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A hot box full of Satan!!! Answered

I'm already preparing for Halloween. One of the props I would like to build is a box to hold "Satan." I'm not yet sure what I want it to look like (rock? metal?)... but I do know that I want it to be warm to the touch. Not HOT... nothing that would actually harm anyone... but obviously - and devilishly - warm. My first best thought is to take something like an old-school metal lunchbox, create false walls on the top and bottom, and then put SOMETHING in the in-between spot. But what? Chemical hand warmers? Something battery-operated. Your ideas are welcomed. And if a little bit of smoke could come out, all the better. Please shout if you need any clarification!!! Thanks!!!

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Purple Chez (author)2018-04-01

I am loving all of the great info you guys are sharing. I am most drawn to the plan of attaching resistors to aluminum. Any additional referrals to this topic would be most welcome. Happy Easter y'all....

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bravoechonovember1 (author)2018-03-31

look up bird bath heaters. they might work for this type of thing

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randofo (author)2018-03-28

You might want to investigate a Peltier junction:

https://www.adafruit.com/product/1331

One side heats up when electricity is applied. The other side cools down. If you attach the warm side to a metal sheet, it will heat up.


If you are worried about overheating, you can use a temperature sensor to trigger an Arduino to turn it off when it gets to a certain temperature.

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Yonatan24 (author)randofo2018-03-29

I thought of using a peltier element but if they are ~30% efficient at cooling, their intended use, it means you're just wasting 30% of the power used if you only want to use them for heating.Which is why I suggested using resistors.

How about something like this?: https://www.ebay.com/itm/PTC-Aluminum-Ceramic-Heat... I've never seen these before but they might be worth a try.

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Toga_Dan (author)Yonatan242018-03-30

typically when an electric device is inefficient, it means the wasted power turns into heat..

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Yonatan24 (author)Toga_Dan2018-03-31

Yes, but if you want to use a peltier element for heating, then the cooling is the "wasted" power.

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randofo (author)Yonatan242018-03-29

It might be a little less efficient, but it uses less current. You would need some really big resistors and would need to be feeding it a lot of current to get it to heat up a large surface.

They would be better off removing the resistor from the equation and using nichrome wire. There would be a bit of math involved to get the legnth of wire and temperature just right, but that would essentially accomplish the same as a resistor and use less current.

That said, Peltier junctions are still the easiest solution and will solve the problem at hand.

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Yonatan24 (author)Yonatan242018-03-29

I don't know how much you're willing to spend in this, but https://www.ebay.com/itm/Vehicle-70x30x6mm-High-Po... + https://www.ebay.com/itm/12V-40V-10A-PWM-DC-Motor-... + https://www.ebay.com/itm/27-Types-1800-15000mAh-DC... might work if you make sure you are exceeding the maximum amount of current the battery can provide.

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Toga_Dan (author)2018-03-30

melted parafin is reputed to hold a lot of heat. the phase change between liquid and solid releases heat for some time.

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Jack A Lopez (author)2018-03-28

I forgot to link to the Wikipedia page for, "Phase-change material",

https://en.wikipedia.org/wiki/Phase-change_materia...


Also I should mention, one of the cheapest, easiest to find, PCMs, with a melting point that is, "warm", around 50C or so, is paraffin wax.

https://en.wikipedia.org/wiki/Paraffin_wax

The quick summary of this, is that a large mass of wax, like a few kilograms of it, will take a long time to melt, and also take a long time to re-solidify.

By the way, the heat required for the phase change, around 200 kJ/kg ( or 0.2 MJ/kg), is comparable to the specific energy of batteries, i.e. energy stored per unit mass, if I can believe what I read in that table, in the Wiki article for, "Energy density", here:

https://en.wikipedia.org/wiki/Energy_density#Energ...

Regarding safety, I think the main thing is to keep liquid paraffin away from open flame. It is definitely flammable. It is the same stuff they make candles out of.

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Jack A Lopez (author)2018-03-27

By the way, did you know that the Ancient Hebrews used to carry their god around in a box?

https://en.wikipedia.org/wiki/Ark_of_the_Covenant


Anyway, it was a truly freaky artifact. It spontaneously emitted heat, and smoke, and occasionally it would strike people dead, like, seemingly just to prove it could.

https://en.wikipedia.org/wiki/Uzzah

Anyway, the Ark was lost for thousands of years, but thankfully, Indiana Jones found that old thing before the Nazis did (they were both looking for it), and now it is safely stored in a government warehouse, somewhere on a military reservation in Nevada, I think, which is part of the Former United States (FUS).

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Purple Chez (author)Jack A Lopez2018-03-28

Great idea, but I don’t want people struck dead for touching it!!!!

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Jack A Lopez (author)Purple Chez2018-03-28

You make a good point about safety. I mean, whatever you come up with is going to have to be safe enough to withstand being handled, or mishandled, by children, or drunk partygoers, or whoever is coming to your Halloween party.

There was some some old quote about about fire being like government, i.e. a dangerous servant and a fearful master.

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Yonatan24 (author)2018-03-28

Ok, so smaller than I thought.

My first thought was to pour molten aluminum inside somehow, and then to glue 5W resistors to the aluminum once it cools down with thermal adhesive.

How long do you want it to stay hot?

Sound interesting!

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Purple Chez (author)Yonatan242018-03-28

Several hours. What if the box itself is aluminum... in the style of an old school lunch box?

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Yonatan24 (author)Purple Chez2018-03-28

The maybe a hand warmers would be a better option, allowing for them to be replaced once they stop heating.

To make it look like rock I thought pouring epoxy resin, and sprinkling sand over it, but I kind of need more information...

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Jack A Lopez (author)2018-03-27

I humbly suggest looking at the Wikipedia article for, "Hand warmer",

https://en.wikipedia.org/wiki/Hand_warmer

which mentions, iron-air, hydrocarbon-air, and phase change material, type hand warmers.

The Wiki article for, "Smouldering" combustion,

https://en.wikipedia.org/wiki/Smouldering

I also suggest looking at the TVTropes.org articles for, "Artifact of Doom", "Soul Jar", and "Evil is not a Toy"

http://tvtropes.org/pmwiki/pmwiki.php/Main/Artifac...

http://tvtropes.org/pmwiki/pmwiki.php/Main/SoulJar

http://tvtropes.org/pmwiki/pmwiki.php/PlayingWith/...

Also, please consider the idea of doing something else, anything else, for your planned Halloween prop, costume, whatever, while there is maybe still time to save your soul.

;-)

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Purple Chez (author)Jack A Lopez2018-03-28

Thanks!!!!

As for my soul... it’s actually going to be linked to cartoony demons, like the Red Guy from Cow and Chicken, and Jon Lovitz’s devil. It’s not really a devotional item

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