorted to ground and open circuit.  This mode is useful to allow the 3.3V outputs to drive +5V optos where the LED anode is connected to +5V.  When the output shorts to ground, the opto “sees” +5V and turns on.  When the output “open circuits” the LED turns off.  (In reality the output pin has an ESD protection diode that is connected to the 3.3V supply, so the open circuit is only allowed to float to a maximum of ~4V and the opto diode will still “see” ~1V.  Most all LED’s require more than 1V to turn on).

 

To test this mode with a voltmeter or oscilloscope:  Cycle power on KFlop so that it is in the default configuration.  Using the Digital I/O screen check and uncheck the checkbox in the “Output” column while the checkbox in the “State” column is unchecked.  Note that if no pull-up source is connected to an Open Collector output the pin will remain at ~0V regardless of whether it is driving to ground or open circuit.

 

To have the Step/Dir generators drive TTL style outputs add 8 to the output channel (specifying output chan0=8 will still drive step/dir generator #0 but in TTL output drive mode instead).  TTL output mode will basically switch the output pin from being connected to either ground or +3.3V.

 

To test this mode with a voltmeter or oscilloscope:  Cycle power on KFlop so that it is in the default configuration.  Using the Digital I/O screen check the checkbox in the “Output” column then check and uncheck the checkbox in the “State” column.  The output should be observed to go from near 0V to near 3.3V with nothing connected.

 

If you post the type of input your drives have and how they are wired, it may help.

 

Regards

Tom Kerekes

DynoMotion, Inc.

 

 

 

Group: DynoMotion Message: 90 From: roman_road Date: 1/1/2010
Subject: Re: Simple Step/Direction with no Feedback
Thank you for your help of the configuration of each of the channels. There is something else that I am missing.

I cycled the power on so that there was a default configuration. Using the digital I/0 screen I was able to get all the motors to step. The unusual thing about it was that the motors would step when I went from a checked output state to and unchecked output state. This is backwards from what I would expect.

Once I enabled the axis I was no longer able to get the motors to step. Even when disabling the axes I am no longer able to get the axis to step.

Do you have a recommendation on what command I should send to the board during testing?

When I press move nothing happens with the motors. When I press step nothing happens with the motors. This is the same for all 3 axes.

So you are saying this board is a sinking output board?

Thank you for your help.
Group: DynoMotion Message: 91 From: TK Date: 1/1/2010
Subject: Re: Simple Step/Direction with no Feedback

Yes, selecting output chan0=0 selects “open collector” mode which is a “sinking” output (meaning it can drain current to ground, but it can’t provide the source of any current).

 

The reason it works before you configure the axis to open collector mode is because 3.3V TTL outputs can both sink and source current (but only to 3.3V).  Apparently your drives will work with 3.3V (but it is hard to say how reliably).  If you switch to Output Chan0=8 instead of Output Chan0=0 your motors will probably step.

 

But it is probably better to wire your drives for a sinking output and use +5V.  (Connect the drive’s (+) input to +5V and the (-) input to the KFlop output).   See attached picture.

 

Regarding your drive stepping when the opto turns off rather than on is dependent on your drive.  Since each step pulse does both it doesn’t really matter.  Stepping on the end of the pulse has the advantage of more setup time if the direction changes.

 

Hope this helps,

TK