Homebrew PCBs

On Sat, 09 Jul 2005 09:37:26 +0200, Phil <phil1960us@...> wrote:

> OK, I'll start asking specific (and ignorant) questions.
> What are the important measurement parameter(s) of the spark? current,
> I'd guess. others?
> What is the optimal spark voltage range?

See the theory on the page with the eden supply.

> How do you measure?  Standard shunt techniques?  ...?

current is limited via a standard shunt / opamp, yes.

> Is the spark long lived enough to measure directly?

certainly.

> What is the relationship of gap to spark current?

The current is limited, no relationship. (If the gap is too big there will  
not be a spark and no current.)
As i understand it once there is a plasma path any amout of current could  
flow, so it is strictly limited by the supply.

> How do you tell between a short and a spark?

voltage.

> Is there a range of spark currents that allow one to adjust electrode
> gap via PID or similar algorithm?

As i understand it gap is adjusted by (gap) voltage, too high -> go  
closer, too low-> short.
I guess one must sample that during spark. the eden edm pages speak about  
you basically minimize the occurence of too high/too low readings. The  
eden supply has only digital outputs for "spark" and "short", it appears.  
I believe a analog measurement of the gap voltage (maybe with sample and  
hold, maybe with a MPU). I do not understand how exactly the eden PSU  
works here, with the diodes on the output it measures something in some  
way. Not sure.

> What effect on the spark does the electrode shape and/or material have.
> By the way, a raster approach could be sped up by using multiple spark
> electrodes.  Might have to offset them a bit though I'm not sure about
> that.

time is not a issue right now, for me. first one must work!

> Any reason why one should not use a bidirectional raster
> approach (LR, RL, LR ...)

backslash

ST