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RE: Trigger Gap Controller Design??



Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Gary.Lau-at-compaq-dot-com>

Blowing 400 Watts on hot resistors is a shame.  Couldn't the dimmer circuit
be modified so that the R-C circuit that triggers the diac is placed across
the incoming H & N lines?  It would mean breaking the connection from the
dimmer cap to the output terminal, and bringing it out to a 3rd terminal
that goes to the "other" mains lead that goes to directly to the coil
terminal.  While it means performing minor surgery on the dimmer, it avoids
the need for power resistors or lamps.

Gary Lau
MA, USA
===================================================


Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi All,

Here is what I have come up with for a triggered gap controller so far.

It is highly experimental, not well tested, zero guarantees....

It seems to have very low noise, full phase control, and might not blow
itself and everything else up.  I don't suggest anyone go out and make it
at this point but if your experimenting or would like to make any
suggestions, here it is as of 8:18pm ;-)

http://hot-streamer-dot-com/temp/TGap1.gif

The filter and dimmer circuit can be separate so they can be used for other
fun things.  That helps to justify the cost a bit.

I seem to need to dual stage filter even if it does cost $28.  May those
less concerned about RFI could do without it but it is easily worth the
cost to me.

The two resistors could probably be replaced with a big light or other ~400
watt pure resistance.  They run about $14 each from DigiKey.

The 2uF cap is a AC motor run type or perhaps a few paralleled capacitors
from DK.

I had some 15kV 500pF door knobs here but a "real" design needs a good
stable source for such a part.

Any comments or suggestions are welcome.  Unfortunately, even though it is
basically seems to be working well, it is fairly costly if one uses new
parts.  The resistors will also draw about 3 amps off the AC line which is
just waste heat.  However, they sure make it run nice!  No great though
into the reliability or fault handling yet...

It is really not too different than what people are using now with the
exception of the power resistors which are probably needed for a stable and
wide range of dwell control which a triggered gap needs.  The top and
bottom circuits can also be widely separated for a nice remote control with
the phase adjustment at the controller.

Again, it is definitely not ready for anyone to go out and make yet, but it
is getting there...

Cheers,

	Terry