Emergency Stop Circuit

This is what I have in mind for my estop circuit. Would like to hear thoughts.

After looking at this I think I can simplify the circuit like this and remove the dedicated kill relay and just rely on the machine ready signal to be closed and open when estop is active. This would allow the control to mechanicly trip the circuit while also ensuring that the control is completely booted prior to allowing you topress the ready button and and power mains.

I can just share with you some ideas. I am currently designing the electric part of my milling machine.
I am not a proffesional but I usually figure things out in the end.

I have based the E-stop circuit around a safety relay. It is all hardware. Linuxcnc is not invited to take part.


In an emergency stop, I need the spindle to stop and the axis's motors to stop.
I can just shut off the power to those, but the spindle will have 2-3 seconds to brake the rotation before shutting power off.

I don't think of linuxcnc's e-stop as a real e-stop. If linuxcnc is operational it can do a controlled stop (c-stop? ), it really doesn't need to shut off the power. I may take the real e-stop signal into linuxcnc so it knows that an e-stop has occured, but that's all.

Hakan,

I'm going to do some research on the safety relays, but I am kind of confused by your post. It sounds like you are saying that you don't just want to cut the mains power via a contactor or something similar when an E-stop is triggered because you are concerned about coasting. Which I think is valid. But at the same time you said that you are not using or trusting LCNC to function as ESTOP which I agree with as well. So what are you planing to do then to prevent the 2-3 second of rotation but not use LCNC to command an off command?

Also looking at your diagram. (which is very nice by the way curious what you used to make it) It looks like you are using contactors/relays to disconnect power to your drives and VFD controlled by the safety relay. I'm assuming the two on each are just for redundancy?

This code will allow you to have an external loop with your power to your drives. I guess that's is what you want. Then there is the Linuxcnc estop circuit which takes an input from the external latch. If linuxcnc throws an estop via whatever, it will drop out your external loop via the output. If your external loop drops out it will fire linuxcnc estop.

The catcher is you need a button that will start your external latch, which could be your cabinet on button, that's what I do.

Just some suggestions,

I am not an expert on this so now that is said.
The VFD has an option to do DC braking on the spindle. I want to use that.
"Real" vfd's for spindles are safety-aware and can go to a safe stop with STO (please google).
My vfd can't, the best it can do is to brake. I'll let it do that, then switch off the power.
So the safety relay will trigger the DC break of the spindle for a settable <3sec period
then switch off the power to the vfd. There is a relay KM6? that forcefully triggers the stop signal
to the vfd. And if that doesn't work for some reason, the power will be shut to the vfd after 3 secs.

There are dual contactors in series to break the power, which I have been advised to use.
And dual E-stop circuits as well.
I think the scenario is that "nothing works" and I just want it to stop. It's the delay that
pushed me to use the safety relay.

The software is QElectroTech, can be downloaded and used without cost.
As always, there is a bit of treshold with new software. It took me maybe somewhere 2-3 hours
to sketch this up