Re: [CAD_CAM_EDM_DRO] Help implementing spindle & coolent on/off

In a message dated 08-Jul-02 12:35:06 Central Daylight Time, eferg@...
writes:

> 2) Can 4 axis, plus spindle & coolant on/off, and limit switches be
> implemented using a single parallel port?<<

Yes, but I can't say your "store-bought" software can necessarily handle
that! There are 8 "bits" (wires?) in the printer-port (plus "ground"). With
those, and cascaded decoders such as the 74HC154 and 74HC4514, you can have
up to 256 separate lines which can be controlled by the LPT-1. If some must
"remain on" until commanded to "go off", you could use such as 74HC574
latches. Can get complicated to explain verbally to a non-electronic type!

A standard SSR usually has a low enough "I-in" at 4-5 VDC that no "buffer" is
necessary between an LPT-1 line and the SSR's "+ in" (connect "- in" to the
LPT-1 "gnd." pins 18-25)

I like to put a 74HC541 with EIGHT 4K7 pull-up resistors to each INput line
from the LPT-1 before "anything else" I want to control with the LPT-1. This
"buffers" the LPT-1 and kinda "isolates" it (no, NOT the same way an
"opto-isolator" does!) from the experimental stuff, which, done wrong, CAN
waste a perfectly good PC!!! KNOW what you are doing before meddling with
ol' LPT-1!!!!!!!

>
> 3) If solid state relays are the solution for spindle & coolant, can
> someone make a recommendation? Are any other components needed to
> interface the PC to the relays? What about power requirements? I
> order most my parts from Jameco.

I-R Crydom and Opto-22 both do good SSR's. There are basically two "ranges"
these days, each with their OWN "ranges". The "little PCB-mount kind" are
good for 2 amps, some only to 120 VAC, and others to 280 VAC. The
"hockey-puck kind" can be had for up to 10, 25, and maybe even 40 amps ($/amp
linear function!). I have seen them also with "working voltage ratings" to
120 VAC, 240 VAC, and 480 VAC. I do not know if there are yet-higher
"standard catalog versions".

Jameco is good. Digikey has lotsa stuff, and is proud of it. JDR is another
decent source. NEWARK and Allied are others, apparently anxious for bidniss,
as they do plastic (last I ordered)!

Lotsa luck! Jan Rowland, Old Troll

P.S: Ah, "limit switches"! There are, what, five lines of address $379
which are "inputs" TO the LPT-1 (sorry, do not have pin-numbers of those at
hand, but see
<A HREF="http://www.lvr.com/parport.htm">The PC's Parallel Port</A> . The "printer port" 8-output lines are @ $378 (888
decimal)




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