Homebrew PCBs

I don't think the power supply has to be that complicated for this 
application. Many moons ago I used to own a Sincleir ZX81 computer. The 
Sinclair printer used special paper that was basically a thin coating of 
aliminium over a black background. The printer used a toothed belt to 
drag a metal stylus over the paper and wherever it needed to print a dot 
it applied a voltage to the stylus and vapourised the coating. Being a 
Sinclair product you can be sure the circuitry was very basic. Our needs 
are very similar, the only real difference is that the coating is thicker.

Normal EDM needs a carefully designed power supply because each spark 
removes a very small amount of material. We don't need that kind of 
accuracy so we can use a much higher energy density. I think that if we 
use a large capacitor and keep it charged through a simple linear power 
supply the sparking will be pretty much self regulating. All we need is 
a big beefy transistor to turn on the power when we want to remove 
material. The transistor does not need to switch for every spark, it is 
simply held on for as long as we need to remove copper. As a kid I used 
to cut patterns in aluminium foil using just a 12V car battery as the 
power source and it worked quite well.

Les


lcdpublishing wrote:

>Stefan,
>
>I looked over that schematic for the power supply - ouch, my head 
>hurts from all the complexity of it.  I think I will have to wait a 
>while before I have enough "Smarts" to understand it.  Now if I 
>could do all that with a PIC I might have a fighting chance :-)
>
>  
>