Re: Stepper drivers at http://www.oatleyelectronics.com/stepper.html

At 11:21 AM 10/17/99 -0400, you wrote:

>
>Does anybody know anything about the stepper driver kits available from
>Oatley Electronics? I'm talking about their MOSFET CNC STEPPER MOTOR
>CONTROLLER KIT on the top of this page

They say:

>MOSFET CNC STEPPER MOTOR CONTROLLER KIT: (CNC - Computer Numerical
>Control). This kit allows you to drive a stepper motor from a PC's

parallel port. Opto isloation is

>provided and kit will drive 5V to 100V stepper motors with a maximum

current of 14A (with good

>heatsinking). A total of 3 axes can be driven which will require the

purchase of three kits. The driver

>can be driven from software available on the internet called DANCAD. This

web site has

>suggestions for various setups. A combination of this kit and the Dancad

software could be used

>with home or professionally built milling machines, lathes, engravers or

cutters etc. Software has

>provision for home switches, limit switches, backlash compensation and has

a high degree of

>movement accuracy which can be better than 0.001". We supply the kit with

PCB & all on-board

>components. Heatsinks are not included but are only required if the motor

current is above 2A.

>Software is NOT included: (K142) $45 per axis kit.
>

Looks like these are nothing but the controller cards. You can buy
controller cards from a number of sources at similar prices, such as
Applied Motion in Watsonville CA. They have features like dip-switch output
level, winding enable or off, auto-current reduction if not used in certain
time span, and are also half-step (.9 deg/step with 200 steps/rev motor).
It sounds as if you also need a PS. Good PS are available from say
Microkinetics.

Software makes a big diff in the success of these projects. My suggestion
would be to consider that part first. I've tried DANCAD and am not knocking
it though I was unable to make it work well for me. The interface is not
intuitive to me though I've used Unigraphics, Generic and AutoCAD with very
short learning curves. Other softwares also drive through parallel port.
You can have more axes per card and drive more cards too with say I-LPT, to
total of six axes. This is handy for operating peripherals, as you can set
output of unused axes to descrete bits. I'm not impressed with .001"
accuracy but the implication that it's a function of controller or software
is wrong anyway. It's a matter of how far your single step drives the
screw. For ex, on mine that's 1/200 mm or .000196". Software backlash comp
is no substitute for a precise driveline and it will not prevent sloppy
screws from causing gouging on surfaces of the work.

I've heard of one G-code interpreter for I-LPT and I have one of my own
that is actually a user interface and code generator for that command set.
Usually with whatever products you use, cabling to the LPT port is the only
difficult part; the PS and output connections are simple and obvious. Some
makers give you very good schematics; with the help I had I got plug-chug
action on my conversion. Also, what will you be doing with 14 amps? Most
steppers in ordinary sizes will fry in short time if you feed tham that
much. I run 450 and 600 oz-in motors on 2.8-3.5A and they will develop
literally tons of thrust on ball screws with ordinary reduction drive ratios.

Best wishes,

Hoyt McKagen


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