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back to article Man powers up PC to pop popcorn

Given the number of film fanatics who watch movies on their laptops, popcorn by your PC is probably just what the doctor ordered. One DIY hardware pioneer has worked out how to make your very own USB-powered popcorn maker. All it takes is a baked bean tin, a jar, an old USB cable, a high-intensity light bulb, and some thermal …

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Coat

Cardboard mixed with razor blades and ball bearings

Does anyone else think popcorn is about as nice as chewing on cardboard? I can't see the continuing appeal of the snack. It seems to me that cinemas only sell popcorn to sell drinks as it's mercilessly dry stuff. The fragments of skin from the kernels is like little razor blades slicing at your gums and firmly wedging itself between your teeth. Then there are the unpopped or semi-popped kernels hiding in there just waiting to cause an unplanned trip to the dentist.

The toffee covered popcorn is not bad however ...

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Not a Stir Crazy..

But a good effort, nevertheless.

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How does a fake like this gets into El Reg??

The is simply not enough power on a USB port to do this.

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Stop

@ How does a fake [...]

Lights say 2.8v , 0.3a.

USB provides 5v @ 0.5a.

So yes, there is enough USB power to run *that bulb*.

Whether that bulb can output enough heat to pop popcorn is the actual sticking point, for me.

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Flame

Paraphrasing Homer Simpson:

Ahhhh the lonely Universal Serial Bus, is there nothing it can't do??

Flames? Cause the Popcorn's' still to hot to handle!!

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JC

@ Ryan

More careful reading would've revealed that nobody said "there isn't enough power on USB to run that light bulb", rather "do that" would obviously be the end result reported about.

Further, if you ran a 2.8V bulb off 5V it'll use more than 0.3a and immediately burn out so obviously it was further current limited. Given a concentrated enough heat it could pop a little but not enough to make it worth the effort or have a snack in a reasonable amount of time.

The disappointing part is to generate more heat to do it instead of using the waste heat from the proceessor. Mount a little aluminum pot with copper bottom over the processoor and you'd have a more suitable and more green popcorn maker, if only you found the load level that keeps the CPU from frying itself.

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Silver badge

2.5 watt popcorn maker?

naah, the movie would be over by the time all the popcorn has popped, besides I'm having trouble believing it actually works because there's a cut in the middle of the video clip where suddenly it's full of popcorn, whereas I CAN believe this USB powered meat cooker is real, granted it does use the power from 30 USB ports...

http://xe.bz/aho/24/

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Boffin

Forest from the trees

The details of the light bulb etc are irrelevant. The spec for USB is to provide a maximum of 2.5 Watts. Corn kernels need to be raised to a nominal 150C (300F) for enough pressure to build inside from the internal moisture to "pop". So the issue is whether the can can be insulated enough for 2.5W to raise the kernels to 150C.

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Anonymous Coward

Film fanatics?!

What in god's name kind of film fanatic would watch a movie on his laptop!?

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Coat

And yet...

All you need to make hot coffee is a copy of GTA...

Mine's the one with the plain brown paper bags in the pocket

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USB spec

USB is spec'ed to provide at least 2.5 watts (.5A at 5V) but any individual implementation is free to provide more. Still the question remains how much power is required to get the bottom plate of this device to the required 400 degree F to pop the corn.

I like popcorn. Is there an icon for that?

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@"Further, if you ran a 2.8V bulb off 5V it'll use more than 0.3a"

There were clearly two bulbs in parallel.

And I don't disbelieve it. I have a low voltage desk lamp at home and it gets insanely hot.

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Linux

Re: How does a fake ...

Perhaps the link to the USB wine tap should be regarded as a hint?

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Flame

Must be fake

Just after the corn stops popping, the guy lifts this METAL can that has to be at least 150C to pop corn and pours the corn out!

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Joke

Don't need a title...

Ah, if only it was running Linux- it'd have a far better Kernel!

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The first few would pop

Any kernel directly in contact with the light bulb might get hot enough to pop, but I doubt the rest would go without a lot of shaking to get each one in turn to touch the bulb.

They poured a small amount of liquid (vegetable oil?) in too; that might have helped transfer heat from the bulb to the kernel.

Also, I reckon the grey gunk was metal-loaded epoxy, not thermal grease. I wouldn't want to eat silicone grease...

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Coat

Actually there were clearly two bulbs in series...

...which would work pretty well off 5 volts.

Power consumption would be in the region of 1.5 watts.

Even assuming:

- 100% efficiency on power transfer to heat within the can

- the system was isolated and within a vacuum

- specific heat capacity of steel as 500 J/kg C

- steel can mass of 100 grammes

by my calculation it would take about an hour and a quarter to increase the temperature of the can by 130 degrees C from a nominal room temperature of 20 degrees C.

In reality the system would reach equilibrium at much lower than that, although there may be localised points at the base of the can that reach the temperature required to pop one or two kernels.

Mines the white one with the pen protector..

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Jebus, did I watch a different video?

The 2 bulbs were sealed into a jar cap that was in turn glued onto the bottom of the tin can, the majority of the heat generated by the bulbs would be trapped and transfer through the bottom of the can where gravity holds corn kernels against the hot parts with oil added for better heat transfer.

The whole can doesn't have to hit 150C and the 'Thermal grease' is on the outside of the can and so doesn't come into contact with the popcorn.

I note an insulator/reflector added to the jar cap, the fact that we can clearly see corn popping before he puts the jar over the top (and while in place), and that on pouring out the popcorn the base of the can shows heat discolouration. Looks like he shockingly cut out ten minutes of cooking time, which is a shame as that would have put this short film right up there with the You Tube classics "my kettle boiling" and "paint drying on sunny day"

Not Fake but I doubt those bulbs would operate for very long making for some expensive pop corn regardless*

*and yet still cheaper than you can buy it at the cinema.

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So...

...slow news day then, yeah?

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Coat

Ah, popcorn...

... If you add butter and salt, it tastes like... well, salty butter...

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By my calculations.

If we assume that we want to heat 10g of popcorn to 150C , then by my calculations:

Using Specific Heat Capacity:

q = mct

c = 4200, t = 130, m = 0.01

Therefore:

q = 4200 * 130 * 0.01 = 5460 J

Now Power is Joules per Second:

p = q / t

p = 2.5 , q = 5460

Therefore in order to raise the temperature of 10g of pop corn to 150C at maximum USB power it would take:

5460 / 2.5 = t = 2,184 Seconds = 36 Minutes

This assumes that heat transfer is 100% efficient and there is no heat loss.

Now providing that the heat input into the system is greater than the heat loss, there should eventually

be some popcorn.

I think the more interesting question is how long it took.

Another thing to note, is that the USB bus does not provide 500mA of power unless requested by the device.

Therefore it is likely in this situation the USB bus is only providing 100mA, IE 0.5W

But that is just my views.

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