RE: why 4 Ohms in PARALLEL with trigger coil primary?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ted Rosenberg by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Ted.Rosenberg-at-radioshack-dot-com>

Hi Scott and thanks for the compliment.
I have some answers for you but please understand, as I said in the paper, I
was the technician. Marc and Terry Fritz deserve the "why" rewards!

I originally had the 4 ohms in-line. the resistors got SO hot that they
would have burned the wood etc etc. I desparately e-mailed Terry as Marc was
unavailable. After some discussion, Terry suggested the new position
and...it works. I really can't give you a better reason. Sorry. Perhaps you
might ask Terry about that. Who knows, I might learn something  :))

I do not own an oscope although I can borrow one.
I had to get this coil into the Hangman's House of Horrors and I was running
out of time. So all seriosu tweaking, checking with scope, adding welders
glass etc, will have to wait until the coil returns home after Oct 31.

As for the Fan vs Lamp control...while I don't have my ring binder here at
the office with my notes, I seem to recall that Terry compared one against
the other and found the fan control more robust. And the cost is essentially
close.

Hope I've been of some help.
The gap itself is, by all standards, almost a no brainer to build and use.
If you can install a lightswitch in a house and solder a kit together from
RadioShack, you can build it. No more salient motors.

Regards

Ted

-----Original Message-----
From: Scott.L.Hanson-at-seagate-dot-com [mailto:Scott.L.Hanson-at-seagate-dot-com]
Sent: Tuesday, October 16, 2001 4:43 PM
To: Ted.Rosenberg-at-radioshack-dot-com
Subject: TSG: why 4 Ohms in PARALLEL with trigger coil primary?


Ted -

Nice paper on the low-cost/home brew TSG.

I have been experimenting with TSG's (trigatron style) from industrial
laser power supplies for switching my 6" X 32", 120ma NST powered coil, but
have been experiencing problems trying to interface with the original
trigger circuitry on the TSG driver board.

One question on your trigger system schematic. If it is used for current
limiting,  why is the 4 Ohm resistor placed across the primary of the
trigger transformer, instead of in series with it? This seems inefficient,
and subjects the triac to higher loads then it would see from the coil
alone.

Have you looked at the output with an o'scope to see the change in trigger
point, relative to the AC input waveform, as the motor control is varied?
If so, how many "degrees" of adjustment are available?

Finally, is there anything special about using a fan control vs an
incandescent lamp dimmer? Do they both "fire" in any controlled
relationship to the input waveform?

Regards,
Scott Hanson