Xylotex e-stop best approach

[Richster]

I'm getting vaguely near to completion of my Solsylva CNC build, which will be controlled by the Xylotex 3-axis board. In terms of the elecontronics:

- I'll be adding switches to the three 'enable' controls so that I can override software settings to take out, for exampe, the Z axis

- There will be home switch on each axis, with additional limit switches on the X and Y axes only

- I intend to add relay control to the spindle. I'll probably build myself a circuit to do this, rather than buying a breakout board. I did one of these on a previous project which drove LEDs via an opto-isolator on one of the parallel outputs, and an external power supply

I'm looking at how to best implement an e-stop currently. The Mach3 manual says not to rely on the software control, or to simply cut the mains to the driver board PSU (which the software would be oblivious to). The Xylotex documentation says not to break the connections to the servos (obviously), or the 24v link between the PSU and the board (though I'm not quite sure why on this one) So what IS the best approach?! I want something which is guaranteed to cut the mains to the router, and also stop the drives moving instantly. There's plenty of examples on this forum, but I haven't spotted anything yet which does quite what I'm after.

Cheers- Rich

[ger21]

I think you need something like this.

http://www.surpluscenter.com/item.as...tname=electric

or gang together a few of these.


http://www.surpluscenter.com/item.as...tname=electric

and one of these.

http://www.surpluscenter.com/item.as...tname=electric

Then you want to use one to send an E-stop signal to the Mach3, which should stop the steppers instantly. Use another to kill power to the power supply. If Mach3 fails to stop it, the power supply should. And you could use another to kill power to the router motor itself.

[Richster]

Thanks for those thoughts. We can get those kind of components over here, but like most things in the UK at the moment they are outrageously expensive. I actually have an e-stop button already. I have been thinking some more about this – I think the main issue is that the router stops, since in the event of a computer crash or similar that would kill the steppers anyway.

I’m planning to build a relay interface to control the router, so the e-stop could be connected to this so it cuts the 12v supply to this circuit, opens the relay and stops the router. There then begs the question over how to let the Mach3 software know the e-stop has been activated, so I was thinking the same 12v supply could be used to send a signal to the appropriate input pin via an opto-isolator? i.e. the photo-transistor is connected between the e-stop pin and PC ground, and the isolator’s input (effectively an LED) is linked into my switchable 12v supply via a suitable resistor.

Does this sound plausible?

[Claude Boudreau]

Thanks for those thoughts. We can get those kind of components over here, but like most things in the UK at the moment they are outrageously expensive. I actually have an e-stop button already. I have been thinking some more about this – I think the main issue is that the router stops, since in the event of a computer crash or similar that would kill the steppers anyway.

I’m planning to build a relay interface to control the router, so the e-stop could be connected to this so it cuts the 12v supply to this circuit, opens the relay and stops the router. There then begs the question over how to let the Mach3 software know the e-stop has been activated, so I was thinking the same 12v supply could be used to send a signal to the appropriate input pin via an opto-isolator? i.e. the photo-transistor is connected between the e-stop pin and PC ground, and the isolator’s input (effectively an LED) is linked into my switchable 12v supply via a suitable resistor.

Does this sound plausible?

Sound good to me , just dont forget that a stopped router can do a lot of damage on a moving axis. My home made router is equipped with 2 estop microswitch on both end of each axis installed just after the software limits, plus a few estop buttons in serie with the same circuit ( all n.c. switch) They control a simple relay that drive the power supply .(simple motor start-stop configuration)you can also use the soft estop , but usually the e-stop in industrial setting should be hardwired. (somewhat failsafe)Hope this help.