Safety relay and e-stop in LCNC?
17 Jul 2024 07:07 #305452
by rodw
Replied by rodw on topic Safety relay and e-stop in LCNC?
There are two ways to do this. You can either run an external latch (which is a momentary switch) that resets the safety relay. In this case, you should connect a signal to a Linuxcnc input which is connected in hal to iocontrol.0.emc-enable-in This is the approach I took.
There is no need to press anything in Linuxcnc
The other way is to use iocontrol.0.user-request-enable instead of your external latch. Linuxcnc sends a pulse on this signal to act as the latch when the on screen estop is reset (S34 in the diagram).
When I researched this, this was compliant provided you isolated Linuxcnc (your controller) with redundant relays (K3 & K4). These needed to be force guided relays where a non conducting pin is forced between the contacts when they are triggered to ensure the contacts cannot become welded closed.
It's good that you used a safety relay with a timer in it can retain control until motion stops.
There is no need to press anything in Linuxcnc
The other way is to use iocontrol.0.user-request-enable instead of your external latch. Linuxcnc sends a pulse on this signal to act as the latch when the on screen estop is reset (S34 in the diagram).
When I researched this, this was compliant provided you isolated Linuxcnc (your controller) with redundant relays (K3 & K4). These needed to be force guided relays where a non conducting pin is forced between the contacts when they are triggered to ensure the contacts cannot become welded closed.
It's good that you used a safety relay with a timer in it can retain control until motion stops.
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17 Jul 2024 09:10 #305463
by thomaseg
Your drives are better than mine. The way logic and power is seperated is very handy! Mine doesn't have that. Neither does my drives support external e-stop input since they run via EtherCAT.
I tried just simply setting the e-stop pin to emc-enable:...but this doesn't work and i also suspect that this isn't actually what i want 
I should have posted a diagram in my previous post, but better late than never. This is my safety circuit:
I'm starting to think that i have to change this. So instead of the resetbutton(S6) goes directly to the safety-relay it actually goes to LinuxCNC. Then LinuxCNC is the only on that can reset the safety relay, just like in Unlogics case mentioned above. The question is then if should have an additional latch inside LinuxCNC or how should i structure the HAL?
A whole other can of worms is that the drives are connected via EtherCAT and uses CIA402, so i need to manage their state when the estop is reset. I have to re-initialize them after a reset, i'm not even sure this is doable via HAL logic...
Replied by thomaseg on topic Safety relay and e-stop in LCNC?
I really like the way you setup reacts. I cannot figure out if your safety relay can actually trip without LinuxCNC being on? From what i can see on your schematic the estop is wired to the drives + IO pin, but not the safety relay?I'm using an ABB safety relay on my CNC converted mill (forum.linuxcnc.org/12-milling/50559-opti...mh50v-cnc-conversion) and I've set it up so that LinuxCNC feeds the e-stop circuit via an output on the Mesa board.
If LinuxCNC isn't up and running the e-stop cannot be reset. If the e-stop is triggered it can only be reset via my physical e-stop reset button, e-stop cannot be reset in software.
I'm using Delta B3 servos which have two different power connections on the servo drives, one connection for the logic section and one for the servo power section. The logic section remains powered all the time (per the Delta manual) but the servo power section is cut via contactors when an e-stop is triggered. The drives also have the e-stop signal connected to them so they can detect an e-stop and stop the servos using the built in brake resistor.
Your drives are better than mine. The way logic and power is seperated is very handy! Mine doesn't have that. Neither does my drives support external e-stop input since they run via EtherCAT.
Yeah, hitting "Power on" in LinucCNC is just fine, it makes good sense. And i agree that estop reset shouldn't restart motion, that is crucial!pippin88 post=305449 userid=16922
Ha e you tried just setting it up in hal as an estop?
I have a simple estop button to LinuxCNC and when I reset the button LinuxCNC comes out of estop.
I still have to hit "power on" on LinuxCNC after reseting estop. This is generally recommended behaviour
Reseting estop should never result in immediate motion
I tried just simply setting the e-stop pin to emc-enable:
net estop lcec.0.DI03.din-0-not => iocontrol.0.emc-enable-inI tried this simple approach with the above HAL-code, but this isn't working(at all)... maybe the emc-enable-in should be pulsed? I'm unsure how the internals of LinuxCNC works with these pins...rodw post=305452 userid=20660
There are two ways to do this. You can either run an external latch (which is a momentary switch) that resets the safety relay. In this case, you should connect a signal to a Linuxcnc input which is connected in hal to iocontrol.0.emc-enable-in This is the approach I took.
