Homebrew PCBs

Dave Mucha wrote:

>Hi Curt,
>
>I am curious about the idea of using what I might call and active
>resistor.
>
>is this somehthing you have some knowlege about ?
>  
>
There was a Radio-Electronics construction article about building such 
an active load that allowed you to use a 2N3055 as variable power 
resistor.  In other words turn a 20K pot, to say 10K,  and the 3055 acts 
like 10 ohm power resistor.  My thinking is that by adjusting the power 
feed to the caps you would have more control over the EDM pulse rate and 
energy

I don't remember the exact RE issue the circuit was in other than it was 
the late 1970's

>I have a Langolis EDM and am not impressed with the speed, I would
>NEVER try to EDM the file, (although I there is no reference in size,
>is it a micro jewelers file ?)
>  
>
Even with the Garden of EDM supply you are limited to removal rates 
measured in cubic inches per hour

>I limit my work to sheetmetal.
>
>Also, I think a pulse output with FET's can be done almost as easy as
>the RC unit, no need to go with the Garden of EDM, that is wayyyyy too
>elaborate.
>
>Dave
>
>
>  
>

I'm looking at using FETs as a replacement for the Garden of EDM's 
IGBTs, but it doesn't save that much money when you factor in the added 
control and protection circuitry that high amperage FETs need to survive 
the real world.

 From some quick one off experiments using Ben's system on 1 ounce PCB I 
would say that it is fast enough to an 8 by 11 inch board in under an 
hour for a lot less money than the Garden of EDM.

I'm about a third of the way through the restoration of "Mudzilla" ( my 
new 1954 Jeep Truck ) so I hope to be back at my PCB- EDM project after 
labor day.

Curt Richards

--- In Homebrew_PCBs@yahoogroups.com, Curtis Richards <cwrxr@e...> 
wrote:
>  From some quick one off experiments using Ben's system on 1 ounce 
PCB I 
> would say that it is fast enough to an 8 by 11 inch board in under 
an 
> hour for a lot less money than the Garden of EDM.
> 

Curt,

I have Robert Langlois's book, but not Ben Fleming's. Can you tell me 
if there is any similarity between Ben's Relaxation Oscillator and 
that of Robert Langlois, or does Ben's have any active control?

Thanks

Roger