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Magnets, how do they work? - Tactical Ninja

Sep. 17th, 2013

09:03 am - Magnets, how do they work?

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Last night I planted some seeds. I have no idea if they'll grow, the only time I've really grown stuff from seed was in commercial conditions - I can grow courgettes like a boss - or clandestine conditions, or in horticulture at school when we grew peas and beans. Oh, and I think I did one of those sponge-and-grass seed things once:



So we shall see. Then I sat down with Dr Wheel and Socrates and some electronic gubbins, and made magic happen.


(15 sec)



So what that is, is Dr Wheel waving a cupboard door magnet at a hall effect sensor, which is sending data to an Arduino, which is in turn telling the LED to get brighter or dimmer according to the proximity of the magnet to the sensor.

This is all running on a breadboard, but when it's complete the magnet will be embedded in a ring, and the sensor will be on Yorick's shaft, so that when the wearer of the ring holds the staff, the LEDs in the eyes of the skill will light up. And they'll only do it for the wearer of the ring.

Or anyone else who happens to have a magnet attached to their hand. *cough*

Now, ideally I'd like it to be more responsive - the magnet is having to get within 7-8cm of the sensor to get a response at the moment, and I'd like to have it responding at about 15-20cm. However, I do understand that with magnets, for twice the distance I'll need four times as strong a magnet because *insert maths here*.

I have investigated rare earth magnets, but everything I've read suggests not putting them in jewellery because they are indiscriminate about what they attract to (think, car doors, fridges, anything made of steel), and because they are so strong they can cause injury. I quite like pombagira and would like not to be responsible for ripping her finger off, so I'm trying to avoid them.


And here's where I'm hoping for advice. Anyone know where I can get a strong normal type magnet that's about 1cm in diameter and about 0.5cm thick?

Meanhwile, Pronunciation Book is now down to Day 8, and the spectrogram made from the videos is nearly complete. Here it is:



More speculation here. Personally I am struck by the similarity between this and the suited faceless character that has come to symbolise Anonymous. I guess we'll know in 9 days.

Comments:

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From:meathiel
Date:September 16th, 2013 10:46 pm (UTC)
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Horticulture? Is that a class in NZ schools?

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From:tatjna
Date:September 16th, 2013 10:52 pm (UTC)
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It was one of the options that was offered in the between years (age13-14ish), when you were supposed to be trying out stuff before deciding what topics to seriously pursue at senior high school level when all the exit exams started.

I don't know if it's still offered but if it isn't, it should be.
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From:pombagira
Date:September 16th, 2013 10:48 pm (UTC)
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whee yoric..

also yes i would like my fingers to stay attached..

*grins*
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From:tatjna
Date:September 16th, 2013 10:52 pm (UTC)
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Tonight I shall make his horns horny. Yep.
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From:ferrouswheel
Date:September 17th, 2013 12:39 am (UTC)
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I realised that, perhaps for Yorick mk2, you could use an RFID reader, which would mean that only pombigira's ring could activate it: https://www.sparkfun.com/products/11828

(also, I want to play with RFID readers/writers because they are in everything!)
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From:tatjna
Date:September 17th, 2013 01:43 am (UTC)
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That didn't even occur to me. What a good idea! Definitely for the next one..

Meanwhile, I have some Samarium Cobalt discs coming from Australia in various sizes. They are slightly less grunty (read: dangerous) than the neodymium ones, and can withstand higher temperatures, thus won't get messed up by the baking process involved in making the ring.
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From:didotwite
Date:September 17th, 2013 02:08 am (UTC)
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strong-ass magnets inside hard drives. get ahold of one you can hulk smash? :)
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From:didotwite
Date:September 17th, 2013 02:11 am (UTC)
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...and i googled, and they're rare-earth. free rare-earth. but yes, they can be dang strong so you might want to test a whole bunch before you go out and about with one on your finger.
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From:tatjna
Date:September 17th, 2013 02:59 am (UTC)
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Still, the opportunity to smash up a hard drive sounds like it's worth taking, eh? ;-)
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From:vernacularity
Date:September 17th, 2013 09:51 am (UTC)
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i use hard drive magnets to hold curtains on the van,they are fucking strong and are dangerous. do not get your finger between two of them snapping together. there has been one on the top of my van roof for months. to be fair there have been normal magnets too at times. which reminds me, bunnings sell packs of 6 or 8 magnets ., various sizes, various shapes. cheap as chups. some where around the nuts and bolts aisle, and cupboard hardware, thereabouts.

Edited at 2013-09-17 09:52 am (UTC)
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From:tatjna
Date:September 17th, 2013 08:36 pm (UTC)
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Yeah, that's where the magnets we used for testing come from. I am going to try a smaller rare earth one and see what happens.
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From:dianavilliers
Date:September 17th, 2013 04:17 am (UTC)
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If you can't do / don't want a stronger magnet can you move the sensor closer to where the hand bearing the ring will grip?
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From:tatjna
Date:September 17th, 2013 08:35 pm (UTC)
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That's the idea. I can put the sensor anywhere on the staff, and close to where it'll be held is good - but with only 7-8cm to play with, I still have to have it very exact or it won't work. I'd prefer to have wider parameters.
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From:vernacularity
Date:September 17th, 2013 09:47 am (UTC)
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from the metshop probably, or from underneath a magnetic draughts piece or similar. $2 shop?
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From:vernacularity
Date:September 17th, 2013 09:51 am (UTC)
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and bunnings sell craft packs.
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From:pundigrion
Date:September 22nd, 2013 12:38 am (UTC)
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It's alive, it's alive!
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