# Trying to generate power from a coil and magnet

#### Yawningtears

Joined Jul 16, 2020
42
I am looking for an inductor and magnet setup, where when the magnet moves relative to the inductor it creates electricity, probably a very basic thing for most of you.

Im sure you might have a ton of questions for me, but as a beginner, I don’t know what to provide.
Ultimately, a couple links of a neodymium magnet that would work well with an specific inductor... not sure if I would need a toroidal or what exactly.

I will likely make several of these and put them in series and in parallel.

I’m and looking for cheap and small, where a multitude of them will end up creating however much power.

Not sure if this is possible, but thought this was a good place to start a discussion, I’ve tried to do some research but it’s def a little hard to digest and understand for a newbie.

Here is a rough amateur diagram of what I’m trying to mock up, but I don’t know exactly which kind to get and would love a link to a specific inductor and magnet as well:

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#### Papabravo

Joined Feb 24, 2006
14,197
Are you sure that a magnet moving relative to an inductor creates DC (Direct Current)?

The magnitude of the voltage is proportional to the relative velocity. If you start from rest, accelerate one with respect to the other, the voltage will rise from zero to some value. If the velocity remains constant, then so will the voltage. At some point you will have to decelerate and come to rest. When you do this the voltage drops back to zero. Then you repeat in the other direction: accelerate, run, decelerate. Sounds like the voltage and induced current will be changing, and that's AC - not DC.

If you can arrange for the two to move continuously with respect to each other, at a constant velocity (as in an actual motor) then you can get a constant output. That is kinda hard to do by hand with separate pieces.

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#### MrChips

Joined Oct 2, 2009
21,618
You will be very disappointed with trying to create a lot of power.

btw, think of the usefulness of a thread title such as "A little beginner help?"

A title such as "Trying to generate power from a coil and magnet" is more to the point of your query.

#### DarthVolta

Joined Jan 27, 2015
499
Well how much power do those wind-up radio's use, how loud is the speaker ? How many LEDs could they power at 10's of mW a piece?

If you wanted to make a human powered generator, what about the type where you put a little generator on a stationary bike/exercise bike ? They can power old style lightbulbs, of 10's of Watts, so thats quite a bit of power.

#### SamR

Joined Mar 19, 2019
2,386
Made me wonder just how small he was... Welcome to AAC!

#### ThePanMan

Joined Mar 13, 2020
36
Somewhere, I think on YouTube, I saw an olympic bike racer try to generate enough power to toast a single slice of bread. He could barely do it.

#### Yawningtears

Joined Jul 16, 2020
42
Wow guys, what an overwhelming response, you all clearly have quite an active community here and that is awesome!
I will try my best to address everyone here.

#### Yawningtears

Joined Jul 16, 2020
42
Are you sure that a magnet moving relative to an inductor creates DC (Direct Current)?

The magnitude of the voltage is proportional to the relative velocity. If you start from rest, accelerate one with respect to the other, the voltage will rise from zero to some value. If the velocity remains constant, then so will the voltage. At some point you will have to decelerate and come to rest. When you do this the voltage drops back to zero. Then you repeat in the other direction: accelerate, run, decelerate. Sounds like the voltage and induced current will be changing, and that's AC - not DC.

If you can arrange for the two to move continuously with respect to each other, at a constant velocity (as in an actual motor) then you can get a constant output. That is kinda hard to do by hand with separate pieces.
You break it down very nicely, I guess maybe my goal is not possible.

I probably should have just said what I wanted to make, it’s basically a modified version of what this guy made and for some reason I thought it was DC:

I am looking for cheap inductors and magnets that would work for this.

#### Yawningtears

Joined Jul 16, 2020
42
You will be very disappointed with trying to create a lot of power.

btw, think of the usefulness of a thread title such as "A little beginner help?"

A title such as "Trying to generate power from a coil and magnet" is more to the point of your query.
sorry about the thread title, you are correct, I will see if I can change it.

#### SamR

Joined Mar 19, 2019
2,386
Haven't seen one in a while but there was a 2 D cell sized flashlight that worked by shaking it back and forth to charge it. Never tore one apart but assumed it was a magnetic rod and coil design that charged up after a moderate number of cycles and kept working for a while after shaking. Interesting device. Not sure if it was LED or not. I do remember seeing the old military hand-cranked generators for tube radios.

#### Yawningtears

Joined Jul 16, 2020
42
Haven't seen one in a while but there was a 2 D cell sized flashlight that worked by shaking it back and forth to charge it. Never tore one apart but assumed it was a magnetic rod and coil design that charged up after a moderate number of cycles and kept working for a while after shaking. Interesting device. Not sure if it was LED or not. I do remember seeing the old military hand-cranked generators for tube radios.
I feel like I have heard of that flash light before. That is interesting and would definitely be curious how that works and wonder if it is DC since it sounds like either magnets or coils could be passing through each other and as mentioned above sounds like it would generate A/C.

