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parallel port

Discussion in 'Misc Electronics' started by Allan Adler, Sep 9, 2006.

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  1. Allan Adler

    Allan Adler Guest

    I've been reading James "J.J" Barbarello's book, Real-World Interfacing
    With Your PC, 2d ed., and now I'd like to try to actually do something.
    The first thing one has to do is to make a "break-out cable", which
    he describes early in the book. As it happens, I found a discarded
    printer several months ago and scavenged its printer cable, one end
    of which plugs into the PC. So, I think I don't need to build a break
    out cable according to his prescriptions, I just have to cut the cable
    somewhere. If I had any way to make use of the end that goes to the
    printer, I wouldn't need to cut the cable at all. It looks like
    it is supposed to receive some kind of card edge. Maybe if I had
    also scavenged the printer, I would have been able to extract its
    card and remove all the electronics and use it for my own experiments.
    Without it, I'm not sure what to buy and for how much to use the
    cable intact.

    Barbarello is very specific about the lengths he wants one to use to
    make the break-out cable and the jumper cable one needs to connect the
    break-out cable to the breadboard one is using for experiments. He wants
    4 inch lengths of #22 wire to make the break-out cable from a DB25 connector
    and he wants a 5 inch length for the jumper cable. This seems to take nothing
    into account about the actual distances between the computer and the
    breadboard. I know from experience, from which I unfortunately did not
    learn enough, that funny things can happen when one uses long wires in
    digital circuits. So, I'm allowing for the possibility that Barbarello
    really means that the wires should be fairly short. On the other hand,
    the printer cable is clearly much longer than that, but it is much more
    carefully designed and maybe that matters.

    I also looked at another book, Parallel Port Complete, by Jan Axelson,
    but it seems to be mostly concerned with software and gives almost
    no guidance in actually building anything. Also, it seems to be oriented
    towards Windows, while Barbarello is oriented towards DOS, which I prefer.

    If there are more interfacing books with simple parallel port projects,
    I'd also be interested in looking at them. Ultimately, I'd like to build
    some kind of simple apparatus for simple experiments in areas other than
    electronics (safe stuff that can be done in the home) and have it controlled
    and monitored by the computer via the parallel port. At the moment, I'm
    keeping an open mind about what I'd like to do and would be glad to know
    about books that contain specific projects that can be done very cheaply.
    Barbarello mostly discusses using DAC's and temperature sensors.
  2. DaveM

    DaveM Guest

    Don't worry about the length of the printer cable. The parallel port isn't
    really what you would call "high-speed", and the normal PC parallel port can
    handle cable lengths of 15 feet or more. Just cut the cable that you have to
    the length you need and you should be just fine.
    Since this is an unusual manufactured cable, you will obviously need to make
    sure that all the wires you need for your experiments are wired into the cable.
    Some of the early printers (Radio-Shack, Commodore, etc.) didn't have the
    standard Centronics interface that more modern printers have used.


    Dave M
    MasonDG44 at comcast dot net (Just substitute the appropriate characters in the

    If a mute swears, does his mother wash his hands with soap?
  3. Si Ballenger

    Si Ballenger Guest

  4. jasen

    jasen Guest

    the plug that the other end goes to is a centronics 36-way plug should you
    want to purchase one (might be easier to grab a discarded printer)
    he probably had it short to save money, unless he's running that port at a
    really high data rate length won't be much of a problem. (not with
    breadboard projects atleast)
    I've seen printers on the end of 30m ribbon cables and those round cables
    are often superior to ribbon cables.

