Edison dynamo

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New Member
Feb 20, 2010
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I'm sorry to hear your having trouble. I too had a hard time to get my dynamo running. I also experienced high current when running the dynamo as a motor. However after I gave it a helping spin, off she went and after a time the current came down. I think 4 amps is probably reasonable.

I don't know anything about magnetic theory, but I wound both of my coils in the same direction. It's like they are connected S/N to S/N, sort of in series. I look at the Bi-Pole arrangement like a horseshoe magnet.

I wonder, what is the purpose of neodymium magnets??

Wish I could be of more help.


Feb 21, 2020
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I too have built an Edison Bipolar Dynamo, based on google images, and fun facts of electromagnetism from my college physics text. Its not quite as detailed as the awesome work displayed in this project, but you can see some photos at http://www.baemclub.com/crkcallarchive/jan20nl.pdf

The armature was a replacement part for an electric drill from eBay, everything else is from bar-stock. I designed the field coils for 12 volts at 1200 RPM, and hit the mark pretty well, I got about 11.7, not too shabby.
The dynamo built around a 1.5" diam armature is a good looking match for the 1.5" bore Stuart-9 I'm powering it with.

If there's interest I will write up the equations for the field coil and have it added to the baemclub newsletter as a "tech topic".

Peter A Lawrence, San Jose, CA.


Well-Known Member
Aug 6, 2012
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You probably don't need to do a complete rewind just reverse one pole with respect to the other and have another go. This would happen quite often in full size practice and when you are dealing with a four pole split compound machine with interpoles and compensating windings it can get pretty complicated. You can end up with different windings "fighting" each other and often at different parts of the RPM range.

We had the occasional "runaway" through these sorts of effects. Quite scary on a large machine, you need to be "quick on the breakers" to stop it damaging itself.

The neodymium magnets are probably to retain some residual magnetism as I mentioned previously. It might be worthwhile inverting one or both of these also to see what effect it has

Best Regards Mark


Well-Known Member
Apr 22, 2014
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Dave I have this image saved and will be winding mine as per the lefthand illustration, windings in opposite direction.
The left and right diagrams are correct.
The centre diagram is incorrect.
Reason being one must have a north and a south pole.

Where the confusion came with the centre top illustration is, it is common to connect start of one winding to the finish of the next to reverse the poles.
This only applies where the winding was all done in the same direction.
It can clearly be seen this is not the case here.
Centre diagram has 2 north ( or 2 south )poles, depending on which way the current flows.
A tip for generators and motors is the right or left hand rule respectively.

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