On Saturday 24 November 2018 15:32:04 Peter C. Wallace wrote:
> On Sat, 24 Nov 2018, Gene Heskett wrote:
> > Date: Sat, 24 Nov 2018 14:29:55 -0500
> > From: Gene Heskett <[email protected]>
> > Reply-To: "Enhanced Machine Controller (EMC)"
> > <[email protected]>
> > To: [email protected]
> > Subject: Re: [Emc-users] Waiting on the mail
> >
> > On Friday 23 November 2018 17:55:57 Gene Heskett wrote:
> >> Greetings all
> >>
> >> I'm going to try something thats probably crazy, and until the mail
> >> brings me a 7i76D expected tomorrow maybe I'm going to assmue it
> >> will work.
> >
> > Which it turned out was actually delivered yesterday at 16:39,
> > nominally 10 minutes after I had made a last trip to the mailbox an
> > hour and a half after his normal time to come thru this
> > neighborhood, so it sat on a red seat cushion beside the door all
> > night.
> >
> > Question for PCW, I see it does have some free-wheeling diodes built
> > in, but are they sufficient to protect it from a 24 volt dpst p&b
> > Ice cube" relay, as I have some of those tied to the flood and mist
> > coolant outputs using a 2 relay approach so as not to have big
> > motors being bumped during power up. It would be nice to ditch the
> > second relay and control them directly by using 24 volt field power.
>
> The normal limit is around 60 mA (> 60 mA needs a flyback)
>
> In general flybacks are better because they limit the EMI somewhat
> (and dissipate the inductive energy in the coil rather than the
> MOSFET)
>
> One advantage of the built in protection is that it allows faster off
> times (it clamps at ~40V rather than the < 1V a flyback diode drops)
\
So that the bottom line here, Peter is that flybacks are needed. I've a
coule hundred 1n914's for that. I jut checked a similar relay I could
use with a 12 volt field supply, and its coil current is triple that 60
ma at 0.173913043478 amps to hold it closed. And I expect 12 volts will
be easier on the onboard stepdown. But I'll have to total up the current
draw as this particular 12 volt supply is only rated for 1.75 amps.
Teeny little thing. Fits nicely in this box however.
> > One fuss though Peter, about the mechanical drawing on the last page
> > of the doc pdf. Way too fine a line to reproduce well in my ink
> > squirter, could sure use a scale up and fully black ink instead of
> > the light grey. I have to use a projection lens intended for a 16mm
> > movie projector to read the dimensions. Which is my next move, mount
> > it.
This I made usable by printing the last page on my little brother laser,
scaled up until it was about to run off the right edge of the paper. At
least I can read the dimensions now.
Andy: I looked up how I did it when I redrilled the backplate for the
Bison chuck on the Sheldon lathe, which did not try to use the
incremental mode, but measured the existing holes and recorded them,
then used coordinate rotation to place the new holes after finding the
center of the backplate. So I added the holes x offset to the x absolute
by passing it as #1 to the sub. Worked perfectly in a test cut, but
needs to have the connector shell stretched another 10 thou lengthwise,
and the holes enlarged another 5 thou. So that problem is now solved.
Time to go see about some food for the two of us.
Thanks & take care, everybody.
--
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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