Re: [CAD_CAM_EDM_DRO] Paper Tape Reader?

On Friday 28 March 2003 22:04, Raymond Heckert wrote:

> Does anybody have a circuit to build a LED-type, RS-274 Paper tape reader
> for my CNC machine? Also, I'd like to be able to verify some part files,
> and possibly archive some program tapes. I have an old KSR-33 type machine,
> but it's punches hang up, and the printwheel doesn't always print the
> correct characters, and also, it doesn't 'read' the binary program code
> that I want to archive. Circuit or schematic, anybody, please? Or is this
> O.T.?
>
> RayHex

You might look in some of the early Byte and/or Kilobauc <sp?>, or Popular
Electronics magazines.

In my opinion one of the best designs was by SloSyn (I think I still have the
manual w/schematic around somewhere). They used a cartridge-type light with
the filament running on DC. It had eight phototransistors. One for each of
the eight data channels. IIRC they used a stepper motor to move the paper
tape; the reader program commanded the tape to move for each character.

There were several other designs that either used a simple motor or even hand
pulling. These used nine photoransistors with the nineth picking up the
sprocket holes for a data strobe. You could make one of these fairly easily.
Machine a piece of aluminum to guide the tape; slot a block for the tape to
pass through with nine holes lined up with the tape holes. Mount your LEDs on
one side and the photortansistors on the other. Feed the output of the
transistors through a Schmidt trigger (74LS14?) to square up the signals.
Feed it to a parallel port.

--
Keith Bowers - Thomasville, NC