  5. Wrong way around. Radio Shack ALWAYS used the standard Centronics
    interface - they made their standard from Centronics' design. It was IBM who
    stuffed it all up by using the standard DB25 serial connector for the
    printer and a reversed connector for the serial port. They also misconnected
    some of the wires making it even less like the standard. Curse their black
  6. Allan Adler

    Allan Adler Guest

    Coincidentally, I just found an electric motor in a dumpster. Assuming it
    still works and I can figure out how to use it (I've never done this before),
    one project can be to control this motor from the parallel port. It was sitting
    next to a fan enclosure in the dumpster, so I'm guessing it was used to turn
    the fan. It has something on the spindle that probably is inteneded to hold
    a loop to turn the fan. It's dirty and heavy and I found the following
    information on the body of the motor (= signs mine for readability):

    Howell Motors 6146 HP=3/4 PH=1 DUTY=CONT. FRAME=N56
    FRQ=60 RPM=3450
    L 203 230 4 . 5 1.25

    CODE=L C^o RISE=40 (C^o means C superscript o, as in (I think) deg C).
    Thermally protected
    AUTO 70377900
    SF AMPS 5.0

    I think the AMPS field is 4.5A, but maybe it means between 4 and 5 amps.

    Before using it, I'll probably need to mount it and probably on a thick
    board, but I don't know yet how strong it needs to be and what that implies
    for the choice of board. I don't think I can tell the computer to control
    the motor until I know how to do it myself. After that, there is the problem
    of setting up the circuits to power and control the motor, but one thing
    at a time.
  7. Allan Adler

    Allan Adler Guest

    What do you mean by the standard Centronics interface?
  8. Allan Adler

    Allan Adler Guest

    Thanks. I'll try looking at them on a better computer than I have.
    I took a look with my browser on my computer and Netscape hung while
    I was trying to bookmark them. Then the whole computer hung. When I
    rebooted and the PC tried to correct the errors due to having failed
    to unmount the disk cleanly, I got an unusual message about how the file
    system had become inconsistent. I had to log in as root and run fsck
    manually to correct the problem. I'm not saying it is your fault, just
    that my machine and its browser seems to have some deficits.
  9. A 3/4 horse motor is a honking big motor and can only be on or off. No other
    control is possible.

    You'd do better to pick up a Radio Shack Color Computer (about $10) and look
    at some of the interfacing books on various sites: -

    They'll have practical projects and how-tos.
  10. Jamie

    Jamie Guest

    and its most likely no good..
  11. Allan Adler

    Allan Adler Guest

    Let me take these points in turn.
    (1) Who will sell me a Radio Shack Color Computer for $10? Will it cost more
    than $10 to ship it to me?
    (2) Does anyone else think that I should get a Radio Shack Color Computer?
    (3) The first website deals with emulators for TRS computers. If I ran
    such an emulator on a PC running Windows (which would not be one of my
    PC's, which all run Linux), and ran software for interfacing a TRS through
    its parallel port, would that software run under the emulator and
    would the project thereby work on the PC in question?
    (4) I could be mistaken, but I would think that the most useful information
    to be extracted from the practical projects and how-tos would be
    adaptable to the PC's I'm actually using. I'm planning to use FREEDOS
    at first and Linux if I can ever get an overview of how it talks to the
    parallel port. I'm somewhat optimistic that I can since I once downloaded
    some software for Linux that does just that and it said that it was
    working. Also, I have the book, Linux Device Drivers, 2d ed, and it
    has a project of talking to the parallel port in one of the chapters.
    Anyway, one the premise that the information in the TRS guides to
    interfacing and projects is exportable, I don't think I need to get
    a Radio Shack Color Computer.

    Apologies if I didn't realize you were joking.
  12. Not joking. Coco's have been used for all sorts of things like this. IIRC,
    someone used one to replace a $20,000 video controller. There are books on
    interfacing them, which is real easy to do. Even an old 8088 PC is a bitch
    in comparison, and that is when you could buy boards to do this.

    I also recall a Model 100 used to control a road resurfacing machine. Ports
    are handy.
  13. Allan Adler

    Allan Adler Guest

    OK. I'm not ready for ebay. I don't know if I ever will be. On the other
    hand, I did once look over the vendors at ebay and found one with a good
    reputation and made a deal with him for an item that he didn't happen to
    be auctioning. So, maybe I'll try something like that.
    Thanks very much for telling me about this.
  14. jasen

    jasen Guest

    have a look at the "linux-coffee howto" a good introduntion to ad-hoc
    hardware and the parallel port under linux.
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