Re: [CAD_CAM_EDM_DRO] Re: EDM spark control system

thscarince@... wrote:

> First: Thanks Jon, you answered every one of my questions!
>
> There seems to be a bit of interest in this topic...
>
> Although "officially" I'm a mechanical guy, I've got a few
> electronics tricks up my sleeve as well, so here's a few thoughts.
>
> Jon wrote:
> >an electronic switch that cuts off current
>
> It looks like the "electronic switch" would be a power transistor
> (MOSFET or bipolar) that would have to tolerate fairly high current
> pulses. Perhaps much higher than the "1/4 to 1/2 amp" average
> current. Once that parameter is nailed down, it's easy to generate
> whatever pulse rate and duration you want.

Since this is essentially a short circuit during the spark, a MOSFET would
be the best choice, as it resists secondary breakdown. i would guess
about 4 of a 25 A 100 V transistor in parallel would be a good start.
I already scribbled down a circuit with a current sense resistor (although
a transformer-type current pickup would also work) a 556 dual timer
and a MOSFET gate driver. It would have pots to adjust on and off
time, and could also output a signal to the CNC telling it when to proceed
and when to stop the feed.

I could enter this as a schematic and post it to the drop box. I'm a bit
too busy with commercial work to do any construction and testing of it
right now, but would be glad to help anyone who wanted to build it.

Jon