Re: looking for a XYZ cnc circuit throug lpt

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "eli_cohen00"
<eli.cohen@g...> wrote:

>
>
> hi,
> i'm loking for a XYZ cnc circuit throug lpt
> i need a simple circuit that works
> i'll use 3 steper motors - there is difference between steper

motors?

>
> i found this circuit
> http://hans-w.com/9908-09A.gif
>
> and this(not test yet)
> http://hans-w.com/modular_cnc.htm
>

Hi Eli,

Many people have made their own boards and their own driver
circuits. You need to determine how much power you need, and how
good of a circuit designer you are.

In a simple form, a full step driver is pretty easy to build. Even
just MOSFETS connected to the parallel port will run a motor.
TurboCNC has this output ability, but it takes 4 pins per motor.


You can make your own driver from designes on the web. The simplest
are all full step and have somewhat limited amperage ( or current
rating if you prefer that term)

With your PCB machine, and 1/4-20 (or metric equalavent) leadscrew,
you have 20 rotations per inch, times (I assume) 200 motor steps per
inch, for 4,000 full steps per inch. this is great for full step
driver. Considder that fine thread of 28 tpi with a 7.5 degree
stepper (pulled stepper from printers) wouild still yield 1,344 steps
per inch. Again more than accurate enough for a pcb machine.

half and quarter step driver circuits are harder to build and harder
to find. As you noticed, there are some driver circuits that use
PIC microcontrollers.

I would recomend you start simple, with a simple dual H-bridge for a
bi-polar, or the simplier uni-polar driver. Much faster to get the
motors to spin.

Another benifit is that you may find it has more then enough speed
and power for your machine, or that once you have your machine, it is
easy to make more complex drivers with it.

For a first time board, I would not use a PIC type as you will never
know if your problems are software or hardware.

check out the second sketch http://eio.com/jasstep.htm simple 4 pins
from the PC to a uni-polar motor. it will take 12 port pins to run,
but getting a second parallel port and this simple circuit is
probably the fastest route to a working machine.

But, I would say that building the machine before the drivers will be
well worth your efforts. It has been pointed out that many people
take months to make a circuit, spend hours and hours, then spin the
motors and give up. Whereas those that build the machine, then want
to see it move, make simple circuits and have machines that are
running.

Dave