DIY Home buildable controller

[AndyL]

G'day all,

Perhaps some colaboration will drive me to a better more universal design... Throwing this together in kicad anyway - perhaps others will want to build it too...

Tired of LPT ports... An Arduino has enough power to run a CNC, software exists thanks to the reprap project, grbl and arduinocnc. Who needs a legacy PC with an LPT port?

Yes there's this new grblshield out, which is good, but - a bit pricey and it misses that major component that grbl can handle - the SDcard reader. I dunno about you guys, but I'd rather plug a memory card into my CNC than a PC/laptop... I've seen my workshop

Basically here's the goal, User buildable - put it together on a breadboard - test it by cutting your PCB with the breadboard circuit. Then be able to assemble it into an easy plug in shield (think about those PC isa/pci/??/ cards - simple plug in component). No fancy unobtainable components, no surface mount components. something anyone with a soldering iron can put together...

Still eyeballing H bridges, L293 was the obvious choice, until I started to realize, there's 500 manufacturers offering them, and a L293D isn't an L293D... They vary from batch to batch manufacturer to manufacturer... TI's SN754410 looks better - backwards compatible with the L293, but 2amp capacity and still stackable. Still cheap - 3$ each at digikey

I think most of us use 4 wire steppers? But it is possible to breakout for up to 8 leads - should I just run the 8 leads out - little more reading required to hook up, but more universal in the end... Then the question becomes connector - plug style? Pin headers? jumper style pinouts? or the screw terminal scenario?

Still hunting out the SD card socket, that's turning into a challenge, haven't found one that isn't a surface mount component so far... But I have a few ideas for that one... it's not a radically hard problem to solve.

I'll post up some design files here in the next day or two as things get a little more sorted out... Google will help you find Kicad - basically eagle but free and open source.

[jsheerin]

Nothing really to add, but how do you envision this working? How would you zero out your machine, set up work offsets, etc. with just an arduino as a controller? I can see how you would do it with a 3d printer - you're always building something on the same surface within the same limits. But on a router, a lot of the time you have to setup work in different places and you have different length tools in the spindle. It just seems like it would be tough to do without a screen to get information from. Having said that, I think Gecko is working on a controller that does the same kind of thing. I can see it being useful in a production environment where you were going to make a given part over and over so the setup time was worth it and you had a tool changer with all your tools preset.

[mmcp42]

I'm in!

looking for bipolar at least 2A 65V

I already have a gcode interpreter running on UNO with EasyDrivers
so any STEP/DIR driver would be a piece of cake

more power to your elbow, sir!

[techrat]

Regarding the type of control that arduino type controllers provide; In my experience they are typically either drip fed G-Code Serially over usb or read G Code from a memory card. In either case, to address the issue of homing, offsets etc, this will typically need to be managed by the "Host" software that is generating the G-Code.

There are absolutely other ways to address this but if it were to work the way that I am used to for 3D printers, the offsets (Work & Tool) would need to affect a change in the G-Code being interpreted in order to have an effect on the workpiece.

I am very interested in this topic and look forward to seeing where this goes.

[AndyL]

65v will be a problem, I'll poke around a bit, but most DIP package h bridges max out at 48v... The SN754410 is a 36v max, L298 Could be easier to heatsink - and is up to 48v - but could only handle a 4wire...

Hadn't thought much about homing; 99.99% of the time, I'm coming out off the limit switches in the corner As mentioned above, tool length and offsets best adjusted when generating gcode - thats what I've taught myself anyway. Adding some digital buttons or a keypad to jog - that's fairly simple to handle.

I really prefer the SD card solution, might turn into a micro SD in practice; as it seems the easiest way to add it... Every micro SD I've bought came with the fullsize adapter; adapter makes a perfect card slot, just solder some wires to it... Why order a specialty part from china when we have them lying around?

[mmcp42]

I've been finding the same problem with the 65v requirement, so will probably settle for something lower
My steppers would need 65v 2.1A series or 33v 4.2A parallel

Despite the bad press that the chinese TB6560 controllers seem to get, I'm quite drawn to it
it's chunky enough to be soldered by those with more thumbs than fingers
and it takes a decent heatsink
I'm sure we can learn from others mistakes and build something that's TB6560 based - and works properly

I looked at prices. single chips work out about £15 each here in the UK, almost cheaper to buy a chinese controller and scavenge it for parts!

as for homing, that would be a doddle to implement
in fact, if I recall correctly,
G92 is "set home",
G28 is "go to origin",
I have already added
M114 "get current position"
so most of the code is already written!

we can always hijack/invent another (unused) G/M code for "homing"
just need a clear(ish) definition of what people expect it to do

I'm very happy to put my code in the public domain as part of the project

[Ron Dunn]

There are some comments in this thread:

http://www.cnczone.com/forums/genera..._firmware.html

on my experiences with both microSD and USB mass storage for DIY controllers.

I continue to look for a better options, ideally a board with built-in USB hosting. The Teensy++ Arduino-compatible looked good, but they have had continual supply problems in the time I've watched them. There are a few PIC boards available, but the cost of the development tools makes them a little unattractive, especially when my wife already thinks my CNC is the reason she didn't get diamonds for Christmas!

She is kind-of right. The code I wrote as a PC-free alternative to Mach3 has now cost quite a bit more than the price of a cheap PC and a Mach3 licence. I've got several Arduinos, breadboards, switches, encoders, buttons, resistors, microSD interfaces, USB interfaces, LCDs, miles of wire, a multimeter, a soldering iron and other miscellany; and I'm STILL working my way through the physical design. The code is the easy part!

Ron.

[AndyL]

Yeah, there's going to be some compromises - always are...

I'm using the freeduino sb - atmel328 so I'm starting with 32k of flash and 2048 of sram; gotta support the local suppliers.

Gotta say was just poking around ... Easy Bluetooth Module (SKU: 30242) - HVW Technologies this has me thinking bad bad thoughts Do you think there's an app for that? Rather than the SD card and a dumb interface - use bluetooth to transfer the gcode; bet we could do some of the more typical cnc setup setting home, jogging - pauses, hard stops etc via a smartphone or other 'smart' BT enabled device...

It's an interesting thought...

[jjobezo]

As long as you're thinking along that route, there are some SD modules available with built in BT. They are used for cameras but they could prove usefull for CNC use.

[mmcp42]

ok, not sure of the protocol here, but here goes anyway
I decided to look at a Toshiba TB6560 based driver
leaning heavily on the "how I fixed my TB6560 controller" thread together with the Toshiba data sheet, here's "one I made earlier"
(or rather threw together with Eagle)

please take a look
very happy to get feedback
if I'm barking up the wrong tree,
or it's not where you wanted to head - I'm sure you'll tell me

so - something to start the ball rolling:

oh and if you want I'm happy to upload the Eagle file(s) too
cheers
Mike

PS always the way
as soon as I uploaded it - found a bug!
bug now squished

Mike

[Drools]

I would be interested in the Eagle layout for the TB6560, thanks.

[mmcp42]

and here's the Eagle schematic

caveat emptor
it's untested and unproven