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.