Re: [CAD_CAM_EDM_DRO] Simple Parallel Port controller

Eric:

You could use just ONE bit of the eight of the parallel-printer-port to turn
that ONE relay on or off, or, you could even use some cascaded decoder-logic
(74HCT4514, for example) to control up to 255 separate relays. But NO ONE
has given you a hint how to "do that" from software!

If you are using simple BASIC, you can OUT 888,n (888 is the decimal address
of the printer-port, or, $378 in HEX). If you connect your relay to bit-0,
then OUT 888,1 makes that bit "go high", and OUT 888,0 makes it (all-8) "go
low" again.

The solid-state relay another in the group suggested is a sure-fire way to do
it, but you COULD use HCT logic and "any" SSR, or even an electromagnetic
relay, if you used the right "sink driver". But I have no clue how much
"electronics" you know.

In a BASIC program, when you come to an "OUT 888,n", that "n" will be put on
the port (binary equivalent of zero or 1 through 255) until changed by a
later "OUT...".

For example: 10 OUT 888,1
30 OUT 888,0

will "toggle" bit-zero for a couple of microseconds or so (depending upon how
fast your particular computer is). Or, if you add a line 20 FOR D=1 to
10000:NEXT, it will "stretch" the "on-time" of bit-zero (making the 10000
larger will stretch it proportionately more, of course).

If you do NOT included line-30 above, that bit will REMAIN high until you
turn off the computer, or some other program changes that bit! This can
confuse things if you have little experience with such, and/or, no "pilot
lights" on the 8 port-bits.

Lotsa luck! Jan Rowland, Old Troll




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