Limits, homes, override switch

[eurikain]

It's case of not being repeatable. [...] The random delay between when switch is triggered and time takes relay to open it's contacts to allow message to control makes repeatabilty impossible.

Get it :) Sounds obvious now :)

I use the LJ12A3-4-Z/BX proximity sensors. Brown wire is to supply +ve, Blue to GND and the Black wire switches to GND

I looked up on AliExpress but not sure I get original ones... where do you get them from ? Also, If I understand well the wiring you explain and look at the documentation as well, it seems that you're connecting them as PNP type sensor and that blue connects to both 24V PSU GND pin and BOB's input terminal's GND pin ? Is it not an issue that they share they share the same GND though they are circuits operating at different voltages ? I guess GND is GND, doesn't matter the voltage ? I like to fully understand things, that's why I ask ;)

You will also want to wire the alarm outputs from your drive through a relay to the same limits + e-stop relay loop. In this case if one drive gives an error, the other will stop as well.

That's a very important thing you note here, and I will modify my circuit to take drives alarms into account, in fact, last week I made a mistake in Mach3 and while running un-regenerated toolpath and bad configuration, motors stalled, so I almost broke my X axis, because the alarm went off, but obviously was not connected to anything, so X2 kept running... To avoid that in the future I'll wire the alarm outputs as you explained, thought the limits don't belogn to the e-stop circuit. Thanks for the advice :)

[paulus.v]

Also, If I understand well the wiring you explain and look at the documentation as well, it seems that you're connecting them as PNP type sensor and that blue connects to both 24V PSU GND pin and BOB's input terminal's GND pin ? Is it not an issue that they share they share the same GND though they are circuits operating at different voltages ? I guess GND is GND, doesn't matter the voltage ? I like to fully understand things, that's why I ask ;)

You may connect all your DC 0 volt (GND) lines to ground/earth. There is no problem. Sometimes it helps solve interference issue but most of the time it doesn't really matter if you have them floating or not.

What is you BoB model?

[eurikain]

Good to know :) My BOB is the typical Chinese Mach3 5 Axis BOB: User Manual of 5Axis Breakout Board - Mach3

[paulus.v]

Your inputs have common ground. You can use only PNP sensors. You may use 24V if you wire the input through a resistor of a calculated value. There is no info of the inputs voltage in the manual, but you could find out by reading the resistor values and/or optocoupler model.

[eurikain]

I think all the inputs are 5V. How would I wire the resistor (I mean, I know it's a simple wiring diagram), but how do you actually wire it. Is there any kind of "terminal resistor" ?

[paulus.v]

I think all the inputs are 5V. How would I wire the resistor (I mean, I know it's a simple wiring diagram), but how do you actually wire it. Is there any kind of "terminal resistor" ?

I saw only once a special resistor socket to be inserted in terminal block. And there are terminal blocks with resistors, diodes, electronics fitted inside.

The simple way is to solder the resistor to the wire end. The third method is not recommended unless you solder the input wires together.

[cropwell]

Your inputs have common ground. You can use only PNP sensors. You may use 24V if you wire the input through a resistor of a calculated value. There is no info of the inputs voltage in the manual, but you could find out by reading the resistor values and/or optocoupler model.

The LJ12A3-4-Z/BX sensors I use with this board are NPN - the output of the sensor goes to GND when triggered - which is what you want. The board has pull-up resistors so that the untriggered state is strapped to 5v. You don't need resistors as the 24v power to the sensor is limited in current to 2.4mA and in voltage by an internal zener diode in the switching circuit.

These sensors have been designed to make connection simple and to have wide application, why do people then have to make things complicated. If you complicate you introduce the possibility of design faults and unreliability.

I lose the will to live every time someone mentions a relay in a homes circuit.

For Pete's sake, there is plenty of info and advice on t'Interweb. Do a bit of searching online before you regurgitate the same old questions.

Happy bloody christmas !!!!

Rob