Submitted by Fraa on Sun, 11/13/2011 - 13:55
Posted in
So I ordered the MX2 controller and it works just fine, the only issue I'm having is that the distances are off.
I tried calibrating with a ruler, setting the RPM and the Distance per revolution, but they're still off.
I have a Rack and pinion driven system, a Motorcraft RB35 9RPM motor (pulls about 300ma) and a 4:1 gear ratio behind the motor.
Here's a pic of the prototype:
I've set the RPM in the MX2 controller to "2,25" -> 9RPM/4=2,25.
I've set the Distance per revolution to "4,92" in the controller.
Maybe it's the last setting that's not correct?
Since I'm from Belgium and used to the metric system, I converted the measurements to inch before inputting them ofcourse.
My main gear is 40mm in diameter, so that makes 1,57inch, that times pi (3,14) is 4,92, so I assume it's correct.
So far so fine.
Now comes the part when I notice that something is off.
When calibrating the motor it runs through 6 calibration steps, the first two steps run fine.
But when the controller wants to do step 3 & 4, I hear the motor "tapping", but it doesn't really move (maybe 1mm or something).
I don't really know what distance I should give it, so I just left it at what it said.
Step 5 & 6 are just fine again.
Anyway, I don't really know what I'm doing wrong, or maybe it's just the motor...
Thanks for any help I might get though :)
Fraa, Adjust the min pulse
Fraa,
Adjust the min pulse setting under Motor, the last four calibration steps use the pulsing mode and some motors won't build up enough torque to break over the static friction of the drive train (esp. under load) without being pulsed for longer.
After calibrating, if it's still off at the calibration target speeds, adjust the Cal. Constant which determines how much of the calibration is actually applied. Unfortunately, DC motors are non-linear when being pulsed like this, so without feedback, it will be a little off - but between these settings you can get the two target speeds very very close.
!c
Thanks for the info! I'm
Thanks for the info!
I'm gonna try that right away.
I did see the min pulse setting, but since the manual says "keep it as low as possible", I didn't change it.
I'll try to experiment with it a little bit :)
hi there, did you managed to
hi there,
did you managed to calibrate your system? I have the same problem. Would be great to hear from you.
Hey, sorry for the long delay
Hey, sorry for the long delay as I didn't check back on the topic, but yes I calibrated it successfully.
The Min Pulse setting is the one that did it for me, also the Calibration Constant setting finetuned the final distance results for me.
Just be sure that your RPM, DistancePerRevolution and Min Pulse setting are correct.
I had to put the Min Pulse to 200, it just depends on your motor.
After you calibrated it, use the Calibration Constant setting (mine is at 1.00, default is 0.69) to finetune the amount of calibration applied.
By putting that setting higher the distance it actually moves is now about 1mm off compared to the distance that's on the screen, so that just about perfect for me :)