Help requested - installing end stop sensors onto my chinese 3018 Pro

[favouritesky]

Hi all,

I've recently bought myself a chinese 3018 cnc from ebay and having played around with it for a couple of weeks have gotten a hang of most of the basics. I've been insipred by the likes of Cosmo Channel and Minh's Man Cave on youtube to add a few small upgrades onto it.
I'm not a total CNC newbie - I did a Mechanical Engineering degree way back when, so the physical side is fairly logical to me but I'm much less confident and competent on the electrical and programming side.
I managed to find a guide to GRBL settings and 'un-reverse' the Z travel direction (as the machine arrived with it reversed $=4 for some reason).

I'm now trying to install my limit switches, which is giving me a few more grey hairs...
I bought a set of these switches (based on the recommendation of Cosmo Channel); https://www.banggood.com/10Pcs-Geekc...r_warehouse=UK

The physical install and basic wiring has been ok, I've repurposed some leftover IKEA brackets as I dpn't have a 3D printer to make anything perfectly tailored yet.
I've managed to wire each pair of switches in parallel, carried out a little test by moving the bed and spindle into each switch and they seem to stop the machine OK.

* Question 1: I've connected the switches with the green wire to the + and the black to the - on the controller board - does that seem right?
The switch document says that;
"Red line connecting VCC (ramps of +)
Connect the black wire GND (ramps of -)
Green line connection Signal (ramps of s)" - which I can't say that I understand.

When I do depress the switch, I think the wires are starting to heat up until it is released and it disconnects the machine from my laptop.It also dims the 'P' LED, which illuminates when I have either power or USB connected, so it seems to be drawing current (forgive me for such a basic statement, electricity isn't my strong point!).
I haven't yet tried to deliberately crash into the limits whilst working to see what happens yet.

A lot of the guides online that I've found seen specific to Arduino or Woodpecker based hardware and I'm fairly sure mine is different, it's made by Shenzhen Moski Technology Co.


Here's a couple of photos of the controller board, not sure what else would be helpful to provide.

* Question 2: What behaviour should I expect when the switches are triggered? Is there a setting within GRBL so that instead of acting like an emergency stop, the spindle will retract back to a previous position? My assumption is yes, as that would seem likely to me for how a homing setup would work. So far I've just been moving the spindle manually from my G-code sender (UGS) - maybe it behaves differently during a proper cut?

Thanks in advance for anyone that read this far, and even more if you're able to offer any assistance!

[Doddy]

I can't open the link to Banggood - site down at this time (at least for me) at this time. However, I've found other RAMPS 1.4 limit switches with green/black/red wiring.

STOP!, recheck your wiring.

Green to +, black to -?, no, you provide the correct instruction - red to +, black to -, and green to 'S' (guess, "Switch" or "Sense"). What you have described with Green to + is that when you actuate the switch you're shorting the PSU to the RAMPS drivers. Chances are that's crowbarring the supply to the microcontroller and that's why the machine is losing comms with your PC.

The limit switches on the control card should have 3 pins - get us a photo of that, or just review what you've done with the above in mind. I wouldn't power the machine until you've done that.

[favouritesky]

Hi, thanks for the really quick response Doddy, appreciate your help.

I've attached photos showing the relevant part of the controller board.



"Green to +, black to -" - yes, this is how I had it previously (and red to S). So it perhaps seems like a simple case of having put the plug on upside down onto the controller board?


This is the actual switch I have (though just to add to the confusion, it's shown there with yellow in place of green, black and red are shown correctly).

[Doddy]

Hi, thanks for the really quick response Doddy, appreciate your help.

I've attached photos showing the relevant part of the controller board.



"Green to +, black to -" - yes, this is how I had it previously (and red to S). So it perhaps seems like a simple case of having put the plug on upside down onto the controller board?


This is the actual switch I have (though just to add to the confusion, it's shown there with yellow in place of green, black and red are shown correctly).

Yeah, those connectors provided with the switches aren't polarised - Orientate them with red=+, black=-, green=S. Ironically the connectors on the controller are polarised (different connector) so blame the accountants for penny pinching.

You shouldn't have damaged anything... much (perhaps lifed a microswitch or two), provided the PCB has survived.

[Doddy]

If, however, I've missed the point - if the connectors ONLY plug in one way around onto the controller card then we need a plan B. Let me know.

[dazp1976]

If, however, I've missed the point - if the connectors ONLY plug in one way around onto the controller card then we need a plan B. Let me know.

They are the same as lipo battery balance connectors.
If you're gentle you can push on the tabs of the metal connectors with a stanley knife and slide them out of the connector block.
Then swap them over, slide back in.
Jump to 2 mins 10 secs in on the video below.
https://www.youtube.com/watch?v=dYkTjXpTJaQ

[Doddy]

Dazp - the reason I posted what I did is because of this image from both Banggood and Aliexpress, there's a similar but less well defined image on Amazon. These taken from a search on RAMPS 1.4 End Stop from the URL OP provided that just didn't work for me.



Which shows a Dupont connector (non-polarised) at one end which allows for incorrect insertion into the controller card.

If, of course, the cable is different with the OP's switches and the appropriate mating connector has been used, but the pin order is incorrect - then I'd agree - depress the retention clip on each socket and remove, reorder and re-insert.

[favouritesky]

Thank you - the connectors to the board can be plugged in either way, so it was a simple enough job to turn them around. It now seems to be working as I think I expected - when I'm connected (using UGS) and I manually drive it into any switch, I now have an error returned;

An unexpected error was detected: ALARM: Hard limit
[Reset to continue]

Really appreciate your help with this one!

[Doddy]

Thanks for feeding back, it can help others later down the line.

I don't know UGS but suggest you investigate if you can use the switches for homing, and whether you can set soft-limits

[favouritesky]

That's exactly what I'm trying to get my head around now! Haven't quite cracked it as the machine returns an error when it first hits the upper Z switch as the first step of the homing cycle. I'll post back here if/when I manage to implement it - wish me luck!