Lock Box

[onestrangeguy]

A magnet like that is designed to hold an outside door closed against the pull of someone at least as determinened as Mistress jenny! It would be almost overkill to use it to hold a box closed.

Many keys are made of brass, and thus cannot be held by magnets. Of course, you could always attach an iron key ring, or tab to those keys. The striker plate that comes with these magnets that are designed to be affixed to the door would work, but these plates weigh quite a bit and would be a danger if they were to strike someone when falling.

A step down in magnetic strength, and perhaps a little smaller and more practical for what you want. You might look for magnets designed to hold interior doors open. These use about the same amount of electrical current. These magnets are used to hold interior hallway doors open. The magnets are used so that they can be deactivated in case of a fire, thus closing the doors. They are generally available in the same type of industrial supply place that door locking magnets are sold.

[nitro]

Yes I have looked at the fire safety door magnets. This one looked more interesting because it is made for a small cabinet. Unlike the 300-1200 lb versions for an entry door, this one is only rated 80 lb pull and is only 2 3/4" x 13/16" x 1 1/4" (70mm x 20mm x 31mm). The strike plate is not so ominous either at 2 3/8" x 23/64" x 1 1/4" (60mm x 9mm x 31mm). The unit with the plate weighs 0.9 lbs so the striker plate is not so heavy, although I still would not like to get hit in the head with it. This unit looks like it would easily fit inside the box in the original post or one similar in size.

The exterior door electromagnets I have seen are 2-4x current draw and are quite a bit bigger. (see some of the other links on the referenced page, as they sell them too.)

[iPain]

i got an idea when i first saw this..
i like attaching vibrators on the ropes, because rope transfers the vibrations everywhere and it feels like heaven..
im tired of replacing batteries and all that stuff...

here's the deal.. :
i was thinking of making a BOX like this with 3Volts(or w/e voltage the vibr. can take) power supply with 4-5 outputs , so i can connect the vibrators there so there no batteries anymore..i would just put wires where the batteries go..then connect them to the box.
i don't have electronic knowledge or something..
i would really like some help on this
like a guide on what components to use and all that stuff..
what do you think?



thats the closest box in design i could find ..
say 5 vibrator outputs(front) and on/off switch(top), and 3V(or higher) power supply(right) coming from a regulator like this
http://www.ebest24.co.uk/images/product ... bi82em.jpg

[nitro]

Sounds like it would work,
I would normally add a GFCI and maybe a fuse for safety but since the vibrators are not inserted that may be overkill. The "wall wart" you need will depend on the vibrator. 2 AA cells would be 3VDC, The closest I found on a quick search is 3.3VDC. http://www.mpja.com/prodinfo.asp?number=18092+PS I would think the extra 10% would not shorten the life of the vibrators too much. It is good for 4.5A so it should handle 4-5 vibrators.
The next problem will be adapting a wire to the vibrators. You might be able to remove the cover and solder to the battery termnals but chances are one of them will be difficult to get to.
Have fun,

[iPain]

how can i calculate how many A i need??
i made a DIY neon lamp box and it burns my neon lamps in a few days.. its like 12V 0.5A and it burns two lamps in 4-5 days..
i dont see any capacity markings on the batteries ..
like ... if i use more amps than it's gotta take , is it going to speed up more and burn or it's got a limit and it simply burns?

about the battery connectors.. i guess i'm gonna use two dummy batteries

[onestrangeguy]

3.3 volts won't harm your vibrators in the least.
as for your neon lamps, if they realy are neon lamps, the ones that produce a red glow, they fire at around 90 volts, and require a balast resistor in series with the lamp. Otherwise they burn out really fast.

Using a GFI (Ground fault) circuit wouldn't be a bad idea, but at 3 volts you're not going to get much of a jolt. The GFI is just there incase something goes wrong. Using a wall wart type of supply would work, but I would be concerned about the amount of power that four or five of these might draw. It might be enough to overload your supply.

In addition, if you're making something as fancy as this you might want to put some sort of plug on your vibrators, and sockets in the switch box. That way you can only plug the vibrators you need into the box and you don't have a box with a lot of attached dangling wires. In addition, if one vibrator dies eventually, you simply plug in another.

[iPain]

they all operate at 3volts.. can i find out how many amps (mili amps actually) a motor drains without looking at the label? (i can't get it out )
if it can me measured with a multimeter or something it would be ideal(i've got one), because i would buy a wall wart supply at 3volts and with the exact, or a little more, amperage ..

[onestrangeguy]

they all operate at 3volts.. can i find out how many amps (mili amps actually) a motor drains without looking at the label? (i can't get it out )
if it can me measured with a multimeter or something it would be ideal(i've got one), because i would buy a wall wart supply at 3volts and with the exact, or a little more, amperage ..

Most multimeters have an amperage setting. Always start at the highest setting and work your way down until you get a good reading. Youre working with DC so polarity is important (Red=Positive). You may get varrying readings, so take an average. Connect your meter in series with the device while it is operating. You can power it with a battery to get your readings. What you have inside the vibrator is a motor with an off-centered weight that causes the vibrations when it spins. I wouldn't expect to find a standard electrical label showing current ratings on this type of device. Typicaly motors draw a large amount of current, but you have a verry small motor that is designed to be battery operated so 'large' here is a relative term, it probably won't draw all that much.
I would say that experimenting with such a thing probably isn't to dangerous. The worst that could happen is you would overload the wall-wart and it might get warm. One might argue that it could start a fire, but I think that's unlikely.
There are lots of places that sell parts. You might try All Electronics. They're a clearing house, and generally have good prices. Their catalog is available online.

Should you need the value in watts, Watts = Volts times Amps.

[nitro]

In reading a related article here http://tim.cexx.org/?p=260 The author brings up an interesting point. In measuring the current draw from a vibrator, he found if you hold the vibrator still it will draw more current trying to overcome the inertia vs letting it hang free.

For reference, the vibrators he measured ranged from 400mA to 1A at 3V,
If you run your vibrator at 3.3V I would expect it would draw a little more than at 3V. The dc coil resistance (ohm meter measurement) would give you an approximate current requirement. Coil heating and the motor field will affect this in actual operation.

(reference equations E = IR, I = E/R, E = Voltage, I = Current, R = Resistance)

[onestrangeguy]

In a project like this, close should be good enough when it comes to power requirements, and I doubt that the difference between a held vibrator and a free one would cause major problems. It is an interesting observation though.
The current requirements you mentioned sound like about what I would expect, although not having done the research I had hesitated to make a guess.
Your equations are correct, however they are for purely DC circuits. When the motor spind it experienced a form of inductance. Put simply, the coil of wire inside the motor rotates in a magnetic field (Usually perminant magnets for a cheap motor like this). The electricity that it generates is oposote that which is applied to run the motor, and causes it to draw less power. Stop the motor with your fingers (If you dare) and the currant drain will rise sharply.
By the way, you could use several power supplies, even one for each switch.