CNC machine
computerized numerically controlled machine

Mechanics

AE-740 Typewriter
Striped down to just what I need.

See: Service manual

12v Stepper motor coil sequence - white -> ground, 1)-red, 2)-yellow, 3)-brown, 4)-blue

Striped down.

Stepper motor coil sequence - green -> ground, 1)-yellow, 2)-red, 3)-blue, 4)-white

Highlighted parts are added to attach typewriter to scanner.
Red part is a pen used in testing.

Scanner controls the Y axis
Typewriter controls the X axis

Electrical

Male parallel port cable wiring.
see: SPP Parallel Port Pin-out

Driver circuit for the typewriter stepper motor

IN- from D0 (pin 2) of the parallel port.
Out - to coil 1 (red) of the stepper motor.
Build 4 -                  IN from D0-D3 (pins 2-5):                       Out to stepper motor 1
NOTE: +vcc is 12V DC

Parts

Resistor
Green, Violet, Red - 51KΩ

NpN Transistor

Resistor
Brown, Black, Red - 1KΩ

Transistor array - µPA1437H PnP
(4) - Darlington transistors
Found in typewriter
See: Data Sheet

Driver circuit for scanner stepper motor

IN- from D4 (pin 6) of the parallel port.
Out - to coil 1 (yellow) of the stepper motor.
Build 4 -                  IN from D4-D7 (pins 6-10):                       Out to stepper motor 2 and then to 12V DC

Parts

NpN Power Transistor - 2N5190
See: Data Sheet

Diode

Computer control

The program I'm using to control the parallel port is "Kemo - Relais Timer".  This program is designed to control a relay  module that could be used to turn on and off lights in the house at specific time.

You can download the program Here -> http://www.vego.nl/kemo/42/42.htm

"Kemo" allows you to save your work in a *.rpt file.
To get this program to drive the stepper motor sequence I had to write a program to automatically create the *.rpt file.
I wrote it in javascript.

I'm not going to go into details about the programming. You'll have to study files...(click on links below)

Basicly my program takes my instructions, and converts then to a format the Relais Timer understands, (.rpt file).

Technical

The parallel port outputs (pins 2-9) maximum   current 24 ma

My Cicuit
parallel port current draw = 68.4  µA & 44.6   @ 4.38 V on Q1-Q4 & Q5-Q8
Circuit at rest current - 1.3 µA
12V line Total max. current normal operation - .88 Amps
12V line max. current all coils on bad operation -   2.97 Amps

Stepper motors resolution
Typewriter     x - 1000 steps = 8.375":            1"=119.402985 steps
Scanner         y - 2000 steps = 6.8125":          1"=293.57798 steps

Range of motion
x - 12"
y - 9.625"

Max Speed
.02 sec/step

Links