Re: Bleed Resistor... Do geckos need a fan?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "industrialhobbies"
<admin@i...> wrote:

> YES you do NEED a bleed resistor.
>
> The resistor provided 2 functions:
>
> It puts a minimal load on the power supply at all times (a Gecko

Does

> Not),

This must be something new. My Gecko's do put a minimal load on my
power supply. But, they are a few years old and maybe the new ones
are more efficient ?

But, then that purpose would be a load resistor, no ?

> this limits an unregulated power supply's tendency to "float
> high".
>
> It will also bleed the excess charge from the cap. With the sort

of

> draw you mentioned you have a pretty healthy power supply and a
> pretty healthy cap.

The driver will use some power from the PS so there will not be
excess charge during no operating times. The maximum voltage will be
a function of the transformer and line voltage. It is a running
motor that offers the potential of adding voltage greater than the
power supply, but, running motors also means the drivers are using
power.


assuming 12 amps, 50 volts, and a 20,000uF cap. a 5 watt 500 ohm
resistor will offer a time constant of just unde 10 seconds so a cap
will blead down in roughly 30 seconds.

> If you've ever been "bitten" by a cap you'll
> know it hurts a lot. Get the resistor.

This goes to the question of why you need or want one. If you are
inside the box often, then a light would be a better indicator than a
hot resistor. If your box is closed and out of the way, you should
not be able to get bitten and in that case, the drivers should bleed
the charge.

It is my opinion that a bleed resistor is completely optional.


Dave

> If you don't believe me, look up a few folks who sell them (I sell
> them as well), they will ALWAYS include a bleed resistor. They

serve

> a valid purpose.
>
> You may also want a dump resistor (tied to an E-Stop), that's you

to

> you.
>
> Also, a Gecko is a solid state device and although the G320's or
> G340's you have are rated for 20A they like to be cool. All solid
> state devices like to be cool, the cooler the better. Get the

goop,

> Radio Shack has if for a few bucks, one tube will cover you.
>
>
> Thanks
> Aaron Moss
> www.IndustrialHobbies.com
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "AbbyKatt" <cnc@a...> wrote:
> > I was wondering..
> >
> > Power supply is all nice and working now, and am about to hook it
> all up
> > to the geckos.
> > I was wondering: Do I need a bleed resistor across my cap? What
> happens
> > if I neglect to put one in?
> >
> > Also, do I need a fan for geckos, I'm only going to be doing a

peak

> of
> > 12 amps @ 50V, and I have it already bolted to some nice

aluminium.

> Will
> > I need thermal paste?
> >
> > Thanks!
> > ~Abby