Help with electronics

[saraf_nikhil]

Im a high school student....DESRIPTION: I have arranged a device consisting of circular magnets which rotates in a magnetic field for about 2-3 minutes once given a triggering torque. Please tell me if there could be an electronic device which can trigger the same without consuming too much electricity.....
THANK YOU

[EDS]

Hello,

I'm sure there's a solution out there, but it may depend on exactly what you need.

If you want to start with a non-moving spinner and trigger it just once, a small solenoid could work. (A solenoid is basically an coil of wire and a little ferromagnetic piston. When you apply a voltage across the wire, it creates a magnetic field that makes the piston move. Some have springs or fancier mechanisms that allow them to move back and forth.)

You could also try to use magnets and a coil of wire to nudge it directly, although it might take some experimention to find a way to do that without interfering with your magnetic suspension.

If you need to keep the spinner going continually, it's going to be a little more difficult. In order to give it a mechanical push, you'd probably have to somehow sense the spiner's position so that it gets pushed at the right time. You could do that, for example by using a LED and a photo-diode to sense the position of spokes on the spinner, but it would require using some circuitry.

An easier option might be to gently blow air on the side of the spinner so as to give it a constant push in the right direction. A small muffin fan with some cardboard channels and or plastic tubes to guide the airflow to the right place could work.

Best,
Erik

[saraf_nikhil]

Thanks erik,
that was a great help to me sir.....however Is such a device available? If I construct it, how exactly do I arrange the coil and piston to the spinner?
THANKS
NIKHIL

[EDS]

Hi Nikhil,

Sorry for the delay in getting back to you. I assume you're talking about the solenoid.

You can find solenoids at electronics parts stores. A small 12 volt one the size of your finger usually goes for something like $5-$10 US new. If you can find a salvage parts store, you can get them for less. I can suggest some online retailers if that's helpful.

You might also be able to pull one out of a broken appliance, although it will take some looking around to find one.

Or, you could make it yourself. Get very thin insulated wire ("magnet wire") if you can and wrap it around a thin non-magnetic tube. If you place a ferromagnetic object (like some nails or screws, or a round steel bar from a hardware store) half way into the tube and connect a battery to the wires, you should be able to make the metal bar move. If you play around with rubber bands or springs, you can probably make the bar jump back when the battery is disconnected.

How you connect that to your spinner will depend on the details of your device. You'll have to play around to figure out what will work.

One note of caution - it's possible to damage your battery (or yourself!) by sending too much current through the coil. If you have an ohm-meter you can use it to measure the resistance of your coil and check that it won't draw more current than your battery will supply. (If you want to do that and don't know how, I'd be happy to help.)

If you don't have a meter, then when you first use your device carefully feel the wire and the battery and make sure neither one gets hot to the touch.

Good luck,
Erik

[saraf_nikhil]

http://www.geocities.com/saraf_nikhil/Revolution01.pdf

Dear sir,
I connected the trigger but found it wasnt sufficient enough for a good torque... Will using a battery of higher emf help? I changed the tube but found no change of triggerring force due to its width...The webpage above contains a horizontal view of my model.... The two long blue rectangles are ring magnets enclosed in the suspended body.... the small blue rectangles are base magnets(two visible and two behind them).....The orange flap was connected to transmit the torque to the whole body... however I dont know much about inducing a current in a coil due to moving magnets....I plan to introduce a stationary coil in the region marked X, i.e., around the rotating body... Can there be current in it? If yes, can th magnetic field due to current in the coil interfere with this arrangement?
P.S.: Im trying my best to create another pic of the view from top... Ill display it as soon as i can.....

Thanks a MILLION!!!!

[saraf_nikhil]

Here is the view from top of my model.....

http://www.geocities.com/saraf_nikhil/Revolution02.pdf

THANKS

[EDS]

Hello,

Sorry for the delay in getting back to you.

Thank you for the drawing - I think I understand the general outline of the rotor now.

But, I'm afraid I don't quite understand the trigger arrangement.

Are you using a solenoid to make a bar hit the orange flap from the side? Sounds like a good idea, but you may find that building a strong solenoid is difficult. Lots of coils of really thin wire are probably necessary. A higher voltage battery might help, but more coils is likely to help more.

Again, make sure that the battery doesn't get too warm when you hook it up - even small batteries can explode and leak nasty chemicals if you draw too much current from them. Putting together several low-voltage batteries in series is probably a better way to get higher voltages than switching to a single small sized high voltage battery. For example, using several 1.5 volt flashlight batteries arranged like this: ( +IIII-------+IIII------+IIII- ) will allow you to draw much more current than a single nine-volt battery.

If you find it impossible to make the solenoid work well, you also might want to consider trying the air-flow method to keep the object turning. A small fan directed across the top of the rotor with a paper tube might work.


>however I dont know much about inducing a
>current in a coil due to moving magnets....
>I plan to introduce a stationary coil in the
>region marked X, i.e., around the rotating body...
>Can there be current in it?

I don't quite understand this bit.

Are you planning to make a generator by inducing a current in the coil? In order to make a generator work, the total amount of magnetic flux (basically the amount of magnetic field in space) going through the center of the coil needs to change. Rotating a coil around an axis perpendicular to the flat face of the coil won't work. Rotating it around an axis that lies along its face will work. (Like a coin spinning on a table.)

But, you will find that in order to generate a current you have to remove some energy from the motion of the rotor. It takes some work to force the coil to turn in a magnetic field, and that energy will case your rotor to slow down faster than it would have without the coil.