Magnetic powererd flashlight

[JJ91284]

I have some question on how to make a magnetic powered flashlight. Bascially I'm going to use one neodymium magnet and some radio shack magnetic wire to create the energy. I am either going to use a small battery or a 1 farrad cappacitor. :idea:

Ok here are the questions.

1. Is it better to use more coils of wire in a small space or spread it out a little.

2. Should I have the magnetic wire wrapped around a small type of plastic tubing and have the magnet slide inside the tubing so it is perfectly smooth

3. Or would it be better to have like a steel pipe with iron in it (wouldn't that make the magnetic field stronger) :roll: or something that the wire would be on the outside of and the magnet would slide inside the pipe ( would the magnet get stuck inside, not quite sure).

4. When I wrap the coil around whatever I decide to use, do I have to wrap it in a specific way (from one side to the other or can I go back and forth over the tube).

5. About the capacitor can you hook two 1 farrad capacitors inline to make a 2 farrad capacitor, or should I just stick with the battery.

6. Can I have multiple coil in a flashlight with multiple magnets, or would it disturb the other magnetic fields in the light.

7. Since the flashlight is going to be magnetically charged it is going to have A.C. current. Is that ok or do I have to use something that makes it direct current only

Thanks for all your help (as I'm trying to learn a little about electronics on my free time when I'm not working on any of my college assignments). One more thing is it possible you think to make it put out like 3 volts or something. Any diagrams would be greatly appreciated.

 

[Phasor]

You might be interested in this for inspiration:

**broken link removed**

As you can see, that one is made from plastic - and yes, if you made it from steel, it would be very difficult to shake the magnet :shock:

BTW when you say 'two 1F capacitors inline', I assume you mean, in series. This would result in 0.5F capacitance, but double the voltage rating of the individual capacitors. For 2F, you need to put them in parallel.

You are on the right track about the AC current - you can't charge your capacitors/battery with AC - you need to rectify it to DC, using diodes.

 

[JJ91284]

Can anyone tell me how to wind a coil. I want to use this coil (for magnetic induction) to produce electricity for my flashlight. I'm confused on how to do this. Not sure if you only use one wire or two wires. And how your suppose to wrap it. Also what kind or diode or should I say size would work to change the A.C. to D.C. Any advice or diagrams would be greatly appreciated.

Thanks

 

[Phasor]

Also what kind or diode or should I say size would work to change the A.C. to D.C.

Any small diode will work for this application, eg 1N4001, seeing as you are not working with large currents or reverse voltages.

I suggest you use two diodes and a center-tapped coil to provide full wave rectification, which will maximise the usefullness of each shake. A single diode will only provide halfwave rectification, and one half of the cycle would be wasted.

 

[McGuinn]

My responses are:

1. Is it better to use more coils of wire in a small space or spread it out a little.
Wrap it tight. A magnet will induce the same current in a looped wire whether it is tight or loose. Keep it tight to maximise space. Leaving it loose doesn't have any justification.

2/3. Should I have the magnetic wire wrapped around a small type of plastic tubing and have the magnet slide inside the tubing so it is perfectly smooth, Or would it be better to have like a steel pipe with iron in it (wouldn't that make the magnetic field stronger) or something that the wire would be on the outside of and the magnet would slide inside the pipe ( would the magnet get stuck inside, not quite sure).

No, steel would shield the field. Light plastic piping with springs on the ends will suffice. What about plastic bottles split and curled? Maybe you could use this as the coil-former?

4. When I wrap the coil around whatever I decide to use, do I have to wrap it in a specific way (from one side to the other or can I go back and forth over the tube).
Go back and forth. You have a magnet moving in two directions, so in this case it is viable to have the coil wrapped in both directions. If the application was different, as in the magnet was moving in a single direction, you would be best served in looping it in one direction.

5. About the capacitor can you hook two 1 farrad capacitors inline to make a 2 farrad capacitor, or should I just stick with the battery.
See Phasor's answer to this, but one thing I am unsure about is where the decision to go with batteries or cap's is defined. I think that as cap's are lossy in general, batts are better for retaining charge. Go with the caps.

6. Can I have multiple coil in a flashlight with multiple magnets, or would it disturb the other magnetic fields in the light.
Yes, by all means. Your task would be to generate as much magnetic flux as possible, so multiple coils, multiple magnets is cool. Just watch for losses when you try combine all these voltages... some will produce higher voltages/currents than others, and a poorly designed system will loose the benefits of this. I don't know what method would be best to achieve this... maybe a real EE will be able to comment!

7. Since the flashlight is going to be magnetically charged it is going to have A.C. current. Is that ok or do I have to use something that makes it direct current only
Yes, but you have already grasped this... (see phasor's answer). I personally think that germanium diodes would be better suited as they have a lower voltage drop (0.7 for 1N4001, but somewhere in the region of 0.4 for germanium, I think) so you will loose less energy!

And my final comment... lets see photos of the project as it runs!!
Best of luck.

 

[Oznog]

This comes down to efficiency, efficiency, efficiency.

Schottkey or germanium rectifiers are probably out of the question due to their high leakage current in the reverse direction. There is little capacity in the system and leakage may kill the stored energy in short order.

What you might consider is a hybrid fullwave bridge with 2 Schottkey diodes (0.3V drop, but a high reverse leakage) with 2 silicon diodes (0.7V, but with a very low reverse leakage). Put the 2 Scottkeys on the negative (or positive) legs of the rectifier, not positive-to-negative. Best of both worlds!

A single diode may end up being more efficient. It's going to mean half the time the coil isn't used, but the rectifier's voltage drop is so huge.

One key of making this work well is the sliding magnet should be able to bounce off the ends, rather than banging into them. The big flashlights did this right, the little ones didn't. Ideally, I think the weight should have been on a spring so it would naturally oscillate rather than bounce.

 

[JJ91284]

Thanks guys for the information you provided. The reason why I posted this 3 different times is maybe people would speak up sooner seeing I am desperate. The magnetic flashlight is not actually what I am building, but I am in the process of possibly having something patented that uses the same principal. So I'm currently trying to design it myself and save the money. Since I'm also in college right now. If all goes well, I will let you know how it work out. However if it doesn't work I'm definately making myself the flashlight.

Thanks