Re: [Emc-developers] 5i25/7i78 question

[Gene H. <ghe...@wd...>]

On Monday 07 July 2014 10:32:44 Peter C. Wallace did opine
And Gene did reply:
> On Sun, 6 Jul 2014, Gene Heskett wrote:
> > Date: Sun, 6 Jul 2014 12:58:28 -0400
> > From: Gene Heskett <ghe...@wd...>
> > Reply-To: EMC developers <emc...@li...>
> > To: emc...@li...
> > Subject: [Emc-developers] 5i25/7i78 question
> > 
> > Greetings;
> > 
> > I am considering, because of the quantization noise in the software
> > encoder output, switching my lathe to the 5i25-7i78 combo as it can
> > do much higher frequency sampling of the ABZ signals.
> > 
> > However when I dl'd the pdf manual, I find its stepper outputs can
> > only source or sink 10 mills when 1 volt away from the supply rails.
> > 
> > My present BOB, a cnc4pc C1G, can do very close to rail to rail while
> > sourcing or sinking 24 mills.
> 
> The only real difference between the C1G and the 7I78 outputs is that
> the 7I78 has 27 Ohm series resistors in its 74ACT buffer output pins
> (and that the 7I78 has differential outputs) It should drive any
> step/dir input just fine
 
The 2M542's inputs are fully isolated opto's.

> If you use the outputs single ended you will get twice as much drive
> (but ~1/3 the noise immunity)
> 
I don't believe the C1G can do differential output w/o sacrificing pins.  
OTOH, there are only 2 steppers on the lathe, so I could, but 4 on the 
mill.  So at some point, when I run out of current projects, you'll see an 
order from me for another 5i25 and a pair of 7i78's.  I assume PncConf 
will by then support the 7i78?  Its been a couple months since I ran it, 
but don't recall seeing the 7i78 in the menu's presented.

Thanks Peter.

Cheers, Gene Heskett
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