Industrial strength dimmer

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

Original poster: "J. B. Weazle McCreath by way of Terry Fritz <twftesla-at-qwest-dot-net>" <weazle-at-hurontel.on.ca>


Hello coilers,

In my continuing experiments with my TSG and the controller for
it based on a light dimmer, I did some more digging for info on
dimmers and found some very good details in an old RCA manual
for transistors, thyristors, and diodes.

Using that info, I built up an "industrial strength" dimmer with
the only original parts from the Leviton unit being the triac
and the metal mounting plate.  A lot of my tinkering time was 
spent on finding the right resistor/capacitor combination that
gave a very smooth and linear control.  I ended up using a one
meg pot with a 0.01 uF. cap, and it's smooth as silk!

The original diac-triac from the Leviton dimmer drives a 20 amp
triac which is protected with a snubber resistor/cap of 100 ohms
in series with a 1 uF. across the two main triac terminals and a
toroidal choke in the output lead to the GM HEIC and 3 uF. motor
run capactor.  The snubber, choke, and 20 amp triac where removed
as a unit from a slide projector controller I had in my junk box.
That part of the circuit very closely matched the one shown in 
the RCA manual.

With the addition of a Corcom filter on the input side and a few
MOV's as per Terry's circuit, I've got myself a hopefully bullet-
proof controller for my TSG.  I think the time I spent juggling
the RC time constant values was well spent, as I get a smoother
operation over a much wider range than I did with the original
variable resistor and cap from the Leviton dimmer.


73, Weazle, VE3EAR/VE3WZL

Listening: 147.030+ and 442.075+
E-mail:    weazle-at-hurontel.on.ca
           or ve3ear-at-rac.ca
Web site:  http://www.hurontel.on.ca/~weazle