Sean Breheny wrote:

> I don't know anything about the format in which the data is stored on
> the strip, but I would immagine that it is independent of the rate at
> which the card is swiped past the magnetic head.

  Well, not quite; it is supposed to be written accurately and to a
particular specification.

> ... we couldn't have manually swiped card readers, and we do have
> them.

  Indeed we do, but they require software with a *very* wide capture
range.  Using a capstan drive simplifies the task tremendously and makes
it far more reliable.

> you may not need to use a stepper motor if the rate is not critical.

  You may not *want* to.  Steppers make the travel jerky and you still
need a flywheel!

> You could simply use a geared-down DC  motor.

  *If* it is cheaper.

> Also, unless the data comes off the card in something similar to RS232
> format, I don't see any reason to try to convert it to RS232,

  This is D�j� v�!  RS-232 is *not* a format, it is a voltage
specification.

> I would just send the amplified/clipped pulses to the PIC.  There is
> certainly no reason not to use TTL levels, since these are the only
> thing that a PIC can accept directly

  .. and in fact, the only thing that "bare" card reader modules as you
propose to use ready-built, give out.

  As was pointed out last round of this discussion, the exercise may be
interesting, but unless you plan on production in the thousands, or
greater, it's more economical to purchase the assembly complete with
motor drive.  The thing to do would be to sniff out who IBM, ICL and so
on, buy them from.  They don't necessarily do it all in-house.

  Cheers,
        Paul B.