DIY induction stove – Frying eggs with magnets | Hacker News Reader

DIY induction stove – Frying eggs with magnets

instructables.com

145 pointsdrmacak47 comments

The easter egg that I love is the actual, physical reference to the Spaceballs movie.

https://cdn.instructables.com/ORIG/FYX/9FR4/JNULHKMJ/FYX9FR4...

As I have seen an induction furnace very quickly melt an aluminum billet, and this device works on an aluminum pan, it is not clear to me why induction stoves do not work on aluminum pans - is it because stoves work at a frequency that depends on magnetic hysteresis losses in ferromagnetic materials for generating most of the heat? Is it likely that this device would work better on an iron or steel pan than the aluminum one used?

From Wikipedia:

"Most induction tops will not heat copper or aluminum vessels because the magnetic field cannot produce a concentrated current; "all metal" induction tops use much higher frequencies to overcome that effect."

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

Holy cow! After some more searching I found only the Panasonic KY-MK3500 single-burner commercial cooktop supporting all metals, it's over two grand. na.panasonic.com/us/food-service-systems/commercial-equipment/induction-cooktops/panasonic-commercial-induction-cooktop

That's a long way from the $40 induction hob I got for the camper.

That's really interesting, I didn't realise you could get induction hobs that worked for all metals before. Would that would for stainless steel that's not designed for induction I wonder. Reading wiki it says "Stainless steel pans will work on an induction cooking surface if the base of the pan is a magnetic grade of stainless steel."

I am virtually certain it would work, as the only thing they depend on is that the pan conducts electricity well (but not perfectly). The heat is generated by inducing currents in the pan, and induction does not depend on the materials being ferromagnetic.

It "fundamentally works", but it's so crappy that it doesn't work in practice: https://en.wikipedia.org/wiki/Induction_cooking#Cookware

You are not crazy.

An induction furnace usually has a graphite crucible around the metal which I believe helps to convert the magnetic field into heat (with the side benefit that it creates a reducing environment as the carbon in the graphite turns into CO2 and CO).

Neat! https://youtu.be/pCON4zfMzjU seems to use the same principle for levitation.

Good thing it doesn't produce more heat, their Lexan sheet would start getting very soft above 150C!

Induction cookers don't transfer heat to anything other than the dialectric pan. The pan itself would have to transfer heat to the sheet bellow it, and I doubt Lexan would be particularly conductive.

Don't you mean conductive pan?

This is an interesting alternative to residential induction stoves that use AC to create the magnetic fields.

I wonder what the power usage difference is. This style of heating up the metal instead of using AC current to generate electromagnetic fields could be better for "off-grid" scenarios.

> This is an interesting alternative to residential induction stoves that use AC to create the magnetic fields.

No, it is not an alternative. It is an inferior method to create the same effect/current with additional losses. As an educational experiment it is very impressive though.

The experiment is not the least bit impressive. If your stove behaved like that, you would throw it out. For the cost of the components, you can buy a new, low-end stove at Home Depot or Lowes. That actually works.

Thus missing the point.

Induction cooker doesn't work on grid AC frequency (50-60Hz), it converts grid AC to DC then converts it to high frequency (24 kHz), so possibly induction cooker can be modified to run straight from DC power

so possibly induction cooker can be modified to run straight from DC power

I ass-u-me that's how the induction stoves in modern RVs/caravans work, rather than wasting house battery inverting DC only to convert it to something else.

EDIT: well, I guess that's why "assume" is hyphenated. According to the company that makes stoves for Winnebago, from their manual: "1. Plug into standard 110 outlet."

That's because running #0 copper gauge is expensive. You use the inverter to go from 24 (or 12)V to 110 or 240, run your standard wiring and then wherever you need power you step back down again. It's far more cost effective that way, and much safer as well because the connections do not carry nearly as much current. Even a small resistance will cause a lot of heat at currents in the 10's or even 100's of amps.

most RV's don't have all that hefty of house battery capacity (my parent's house battery is 2 deep cycle lead acid batteries). Heating things takes a lot of power, probably run those batteries down before you got much more than a single kettle of water hot. Anything that's going to use an electric stove is most likely going to have a generator.

Or gets plugged into an outlet at a campground.

Might be very noisy though, and you're spending extra energy moving the magnets.

You are spending the same energy, plus a few percent loss on the motor's friction/inefficiency.

mind showing the math on this? i really can't see how converting energy twice (ac -> motor -> magnets) can only be a few percent difference in efficiency instead of converting it once (ac -> electric stove).

Using the electric induction stove and rotating magnets achieve the same effect: alternating magnetic field in a ferrous mass. Electric motors have efficiency up to 95%, and there's no further loss in this system.

If you are truly off the grid, you'd come about even using the rotating magnets from mechanical power (say, an ICE) vs converting that power via generator and powering a stove.

I wonder a) if this would "pull" more energy with a traditional steel induction ready pan (not sure about the rate of spin/frequency) - but more importantly b) would this make sense as a pure movement to heat system, using a bike, water wheel or windmill?

How fast, hard and long does one have to pedal to boil a litre of water? :)

I'd prefer a regular wood-burning stove for that. Those can also double for providing heat.

Better not leave your phone in your pocket while you cook breakfast, though.

K&J Magnetics gave it a try: https://www.kjmagnetics.com/blog.asp?p=induction-stove

This article was written by K&J Magnetics.

Whoops. Saw it there first and didn't realize.

Isn't this leaving a lot of magnetic field on the table (literally) where you could improve by directing the fields more into the pan and closing the spacing to the pan significantly?

It doesn't spread the energy like heat, but the things which conduct will produce a force in the opposite direction of spinning, and that's where the energy is given. If there is nothing in vicinity, there won't be eddy currents, and no energy lost.

Does the same apply to wireless chargers? i was worried they would waste a lot of energy

Very interesting indeed! But those guys could use some cooking lesson for frying eggs... :-D

Efficiency?

low. you're better to just use induction plate instead(which does not need any moving parts).

I misread that as maggots. I recall reading that the heat generated by a mass of maggots causes them to break out in to smaller groups. So my initial thought was whether someone had figured out how to fry an egg by harnessing that heat. https://www.wired.com/2014/04/maggots-bring-the-heat/

You need a few leeches for that.

https://phys.org/news/2011-05-serotonin-role-leeches-abiliti...

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3210650/

With a series of heat pumps and enough maggots...

If you have enough maggots you don't even need the heat pumps.

https://what-if.xkcd.com/4/

Yeah... it's interesting. XKCD is such a large body of work, (hehe) that for almost any discussion, there is an apt XKCD.

Which is why it would be great if people stopped linking to them all the time. I've called XKCD the smart persons reaction gif, and just like reaction gifs they are 'fun' in small doses but get extremely annoying in larger doses.

I think a problem is there is a constant influx of XKCD readers. These will find XKCD novel and feel a need to educate everyone else. XKCD is on its way to become a real cultural thing.

This is a failed experiment that was posted.

Which is a great way to do science

> I have not failed. I've just found 10,000 ways that won't work

Thomas Edison

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