Build thread - UCNC: First Step - Electronics

[kuolas]

Hello wolrd!

I'm building my first CNC Router project, UCNC, a play of words for "You CNC".

The first step: the Electronics.

In the beginning I wanted to do a simple NC Drill (for building LED Matrices), but soon after I discovered EMC2 and changed my mind to do a full blown CNC Router.

The simplest way to use EMC2 is with a parallel port and stepper motors: EMC2 drives the steps/direction directly from the parport.

I've seen a lot of design for MACH3 and EMC2, including the excellent designs of PMinMO, but as an exercise I designed and build my own version of the controllers and interfaces.

This are the first boards and schematics I ever made on CAD/CAE Software (Eagle 5.10). They are designed with my needs in mind, and my own quirks too.

[kuolas]

Stepper Controller Board 42V 2A

I made this using the old and trusties L297/L298 combo. I decided to use this pair because they simplify design, L298N can handle 2A of current and most important they are cheap as chips.

I got a lot of ideas from the PMinMO design, but this controller is different, the most important difference is the oscillator frequency and the lack of on-board 5V regulator.

The lack of the 5V regulator is because I made my board with the assumption that the power comes from the BOB in the PMinMO connector, this obligate the use of a second power source: the main stepper 42V power source and a second, clean, 5V power source.

Another important difference is the use of a 6400 Heatsink from Spark Fun.

[kuolas]

Parallel Port Break Out Board 5 Axis Opto-Coupled

This one is different from the rest of the other open source boards that I've seen. It is based on the same assumptions as the SCB, this boards "routes" the power to the SCB attached to it, so the traces are big enough to handle it. It is compatible with PMinMO boards because PMinMO boards have a jumper to select the power source.

Other important feature of this board is the use of the standard IDC 26 pins to DB25 Female connector that's been in use on PCs for decades now, this connectors can be found cheaply and readily. I think that this approach is better that to solder a DB25F directly to the board.

Inputs are 5V, but buffered with a 74HC14, the same chip used in the SCB (for the sake of the BOM of both boards).

There is a PWM signal output, generated by software. It is meant for being attached to another board that I'm developing for controlling the spindle. But it's fairly simple to use.

The Enable jumper, I was thinking of using this jumper for the E-Stop switch, but works as a jumper standalone, though.

[kuolas]

All this boards and layouts are untested. They are made with the asumption that "they should work". I, by no means, are responsible for any damages, crazy CNCs or robots with sentient minds trying to controll the world, that can happen because of using my designs. I warn you... but I think that the boards, even untested, works. Let's see how Murphy's laws apply to this boards.

I'm going to build them... ASAP, and begin the "Test" phase. Then comes the mechanical part.

Any ideas, thoughts, critics and insults about the board (or anything else for that matter) are welcome.

[hesham morsy]

the Board look impressive especially the 5 Axis Break Out Board

good luck

(Let's see how Murphy's laws apply to this boards)
i have bhd in Murphy's laws

[RomanLini]

I like your designs and CAD work, both are very attractive and well laid out.

But you may be better suited with microstepping drivers, there are quite a few inexpensive and proven kits around that will save you the cost and/or work of making your own PCBs and overall won't cost that much more than the cost of parts and PCBs.

However if you are set on the idea of designing your own from scratch for satisfaction etc then you might want to look at some of the popular microstepping driver chips, as the 297/298 combo is pretty dated.

[kuolas]

Right now I want and need something quick and dirty. L297/L298 are proven and reliable, not the best solution of course, but for now It will do.

I'm a EE student, and I want to design and understand as much as as I can, everything if it's possible. I don't want the machine by itself... I'm doing this for the satisfaction and fun of designing something like this.

Now with all the technology and INTERNET we can do this, I mean we can think and design. Open communities like this are wonderful. In the past only the people with the thousands of dollar CAD/CAE Workstation could do this, only the Engineers with the Databooks could, today everyone with enough interest and time can!

My next design will be based on Microstepping, but microstepping is really complicated. Also, I want to design a BLDC VFD, intended to be used on the spindle (you should see rcgroups.com were Takao Shimizu and Bernhard Konze have designed more than one BLMC, that's impressive, they are my heroes).

But, after all, I will do as every other member in this forum does... build the First CNC so that machine builds the Second CNC.