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Topic: Solenoid Artistic Function - Magnet and Glass Tube (Read 1 time) previous topic - next topic

retrolefty

Biggest missing element if you want the arduino to be able to control the position of the internal magnet is that you need a feedback measurement method to know where the magnet is at any given time so the controls know how much and in what direction to power the electromagnet(s). A software PID controller would have to be set up most likely. While the overall effect would be very cool and appear simple the complexity of control is much more difficult then what one might expect. And on being able to reverse the polarity of a electromagnet requires an H-drive much like used for DC motors where you want to be able to change the direction (polarity) as well as speed (amount of average power).

Lefty

Grumpy_Mike

Quote
for a 1 foot tube 2 inches wide, with a strong magnet from magnetic key box you'd stick under your car

With these dimensions you have no chance to get it to work. Even if you could get enough magnetic field the magnet when it moved would break the end of the tube. What is likely to happen is that the magnet would not move along the tube but just flip over. 

arduinoadrian


Not sure if it will work. If you power the solenoid it will suck the magnet in to the middle if you power it the other way, it will try to turn the magnet, not really pushing it to an end.


I don't think so. When the coil polarity reverses the force will reverse as the magnet poles are still in the same position. The round tube will not allow the magnet to rotate to reverse its poles. Think about why swolenoids work. If the magnet and coil poles are opposite the thing will fly to the closest end as that will be the dominant attracting force and the closer it gets the stronger the force.\

The end breaking problem by the magnet when hit can be solved by using a small magnet covered in 2 layers of soft material on both flat sides.

The feedback signal for the control loop I'm still thinking on that one... :D
Perseverance is 90% of the solution. The remaining 10% is more perseverance.

liudr



Not sure if it will work. If you power the solenoid it will suck the magnet in to the middle if you power it the other way, it will try to turn the magnet, not really pushing it to an end.


I don't think so. When the coil polarity reverses the force will reverse as the magnet poles are still in the same position. The round tube will not allow the magnet to rotate to reverse its poles. Think about why swolenoids work. If the magnet and coil poles are opposite the thing will fly to the closest end as that will be the dominant attracting force and the closer it gets the stronger the force.\

The end breaking problem by the magnet when hit can be solved by using a small magnet covered in 2 layers of soft material on both flat sides.

The feedback signal for the control loop I'm still thinking on that one... :D


You did this before? Any proofs beyond your reasoning that it would work? What is the expression of magnetic force on a magnetic dipole?

arduinoadrian

Maybe the feedback siganl can be solved like this. Just maybe. Let' see what they find wrong with it and maybe we can improve it.

You can't touch the magnet with anything as it will affect the position and look awful; but..

You can place a round piece of reflecting something in top of the magnet thing. At the end of the tube you palce an LED and an LDR (light depending resistor) then you get the reflected light from the mirror and convert it to voltage with the LDR. The closer the magnet the more reflection you'll get and the higer the voltage. You will need to use infrared or something to avoid ambient light from affecting the thing.

Whatever you do with the magnet it has to move freely and you may need a hole in the middle or something to allow the air flow back and forth otherwise the piston efect it will create will slow it down or prevent it from moving altogether when the air gets compresssed. You can also vaccum the tube after done and seal it again as they did it the past with vaccum tubes. Vaccum tubes again? =(
Perseverance is 90% of the solution. The remaining 10% is more perseverance.

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