There is no need to press anything in Linuxcnc
rodw post=305452 userid=20660
The other way is to use iocontrol.0.user-request-enable instead of your external latch. Linuxcnc sends a pulse on this signal to act as the latch when the on screen estop is reset (S34 in the diagram).
When I researched this, this was compliant provided you isolated Linuxcnc (your controller) with redundant relays (K3 & K4). These needed to be force guided relays where a non conducting pin is forced between the contacts when they are triggered to ensure the contacts cannot become welded closed.
I should have posted a diagram in my previous post, but better late than never. This is my safety circuit:
I'm starting to think that i have to change this. So instead of the resetbutton(S6) goes directly to the safety-relay it actually goes to LinuxCNC. Then LinuxCNC is the only on that can reset the safety relay, just like in Unlogics case mentioned above. The question is then if should have an additional latch inside LinuxCNC or how should i structure the HAL?
A whole other can of worms is that the drives are connected via EtherCAT and uses CIA402, so i need to manage their state when the estop is reset. I have to re-initialize them after a reset, i'm not even sure this is doable via HAL logic...
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17 Jul 2024 09:16 #305464
by thomaseg
Replied by thomaseg on topic Safety relay and e-stop in LCNC?
Just to give a bit of "physical context", here is how it looks in "real life":
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17 Jul 2024 12:19 #305479
by rodw
Replied by rodw on topic Safety relay and e-stop in LCNC?
Looks Good
This is mine on a Mesa setup but also have the same on an Ethercat machine
Red Safety Relay, two force guided relays in front of it.
The only thing I can see a bit different is your estop does not have dual circuits. I bought new ones for these safety relays that did. Back of switch shown here. (Brand is Idem, same as relay)
On my ethercat machine, I drop power to the steppers but also use the disable signal on the motors.
This is mine on a Mesa setup but also have the same on an Ethercat machine
Red Safety Relay, two force guided relays in front of it.
The only thing I can see a bit different is your estop does not have dual circuits. I bought new ones for these safety relays that did. Back of switch shown here. (Brand is Idem, same as relay)
On my ethercat machine, I drop power to the steppers but also use the disable signal on the motors.
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17 Jul 2024 12:43 - 17 Jul 2024 12:43 #305483
by thomaseg
Replied by thomaseg on topic Safety relay and e-stop in LCNC?
Yeah i saw your description in another post and they look very similar. After seeing the discussion you had, i've already decided to do a minor change to the estop-button-circuit. The button itself have a NC and a NO connector, but i'm going to change the NO-contactor so i'm getting 2xNC instead and then put them in series and make that part redundant aswell... thanks for the inspiration 
Does that make sense? As far as i can see i get "the best of both worlds", right? The only missing part is that i won't be able to trigger an estop from software, but i'm not sure i need that? It could be solved by a redundant relay in the physical estop chain, triggered by IO from LinuxCNC...but not sure if it is needed in any way...
/Thomas
yes, i've studied that part, but i'm very unsure how to couple it with the hardware latch in the safety relay. My thoughts so far, see if it is clear and makes sense:I also should have mentioned the estop-latch component allows you to build an estop chain in hal.
- The physical estop triggers, this sends estop-signal to LinuxCNC and automatically kills servos after set amount of time.
- The estop-signal sent to LinuxCNC triggers the estop-latch inside LinuxCNC and stops everything "on the software side" including estopping servers via EtherCAT.
- The physical reset-button is connected to IO-pin instead of directly to safety relay. When pushed it sends signal to LinuxCNC estop latch to "open" disabling software estop.
- When LinuxCNC estop goes into normal operation mode it sends a "oneshot" signal to the safety-relay to cause a reset of the physical latch
Does that make sense? As far as i can see i get "the best of both worlds", right? The only missing part is that i won't be able to trigger an estop from software, but i'm not sure i need that? It could be solved by a redundant relay in the physical estop chain, triggered by IO from LinuxCNC...but not sure if it is needed in any way...
/Thomas
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