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Do-more™ PLC: Video - CTRIO2 Motion Using Limits

Video Transcript:

CTAXLIMT instruction ramps up to speed, then when it hits the limit it ramps back down. It can also go back and find that limit or continue on to find a second limit at a creep frequency.

For this example, we have a proximity sensor mounted on the side over here and it detects this paperclip when it passes by. The Prox sensor is an NPN and is connected to CTRIO2 Channel 1, input C, right here. Check out the hardware video for a parts list and wiring diagram of the system.

To do this we need to modify the module configuration. System Configuration, Module Configuration, select our module – we only have one in the rack. Let's give it a name, and configure the IO. Over here are my outputs. I want to dedicate 0 and 1 to driving the stepper motor via pulse step and direction. That will take up these two outputs.

Once I have selected that, over here I get the option of putting a limit on that. So I'm going to use input channel 1C as the limit on Out zero. I also could have used D for that.

Notice that if I had defined these other channels, let's say this one, I could have put a limit on out2. We don't need to do that so we'll get rid of it. Click on OK, OK, OK. And now our hardware is setup.

We'll use the same CTAXCFG we used in the previous examples. Make sure we have our module selected – we do. And all the same parameters apply. Let's bring up the CTAXLIMT instruction. CT AXis LIMT.

In this instruction, we want our device – this Demo_Out – we want the limit to trip on the channel that we wired and setup in that system hardware configuration dialog a second ago. So we choose channel 1C. And we want it to trip on the rising edge of that signal.

After the carriage has finished ramping down, we are going to have it return to that limit by specifying a zero offset here. We'll leave everything else the same, so we'll say OK.

We need to wire up the inputs for this. Let's enable this guy with X7. We'll have the direction be controlled by X6. And suspend will be X5. Apply. Save. Write to PLC. And we are ready to go.

If I reach down and flip X7 to enable this function, sure enough the carriage ramps up, travels down the guide, finds the limit switch, and backs up to it.

And that's all there is to using motion with a limit.

If you go back into this dialog, notice that if instead of going back to the original position, we could actually tell it to go to a second limit switch if we wanted to. It would hit the first limit switch, ramp down, and then creep at whatever frequency you specify here until it finds the second limit switch.

We could also click on reverse at limit 1. So limit 1 will complete, it will ramp down, reverse the direction and you could have it actually return back to limit 1 using this function. Which is the exact same thing as this one, except now you get to specify the creep frequency.

We'll, That's all there is to implementing motion using the LIMIT instruction. Be sure to check out the other videos in this series for more on using motion. And as always, please send us any comments you may have, we appreciate the feedback.

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