Thanks photomankc, Ravenous for your replies.
To be honest, I don't have any specific use case for the CNC I was thinking of making. My only motivations are:
1. Build a CNC using RPI: stumbled on a lot of DIY CNC videos, articles on servos/steppers etc and its fascinating.
2. It not be a toy: that I make and keep aside after playing with it for a few days after bldg it.
Photomankc: do you have a blog where you have described bldg your 2500$ CNC, including parts etc. The main reason I thought of bldg my own stepper driver are:
1. I live in India , don't have easy access to spark fun, maplin, amzn,RadioShack etc, its usually easier to build things from parts myself or i d end up paying high prices ( import duty etc)
2. Its more fun, but more importantly if something goes wrong I have depth to fix it.
Re: micro stepping , the same article I pointed to, shows how to use a stepper IC ucn5804, to make things simple.http://www.imagesco.com/articles/picstepper/06.html
. if I put tip120 after the if, shldnt I be able to drive 5a motors and get all complex features like micro stepping ?
Also, if some one could point out two things it would be extremely helpful:
1. How to use external power to drive the load ckt? For eg. The stepper or even a simple led- specifically, do the gnd of external power and the RPI/pic gnd need to be connected? If yes, do I need to put a high resistor between the stepper/led and RPI/pic gnd so that the high load voltage/current doesn't fry the pi? A simple ckt dia would be very helpful.
2. The enema 34 stepper I saw online was AC driven. How to drive an AC load ckt with a smaller DC logic ckt?