Re: EDM questions

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Richard" <phrh@w...> wrote:

>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mark Stacey" <pav@x> wrote:
>
> My two cents worth---I believe that the lightbulb /rectifier power
> supply is similar to the one I suggested to Dave Mucha some time

ago.

> Dave mentions a resistor is required, the light bulb is the
> resistance and the RC combination across the electrode/work gap(
> which mimics a gas tube) supplies a sawtooth voltage (relaxation
> oscillator) for the spark. It is my opinion that the capacitor size
> (within limits) is not too important as the frequency changes
> according to the RC constant and the cutting rate is controlled.

<snip>

Look at Jon Elson's circuit.

Main power, rectifier, filter/storage cap.

R1-resistor and Amp meter, then small cap.

The resistor is needed in some form.

The resistor can be exchanged with a lightbulb as a low cost resistor.

A meter of some sort is needed. I chose to use voltage across the
part. you can watch the voltage drop about 20% as it is sparking and
never bottom out unless it is shorted.

I also made a simple comparitor to raise and lower the electrode
based on voltage.

I kinda cheated and used a spare PLC I had sitting around. : )

Dave