Limit switches and AX3500

15 years 3 days ago #4708223 by sww
Limit switches and AX3500 was created by sww
After testing the AX3500 with limit switches, I have decided they do not work as I would expect (or hope). The limit switches seem to add very little value to the system.

If you are in Close Loop Speed Mode, the hitting a limit switch actually causes the motor to go to full power!
Now, I have to poll the motor controller for the status of the switches and then send a stop command. You can effectively do this without switches by checking the encoder count, so why add the switches? I realize the switches give you a little more information, but I think they should stop the motor also.

Is there something, I am missing?

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15 years 2 days ago #4717807 by cosma
Replied by cosma on topic Re:Limit switches and AX3500
<P style="MARGIN: 0px">It is correct that using the multi-level signaling to share the encoder inputs with limit swiches will have the adverse effect of causing the measured speed or position capture to stop (speed drop to 0, count stays at last position).
<P style="MARGIN: 0px">
<P style="MARGIN: 0px">Either way, the motors would runnaway if operating in closed loop.
<P style="MARGIN: 0px">
<P style="MARGIN: 0px">This is clearly undesirable and we are working of implementing a few basic responses that will be taken by the controller automatically when the limits are reached. This will be included in the next release of the software. Let me know if you would be interested to test it and how much time you can wait.

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14 years 9 months ago #5912044 by sww
Replied by sww on topic Re:Limit switches and AX3500
Any progress on this? We ended up working around the problem with our higher level control code, but it is not as good as a hardware solution.

I toyed with the idea of tying the limit switches the the emergency stop line, but that would require software work around to deal with the 'frozen' controller.



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14 years 9 months ago #5922133 by cosma
Replied by cosma on topic Re:Limit switches and AX3500

There has been no progress on this. It is an important feature to fix and will be in the 2.0 release for Q4.

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