The CNC mill got into a working state right before christmas eve. I know it’s not a present in that sense, but still! :3
Some parts of it are still fixed with a lot of glue and tape (or zip-ties ^^), but for now that’s perfectly sufficient. Right now. it can already mill hard wood and MDF, so I will be redoing some critical parts that lack in precision and/or quality before I write up the whole project as one. Unfortunately, I fear that the original plan about using an (older) EPIA 800 board as a controller can not be followed, EMC2 just refuses to start on that thing. Grrrr…
More pictures and text will follow in a few day’s time. Until then, enjoy the holidays and have a nice and safe start into the new year!
Oh, right, and two Stellaris Launchpad eval-kits from TI that I ordered back in September arrived JUST ON the 24th. How great of a timing is that? I don’t care about the wait, it was well worth it and I knew up front – but thanks again to the girls and guys of the TI support, for solving all the technical difficulties along the way :-)
Work on the CNC continues…the end draws nearer. I am currently disassembling the whole thing as far as necessary to clean up all the edges and burrs and fix the positions of the parts relative to each other using hammered-in stainless steel pins. After that, it is just coupling the threaded rods to the moving parts and bring the stepper drivers alive.
So much for the current status of the CNC milling machine. I have made some first experiments with L297/298 motor drivers and found out the hard way that these are quite overloaded with such strong motors. Burnt out in a matter of seconds. But, as BJT driver bridges are not state of the art anyways, and I want to take a lesson from this project, I decided to finally get myself some of those specialized ATMEL controllers (AT90PWM1) and try to design my own FET bridge driver.
I even have one in spare that I can use for experiments with a self-designed high intensity discharge lamp driver – I have attached an image of an early prototype to the gallery for your entertainment. Worked quite well for some time, but the driving was very crude – there are some logic gates on the bottom of that small pcb that generate half-bridge signals for the two FETs, but no care taken about anti-shoot-through and so on. VERY crude. I will report how well the new controllers work out, seeing that very few experiences are found :-)
As for the CNC, I am quite confident that I will finish the mechanics part within the next holidays (around easter). Then, all that remains is the ‘intelligent’ part.
Last but not least, I notice that I still do not manage to describe my projects in my self-desired level of detail. Thus I will focus more on taking pictures during the process and explaining from now on.
Just a little heads-up for the time being: This is one of the things I am currently working on. I have some things with DFN-packaged parts in the making, this also belongs in that category. The IC is a Texas TLC5941 16-channel programmable LED pwm controller, and the whole thing will be an ambilight system that can be easily scaled by adding more of these stripes. Each stripe will contain 5 individually adressable RGB-LEDs, equal to 5 individual zones. The master signal will be delivered by the pc (no, unfortunately I have no plans in stock to decode VGA or DVI so far, as this system is inteded purely for pc-aided use) via serial comm and formatted by an Atmel ATMEGA to fit the daisy-chaining protocol of the TLC chips. This also means that additional boards can be connected without much hassle.
Hopefully, I can produce the first PCBs myself. The biggest problem are the through-hole contacts, but I guess this can be done using 0,6mm contact rivets. Of course, I am in no mood to do this for all the 50-some boards that will be needed – I am not the only person interested. The angled pinhead connectors at both ends will be replaced by rows of soldering pads so that two pcbs can be soldered together without a gap. Alternatively, they can be connected by soldering flat cable or even single wires in between.
I already have all the necessary chips and a whole lot of LEDs for some prototype boards, but I need the reflow oven to work properly for this – the chips are DFN, as mentioned. I soldered one of them bottom up to some pinheaders using thin enameled wires: Avoid if you can, it’s NO fun at all! The chip survived the torture, surprisingly.
Hopefully I can make some progress on the oven tonight. I already equipped one of these things with a diy controller before for a friend, so the software is kind of done.