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Can I cable a GRBL Arduino to the parallel connector of my CNC controller?

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vtsteam:
 :lol: I like that expression, Bill! I have to remember that. Today I finally got my old hot wire foam cutter going again with an ancient program on an equally ancient laptop running windows XP. With that out of the way, I'm going to throw the switch tomorrow on the GRBL/Arduino parallel cable experiment and see whether I'll be in the market for a wooden leg. Actually, just, at worst, a spare arduino out of the box of them I have. Fingers crossed!  :zap:

BillTodd:
That was one of Dave's (Dave Bickers)  favourite sayings, I thought it would have made a good title for his biography.

AdeV:
The max input voltage for the 817 opto isolators is 1.4v (with 1.2v typical)... however, an inline (series) resistor of ~370ohm will drop 5v to around that level. If you've got the eyesight & the dexterity - if you can get a multimeter onto one of the series resistors, you should be able to determine whether it wants 3.3v, 5v - with 5v the most likely.

The issue with the opto isolators only tolerating such a low voltage is you'll burn them out long before the Arduino lets out the magic smoke: But... given a standard parallel port can be expected to be 5v, I think you'll be safe enough.

vtsteam:
Thanks Ade! :beer: I didn't have the magnifying glass this afternoon, but spent a lot of time with a multimeter probing the parallel cable I have. It originally had a Centronics 36 pin connector at one end, and a DB25 at the other.

I chopped off the 36 pin end and will use the DB25 end. It was a really well made cable BTW. Heavy woven shield, then foil, then multicolored twisted pairs - 18 of pairs and a bare ground wire.

The pin assignments and colors worked out to:

Pairs:

white   17
white blk   25
   
pink brn   23
grey brn   15
   
purple brn 24
blue brn   13
   
orange brn 8
green brn    22
   
green   10
green blk   24
   
brown    3
grey red   19
   
yellow brn 20
red brn    5
   
yellow blk 10
yellow   9
   
brown         1
brown blk     18
   
blue      12
blue blk   13
   
yellow wht   21
orange wht   7
   
orange      6
orange blk   21
   
grey wht          25
purple wht   16
   
green wht   11
blue wht           23
   
red           4
red blk   3
   
red wht         19
brown wht   2
   
purple     14
purple blk  25
   
pink           N/C
pink blk   N/C

phew!  :coffee:
   

AdeV:

--- Quote ---white blk   25
grey wht          25
purple blk  25

--- End quote ---

Seems odd? Although I guess if it's got Centronics on the other end, that does make some sene, IIRC the Centronics connector was a 36 pin...

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