RE: [CAD_CAM_EDM_DRO] Clarifications needed -

> -----Original Message-----
> > The length of the motor cables is not something that cause
> you to need
> > the caps at the input to the Geckos. My test is pretty straight
> > forward. Hook it up and run it. If the large internal cap
> on the Gecko
> > gets hot then you need the caps at the drive. Suggested caps are
> > listed on the instruction sheet.
>
> What causes them to get hot? (just curious)
> Okay, just saw the 470uf callout...

Rapidly discharging and recharging the cap causes it to heat. If you are
using a large motor and you have either long wires from the power supply
or a fuse in the line then the onboard cap will be discharged when the
coils are energized (20 kHz chop I think) as sufficient current can not
be supplied by the incoming power lines so the cap provides the current.
Putting another cap at the terminals of the drive will help share the
load so to speak and reduce the heating.

> > > Third - the +5V.
> > > Assuming that I want to work with what I have right now
> and not need
> > > to spend more money, do I get that +5V from the computer power
> > > supply or does it come from somewhere in the parallel port?
> >
> > There is no +5 on the parallel port. Get it from the computer power
> > supply or from a game port or from a USB.
>
> I always get confused here, so I'll ask what the majority
> common practice is -
>
> Use the ground of the parallel port, or +5V
> off of one of the computer power supply leads?
> I've built the controller enclosure to house everything, so
> picking off of one
> of the power wires isn't a problem; I just need to get the
> right direction to
> head in. I'd like to understand *why* as well...

Gecko G201 must use +5. G210s allow you to pick. The parallel port can
do a better job if it is sinking the current and you are sourcing from a
+5 v line.

>
> Another good point. I'll hafta look into what the UPS's rating are.

To me plugging in the motor power supply is like putting a laser printer
on a UPS. If I remember you are a systems admin? If so I am sure you
have seen the result when this happens. Quick way to reduce even a large
UPS to trash. I have never tried it with a CNC power supply though.

Tim
[Denver, CO]
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