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:
> >
> > 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