Helllo, any advice would be greatly appreciated. I made a contactless dynamo for my bicycle and it is turning fine but not creating any current.
Please see attached picture. I have the 4 magnets facing N, S, N, S. and it turned super fast. Is there a particular copper wire I should be using? ( I stripped this copper from an old cable) Or do I need more turns? Or is there something else wrong?
the LED doesn’t light up and I get no reading on the multi meter
(Also, I am not sure what setting for the multimeter so I tried them all

 

In the picture that shows the LED, it looks like the wire coming directly from the dynamo is shorting both of the leads from the LED.

Is the copper bare? If so, then it is shorting itself out all over the place. You need insulated wire for your coils, and probably lots more turns.

What is the object to the left of your LED? What purpose is it supposed to be serving?

How fast is "super fast"?

What are the small coils of wire inside the magnets? Are those just left over from whatever you took the spindle from? What did you take the spindle from?

One of the problems you are going to have with your arrangement is that as the shaft turns, you have a magnet with the same polarity on opposite sides of the coil. One magnet is going to be trying to push current downward in the wire and the other will be trying to push it upward, with the effect that they largely cancel each other out.

Another you will have is that, even if you get that all dealt with, you are going to be generating AC and your LED is going to block it half the time.

Yet another is that you run the risk of destroying your LED, either by having too much current when it is conducting, or too much voltage when it is reverse biased.

 

In the picture that shows the LED, it looks like the wire coming directly from the dynamo is shorting both of the leads from the LED.

Is the copper bare? If so, then it is shorting itself out all over the place. You need insulated wire for your coils, and probably lots more turns.

What is the object to the left of your LED? What purpose is it supposed to be serving?

How fast is "super fast"?

What are the small coils of wire inside the magnets? Are those just left over from whatever you took the spindle from? What did you take the spindle from?

One of the problems you are going to have with your arrangement is that as the shaft turns, you have a magnet with the same polarity on opposite sides of the coil. One magnet is going to be trying to push current downward in the wire and the other will be trying to push it upward, with the effect that they largely cancel each other out.

Another you will have is that, even if you get that all dealt with, you are going to be generating AC and your LED is going to block it half the time.

Yet another is that you run the risk of destroying your LED, either by having too much current when it is conducting, or too much voltage when it is reverse biased.

Thank you for your reply. I got the bearing from an old computer HDD and I have changed the coil to insulated copper as I have no coated copper. Will the insulation interfere?
The rotation is caused by the eddy current interference between the magnets and the Aluminium rim so there is no friction so speed is definitely not the issue. I have taken a video of it spinning but can’t upload it here. I have added another picture of the new arrangement. still no LED light. The LED does work as I have tested with a battery.

 

There is too much space between the Magnets and the Coil.
The Magnetic force of the Magnets must be concentrated into the Wires of the Coil.
Your Current design has over ~90% of the Coil out of the Magnetic-Field of the Magnets.

It's very difficult to DIY an Alternator that is strong enough, and precise enough, to do useful work.
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.
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There is too much space between the Magnets and the Coil.
The Magnetic force of the Magnets must be concentrated into the Wires of the Coil.
Your Current design has over ~90% of the Coil out of the Magnetic-Field of the Magnets.

It's very difficult to DIY an Alternator that is strong enough, and precise enough, to do useful work.
.
.
.

I am attempting to recreate this for my science project
https://www.instructables.com/DIY-contactless-magnetic-bike-rim-dynamo/?amp_page=true
So far all I have managed to do is get it to spin.

 

Even if it works perfectly,
it will probably not exceed ~10mA of Current,
just enough to light one small LED.
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.
.

 

Thank you for your reply. I got the bearing from an old computer HDD and I have changed the coil to insulated copper as I have no coated copper. Will the insulation interfere?
The rotation is caused by the eddy current interference between the magnets and the Aluminium rim so there is no friction so speed is definitely not the issue. I have taken a video of it spinning but can’t upload it here. I have added another picture of the new arrangement. still no LED light. The LED does work as I have tested with a battery.

Welcome to AAC.

First of all, “there is no friction” is misleading. Though it is very small, the rotor of your dynamo is a load, and if it generates any power it will add to that load. You can’t get something for nothing. This means that at a certain point the load on the dynamo will overwhelm the eddy current forces and the rotor will stall. you are pitting induced currents in the rim with induced currents in the stator.

Second, magnetic field strength follows Coulomb’s inverse square law. That is, the strength diminishes by the square of the distance. This means that very small differences in distance can have very big effects on field strength.

​

This means that the gap between your rotor and stator is very significant. The large gap may be reducing the potential output to almost nothing. Measuring the output with the LED is not very effective. The LED will not light visibly before a certain forward voltage is achieved. It may be glowing now, but in daylight you’d never see it.

You need to use a voltmeter to determine if there is voltage present. Ultimately you will probably want to measure current as well. A DMM (it doesn’t need to be a great one, you can get them for a few dollars) is a required tool to work on this project. Without it, it will all be guessing.

