Large Magnets Spark On Halloween, Who Knew?

This overly large magnet certainly completes the mad scientist look (for an even crazier look, take a jar of water with red food coloring and place in one large cauliflower, instant brain in a jar).

The base of the magnet is painted foam cut with a makeshift hot-knife; to get the magnet sparking [Macegr] laser etched acrylic with a fractal pattern and embedded LEDs in the ends of the acrylic. An Arduino handles the flashing LEDs and also produces a 60Hz PWM pulse for the spark’s hum. The end result is satisfyingly mad, and while practicing your evil ominous laugh catch a video of the magnet after the jump.


28 thoughts on “Large Magnets Spark On Halloween, Who Knew?

  1. Very cool. Only change I would make is to fire real sparks instead of simply using a few lights. Great job, but actually scaring the heck out of people every time you push that lovely little button seems like an honestly mighty idea.

  2. I agree with tulcod. I like this very much, which is why I submitted the tip along with my LED labcoat mentioned in the first group of links today. But when I build mine next year, it will be real sparking via flyback transformers. I am a Electrical Engineering kind of mad scientist after-all.

  3. 1. Square wave on the PWM sounds off. It sounds nothing like an arc.

    2. Should have used a single piece of acrylic – the seams ruin the appearance or sparks.

    3. Way overkill on the electronics. You could probably salvage the necessary parts from a singing greeting card or something, instead of using $60+ worth of arduino crap to flash some LEDs.

  4. Only change I’d make would be internalizing the electronics.

    On all those saying real sparks:
    Halloween= dark crowded places, with many people wearing flowy, lacy, or otherwise high surface area, flammable costumes. Also, foam burns. Also also, drunk people poke at things, including bright sparks. Using a real transformer would be great if he’s running a haunted garage, but if he’s going out it would be the worst idea in the world.

    On those saying use a single acryllic:
    That’s the most obvious way to do it, and was surely considered. However, he would not be able to isolate the sparks then. No way he upped the parts count and working time that much without valid reason.

  5. for those of you wishing to build one firing real sparks, please realize that you’d need to generate roughly (30cm)*(30kV/cm)=900kV (*), which is slighty bigger than what you’d find in your computer’s PSU. oh, and at the technical university of delft, where i’m studying, they can generate the highest voltages in the country, and those max out at just a couple of megavolts IIRC. as a possible solution, you could release helium in the area where you want to spark, which has a dielectric strength of just 1500V/cm. or perhaps hydrogen, which i think has a lower dielectric strength as well and will also give you an extra “BANG”.

    * the dielectric strength of air is roughly 30kV/cm, and i guessed the 30cm.

  6. @Bon:
    What do you want to see mate? I don’t make a habit of building fake 3-foot styro magnets. I can build and take some pics of a blinking LED circuit if you’d like…

    I do, however, have a lot of experience etching acrylic for case mods and light fixtures(though I usually use tape and a media blaster).

    I also have many years experience in programming PIC/AVR/ARM micros, and I began tutoring in electronics and particle physics by the dean of the engineering school at a Big-10 university by the time I was 8.

    I built my first tesla coil/jacobs ladder when I was 9.

    Is this a job interview? Wheee!

    Do they sell bull-nosed acrylic? I’ve never seen it for sale, but I think that would be ideal.

  7. @M4CGYV3R

    Your point? And how do your ‘credentials’ justify you being such a nit-picky negative Nancy? How do you watch TV without getting upset about everything that doesn’t quite fit into your perfect world?

    For something that’s fairly original, and most likely built in a day, it’s pretty awesome.

    I’m mean, really, It’s a giant foam magnet that sparks and you are going to argue about how realistic the sparks are?

  8. Yeah it’s overkill. I could have done it with an ATTiny, but didn’t want to build up a PCB on limited time. The acrylic is separated because otherwise all the sparks would light at the same time. Painting the edges black would have improved things and an experiment was done with a sharpie, but time was a factor again. Buzzing was close enough, I tried some 1-bit audio a la Roman Black, but there was too much hiss. It was cool anyway, got lots of comments on the street…none negative :)

  9. @tulcod yeah, you can kludge a plasma globe using helium in a jar, this has been around since the early 1960’s…
    the best bet according to Bill Beaty is to use a mixture of pure argon (the Ar+CO2 stuff does not work) and helium at 1 atm, making sure to seal the jar and vacuum it out for 24 hrs or so to remove all the gas poisoning agents released from the glue.

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