Re: [CAD_CAM_EDM_DRO] Re: CNC power supply question

One main item to consider when building your controller (including your
power supply) is to include a breakout board. The Mach2 sound logic breakout
board that I sell has a number of safety features along with making your
wiring a lot neater and easier to do.

Some of the items on the board are: The Mach2 charge pump feature lets you
use solid-state relays to turn on things like spindles and pumps without
worrying about them coming on when Mach2 doesn't have control.

If you are using Gecko drives, then your PC ground is optically isolated
from your control box.

Having a 5 volt power supply built into the breakout board provides the 5
volts necessary to power the optical isolators in your Gecko drives.

There are a number of other nice features.

Bob Campbell
Bob@...
www.campbelldesigns.com
Breakout board
THC board sets
CNC router plans
Stepper Motors

----- Original Message -----
From: "snagglexr650" <snaggletto@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Sunday, March 07, 2004 9:00 PM
Subject: [CAD_CAM_EDM_DRO] Re: CNC power supply question


> Hey,
> Thanks for the great, informative replies. I'm learning alot, but
> still have tons more to learn, especially on the electrical side.
>
> I've been looking at some of the extra 'features' you can add to
> homemade PS's. For example, Mariss's capacitor bleed circuit, and
> I've seen precharge circuits that limit the initial current when the
> PS is first powered on like Mr. Fortune uses on his 1kw/1.5kw
> monsters. These added features seem like they could almost be
> considered essential even for smaller/less powerful supplies. What
> other safety/component protection circuits are common for a full
> featured power supply?
>
> Thanks again for all the help, you people are great.
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
> >
> >
> > snagglexr650 wrote:
> >
> > >Hello,
> > >
> > > I'm trying to get the 'big picture' on designing my own servo
> > >based cnc control using a Gecko based system. I'm currently
> trying
> > >to tackle the power supply issue; Why some kinds are better than
> > >others and how to determine PS size from the motor specs in
> general.
> > >
> > > I've read here and elsewhere that the varying loads associated
> > >with CNC motor control is a problem for commonly available
> > >regulated/switched power supplies.
> > >
> > > What makes a 'homemade', unregulated(?), PS (Jerry's PS, or Doug
> > >Fortunes 1kw/1.5kw monsters) better at handling varying loads than
> > >the 'comercial/professional' grade regulated PS you see on Ebay or
> > >other retailers?
> > >
> > >
> > Regulated power supplies are almost always current limiting. So,
> if a peak
> > current is required when all 3 axes are accelerating, the regulated
> power
> > supply may go into current limit, dropping the voltage until the
> current
> > peak eases. This will cause all sorts of problems with the servo
> drives.
> > A bulk, unregulated power supply can handle momentary surges without
> > any trouble. it can handle a very large surge for a very short
> interval,
> > or a moderately large surge, like 2X the continuous rating, for
> maybe
> > 1/2 to one second, repeated every minute.
> >
> > Also, regulated power supplies often have overvoltage "crowbar"
> circuits
> > to short the power supply if the voltage rises above some set limit.
> > Many larger motors can return energy to the power supply when
> decelerating.
> > This can be true of both stepper and servo motors where the
> inductance is
> > large. If the power supply activates its crowbar, it could cause
> damage
> > to the machine, the drives, and possibly the power supply, too.
> >
> > On the other hand, a number of users have reported excellent results
> > using commercial switching power supplies on stepper and servo
> motion
> > control systems.
> >
> > Jon
>
>
>
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