Trying to clarify, for newbie as me. Comments pls

[pigifly]

Hi all,
it's quite a lot I' m thinking to cnc my micromill, and I was searching for a DIY solution.
I've read all the looong thread talking about http://webpages.charter.net/pminmo/cncelectronics.htm docs, but a lot of things are yet obscure to me, so I write it down here, asking for confirmation, and leaving this thread for those like me, which are (yet) far from CNC and electronics (and also don't understand well english).
My understanding from those circuits are:

1) tachus42's 3 Channel Discrete Unipolar Board :
This board can be connected directly to PC from the DB25 connector, and to UNIPOLAR motors from the S2-S7 connectors, and is not optoisolated thus don't prevent damages to parallel port in case of some shortcircuits or other problems on the board.
Questions:
1) How the motors should be wired, being that an unipolar motor has 6 wires and the connector for each direction are only four ?
2) Am I right in my understanding ?
3) Can some one post the DRC file as when I import it in eagle the DRC fails showing some clearance errors ?

2) tachus42's 3 Axis Chopper Adapter For the above Unipolar Driver:
Can't absolutelly image what a Chopper is ....

3) Plain DB25 (Break Out Board):
A Break Out Board is a board that connects to pc, and can be connected either to an unipolar than to a bipolar driver to drive those ind of motors

4) Compatable 3 Axis DB25 to Single Axis Boards Interface Board (Break Out Board):
Can't absolutelly image what this is ....

5) Unipolar Discrete:
This is a driver for unipolar motors, that can be connected to a BOB, and has only discrete components.

6) Allegro 3977 / L297/L298 board compatable and interchangable with this set :
Those are drivers for bipolar motors, that can be connected to a BOB using differents chipset to drive the motors.

7) 5804 board based on original prototype but compatable with this set :
This is a driver for unipolar motors, that can be connected to a BOB, and has a chipset specific to drive the motors.

8) Opto Isoloated Break Out Board:
This Break Out Board is a board that connects to pc, and can be connected either to an unipolar than to a bipolar driver to drive those ind of motors, and is optoisolated to prevent damages to PC.


At this point, If my understanding are right, to start with my unipolar motors I will need :

1) tachus42's 3 Channel Discrete Unipolar Board, three motors, and nothing more, or

2) A BOB ( optoisolated or not ) and 1 to 3 Unipolar Discrete or 5804 board

Are my understanding right ?


Thanks in advance
Pigi

[tachus42]

Pigi
You have got it right. The Common connections of the steppers is connected to the positive supply though some current limiting resistors which are mounted off the board.
The chopper board can be used instead of the resistors and gives better preformance and generates less heat (and wasted power) than using resistors.

[pigifly]

Originally Posted by tachus42 The Common connections of the steppers is connected to the positive supply though some current limiting resistors which are mounted off the board.

A bit of clarify yet. Is that kind of connection the one I have attached ?

Originally Posted by tachus42 The chopper board can be used instead of the resistors and gives better preformance and generates less heat (and wasted power) than using resistors.

For this chopper board, is it possible to have an image of wiring diagram to the driver ( or whatever ) board ?

Thanks in advance.

Pigi

[tachus42]

Without the chopper board the connection is like your diagram, but if the power supply voltage is higher than the stepper voltage you would also have a resistor in series with each common connection.

The chopper board sits on top of the 3 axis driver and gives 2 common connections for each stepper lined up with the 4 phase connections below.

[Ferenczyg]

2) tachus42's 3 Axis Chopper Adapter For the above Unipolar Driver:
Can't absolutelly image what a Chopper is ....
-----
Not strictly technical speaking, but in a stepper the current provides the torque and the voltage provides the speed. With a 'chopper' board you 'chop' the voltage applied to the windings. Usually, from ohm law (I=V/R) given a voltage (from the power supply) and a resistance (from the winding) you have a given current in the winding. By chopping the voltage you can increase the voltage applied to the winding but because the chopping technic you maintain a fixed amount of *average* current in the winding.

This way you have the best torque (matching the average current in the winding to the motor specs) and better speed (putting voltage way above specs, usually 10x to 15x).

In a non-chopper board, if you want to increase speed you must add external resistances (that adds in serial to the windings resistance) to keep the current tamed, and that external resistors waste power, are expensive and can become really hot.

==========

4) Compatable 3 Axis DB25 to Single Axis Boards Interface Board (Break Out Board):
Can't absolutelly image what this is ....
------------

A breakout board is a interface board that permits to select what wire from your parallel port (DB25) you design as your step (or clock) pin signal and direction pin signal. If is a 3 axis, it means that is capable of select at least 3 pairs of step (or clock) and direction pins.

A axis board take the step and direction signals and 'converts it' to the power signals that you inject to a stepper.

So a 3 Axis db25 to single axis interface board is a interface board that plugs in one side to the db25 lpt port, and on the other side is able to provide signals of step and direction to up to three independent (or 'single axis') boards, everyone of them capable of provide current and voltage to driving a single stepper.

Independent drive boards are better than 'all axis driven equal in the same board' because you can select the best driver board for every axis of your machine or purpose and mix it to suit your needs. And every axis driver is easier to replace if fails or something similar.



Hope it helps
/Fer