Like Ra's Naughty Forum

Found some suitable montable plastic cases here: http://www.reichelt.nl/Case-Enclosures/2...OUPID=3356

Hey, LikeRa asked me in "my" thread whether I knew a source of electromagnets - wanted to reply here, since the question contained a link to this thread.
I don't know a supplier - even in the age where (apparently) everyone has an arduino, noone seems to want to make tiny magnets... 😟
I ended up purchasing a 5 lbs holding magnet for something like 20 gramms of keys. Unneccessary power waste, but it is the smallest around. Also, I tried making magnets myself (wrapping thin wire around an iron core, that is all) - ended up either with almost no magnetism, overheating resistors/coils or a magnetized iron core. Considering this a failure.
Sorry I can't help you with that.

Regards
madscientist
Currently sitting beside an former electromagnet (read: now permanent magnet in useless coil) waiting for the screw to fall (Luckily it was a screw, not a key).

(17 Mar 2015, 20:50 )madscientist Wrote: [ -> ]Hey, LikeRa asked me in "my" thread whether I knew a source of electromagnets - wanted to reply here, since the question contained a link to this thread.
I don't know a supplier - even in the age where (apparently) everyone has an arduino, noone seems to want to make tiny magnets... 😟
I ended up purchasing a 5 lbs holding magnet for something like 20 gramms of keys. Unneccessary power waste, but it is the smallest around. Also, I tried making magnets myself (wrapping thin wire around an iron core, that is all) - ended up either with almost no magnetism, overheating resistors/coils or a magnetized iron core. Considering this a failure.
Sorry I can't help you with that.

Regards
madscientist
Currently sitting beside an former electromagnet (read: now permanent magnet in useless coil) waiting for the screw to fall (Luckily it was a screw, not a key).

Ha, the problem is the fixed iron core.
Wind wire around a plastic pipe with a hole of about 1cm.
Insert a piece of iron in the pipe. If the pipe is vertical and the power goes, the piece of iron falls out immediately. The load it supports depends on the number of
windings and the thickness of the wire which determines the current. If you draw too much current and you can hold enough load, you can put a resistor in series
to lower the current.

Hope this helps.
Zooy

(17 Mar 2015, 20:50 )madscientist Wrote: [ -> ]Hey, LikeRa asked me in "my" thread whether I knew a source of electromagnets - wanted to reply here, since the question contained a link to this thread.
I don't know a supplier - even in the age where (apparently) everyone has an arduino, noone seems to want to make tiny magnets... 😟
I ended up purchasing a 5 lbs holding magnet for something like 20 gramms of keys. Unneccessary power waste, but it is the smallest around. Also, I tried making magnets myself (wrapping thin wire around an iron core, that is all) - ended up either with almost no magnetism, overheating resistors/coils or a magnetized iron core. Considering this a failure.
Sorry I can't help you with that.

Regards
madscientist
Currently sitting beside an former electromagnet (read: now permanent magnet in useless coil) waiting for the screw to fall (Luckily it was a screw, not a key).

I'm thinking about periodically changing current direction on magnet - it can help with core magnetizing. Something like feeding power through H-bridge, or motor driver. Needs experimenting, of course.

Oh, and I think that if your keys are too light, you can always add weight with locks or something. Actually, I believe that lasting magnetic force of iron core can't be of same power as actually powered up electromagnet. So, you can adjust weight of "keyload" to be bigger than iron core power, but less then electromagnet holding force.

Thanks for your advice. Sure, more weight or altering polarity would be it (unless the key gets magnetized and pushed off). After roundabout 4 hours, the effect had worn off far enough that my test screw fell down (was in the middle of the night and I had a piece of tin under it).
But I have to admit I am sick of homemade magnets. I'm still waiting for my ordered one. I'm sick of waiting as well, but I can't fly over to china and pick that thing up, can I? I sure would like to.

Anyway, weight brings its own trouble, too much of it can turn your "release" into an unpredictable risk (for obvious reasons).

Regards

madscientist

(17 Mar 2015, 20:50 )madscientist Wrote: [ -> ]I ended up purchasing a 5 lbs holding magnet

Where?

Amazon (http://www.amazon.de/6lbs-Haltendes-Elec...B008RFOI8U ). Conrad also sells them, but they're overpriced and take ages to deliver. Mine didn't arrive yet.
Guess noone apart us SB'ers really needs magnets like this, so they're rare.

Regards

madscientist.

I think this one should be perfect for handcuffs: http://www.amazon.de/lbs-haltenden-Elekt...F8STJQEFKR

90 lbs DC 12V - just fine for a 9V accumulator. But the comments are completely opposite...

Any ideas where to get a suitable metal plate for the second cuff?

Found more:

http://www.amazon.de/65x30mm-Disketten-M...romagneten

http://www.amazon.de/65mm-haltenden-Elek...romagneten