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Electronic bondage, magnets, and mathematics. - Printable Version

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Electronic bondage, magnets, and mathematics. - bluedragontao - 30 Sep 2010

Greetings all! Let me get some things out of the way before I begin this post. There will be ... science. (horror!)

Hopefully not too much, as we do have the fun of selfbondage to take care of.

As a disclaimer, most of the things I post here come from a mix of pure logic and reasoning, as well as some science background. (Yay college)
However, I do not claim to be a whiz or expert in any of this.

This thread is primarily designed to help people design and conceive selfbondage ideas that rely (excluding the safety release) on a principle found in electronics, specifically in electromagnets.

One of the first things that comes to mind is... precisely what is an electromagnet?

Most people who have played with wire and done middle-school physics know what they are, but not how they precisely work. An electromagnet, in its simplest form, is a coil of wire that possesses a magnetic field when a current is applied across it. Some of them stick with air, others have an iron core, and some even have such things as exotic ceramics or liquid metals.

My first point: Stay away from iron-core, for the most part.

This is because iron-core electromagnets exhibit something known as "Hysteresis", which means that it has memory. If your coil turns off, the iron itself would preserve a sort of magnetic fingerprint. This would be weak, but it might be just strong enough to throw one big wrench into the works.

So, let's take a look at the icky science part, assuming that you don't mind wrapping your own coils.

Assume you have a key on a metal fob that you wish to suspend, and that this weighs about three ounces, all totaled.

This little goober is going to be the source of our experimentation. I could go through and give everyone the benefit of calculus rendered in straight text and my meandering explanations, but instead, let's leave it to dicking around with bits of wire.

One of the things you will need is a selection of small cylinders, such as film-canisters, pencils, or something between.

You will also need a number of lengths of wire, preferably between 10 and 20 gauge. Also, a table of the resistances that these have would be quite useful.

Finally, a regulated DC power supply, which goes from 1.5 to 12 volts in steps. These can be had for a few bucks at any electronics hobby shop.

The idea is to experiment with different types of coils, varying on size, number of turns, and number of layers, to see what can lift your key, and at what voltage. Keep in mind you use a small resistor (such as a 100 ohm or the like) between the wire and the power supply. The resistor can be ideally calculated by V = I R, where V is the voltage, R is the total resistance, and I is the current resulting. I'd recommend keeping I below 800 mA and above 200 mA.

Once you have a few in mind, you should note down their resistances, which can be calculated from the wire's spec-sheet, and then calculate the new current usage.

This can be used to choose a battery. (Yes, a battery) for use with your new electromagnet. The battery should be able to output the same amount of Voltage that you picked for your electromagnet. Let's assume that your coil works well on something near 5 volts. Unfortunately, not many batteries are made in 5 volt, so we can go up to the next, which is a 6 volt battery. Recalculate for 6 volts.

This is the fun bit, where you can design how long you want to be helpless.

Every battery comes with a rating in mAH, which means Milliampere-Hours. This is, naturally, the number of mA that the battery can support per hour.

Ooh, remember how I suggested keeping it between 200 and 800 mA? For this, let's assume 400.

Let's take a look at a few batteries. First up, the big old honkin' 6V lantern battery. These look like bricks with small springs stuck to the end.

Now, differently constructed batteries have different mAH ratings. For instance, a Zinc Chloride, also called Carbon Zinc and "Heavy Duty" cells, have an mAH rating of around 11,000. This means that with a 400 mA draw, the battery will go dead after 27.5 hours. Now, the key will probably drop before that, as the magnetic field will be too weak to hold it up at some point. Keeps ya guessing, hm?

However, there's a Zinc/Manganese Dioxide battery which lasts for 52,000 mAH, which would keep you all trussed up for 130 hours, or 5.4 days.

Now, there's also the possibility that you want to be a bit more free in only a few hours. There are 6V batteries, usually the Lithium type, which are rated at 160, which is a few minutes, to around 1300, which is 3-ish hours.

