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Author Topic: smooth stepper and modbus I/O  (Read 3657 times)
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kid
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« on: April 28, 2012, 12:51:05 PM »

I had Mach system running thru parallel port with serial modbus from DL06 to control inputs/outputs and limit switches. Old computer with parallel port died. So i decided to upgrade to new computer with Windows 7 and go with Smooth Stepper plug-in. Everything seems to work but limit switches, I see the LEDs change state but no function. what I mean is: During testing if an axis is running (say X) and i trigger a over travel limit switch (X++) nothing happens, LED lights but axis keeps running. DL06 sends it, Mach gets it but Smooth Stepper seems to ignore it. Any ideas, or am i missing something in my configuration.
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Hood
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« Reply #1 on: April 28, 2012, 01:44:03 PM »

Never tried running the limits into Mach via the PLC. I do however put my limits to the PLC but they dont actually go to Mach as limits but rather an e-stop signal. I have all my limits along with drive fault signals etc in the ladder set up so they send an E-Stop to Mach, they also are in another rung taking the enables away from my drives.
I dont see why it wouldnt work the way you have it set up but would have to test and afraid I dont have a PLC here at home.
Hood
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kid
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« Reply #2 on: April 28, 2012, 09:06:09 PM »

Thanks for your response Hood, That's a good idea with the logic. I think I will have to do the same thing.
 After some testing and curiosity I also checked some other Mach pin inputs. Home limits will not work either and you also get a SS message pins not assigned to SS.
But..... ESTOP does work???  So that means SS can see them.
 When I get time I will play around more, But for now changing some logic should get me back up and running.

Thanks again, Kid

Please post if you find out anything.
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Hood
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« Reply #3 on: April 29, 2012, 02:31:07 AM »

I have just looked at a ladder and I was misspeaking, sorry. I have the output from the PLC going into an input on the controller as an E-Stop signal so it is not going via modbus.
Will try and test things out today for you. Below is a sample of the E-Stop string I have on the Scorpion which is basically a slightly grown up version of the SS.
Hood


* ScreenHunter_01 Apr. 28 19.38.jpg (36.87 KB, 1190x716 - viewed 174 times.)
« Last Edit: April 29, 2012, 02:32:57 AM by Hood » Logged

Hood
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« Reply #4 on: April 29, 2012, 03:52:19 AM »

Ok just grabbed the PLC and did a simple ladder with two inputs that then go to Mach via Modbus. I set one as a limit in Ports and Pins and the other as E-Stop. E-Stop works fine but as you found the limit is ignored. When I say E-Stop works fine, it does with the exception of the annoying message that no E-Stop is configured for SS, this is even with the option not to report pin errors in the SS plugin. It wouldnt be too bad I suppose but occasionally it pops up under Mach and there is nothing in the taskbar letting you know it is there and you can wonder why Mach will not reset. It is only when you minimise Mach that you see the message underneath it, real PITA.
Hood
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Hood
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« Reply #5 on: April 29, 2012, 03:57:40 AM »

I have also just tested with a modbus input to a brain which should activate the limit switch, it does but SS again ignores. Looks like the E-Stop is the only way.
Hood
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Jeff_Birt
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« Reply #6 on: April 29, 2012, 09:51:04 AM »

Quote
I had Mach system running thru parallel port with serial modbus from DL06 to control inputs/outputs and limit switches.


in general this is a really bad idea. Signals like limit switches, home switches, EStop, etc, should NOT be run though a PLC or any other sort of external device. They must be hooked directly to the motion controller (i.e. parallel port or SmoothStepper) to work properly. You have a LOT of I/O with the SmoothStepper so you can wire up your limit switches to it directly.
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Happy machining , Jeff Birt
 
Hood
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« Reply #7 on: April 29, 2012, 12:00:43 PM »

Have to sort of disagree with that Jeff, it all depends on how you are handling things. I agree 100% if you are simply passing the signals via the PLC to the software then it is best to do it via the motion controller. Doing it via the PP probably makes little difference as it would then be relying totally on software no matter whether they went via Modbus or in via the PP.
 My preference is that the signals from limits, E-Stop etc are handled in the PLC which drops out enables or contactors etc and then the signal is also passed on  to Mach via Modbus or Controller.
Hood
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simpson36
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« Reply #8 on: May 16, 2012, 03:06:41 PM »

My preference is that the signals from limits, E-Stop etc are handled in the PLC which drops out enables or contactors etc and then the signal is also passed on  to Mach via Modbus or Controller.

Do I understand this correctly that you are passing E-stop to Mach thru modbus? I am curious about that because I am sort of wrestling with that whole concept right now.
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Hood
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« Reply #9 on: May 16, 2012, 03:22:14 PM »

My PLC's take the E-Stop, Limits, Drive Fault signals etc and take away the enables from my servo drives if iany of these are seen, that is on one rung of the ladder. There is another rung that also uses the limit, Estop, Faults etc and this operates a relay output on the PLC and this goes to Mach via the controller (Scorpion or SS or ESS) as an E-Stop input to Mach.
Because my limits do not go to Mach I have a button on my panel which can override them so that I can jog off a limit. See pic of rung in previous post and also the other in this.
My E-Stop switch also drops out all the contactors that control motors.

Hood


* ScreenHunter_01 May. 16 21.21.jpg (41.68 KB, 1204x456 - viewed 157 times.)
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