# Electromagnetic Induction

Discussion in 'General Electronics Discussion' started by nabberuk, Jul 25, 2012.

1. ### nabberuk

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Jul 25, 2012
I've been looking at using electromagnetic induction to trickle charge batteries on a model sailing boat (1.5meter). The idea was to have a U shaped tube with the copper wire coiled around it. There would be a magnetic ball inside the tube so when the boat rocked it rolled around the tube.

From my understanding, depending on the polarity of the magnet you'll get a + or - voltage output, now as the magnet would be a ball I'm a little unsure on what would happen. Can I use any circuitry to harvest this regardless of the -/+.

If i can make use of the above, I'm a little unsure on the most efficient way. i.e is it more turns of the copper wire, stronger magnet?

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,490
2,832
Jan 21, 2010
Here's some random thoughts from someone who really doesn't do models.

It may work, however the energy you get out may be quite small.

The solution you're after is a bridge rectifier. This will ensure that he polarity is always right and the batteries won't discharge into the coil.

Yes, more turns will generate you a higher voltage, and for a constant speed of the magnet through the turns, a higher power. However, the weight of the magnet needs to be sufficient that it can release that much potential energy as it falls from one part of the U to another.

It may be better to make some little solar panels to place on your vessel (assuming that it's not a model of a ship which pre-dates solar panels)

The magnet also needs (pretty much) to retain its orientation as it moves through the coil. I'm not sure that's easy to do.

One option is to make a long curved section of magnets arranged NS SN NS SN NS... and have this swing back and forth with the motion of the model. A relatively thin coil could then be places so that the magnets pass through it.

Tricky to make the magnet stick, because it has to be curved, you need strong magnets, and the magnets are arranged so they repel from each other.

If toy add balancing masses on either end of the magnet stick, you increase the energy available (and the mass doesn't need to pass through the coil -- which makes life easier).

One other useful property may be that this will damp the rolling of your model, possibly making it look like a much heavier craft.

3. ### KrisBlueNZSadly passed away in 2015

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Nov 28, 2011
Good advice from Steve, as usual.

Most importantly, I don't believe you'll get any useful amount of power. You can get significant power from tidal energy, but something bobbing on the waves can only generate a tiny amount of power. Enough to power a device that's designed with a very low power consumption, like a transmitter that sends a tiny burst of signal every hour or so, but not an electric motor. In fact I would say the self-discharge of your battery would be greater than the energy you could generate.

4. ### nabberuk

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Jul 25, 2012
Hi,

I had another idea in order to up the voltage/power created by this. Would having smaller versions but more of them make it a better idea as the magnet's would transfer to more than 1 coil when they pass?

thanks

5. ### KrisBlueNZSadly passed away in 2015

8,393
1,271
Nov 28, 2011
This fallacy seems to be popular with "over-unity" folks as well. You're talking about converting energy in the form of motion and force into electrical energy. There is a very limited amount of energy available; whether you convert small amounts of it separately and add them together, or convert all of it in one place, makes little difference. The energy output cannot be greater than the energy input.

6. ### john monks

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Mar 9, 2012
The energy out has nothing to do with the number of turns. The more turns the more voltage out and the less current. This will be an interesting experiment but my gut tells me that the poles of the magnet will tend to line up perpendicular to the direction of travel and therefore minimizing your output. So you might end up coming up with a shape other that U shaped. Ideally with poles will need to be parallel to the direction of travel.

7. ### elektroinstalace

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Jul 28, 2012
Hi, gr8 post thanks for posting. Information is greatful!