Raspberry Pi, Arduino, Shield, GRBL, CNC, etc.

[vtsteam]

I had problems connecting to the RPi from the Android tablet. The laptop seemed more stable, but it also failed a few times.

After a lot of trials I found that the problem seemed to lie with the WPA supplicant in the RPi. It seems to periodically lose lock with the wireless router, and reinitialize the connection. This leaves an RDP connection in the cold, and they never seem to re-connect without re booting the RPi.

So other possibilities are running the RPi in ad-hoc mode (which would make better sense anyway for something like this). Or running the RPi from a hard wired (ethernet) connection. Unfortunately for that last option, it wouldn't work with a tablet, since I've never heard of a tablet that has an ethernet connection (kinda defeats the purpose of a tablet!). But I suppose Pi could be hard wired to a wireless router to dispense with WPA, and then the router connects to the Tablet via wireless connection. That might be stable.

Or one other possibility -- wait for the new RPi touchscreen to be announced and just run the RPi stand alone -- which would probably be ideal, except for the wait. And possible extra cost. The only problem might be whether it has enough resolution @ 7" screen size to be usable with the Grbl controller software.

BTW, ordered three 425 in.oz  steppers at a price I couldn't pass up.

[vtsteam]

I copied the root partition of the Raspberry Pi to an older 80 gig portable USB powered hard drive, and made a couple edits to the config file, so now the Pi boots from the SD card only and then immediately transfers over to running from the hard drive.

80 gigs is kinda overkill for this application, but it was a case of using what I had. the drive is only the size of the Rpi board and about 1/2" thick, so it's still a very compact package.

I'm thinking about making a micro rack tower to hold the boards, drive, and stepper drivers. Everything has a similar footprint, and I'd rather go vertical than have it spread out over precious benchtop space. I think a micro server rack would look kind of cute, too.

[awemawson]

Fit in with the new small workshop theme as well 

[gerritv]

Don't neglect the ceiling, when horizontal space is limited, vertical is the way to go.

[vtsteam]

My thoughts exactly, guys. 

For anybody interested, here's a nice website with a bunch of projects and interfacing information for the Raspberry Pi computer:

http://raspberrypihobbyist.blogspot.com

[vtsteam]

Spent the morning testing a new version of Puppy Linux (Tahrpup 6.0 CE) and it's really nce so far. Super fast and quite clean with better user interfaces for just about everything. It is built out of Ubuntu Tahr binaries, and loads Ubuntu repositories and software. But about one tenth the size, a completely visible system with dynamite utilities and tools, and a much faster OS.

Anyway, the reason I bring it up here is, I decided to see if I could compile Grbl Controller to run on this cool version of Puppy, and after a few false starts, and rounding up enough dependencies from the Ubuntu repositories andcreating a font link to temporarily fool the program installer, I was able to build a running app. So now I have a Grbl controller app running on my laptop (or any other computer that can run this version of Puppy Linux).

What that means is, I don't actually need the Raspbery Pi -- I can just run CNC from the laptop.

Since I also do all my design work on this laptop, that makes things pretty simple:. Just create the G-code file from Sketch-up/Sketch-U-Cam, or CamBam, or whatever, then plug in a USB cable to the Arduino, and start cutting.

I used the Pi before because I didn't have a Grbl controller program for my normal Linux OS, but now I do.

Another interesting possibility for people running other OS's is, Puppy  Linux will run under or alongside your OS without disturbing it. It's so small (less than 200 megabytes) and self contained that it can run from a folder on another OS, or from a thumb drive, or from a CD. So you could just load it up to do CNC cutting, if desired.

Obviously, Grbl Contrller isn't going to compete with something like Mach 5 on Windows. But for a simple system, and to get a job done, you can actually get away with two $7 boards, and a free OS and program -- all you need are steppers, their drivers and a power supply.

Stepper drivers for decent sized motors capable of driving a full sized mill are $15 to $20 per axis these days through Ebay. And a set of three 425 in oz steppers cost me $125 recently.