Re: Power supply for Servos - Energy dump and such

--- 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:
> >
> > --- 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

A 60W 120V bulb draws I = P/E So 60W/120V = .5 amp, not 6 amps.

Yes a cold bulb draws more power when it heats up, but in this
application i do not think it would be enough power or long enough...

If you have your heart set on ligh bulbs you could paralell a bunch
of them.


Wally