Cheap "variac"?

From: Charles A Davis <cad_at_gamewood.net>
Date: Sun Oct 5 10:11:25 1997

Sam Ismail wrote:
>
> Today at a local flea market, I picked up a PRO (Made in Taiwan) Soldering
> Iron Controller. It has a three-prong power outlet and a heavy duty
> potentiometer for controlling the voltage level of the outlet.
>
> The labeling indicates "MAX. 800 WATTS-120 V.A.C." My math tells me that
> this unit can handle a maximum of 6 amps. Would this be safe to use as a
> variac on, say, a sparsely loaded IMSAI?
>
> It was only a buck.
>
> Sam Alternate e-mail: dastar_at_siconic.com
> -------------------------------------------------------------------------------
> Ever onward.
>
> Coming in 1999: Vintage Computer Festival 3.0
> See http://www.vintage.org/vcf for details!
> [Last web site update: 09/21/98]
Hi Sam:

Safe??? --- That's a loaded question.

Consider the differences in output ---

The 'Variac' (or equivalent variable transformer), will be putting out a
comparitively _clean_ 'sine wave'. (It will even have filtered out
_soome_ of the garbage that is on the normal 110v AC line.)

The 'Soldering Iron Controller', is _probably_ an SCR and control
circuits. The output of that will be a _very_ chopped up AC (I.E. the
wattage control, is varying the 'turn on point' during the AC cycle to
control the effective power.)

The 'Soldering Iron Controller', is suitable for _resistive_ loads, that
don't care about the wave form of the incoming power. I.E. soldering
irons, light bulbs (but NOT fluorescent fixtures), lightly loaded
_universal_ motors.)

Chuck

-- 
-----------------------------------------------------------
He, who will not reason, is a bigot;       William Drumond,
he, who cannot, is a fool;                  Scottish writer
and he, who dares not, is a slave.              (1585-1649)
While he that does, is a free man!          Joseph P. 1955-
-----------------------------------------------------------
Chuck Davis  /  Sutherlin Industries   FAX # (804) 799-0940
1973 Reeves Mill Road            E-Mail -- cad_at_gamewood.net
Sutherlin, Virginia 24594            Voice # (804) 799-5803
Received on Sun Oct 05 1997 - 10:11:25 BST

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