Newsgroups: comp.os.msdos.djgpp
Subject: Re: how to order motors via parallel port
From: richard AT stardate DOT bc DOT ca (Richard Sanders)
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Date: 23 May 2000 19:55:59 -0800
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To: djgpp AT delorie DOT com
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In article <392AFDC1 DOT 68AFE922 AT mtu-net DOT ru>, alex DOT fru AT mtu-net DOT ru says...
>
>are you inventing a plotter/printer?
>
>actually the problem is more complex than you can expect. with paralle
>l
>ports you may send bytes to those motors. but motors don't work with b
>ytes,
>they work with particular voltage and current. usually speed is voltag
>e
>dependant but your curve does not represent speed/voltage, it represen
>ts
>coordinates. so you need to convert coords to speed/voltage and then m
>ake
>your motors driven by bytes being sent via parallel ports.
>

Not so hard if 3 pole stepper motors are used.  Six bits of the parallel port 
are all that is needed. Six ttl level relays to power the stepper motors.

For a single stepper motor, using the low order 3 bits.
One bit (only one) must be on at all times.  To rotate the motor clockwise, 
rotate the on bit from left to right, wrapping around to bit 2 when rotating 
from bit zero.  To reverse the motor, walk the bit the other way.  To hold 
position, maintain the current on bit in the on position.

A program could be verified by using LEDs in place of relays and a stepper 
motor. 

More exotic motor drivers could be used in place of relays.

Cheers Richard