Limits, homes, override switch

[cropwell]

Jazz can probably explain it better than me, but you can use the same switches as home and limits as Mach3 can disable limits when homing.

Microswitches are cheap enough (I don't pay more than €2 each) and it looks as though you have standard microswitches, so forget what I said about inductive sensors.

It is not usual to have a Z-- switch. If the object of the Z-- limit is to stop you crashing the tool into the machine bed, you need to know the tool length, so Z-- is pointless.

You should arrange the switches so the actuating is not done by end on contact, but by an arm passing by the switch. That way the switch won't get crushed.


I haven't looked in proper detail at your wiring diagram, but my first impression was that it was over-complicated. I can't understand why you are talking about 10v and 24v as the BoB input pins are 5v, any higher and you could fry the board.

Estop should kill power to the drives and VFD and report to Mach3 that an Estop has happened, which is what you have.

Cheers,

Rob

[JAZZCNC]

You can and you can't share the Switches for both jobs.???? . . . . . . You can if you don't put the switches thru the Relay. The relay is a problem for Homing because of delay which you don't want.

If you want the Limits to run thru a relay then you need separate set of switches for homes.

Now personaly I don't have problem with running Limits straight to inputs provided the input can accept 24V to lessen chances of noise. Lots of BOB's are 5V only so this why relay is used so can still run 24v thru the long path to switches but keep the 5v signal line short and lessen chances of false triggers etc.

If your BOB can take 24V then Mach will allow you to share switches to do both Jobs.
So if you want Home switches (which I suggest you do) and don't want to fit extra switches (which I suggest you do) then remove from going thru the relay. Just keep relay for emergency stop.

End of the day Limits are Not Emergency stop but rather positional loss and has such only need to stop the control or disable the drives. They don't need to kill power completely.

But for sake of couple of £££ then I'd fit Home switches. In fact if had to lose one or other then I'd have Home switches before Limits if as they are far more useful and you can use Soft limits if need be.!

[eurikain]

It is not usual to have a Z-- switch. If the object of the Z-- limit is to stop you crashing the tool into the machine bed, you need to know the tool length, so Z-- is pointless.

Not sure I follow you, I have to learn / watch / read more about homes in order to do so. I'll watch the links you gave me later tonight :)

I haven't looked in proper detail at your wiring diagram, but my first impression was that it was over-complicated. I can't understand why you are talking about 10v and 24v as the BoB input pins are 5v, any higher and you could fry the board.

Yes sorry I meant 24V and 5V. 10V is for the spindle speed control interface.

Now personaly I don't have problem with running Limits straight to inputs provided the input can accept 24V to lessen chances of noise. Lots of BOB's are 5V only so this why relay is used so can still run 24v thru the long path to switches but keep the 5v signal line short and lessen chances of false triggers etc.

Yes, this is why I use a relay for my limit switches. My BOB can't take in 24V.


For now, I've wired all six switches together in series, and the limits now work fine. So does the override switch and buzzer. I can't work the process of getting off a triggered switch no problem. But I'm missing homes. I could share the job on the same switches, but the relay implies some risky delay (are miliseconds really that risk JAZZ ? That's where I'm not too sure...). I'll order three more switches online for the sake of completeness of the machine, but I'll use it without homes until they arrive. Now, can you tell me what kind of switches I should get ? Laser or same type of mechanical switch ?

[JAZZCNC]

I could share the job on the same switches, but the relay implies some risky delay (are miliseconds really that risk JAZZ ? That's where I'm not too sure...).

Not case of being risky. It's case of not being repeatable. The whole point of HOME switches is to be able to repeatabily return to Fixed position every time. 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.
The delay for limits isn't so important because like you say it's milliseconds but for repeatabilty purposes that is life time plus it's random amount of time.

I'll order three more switches online for the sake of completeness of the machine, but I'll use it without homes until they arrive. Now, can you tell me what kind of switches I should get ? Laser or same type of mechanical switch ?

Again because of repeatabilty you wan't slightly better switch for homes. Personally I like using inductive Proximity sensors because they are accurate and repeatable. Well more than enough for router anyway.

[cropwell]

I use the LJ12A3-4-Z/BX proximity sensors. You can run them off 24v (10-36v) and the wiring is simple. They are Normally Open switches, so you can put as many as you like with the outputs all connected to one active low input on the BoB. They are specced as 6-36v but don't switch reliably below 10v. Brown wire is to supply +ve, Blue to GND and the Black wire switches to GND when Ferrous metal is within 4mm of the sensor head. Again I say, mount the sensor so that the metal passes by it not end on, cause it will get crushed.

Cheers,

Rob

[Clive S]

Plus one us pensioners have to stick together

[JAZZCNC]

Plus one us pensioners have to stick together

Ye and you stick together in bloody sunshine while us poor buggers freeze to death..

[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