Re: ATM Re: atm-digest V1 #613

[kevin@aquilagroup.com (Kevin Ferguson)]

> Brand new Dc motor controller or variac are quite expensive in
>Canada ($240.00.each). I would like to know if there is an alternative .
>I would realy appreciate if someone can help me. 

Some alternatives:

I often see Variacs in surplus stores.  Most are designed with 
replaceable brushes, and are sometimes replaced when the first
brush wears out. The varnish insulation usually chars visably
if the variac is truely ruined.  

Many of the treadmill exercise machines have sutable speed controllers
built into them...maybe you can find a used/broken one.

I have had success running AC universal motors on _heavy_duty_ 
light dimming control (triac circuit) The heavy duty controls 
cost ca. US$20 in electrical department of home center store. 
(vs ~$3 for "normal" duty units)  For your DC motors you would 
need to follow this with a diode rectifier bridge.  In
my experience the speed/load regulation using these triac
circuits is somewhat inferior to variac control. 

A few months ago "Home Shop Machinist" magazine published an SCR
based DC motor speed control circuit, though from discussion
in rec.crafts.metalworking, some fellows had trouble getting
it to work properly.  

-Kevin Ferguson