Wiring limit switches to latest Banggood 3018 control board

[JBaz]

Although I have been making things for over 50 years, this is my first foray into CNC with a Banggood 3018.

The machine works fine and I used it to make the brackets to mount the limit switches. However, when I come to wire them in I find the latest Banggood control board only has 3 connectors for limit switches - one for each axis - and I have 5 limit switches.



I have connected 3 of the switches - one for each axis - and set $21=1 and the stepper motors cut out when I activate the switch; so now I am wondering how to connect the other 2 switches?

The connectors on the board have the pins marked as X+, COM and X-, (same for other 2 axes) so does this mean I should connect the active terminal (I assuming only 2 of the 3 pins on the switch are active - NO or NC) from the switches at each end of the axis travel to the corresponding pin on the control board and the connect the common pin wires together?



Alternatively, do I just cut the wires and use a block connector to connect the switches at each end of the axis in parallel?

Are there any other options?

If anybody can offer help I would appreciate it.

[cropwell]

Hi,

First can you check $5=0 This means that grounding a limit pin triggers a limit. Then it is fairly simple to wire the switches in parallel. Having said that, I notice on your GRBL board that each limit input has +, GND and -. Also your limit switches look as though they have LEDs on them, so maybe one of the board pins provides power for the LED. This probably only means that LEDs will shine at both ends when limit operates. So my best guess is that Red = +5v, Black = GND and White is the Limit sw which goes to ground when triggered.

Hope this helps. It is a pity that we have a plague on as I am only 15 miles up the Fosse from you.

Cheers,

Rob

[JBaz]

Rob

Thanks for the response (and I like the cheese from up there).

As it happens I hijacked somebody else's thread over the weekend and have been advised to consider using only 3 limit switches, set them up as a "home" position for the spindle and use soft limits for the ends of the x and y axes.

With there only being 3 limit switch connectors on the GRBL board, this could be what was intended, so I thought I would give it a try before cutting any wires.

It will mean more reading up on t'internet, but I've got a bit of time to fill until The Star (Thrussington) opens again.

Cheers

[cropwell]

You could arrange it so the limit switch travels and hits limit stops at each end. That is my intention when I get round to recommissioning my machine after the refurb of my 'den'.

[JBaz]

Rob

Good idea.

I've got the switches travelling on the x axis, but I hadn't thought to have a single switch mounted to cover both travel limits. It wouldn't be difficult to set up either.

I'll see if the 3 switches and soft limits work well enough for me, as that would allow me to use the mounting brackets I've already made, but your idea is a good option if I'm not happy with that set up.

ATB

John

[Capella CNC]

John,

I've been working with this type of board quite a bit recently. Your original assumption would seem to be correct to me, that the centre GND pin on each of the connectors on your board should be connected to both common pins on the pair of switches you use for each axis. The X+ board connection should go to the NO connection on the limit switch at the positive limit of travel on the X-axis and the X- board connection should go to the NO connection at the negative limit of travel.

The ATmega328P microcontrollers used on these boards only use three input interrupt pins for the end stops - one for each axis, so you will probably find that the X+/X- header pins on your board are connected in parallel anyway. You should be able to confirm this by examining the tracks on the board or with a multimeter.

I have documented connecting end stop limit switches to a similar board to this on my website at https://capellacnc.co.uk/electronics...es/project.php and also show how I connected z-axis limit switches in parallel when only one controller board pin header was available in Step 14 on https://capellacnc.co.uk/electronics...er/project.php

Hope this helps!

Steve