Re: EDM home brew units ?

>
> So you apply a fully charged cap to the gap, what do you use as your
> feedback to the control? Normally it is derived from the voltage
> that the gap brakes down and starts discharging the capacitor.
>
> Graham
>

The scope pattern of the spark goes high and then trails off.

If one allows the supply to remain connected durning the entire
saprking cycle, the cycle will take longer due to the connectoin ofh
te power supply. the power supply will be charging hte caps while the
cap is discharging. This will have the effect of the voltage trailing
off and the process taking longer the work being performed happens.

If one interupts the power supply at the start of the spark cycle, the
cap will discharge faster, but the scope trace will still show a large
pulse, followed by a trailing off of the energy.

if the spark gap was set for a 50 volt spark, the capacitor will start
to discharge around that 50 volts, but once the electrical path is
created from the spark, it will continue well below the 50 volts.

If one were to set a lower limit of, say, 35 volt, and open the
electrode at that point, a shorter pulse would occur, but also the
pulse would have signifigantly more energy per pulse.

the duty cycle would be faster as well.

if one were to use two, parallel circuits, but with each being set to
charge while the other is pulsing, then a rapid fire pulse train would
be seen at the electrode.

Dave