Re: Power supply for Servos - Energy dump and such

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "cnc_4_me" <cnc4me@g...>
wrote:

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
> <dave_mucha@y...> wrote:
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "cnc_4_me" <cnc4me@g...>
> > wrote:
> > >
> > > I never had the link...The explanation i posted was posted in
> same
> > > folder as the PDF...BTW as of yesterday i think a new updated

pdf

> > was
> > > put in files section on gecko site, i think in G201 folder...It
> > > dosn't say anything else than what i posted though...
> > >
> > > Wally
> >
> >
> > Actually, your link is what gave me the insight to read the
> thread.
> > Upon reading the thread, I found Mariss's note.
> >
> > Since the pdf did not print well, (the lines were much too thin

for

> > my printer) I had to redo the schematic so I could read it.
> >
> > I've laid it out and will be making the board shortly.
> >
> > Instead of the 20 watt resistor, I am thining of trying an
> > incandescent light bulb. It worked for my EMD..... so why not ?
> >
> > Dave
>
>
> assuming you are talking about a 120v light bulb you are only

talking

> a 1 amp load at 120v. Way to small to be of any use here.
>
> you need to pick a resistor value close to your rated power supply
> cuerrent. If your supply is rated 10A at 80VDC then R = E/I, so
> 80VDC/10A = 8 ohms and P = I x E so 80VDC x 10ADC = 800 watts.
>
> If you had a 800 watt light bulb at 80 VDC you would have a nice

load.

>
> Mariss says use a 20w resistor because the duty cycle is so low.
> This circuit should only turn on for fractions of a second. And it
> should turn on very rarely or something is wrong.
>
> But as i calculated above something around 8 ohm should work, i

would

> say 8 to 10 ohms. This is based on the energy dump pdf that says
> choose resistor size according to the power supply current rating.
>
> You need the high current drain to quickly lower the power supply
> voltage and prevent harm to the gecko.
>
>
> Wally

This is something I could never find data on. The light bulb is a
dead short so it should be similar to a zero ohm resistor and should
dump the energy fast.

However, as the current increases, the resistor (filament) heats,
increasing resistance, but also using power so would also act as a
current limiter.

a simple 60 watt bulb rated for 110 VAC may only be 6 amps, but that
would be at 110VAC. that would appear to be about 18 ohms, but that
is not the resistance of the cold bulb, or bulb at the lower voltage.

Dave