Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "curt_rxr" <cwrxr@e...> wrote:
> 
> If anyone were going to experiment with really high pulse speed I'd
> recommend using two SCRs controlled by optoisolated signals from a
> PIC.  The IPS is the limiting factor in my tests as it takes ~65 
usec
> to turn off.  Using two SCRs would allow faster switching, but with
> attendant commutation problems.  A PIC should have enough speed to
> test for commutation of the SCRs while monitoring gap breakdown
> voltage and current.  Using SCRs simplifies the support circuitry
> whereas IGBTs or FETs add condiderable cost.  If you can settle for 
30
> to 60 inch per scond travel the IPS solution seems to work OK, but
> remember with allowances for acceleration at the traverse endpoints
> it'll take 20-25 minutes to cover a 8 x 11 board.
> 
> I'll try to convert my "napkin scribbles" into a circuit diagram 
this
> evening.
> 
> Curt


Curt,

I assume it would be neccessary to use a raw rectified feed thru the 
first scr to the discharge cap, so that the voltage drops below the 
scr holding voltage every cycle so that when the cap has reached the 
charged state, the scr will switch off, or can you get scr's which 
can be triggered off as well as on?


As you may guess, I haven't had much to do with scr's.

Roger