Your stator needs to be rewound at the very least. It should be no taller than will accommodate the rotor and no further from it that mechanical considerations require. Expect that once you start generating any significant current, the rotor will slow and possibly stall.

Also consider the effect of magnet polarity on induced current. What effect would the orientation of the magnets have on successfully generating current?

​

 

Welcome to AAC.

First of all, “there is no friction” is misleading. Though it is very small, the rotor of your dynamo is a load, and if it generates any power it will add to that load. You can’t get something for nothing. This means that at a certain point the load on the dynamo will overwhelm the eddy current forces and the rotor will stall. you are pitting induced currents in the rim with induced currents in the stator.

Second, magnetic field strength follows Coulomb’s inverse square law. That is, the strength diminishes by the square of the distance. This means that very small differences in distance can have very big effects on field strength.

View attachment 296413
​

This means that the gap between your rotor and stator is very significant. The large gap may be reducing the potential output to almost nothing. Measuring the output with the LED is not very effective. The LED will not light visibly before a certain forward voltage is achieved. It may be glowing now, but in daylight you’d never see it.

You need to use a voltmeter to determine if there is voltage present. Ultimately you will probably want to measure current as well. A DMM (it doesn’t need to be a great one, you can get them for a few dollars) is a required tool to work on this project. Without it, it will all be guessing.

Your stator needs to be rewound at the very least. It should be no taller than will accommodate the rotor and no further from it that mechanical considerations require. Expect that once you start generating any significant current, the rotor will slow and possibly stall.

Also consider the effect of magnet polarity on induced current. What effect would the orientation of the magnets have on successfully generating current?

​

Thankyou for your reply. I am a little confused but will work through your reply. I am only 13 and only trying to replicate what I have seen using mostly household parts and a very small budget. I see how I was being misleading, by frictionless I only mean that the pinion wheel doesn’t actually touch the bicycle wheel and is pulled around by the eddy current effect. ( this part is actually working really well.) thanks again for your help but it seems I may have bitten off more than I can chew

 

as far as the lack of enameled magnet wire, electronic-goldmine has some on sale for cheap. 25ft for 4$. Great place to find maybe not the exact part you need, but cheaper alternate/older components that you can breadboard and mess with on the cheap.
https://theelectronicgoldmine.com/products/g27113 Being only 13 you may have issues with ordering stuff, so maybe not an option for you. You could rip apart a solenoid or transformer carefully to get the enameled wire.

 

Thankyou for your reply. I am a little confused but will work through your reply. I am only 13 and only trying to replicate what I have seen using mostly household parts and a very small budget. I see how I was being misleading, by frictionless I only mean that the pinion wheel doesn’t actually touch the bicycle wheel and is pulled around by the eddy current effect. ( this part is actually working really well.) thanks again for your help but it seems I may have bitten off more than I can chew

I don’t think you can’t finish your project, you just need to be systematic.

Are you following someone else’s design or just putting the pieces together on your own?

 

The Link to the Project is in Post #5.
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hi,
The video has been withdrawn by YouTube.
E

 

One of the problems you are going to have with your arrangement is that as the shaft turns, you have a magnet with the same polarity on opposite sides of the coil. One magnet is going to be trying to push current downward in the wire and the other will be trying to push it upward, with the effect that they largely cancel each other out.

You (thread starter) have 4 magnets. The original project uses 6. Do you now see why?

 

as far as the lack of enameled magnet wire, electronic-goldmine has some on sale for cheap. 25ft for 4$. Great place to find maybe not the exact part you need, but cheaper alternate/older components that you can breadboard and mess with on the cheap.
https://theelectronicgoldmine.com/products/g27113 Being only 13 you may have issues with ordering stuff, so maybe not an option for you. You could rip apart a solenoid or transformer carefully to get the enameled wire.

Thanks for the tips. I will definitely try to find the correct enameled wire.

 

You (thread starter) have 4 magnets. The original project uses 6. Do you now see why?

I didn’t realise that the number of magnets was a factor but I do have a couple more I can put on. The arrangement I have now has 2 south facing magnets in the coil or 2 north facing magnets in the coil but never both at the same time. Is this not correct?

 

I would suggest that you get a DMM (Digital Multimeter). If you are in the US, you can get one from Harbor Freight for as little as six dollars.

​

Without some kind of voltmeter, you are flying blind. Measurement is very important to troubleshooting! Your dynamo, if properly constructed will be producing alternating current (AC). This is because the magnets should be placed so that they alternate their north and south poles.

You can also use the DMM to check the continuity of your stator (the stationary coil part) to make sure it is actually going to work at all, and possibly to determine if it is shorted somewhere in the middle.

By the way, magnet wire (enameled) is a good thing but far less important than proper construction. PVC insulated wire will make a perfectly working if slightly less powerful electromagnet or effective winding (these are the same thing).

