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## Help with Dynamo types

I have a question for everybody out there. It has been a very long time since I did this type of electrical design work, and for the life of me I can’t remember the principals.

I know there are many different ways to generate electricity by using mechanical motion, and converting a motor into a dynamo is very easy. What I am trying to do is to make a brushless dynamo. I have taken my inspiration from a cheap hand cranked torch, and intend to improve on it a lot. In this torch it has a coil which has a flat disk magnet sitting above it. The magnet is spun creating the charge in the coil and is used by the LED's in the torch. What I want to know is how specifically the voltage (potential difference) is created in the coil. My experience of stationary coils is where the magnet is rotated inside the coil. Could someone please explain it to me?

Many thanks.

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steveastrouk5 years ago
There is relatively no difference between spinning the magnet and spinning the coil. A voltage difference is generated by the change in flux created by the spinning magnet. - Faraday's law. V = n x dPhi/Dt, where Phi is flux and d/Dt is the rate of change thereof....

Steve
Batdragon (author)  steveastrouk5 years ago
Thanks for responding. I understand that the principals are the same if you spin the magnet, or if you spin the coils, and the difference being that if you spin the coils you will need brushes to extract the voltage from the coil. The configuration that I am reffering to is when there is a fixed coil (round) with a shaft through the centre. On that shaft is a free moving disk magnet (hole through the center so can fit on shaft). This magnet spinns on the shaft through a gear system. I would upload a picture but it is not working for me atm so will attempt to draw it.

.                    | .
.                    | .
.        ||||||||||||||||||||||||||||| <---- (Magnet) .
.                    | .
.        ============ <---- (coil) .
.        ============ .
.                    | .
.                    |
I hope this helps to explain what I am meaning as I do think that there is a difference with this than a normal configuration. Many thanks
5 years ago
I think I need to see a picture, but essentially ALL generation happens because you are changing the flux through the system - if it generates, it HAS to have a changing flux.
Batdragon (author)  steveastrouk5 years ago

I hope you can see these

5 years ago
Cunning.

You can see the pole pieces, top and bottom, with a core passing through the core ? One half is 90 degrees out of phase with the other. the core is magnetised radially for a guess. .

Steve
Batdragon (author)  steveastrouk5 years ago
When I saw the metal parts I just assumed that they were to keep it together rather than being an interagal part of it.
Can you see why I was having difficulty in trying to work out what was going on? I covered this over 20 years ago, and did not do much with it then (went into electronice and microprocessors). If I draw something up and give you a look would you be willing to make comment on if it would work? The idea is for a portable power pack, where the energy is created by winding,

Many thanks for you help so far,