You can also use smaller batteries in series, and while their voltages will add, their mAH will not, as they still put out the same mAH, at just a higher voltage, distributed across all.

So, you have your magnet and all's ready for you to use it. But you don't know how to set it up. You could tape it to the ceiling and have your keys stuck to it, but there's an easier way.

Once your magnet's manufactured, I'd recommend coating the outside with a varnish or resin to keep it well-wound, as gappy windings can make a bad e-magnet. This will also allow you to make it easier to mount in whatever nefarious contraption you might have at hand.

One such is rather simple. Take a PVC pipe, a foot or so long and about two inches around, internal diameter, as well as the matching end-cap. Then, drill a small hole in the cap, slightly smaller than a pencil, making sure to deburr the hole, right in the middle. Next, drill another hole, off-center and near where the cap begins to turn. Deburr well, and feed the wires from your electromagnet through this, centering the coil over the middle hole. You can then surround the coil with a substance to hold it in place. I like using air-cure modeling clay. Make sure you leave the middle hole open through and through.

Now, take a washer and tie it to a length of twine, about two feet long. The other end should have a loop of fine thread tied into it, which you can then use to tie your keyring on.

Then, you can use whatever method you want to hold it up, so the opening of the pipe is either pointing down or is at a sharp angle downwards.

To use, just tie your keyring and fob to the fine thread, put in the batteries, and pull the twine out, breaking the string if you want. Then get gear'd up and be patient. Eventually, the key will fall out. If not, and you still have mobility, you can get the keys by some method, but not without a considerable struggle.

It's also possible to create devices using a similar method, such as electromagnetic stocks, which I think should -only- be used on batteries strong enough to power them, but not so strong as to keep you in indefinitely. You can also create electromagnetic keysafes, and even play a little game with yourself, if you're in chastity or some predicament where you still have the use of your hands and eyes.

Let me outline two of these safes, one of which is rather simple, the other, plays with your mind.

This kind of device I would deem safe to use with iron-cored magnets, as hysteresis is weak enough it wouldn't impede the function, providing the magnets weren't just over the top and huge.

Let's say you've built a wooden box, one foot cubic. Inside is space for a battery, say a car battery, or lantern battery, or whatever you wish to use, under a covering. The top is hinged so you can access the storage space, and at the two corners opposite the hinges are electromagnets. These should mate to magnetic plates fastened on the lid. The battery is connected with a switch before it goes to the magnets. To operate, you'd just turn on the switch, replace the tray, put the keys in, and let the lid close. the magnets would catch and the box couldn't be opened until the magnets wore out. I'd recommend adding a small spring or two inside so the lid pops up on its own once it's weak enough. If you're clever about the design, you can make the switch a push-button just inside the lid, so it turns on when you close it.

Simple, you say? I have one that would send you mad if taken to the fullest extent....

This requires a modification of the circuit. The path from the battery to the e-magnets will have a kind of electric switch called a relay. Now, you can make a panel on the front where several wires go in and out. One of these is the wire to the e-magnets, in parallel with the relay. Or half. Or however many you choose. The others are in fact one wire which go to the relay, keeping it active, and thus open.

Now, here's the game. Armed only with scissors or wire-cutters, you must 'disarm' the box to earn your freedom. If you cut all the wires to the magnets, the box pops open. If you instead cut a magnet to the relay, it clicks shut, and no matter how many wires you cut, it will still keep current flowing to the magnets, and thus, keeps it shut until the battery runs out naturally.

However, this is rather crude, as every time you play you need to re-wire the circuit. In the next installment, I'll explore the use of logic circuits and automated bondage design.

RE: Electronic bondage, magnets, and mathematics. - bluedragontao - 01 Oct 2010

Awww, no comments? I'll answer any question, you know. If I can. I'll even assist in the designing of your own contraptions, if I'm able.

RE: Electronic bondage, magnets, and mathematics. - Like Ra - 05 Oct 2010

You outlined very good ideas here, but it will take time until someone (with enough courage, time and skills) starts the actual building process (this is where the questions usually appear) and publish some photos or drawings. As you can see we do find it useful!