Re: [CAD_CAM_EDM_DRO] number of conductors ( was Re: cable suppliers - and th...

In a message dated 5/4/2003 9:36:25 AM Central Standard Time,
davemucha@... writes:

> Now it sounds good, but I'm not sure if mixing all those in the same bundle
> is too bright. The router speed contorls are the cheap import style that I
> think are just a voltage change and run the motors on a variable DC
> (rectified only, no caps). to it might be running the motors on DC ? which
> might or might not make a difference on the bundling.<<

Dave: To control the voltage/current of DC to a router, even a fairly small
"Trimmer router", you would need a large and QUITE expensive variable
resistor. The "cheap" style of "dimmer controls" use SCR-type semiconductors
to "chop" some of the sine-waves off as AC passes into them, and these will
NOT work on DC! AND, this type of SCR- or Triac "dimmer" makes electrical
hash (aka EMI noise) to beat the band, especially "cheap" ones! The
trigger-controls in a VSR drill is this same kind of thing. It varies the
"time ON" vs. the "cycle time" of the AC, not the "voltage" per se.

>
> Am I getting too far off base ? would I be better using seperate
> bundles/cables ? should I seperate the 110 from all the other signals ?<<

Yes. Possibly. However, if you could SHIELD the signal-wires separate of
the AC power-lines, these could then be all in the same sheath, if the shield
were properly GROUNDED.

For a large CNC device I once built, the ONE cable-carrier (Gortite!)
contained three-phase, 240 VAC, 90 VDC "chopped" for speed-control of a
quill-up/down motor; and limit-switch lines, all of which ONLY controlled
tiny DC relays which then controlled the "5 VDC logic signals". There were
NO "logic signal lines" ain that gob of conductors, and all worked fine!
Whew!

Now one of my home-brew lathes (see "Home Brew..." in PHOTOS) was constructed
before I knew how to tell time ('84), and it worked OK in the beginning.
Then I had occasion to plug-in a VSR in the same AC circuit; the lathe was
turned ON, but was at rest. The instant I pushed the trigger on the VSR
drill, it began to "buzz" and the lead screws merrily went both ways
intermittantly with no apparent logic at all. This instantly stopped when I
let go of the drill-trigger, and resumed when I'd press, again! So, I go
back to my local surplus dealer and get a large-size (what, 5KVA?) EMI
line-filter---ya know, one of those things neatly packaged in a tin-plated
shell, and then the lid sweat-soldered all around. Put that on the AC-mains
feeding the lathe, and it behaved from that time, on!

While I'm at it: Then I built the second home-brew lathe, using a Superior
Electric driver-box and bipolar steppers. That has worked perfectly from
day-one, and has NEVER "glitched"! But it has OPTO-ISOLATOR inputs, and
built-in EMI filtering on the AC-line coming in. For "shop machinery" with
AC motors, especially ones with "speed-controls" and/or "logic lines", you
just GOTTA do things "fussy" and THINK!!! Jan Rowland





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