Wiring to the actual carriage on the table?

So, I’ve got a working MPCNC, and looking at doing a LR2 as well, so I can keep my laser on the MPCNC. I was wanting to see if anyone would care to share pictures of the control side of their carriages, more importantly, how the wires are connected to the table for power I guess. I know most people are using the stock marlin boards, with the lcd, so really I guess everything is self contained on the rolling chassis, you just feed power to it correct?

I will be doing mine on an arduino grbl controller, so there will be no onboard lcd, as well as I am not sure size for the control box yet. Not sure if I will be attaching it to the rolling axis, or be solid attaching it to the table, and just running the control wires from a central point. Do most people just let their wires hang, or do you attach them with a cable chain, or what. Been able to find very few pictures of anything but the actual table top for reference. Thanks!

Put your grbl contoller on there and attach a raspberry pi with the v1pi image and you can wirelessly control it. The latency of wifi isn’t good enough to stream gcode, but you move the whole file over and press play. The cnc.js software manages to stream the gcode over usb to the grbl board.

Then, yeah, just dangle an extension cord.

I’ve already got a custom Pi image with cncjs in docker that I run, the grbl with. Wasn’t sure how much you can put on that portion safely though. I’m working on a additional arduino, that does a MITM serial relay, for a new jog control pendant for my mpcnc, plan to do the same thing on the LR. I’m using a middle arduino between the grbl and the cncjs, to inject gcode directly into the grbl for inputs from the control box.

There’s a lot of room and the weight is straight through the wheels to the table. The gantry that lifts doesn’t lift the controllers.

Have you seen Jamie’s jog stick for Marlin? It’s using analog inputs to read a stick straight into Marlin. It is pretty slick. Maybe doing that in grbl would.be easier than writing code for a second arduino?

No I haven’t seen it yet, I’ll see if I can find it. From what I have been reading, grbl does have jogging support, which my remote is going to have to sticks, which will send $J= Gx movements direct to the grbl, just using the 2nd arduino as a man in the middle serial relay. I’m just using a mega2560 for the relay, and relaying serial0 to grbl and serial1 to the pi / pc running cncjs. Then using the mega2560 to run the code to read the inputs from buttons and the joysticks. I have the relay working already, and its flawless. Benefit also, I can remove the pendant, and just connect the grbl direct to the pi and it works like normal as well just without the extra inputs. I’m a big fan of let things do their main task and do it well, don’t try to make them do to much extra!

I was debating on what size I’m going to build, was thinking about doing a 4’ wide, so I can go ahead and use full 5’ tubes, then do a 2 or 3’ depth, instead of the 8’. That way later, I just change table size, and replace the belts. Anyone done that? I think it would be nice having the wide table front and not having the rails in the way to access the machine. Would be laid out more like a shapeko or ones I’ve seen, as opposed to being the stock layout. I may just go full size though if I can find the room for it.


Mine is 3’x4’, with the long axis being the pipes. But I haven’t even come close to needing to make it full size. I am thinking of remaking it with the pipes on the short axis to increase rigidity.

There are arduino micros with the ATmega32U4 chip. They have two hardware serial ports, which you could use for the pi and the grbl connection. Might save you some space. The jogging could then be done on software serial or just analog.

That would actually work pretty well… just having the analog sticks read by the little arduino and connect it in between the comouter and the board. I bet someone could sell a couple of those pretty easily.

I tried using a nano first with software serial, but there was issues getting them to communicate. I have heard the micro has dual hw serial. But I have yet to find it on any pinout diagrams. I will see if I can find how to set that up and order one to try out.

I’m not the first to come up with the mitm concept, there’s lots of people doing it. But there are almost zero that have documented it, I am piecing mine together based on lots of tidbits of code I’ve scavenged together. Hoping it will work well. If it does, might be something to at least document so others can do the same easier.

The nanos with the 32u (not the 328p) have a second hw serial. The first is on the usb port and the second is on the pinout.

I just realized why Jamie’s solution is better for Marlin, there is no jog gcode interface in Marlin. So you’re either constantly starting and stopping or you’re overshooting.

Hmm, most of them have serial on both USB and a pinout serial, but they are usually the same. The mega actually has serial 0/1/2/3+, and only 0 is shared with USB. I will get and test the others and see if I can get any to work.


Ah yes, Marlin misses all the good stuff, which is why I never went with that. No workspace coords, no jogging commands, no z touch probe (pretty sure it doesn’t have that right?). Grbl also has a really nice laser mode, which only enables the laser pwm during cutting movements, which is really nice. There are others as well, but it was never designed for cnc, it was 3d printing. The jog commands are really slick, I would check the grbl wiki sometime it tells how it works. I haven’t actually done a live jog test yet, but from what I understand, it will send the movement commands only while stick is moved, but soon as release it should stop, as well as revert anything you changed with the jog, like g92 or feed rates.



You can z probe with Marlin. You can even do mesh levelling. It’s not trivial to set up, but it can be done.

Grbl doesn’t support as many boards. It also can’t put $ commands in a gcode file. I wanted to put a home at the heginning of a routine, and it wouldn’t let me.

They each have their own benefits and they have helped each other a ton.

Yea I know both have their place, and I by no means ment to go off on a tangent rant! Thanks for the info you have provided though, I need to decide what size table I want to build. I can fit a full size it seems, but don’t think I need it. I do think I want to make mine rotated 90 with the rails going front / back to the wall, so I don’t have the belts in the way to lean over the table. Think it would just be more comfortable. That’s the thing I dislike the most on my mpcnc, is the rails getting in the way constantly.