Variac Help. Trying to find the right one.

I'm trying to rebuild a thermal evaporator. We need a power supply to
heat the boats (only precious metals and aluminum). I've seen very
high prices for power supplies at some vendors, and I read that a
VARIAC can be a good, and cheap choice. Now, what is a variac? Can it
be used to evaporate gold, silver, aluminum? Can I have a variac to
control 3 boats? Not at the same time but one after the other? Any
help is appreciated.

A confused undergrad

A variac is a transformer which takes mains ie utility supply
power/voltage in and gives out any voltage from 0 up to the supply
voltage. As for the amps what it will give will depend on its rating.
you will need to do some serious paper work to get you design properly
mapped out to ensure you have the right values for all the equipment you
plan to use.
If what you mean is a sputter in vacumn depositor your aiming rather
high for an undergrad. Have you access to one that you can see working,
has a manual and scematics, and can copy?
Without that your on to a loser with a lot of your own money.
To help you further you will need to give a detailed description of the
kit you plan. If you havnt bothered to look up a technical dictionay for
variac you wont really get very far. Havnt they taught you how to do
research? in your college?

Not sure what it is your using them for as I have no knowledge of the process
your describing. But, a variac is also called an autotransformer and is
essentailly a variable output transformer. They look like a big potentiometer
(volumn control) with a shaft that is used to turn a movable assembly across aa
coil of wound wire. The voltage output is determined by where the tap of the
movable assembly is on the coil of wire in relation to where the voltage inputs
are. They come in different voltage and current ratings and are relatively
inexpensive in the smaller sizes. Chechk on ebay or they are available from
many places like Newark Electronics or maybe even Grainger as well as direct
from several manufactures like Superior. Mike in Arkansas

Andres wrote:
I'm trying to rebuild a thermal evaporator. We need a power supply to
heat the boats (only precious metals and aluminum). I've seen very
high prices for power supplies at some vendors, and I read that a
VARIAC can be a good, and cheap choice. Now, what is a variac? Can it
be used to evaporate gold, silver, aluminum? Can I have a variac to
control 3 boats? Not at the same time but one after the other? Any
help is appreciated.

A confused undergrad


Be very careful, an autotransformer gives no mains supply isolation, and
can fault very easily to mains potentials on the coil.

Be careful too that the load on the "secondary" is not so low that the
current burns out the variac.

Since evaporation usually requires high (but variable) current and low
voltages, a better way is to use a variac to feed a transformer that
THEN drives the evaporator coils. If you want some more details contact
me off the group.

Steve
(Professional electronic engineer and r.c.j lurker)

powerstat is another term. I bought mine on ebay.

fyi

Carl
1 Lucky Texan


Mike72903 wrote:
Not sure what it is your using them for as I have no knowledge of the process
your describing. But, a variac is also called an autotransformer and is
essentailly a variable output transformer. They look like a big potentiometer
(volumn control) with a shaft that is used to turn a movable assembly across aa
coil of wound wire. The voltage output is determined by where the tap of the
movable assembly is on the coil of wire in relation to where the voltage inputs
are. They come in different voltage and current ratings and are relatively
inexpensive in the smaller sizes. Chechk on ebay or they are available from
many places like Newark Electronics or maybe even Grainger as well as direct
from several manufactures like Superior. Mike in Arkansas


--
to reply, change ( .not) to ( .net)