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robbo

Regular Member

Joined: 25/03/2007
Location: Australia
Posts: 71

Posted: 12:48pm 05 Jan 2011

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Hey everyone,
Just wanting to see if anyone has any ideas for a large potentiometer for another project of mine. I am interested in adjusting the input to a heating element(of about 3200 watts)from a 240 volt suorce, but cannot find anything acceptable. Does anyone have any ideas ? It will need to be capable of about 15 amps.

I have an old variac, but the amperage is insufficient for this job. Perhaps someone can think of any scrap items I can scrounge this off of ?

Have a good one...

Rob.

"the Earth was not given to us, by our fathers, rather, it is lent to us by our children".

VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 01:58pm 05 Jan 2011

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Hi Robbo

I have used a speed controller out of an old vacuum cleaner for a similar application, it was rated at 1800 watts but if you put bigger scr in it you could get more current.
It came from an old electrolux but I see the Chinese things they sell now have a controller, and it probably lasts longer than the accessories so should be plenty in the rubbish.

All the best

Bob

Foolin Around

robbo

Regular Member

Joined: 25/03/2007
Location: Australia
Posts: 71

Posted: 02:03pm 05 Jan 2011

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Thanks for your response,
"but if you put bigger scr in it you could get more current."

What does SCR mean ? Still, would you be able to get up to 15 amps. This looks like a big ask for it ?

"the Earth was not given to us, by our fathers, rather, it is lent to us by our children".

Downwind

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Joined: 09/09/2009
Location: Australia
Posts: 2333

Posted: 02:12pm 05 Jan 2011

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Most heating elements are adjusted by duty cycle, meaning the period of time it is on to the period of time it is off.

A standard thermostat works this way.

Why do you need to regulate the current to the element?

Pete.

Ps:- it would have been better to post this in ...electronics or Other stuff, but not in the wanted section.

Sometimes it just works

robbo

Regular Member

Joined: 25/03/2007
Location: Australia
Posts: 71

Posted: 02:25pm 05 Jan 2011

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Pete,

I have a poorly made homebrew still, (purchased from another owner) which is heating a tad too high for my liking. It currently heat the fluid used at 82-84 degrees, when I need it as 78 degrees.
Is there some other way to increase the load on this circuit perhaps ? (or will that just draw more current?).
The original idea is to lower the input voltage to vary the temperature.

Yes, your right, "electronics" would have been better.

"the Earth was not given to us, by our fathers, rather, it is lent to us by our children".

VK4AYQ
Guru

Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 12:19am 06 Jan 2011

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Ghug a lug Chug a lug

Just get a temperature controlled from fleabay V Village has them for around $35

Bob

Foolin Around

GOFJ

Newbie

Joined: 22/12/2009
Location: Australia
Posts: 27

Posted: 06:22am 24 Jan 2011

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I brew ginger beer and use a 350 watt water bed heater (variable temperature controlled running at 28 deg C) under 3 plastic kegs, to controll the wattage (and stop it going up in flames) I use an electric drill speed controller (old Dick Smith kit). The heater is a plastic mat and is designed to have a very large heat sink (bladder full of water) to stop localised hot spots which I no longer have, hence the chopper controller to limit the power.

Jack

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