Re: [CAD_CAM_EDM_DRO] Stepper power supplies, unregulated or regulated? Switc...

In a message dated 01-Dec-00 18:34:48 Central Standard Time,
mcamp@... writes:

> Can anyone tell me what the ins and outs of power supplies are? I am
> planning on buying a couple of Gekko g201 stepper drives and 720 in. oz.
> motors. Should I get a power supply for each drive or one big power
> supply? Unregulated or regulated? Switched or linear?
> Any low cost suggestions? Bob
>
>
>

Bob:

I am an ignernt, uneducated "tinkerer", but I have made many devices which, I
think, operate using electric energy, and I am still alive. So, having not
quite yet reached the degree of heinous andunsavory attitude that would
preclude my willingness to be helpful, I will here try: A "DC Power supply"
consists generally of a transformer, rectifier, filter-capacitor(s),
voltage-regulator, current-limiting device(s), if any, and output-terminals.
Some types might not use a transformer, but those would probably fall into
the category of cheapo home-entertainment devices and apparatus designed by
those with little respect for comfort nor extended life-span.

Generally, steppers of the type you mention (over a couple-hundred oz.in.)
require such low voltage and high amperage that the common, usually-cheaper,
and easier-for-dolts-such-as-me "linear regulator" supplies are not
indicated. "Switchers" for high-current applications require considerable
experience with that particular type circuitry, as "peculiarities" sneak in
there when you get into more than, say, five amps, particularly if the
voltage is below, say, 20, and you are trying for at least 95% regulation.
Possible, but it takes a guru who has been sequestered in a closet in the
design-floor of a many-decades-established DC-supply/user manufacturer.

Anything with sufficient power (steppers) to CNC such as a Bridgeport should
be built ONLY with bipolar "chopper drive" motors and circuits, and it will
cost you much less both initially and in later-grief if you don't, to just
BUY ready-made, specific-for-the-motors-in-mind supplies and drivers, often
in the same "box". I have just finished cobbling two new
application-specific CNC lathes with Superior Electric KML092- motors, and
their SS2000DP4-FF dual-driver/supply (toroidal transformer, bipolar-chopper,
DIP-sw. settable amperage, etc.), and I wanna tell ya! I wonder, now, why I
ever fiddled with the old unipolar tapped-windings MO-92 motors! The KM
stuff (bipolar) are far-and-away more powerful for same-size, and NO heating,
etc. And "break your arm" torque on the lead-screws! WOW! Good I installed
"all-windings-off" switches on the control-panel (the said driver-box has
that connection), as setting-up would be otherwise IMPOSSIBLE with power-on!

IF the drives you specify can be had WITH supply, as are the ones I mention,
then it'd be much more economical to get a "single box" with both (more?)
stepper-drives AND one power-supply in same box. But maybe huge ol' motors
like that will REQUIRE separate supplies for each driver? I have never done
the math nor catalog-search on such since about '85, when I built a MONSTER
with MO-172- and -112 motors. In those days, "bipolar" was not yet a gleam
in S.E.'s eye, nor did I yet know how to tell time.

I can tell you this obvious detail: use wire to the steppers with at least
1000 CM per amp, and either nicely- and expertly-solder all joints, even
where a wire is terminated with a "lug", or, use Amp type "gas-tight" crimps.
A whole science in itself, requiring specific experiene. Best: SOLDER,
using Ersin multicore 60-40! Keep all "signal" lines (from computer to box)
SEPARATED from stepper-lines, and, if they must cross, TRY to make 'em cross
close to 90° (±5°!). Cause, if you run the "logic" lines parallel to 5, 10
amp motor-lines with chopper-current-control for, say, 4", you will have
MULTITUDINOUS knashing of teeth and untoward syntax!

Nuff. If you have specific, "Yeah, but what about..." kinda questions,
e-mail me direct. I am a reTIRED old geriatric, so, won't cut into my income!

Regards, Jan Rowland, Troll with attitude



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