Educate me about estop chains and latches

Pendant e-stop is E-STOP and must be in series with the big mushroom!

tecno wrote: Pendant e-stop is E-STOP and must be in series with the big mushroom!

I think I need to buy a better estop switch so I can add an additional NC mechanism instead of using the cheap one I had in my box of tricks then. I was trying to avoid that as it will just take time to get in.

I always thought E-Stops should stop all hazardous mechanical motion, but not shut off associated equipment.
Merely shutting power to equipment would cause devices to roll to a stop.

LinuxCNC when estop is triggered the drives get disabled and therefore stopping most mechanical motion including spindle rotation. Removing power from an inverter that is driving a spindle would take a few minutes for the spindle to stop instead of using breaking.

When you have requirements for inputs to be in the e-stop chain, energize a relay and place the contacts in series with the e-stop chain. I do this when it is not a safety issue but for mechanical protection like the plasma head falling off.

I never remove power from equipment on an e-stop.

Just my thoughts.

What if a mosfet or IGBT shorts and the machine has no load? It will break something and burn the motor to a crisp and risk killing someone in the proces.
That is why servo systems have e-stop shuting down complete power to moving parts. E-stop is an emergency device and should be treated as such.

I have a friend who built a CNC lathe and used a relay to drop AC power on estop. Subsequently, someone knowledgeable told him that it did not comply with the relevant engineering and workplace safety standards which required AC power to be dropped without any intermediate relays. Between us we established the wiring I am using. We do need to keep the Mesa 7i76e alive so it can tell LCNC to stop gracefully at the same time. To me this makes sense as it protects against a hung computer that can't respond.

I think you guys have helped me establish something I've been aware of for quite a while and that is the current external e-stop switch I am using is not the right type as it is not wired in as a normally closed input on the low voltage signalling side. This means I can't put additional switches in series with it. If I replace it, I can add the pendant relay in series to generate an e-stop but it won't drop power to the stepper motors.

However, I think all of you with the exception of Bevins are describing a simple e-stop chain. If you look at the estop_latch docs
linuxcnc.org/docs/html/man/man9/estop_latch.9.html

It says
I don't want to use Classic Ladder but I would like to see a hal example of a "more complex system" as I am sure that LCNC is more flexible and can tie different estop conditions together in software.

tommylight wrote: What if a mosfet or IGBT shorts and the machine has no load? It will break something and burn the motor to a crisp and risk killing someone in the proces.
That is why servo systems have e-stop shuting down complete power to moving parts. E-stop is an emergency device and should be treated as such.

What if the e-stop button malfunctions and doesn't open the circuit?

I don't think your argument holds water.