#### DarthVolta

Joined Jan 27, 2015
499
Somewhere, I think on YouTube, I saw an olympic bike racer try to generate enough power to toast a single slice of bread. He could barely do it.
Yeah I remember doing calulations on the human body's power output, but never took it a step further to see what the food would cost.

And if you had kids, could you have them exercise, while powering a few lights, and would that be cost effective ?> LOL

#### MrChips

Joined Oct 2, 2009
21,618
I have this:

and this:

The first one is a cheat. There are a number of button cells inside so you get light the instant that you turn it on.
With the second one, if I recall correctly, you have to keep cranking in order to get any light output. There might by a storage component inside but you would have to crank it for a long time to get enough charge stored.

#### WBahn

Joined Mar 31, 2012
26,033
You break it down very nicely, I guess maybe my goal is not possible.

I probably should have just said what I wanted to make, it’s basically a modified version of what this guy made and for some reason I thought it was DC:

I am looking for cheap inductors and magnets that would work for this.
I lost interest in the video after several minutes of nothing but pure babble. My impression is that it is nothing more than a free-energy hoax or scam. Think about it, if they were able to harvest "a lot" of energy, you would see them bolted all up and down the sides of high rise buildings to power it.

#### Yawningtears

Joined Jul 16, 2020
42
I lost interest in the video after several minutes of nothing but pure babble. My impression is that it is nothing more than a free-energy hoax or scam. Think about it, if they were able to harvest "a lot" of energy, you would see them bolted all up and down the sides of high rise buildings to power it.
Nothing is free, it still takes energy to make the magnets etc... it’s vibrational energy, aka the magnet moves from vibrations and you know about magnets moving against coils creating energy.

I’m asking for a simple referral, Amazon is fine, of an inductor and magnet, I’m fine with it being A/C altho i Imagine that flashlight is somehow able to accomplish DC.

#### MrAl

Joined Jun 17, 2014
7,748
I am looking for an inductor and magnet setup, where when the magnet moves relative to the inductor creating DC.

Im sure you might have a ton of questions for me, but as a beginner, I don’t know what to provide.
Ultimately, a couple links of a neodymium magnet that would work well with an specific inductor... not sure if I would need a toroidal or what.

I will likely make several of these andput them in series and in parallel.

I’m and looking for cheap and small, where a multitude of them will end up creating a lot of power.

Not sure if this is possible, but thought this was a good place to start a discussion, I’ve tried to do some research but it’s def a little hard to digest and understand.

Hello there,

Magnets and coils are the basis of most generators. A magnet is forcibly moved near a coil and the coil generates a current. There are details of the construction though that make it work very well or barely work at all.

First, the rare earth magnets are the best because they offer the most flux for the size, so you got that right.
Second, for slower moving forces like a hand crank a magnetically active core material is also used inside the coil.
Third, the proximity of the magnet to the coil (and more important to the core material) is important. The closer the better.
Fourth, the shape of the core material and thus magnetic path.
Fifth, the speed of the movement and the intensity of the force behind that speed.

A usual core material is silicon steel specially made for magnetic applications. The shape should be such that it curves around and almost closes on itself with the magnet moving in the resulting space between core faces. That is when using only one magnet. For multiple magnet constructions the construction would be like a regular DC motor or DC generator.

So the design has some details to it that are not that easy to get right unless you have some special materials and ways to machine them properly. This means that finding a generator that fits your needs and purchasing that is almost always going to be much better than something you can build yourself.

I am not sure how you intend to move the magnet, a crank or lateral side to side movement or something like that. Crank generators are widely available though. One of the flashlights shown elsewhere in this thread is an example of a hand crank generator and they usually have a Li-ion battery or other rechargeable battery inside to store charge while you crank so you can get some light out of it without continually cranking. They create DC by using diodes to rectify the AC into DC and charge the battery.

So look around the web see if you can find something already built. It will work well and you dont have to try to get everything right.

BTW a regular inductor with a magnet may or may not work at all. It depends on the construction of the inductor. Closed inductors have most of the field confined to the inner part of the core so not much of the magnetic field gets out, or can get inside either. That would make a very very poor generator. The only kind that would work would be the open frame type where two ends of the core are accessible. Those kind however are not that great either because the two ends are not close to each other. In that case what might help is one magnet at each end and move both magnets at the same time with opposite magnet pole polarities. Still it is doubtful this will work as well as a generator already manufactured that was designed properly to actually be a decent generator.
Another possibility is to get a U core and use one or two magnets at the open end of the U. You can get U cores by looking for the type of cores that use two U shapes to form a transformer or inductor by winding wire on one or both U's and then placing the two open ends of the U's together to form a continuous unbroken magnetic path. These are sometimes called "C" cores.