LEDs are diodes and so they only conduct electricity in one direction. This means that you will have a blinking LED with a rate one half the rate of the spinning rotor (the moving part of your dynamo). You will only be able to use half the power in this arrangement

One thing you can do is to connect two LEDs in opposite polarities and they will blink in turn as the polarity changes. Alternatively, you can use a rectifier which is one or more (non-light-emitting) diodes arranged alike valves to direct the current in only one direction. This will work well but does involve a loss as each diode has a voltage drop and will reduce the voltage going to whatever you are powering by something less than 1V.

This is sometimes a problem, and can be reduced with specially constructed Schottky diodes but I don’t think you will encounter the problem in your case should you choose to rectify the output.

 

I didn’t realise that the number of magnets was a factor but I do have a couple more I can put on. The arrangement I have now has 2 south facing magnets in the coil or 2 north facing magnets in the coil but never both at the same time. Is this not correct?

Do you know what the magnetic fields produced by the magnets look like? Do you know how they work to induce current into your stator winding? This is very critical. Reading a little about magnetic induction and Fleming’s right hand rule would be a really good idea. It might seem a little daunting at first but once you actually understand the way things have to be arranged, you will be able to answer many of your own questions, and I guarantee things will be much easier!

 

I would suggest that you get a DMM (Digital Multimeter). If you are in the US, you can get one from Harbor Freight for as little as six dollars.

View attachment 296416
​

Without some kind of voltmeter, you are flying blind. Measurement is very important to troubleshooting! Your dynamo, if properly constructed will be producing alternating current (AC). This is because the magnets should be placed so that they alternate their north and south poles.

You can also use the DMM to check the continuity of your stator (the stationary coil part) to make sure it is actually going to work at all, and possibly to determine if it is shorted somewhere in the middle.

By the way, magnet wire (enameled) is a good thing but far less important than proper construction. PVC insulated wire will make a perfectly working if slightly less powerful electromagnet or effective winding (these are the same thing).

LEDs are diodes and so they only conduct electricity in one direction. This means that you will have a blinking LED with a rate one half the rate of the spinning rotor (the moving part of your dynamo). You will only be able to use half the power in this arrangement

One thing you can do is to connect two LEDs in opposite polarities and they will blink in turn as the polarity changes. Alternatively, you can use a rectifier which is one or more (non-light-emitting) diodes arranged alike valves to direct the current in only one direction. This will work well but does involve a loss as each diode has a voltage drop and will reduce the voltage going to whatever you are powering by something less than 1V.

This is sometimes a problem, and can be reduced with specially constructed Schottky diodes but I don’t think you will encounter the problem in your case should you choose to rectify the output.

Thank you for all your information. I really appreciate it and I am learning a lot.
I have borrowed a multimeter but I am unsure how to set it up. I was told it is set up for DC to check car batteries. I will do some research.

 

Thank you for all your information. I really appreciate it and I am learning a lot.
I have borrowed a multimeter but I am unsure how to set it up. I was told it is set up for DC to check car batteries. I will do some research.

The only things to be careful about on a DMM are the current ranges (A, or amps) which appear like a short circuit, and the resistance ranges (Ω or ohms) which can possibly be damaged by applying external voltages.

You should, at first, avoid current measurements altogether. The resistance measurements may be important to you, all you have to do is make sure you never connect the meter to a power source while it is set for resistance. Otherwise experimentation is great.

Yes, batteries produce direct current (DC). DC and AC differ in the way the current flows. DC is constantly in one direction and AC alternates back and forth. AC is what comes from the wall outlets, and from your dynamo. In the US, the AC from the wall is changing at 60Hz, that is 60 full sine waves each second, or 120 alternations from plus to minus.

Your dynamo will be generally alternating much faster than that and depending on the DMM you may find the voltages are inaccurate because of it. If the DMM has a frequency range, you can use it to figure out about how fast it is alternating, assuming it is within the range of the DMM’s ability to measure.

 

The only things to be careful about on a DMM are the current ranges (A, or amps) which appear like a short circuit, and the resistance ranges (Ω or ohms) which can possibly be damaged by applying external voltages.

You should, at first, avoid current measurements altogether. The resistance measurements may be important to you, all you have to do is make sure you never connect the meter to a power source while it is set for resistance. Otherwise experimentation is great.

Yes, batteries produce direct current (DC). DC and AC differ in the way the current flows. DC is constantly in one direction and AC alternates back and forth. AC is what comes from the wall outlets, and from your dynamo. In the US, the AC from the wall is changing at 60Hz, that is 60 full sine waves each second, or 120 alternations from plus to minus.

Your dynamo will be generally alternating much faster than that and depending on the DMM you may find the voltages are inaccurate because of it. If the DMM has a frequency range, you can use it to figure out about how fast it is alternating, assuming it is within the range of the DMM’s ability to measure.

Thanks, I am finding this very interesting and I am actually starting to understand how it works. I also think the multimeter I am using is no good for this as it’s minimum AC setting is 200v. I will rewind my coil smaller and add 2 magnets so only 1 is acting on the coil at a time and see what happens. Thanks again.