Re: Capacitors for Geckos when using fuses

I agree with you on this. for less than $1.00 per cap, you enjoy
increased protection for the $$$ Gecko. I too do this regardless of
how close to the power supply the Gecko's will be.

Dave

--- In CAD_CAM_EDM_DRO@y..., Jim Brown <jagco1998@y...> wrote:
>
> That I dont know, as all of this is very new to me.
> But I'm going to use the 470uF caps anyway as per Mariss' suggestion. After all, he would know better than anyone else, considering the Gecko's are his creation.
> I cant see how it would hurt.
> Thanks for the help.
> Regards,
> Jim
> turbulatordude <davemucha@j...> wrote:Hi Jim,
>
> I think you are correct regarding the switching powers supply.
>
> the calculation does reveal an interesting phenonimon. (sp?)
>
> with the current remaing constant at 9 A,
> a 24 V power supply (home built) requires 20,000uF cap
> a 48 V power supply (home built) a 10,000uF cap.
> the higher the voltage the lower the cap, but in the case of a
> switcher, I think you are correct that it's primary function is
> handling ripple.
>
> The question I would pose then is if one had the switcher remote, and
> the 4,700uF (your app) cap next to the Gecko, would one still benefit
> by the 470uF at the Gecko itself ? I think not.
>
> Dave
>
>
>
>
>
>
> --- In CAD_CAM_EDM_DRO@y..., Jim Brown wrote:
> >
> > According the the gecko white papers(verbatum), "If a linear
> regulated or a switching power supply is used then a large capacitor
> should be placed across the output terminals. A 2000uF-10000uF
> capacitor should do."
> > That is why I chose a 4700uF cap. for the power supply output
> terminals... It's about right in the middle of Mariss' suggestion of
> a capacitor for a switching power supply.
> > He wasnt specific as to what voltage rating for this cap, he was
> only specific as to what uF value (2,000-10,000uF)
> > Your formula for computing the value of a capacitor, I think, is
> for when building your own power supply, in conjunction with a bridge
> rectifier and transformer.
> > I dont think this applies to when you are using a regulated or
> switching power supply. The cap mentioned above, is placed on the
> output terminals to insure that the ripple current stays within the
> demand of the drivers current requirements. That is what I get from
> the papers. I may be wrong about this though.
> >
> > Thanks
> >
> > Regards,
> > Jim
> > turbulatordude wrote:Hi Jim,
> >
> > you ask two questions here.
> >
> > #1 470uF AT THE TERMIANL connector of the Gecko. required if you
> place
> > ANYTHING between the main cap and the gecko OR if the lines are
> longer
> > than the listed 18 inches.
> >
> > there are lots of posts that address this. the main thing is that
> the
> > switching of the gecko will encounter voltage spikes from the
> stepper.
> > the on-board cap on the gecko can handle some of this while the
> main
> > cap handles the rest.
> >
> > and yes, as long as the voltage rating of the cap is well over the
> > power supply the cap is fine. your 24 volts power supply will
> operate
> > fine with a 35V cap.
> >
> > #2 main capacitor. check the gecko white paper on the cap sizing.
> > again, as long as the voltage well above the power supply it is
> fine,
> > but the cap size needs to be suffiecnt for the amp load of the
> system.
> >
> > You didn't list the total amps of all your steppers, but you need
> to
> > total all motors for the main cap sizing.
> >
> > cap uF rating is = (80,000 x total motors amps) / ps voltage
> >
> > example is if you have 3 steppers at 3 amps. you have 9 amps total
> >
> > 80,000 x 9 = 720,000
> > 720,000 / 24 = 30,000uF
> > so you would need a total of 30,000uF with a rating of 35 volts.
> >
> > www.jameco.com has them for low cost, about $5.00 each for 10,000uF/
> > 35volt
> >
> > the 470uF/35volt are less than $1.00 each.
> >
> > Dave
> >
> >
> >
> > --- In CAD_CAM_EDM_DRO@y..., "jagco1998" wrote:
> > > I have a few more dumb questions....
> > > I dont want to burn anything up, in using components that are
> > > incapable of handling voltage/currents correctly.
> > > The gecko white papers say that when using a 5A fast-blow fuse to
> > > protect the drivers, that a 470uF 100V cap needs to be placed on
> > > across power leads.
> > >
> > > My 1st question is this..Can a 470uF 35V cap be used, instead of
> > > 100V as the white papers suggest? I can find them at every elec.
> > > supplier in my small town of residence.
> > >
> > > I am only using a 24Vdc/10A switching power supply to power 3
> gecko
> > > G201's, and have already placed a 4700uF 35V cap across the PS
> > > outputs(I couldnt find anything larger than 35V. I live in the
> > > sticks!)
> > >
> > > Also, is the 4700uF 35V cap going to be sufficient for my PS?
> > > Without the cap, a dig. voltagemeter across the output leads tell
> me
> > > that the power only fluctuates from 24V to 24.2V no load.
> > >
> > > I realize that this probably will become a substantially larger
> > > fluctutation once a load is applied.
> > >
> > > Will a spike or short in the power going to the motors damage
> them
> > > if not protected with a fuse? Would it be wise to also fuse the
> > > lines going to the motors also, or is this necessary?
> > >
> > > Any suggestions or comments will be appreciated.
> > > Thanks.
> > >
> > > Regards,
> > > Jim
> >
> >
> >
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