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# Help with Dynamo types Answered

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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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

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