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#### Bernard

Joined Aug 7, 2008
5,601
Passing the magnet thru coil causes a single bright flash of a white LED in each direction. Coil about .75" dia. X 1 " X .06" wound with .004 wire. Origional had a non rechargeable 3V cell.

#### Audioguru again

Joined Oct 21, 2019
1,721
The video shows the guy hitting the "generator" and producing a momentary peak of 188mA but a voltage of almost zero. Then the momentary power is 188mA x 0= zero. If he continues hitting the generator then since he did not show it powering anything useful then it is simply a waste of time.

#### sparky 1

Joined Nov 3, 2018
286
Robert Murray-Smith does videos mostly replications. There is usually one or two specific aspects about it that he will demonstrate. If it is a good idea he might highlight that. Usually a fair acessment and opinion is unlike a project working toward a goal rather he selects new and useful for the viewer to decide and next week something different. The Google Quota is based on likes and not listed by a qualified pier review basis.

When a project is put into a pdf and uploaded with enough details to follow, it can be useful. A professional paper and a lecture is now competing in an arena that was not easy for just anyone to get published such as a professional journal. Now there are lots of fake papers,misleading ideas ,get mentioned and it is another new headache requires exhaustive study to filter thru.

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#### Yawningtears

Joined Jul 16, 2020
42
Hello there,

Magnets and coils are the basis of most generators. A magnet is forcibly moved near a coil and the coil generates a current. There are details of the construction though that make it work very well or barely work at all.

First, the rare earth magnets are the best because they offer the most flux for the size, so you got that right.
Second, for slower moving forces like a hand crank a magnetically active core material is also used inside the coil.
Third, the proximity of the magnet to the coil (and more important to the core material) is important. The closer the better.
Fourth, the shape of the core material and thus magnetic path.
Fifth, the speed of the movement and the intensity of the force behind that speed.

A usual core material is silicon steel specially made for magnetic applications. The shape should be such that it curves around and almost closes on itself with the magnet moving in the resulting space between core faces. That is when using only one magnet. For multiple magnet constructions the construction would be like a regular DC motor or DC generator.

So the design has some details to it that are not that easy to get right unless you have some special materials and ways to machine them properly. This means that finding a generator that fits your needs and purchasing that is almost always going to be much better than something you can build yourself.

I am not sure how you intend to move the magnet, a crank or lateral side to side movement or something like that. Crank generators are widely available though. One of the flashlights shown elsewhere in this thread is an example of a hand crank generator and they usually have a Li-ion battery or other rechargeable battery inside to store charge while you crank so you can get some light out of it without continually cranking. They create DC by using diodes to rectify the AC into DC and charge the battery.

So look around the web see if you can find something already built. It will work well and you dont have to try to get everything right.

BTW a regular inductor with a magnet may or may not work at all. It depends on the construction of the inductor. Closed inductors have most of the field confined to the inner part of the core so not much of the magnetic field gets out, or can get inside either. That would make a very very poor generator. The only kind that would work would be the open frame type where two ends of the core are accessible. Those kind however are not that great either because the two ends are not close to each other. In that case what might help is one magnet at each end and move both magnets at the same time with opposite magnet pole polarities. Still it is doubtful this will work as well as a generator already manufactured that was designed properly to actually be a decent generator.
Another possibility is to get a U core and use one or two magnets at the open end of the U. You can get U cores by looking for the type of cores that use two U shapes to form a transformer or inductor by winding wire on one or both U's and then placing the two open ends of the U's together to form a continuous unbroken magnetic path. These are sometimes called "C" cores.
I’m looking for side to side movement and yes the magnet will be very close.

If I could fine one already built and cheap I’d be happy to use it.

I was thinking about something either like this:

10pcs Adjustable High-Frequency Ferrite Core Inductor Coil 12T 0.6uh-1.7uh Adjustable Inductor https://www.amazon.com/dp/B083LSMZVG/ref=cm_sw_r_cp_api_i_l9FeFbV6GPR5B

OR would a toroidal work better maybe like this:

DIYhz 20 Pcs Toroid Core Inductor Copper Wire Wind Wound 100uH 6A Coil for LM2596-100uH https://www.amazon.com/dp/B07CMGTC3C/ref=cm_sw_r_cp_api_i_p.FeFbWSSHJE3

OR, maybe even something like this:

50ea Fixed Shield Inductor 100uH chip Inductor Surface Mount Wire Wound Inductor 10X10X4mm Transformer https://www.amazon.com/dp/B079NLP96Z/ref=cm_sw_r_cp_api_i_MaGeFb0PPWCCW

Essentially, the magnet may be fixed to it with rubber in between where it then sort of wobbles from vibrations.

I would totally get one already made, I just don’t know what to look for specifically.