Coil Winding Trouble

If the two halves are in series, that is correct. The wire has to all wrap around the magnets the same way, since each turn makes a contribution to the total voltage.

Have you checked the LEDS to make sure they have not been damaged?

By the way, another neat magnet - generated current demo is to drop a neodymium iron boron or samarium cobalt magnet down a copper pipe not much larger than the magnet. It falls very slowly because of the interaction with the magnetic field produced by the high currents that are generated around the magnet. The forces also keep the magnet away from the pipe. I even got this to work just rolling a cylindrical magnet down an aluminum flat strip. It rolled slowly, and when the magnet got near the edge, the drag forces dropped, that end sped up, and the magnet was steered away from the edge. It zig zagged all across the strip as it crawled to the bottom but never went over the side. An example of a gravity powered mechanical negative feed back loop.

We have an exhibit at our local science museum that is a 3-4' 1" diameter tube with about 150' of wire wrapped around 8" of one end. First 75' were wound, and then another 75'. An LED is connected across the wires. When a cow magnet is dropped down the tube, the LED lights momentarily. Some time ago someone deliberately broke the exhibit. I had to unwind the last 75' to make some repairs. When I try the new configuration out, the LED doesn't light. I'm sure the connections are correct. At least a continuity check at the leads shows a connection. I would think if 1/2 the wire is wound the opposite way from the other 1/2 that maybe no current would appear. Is that right?

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This trick with super magnets works well with flat ones too. Take a strip of aluminum canted at about 15 degrees from vertical and slide a washer down it. It will stay on the aluminum and zip down the length of it. Next, lay a flat super magnet on it and let go. It just crawls down. It really is a good show. BTW, this is how mechanical speedometers work. ERS

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sure

I could have been more specific:

Well, notwithstanding "virtually" means "not really", I'd say, of course. We all have to start somewhere, and as Commander Spock said just before the thin Vulcan Kirstie Alley ("Mister Savik") drove the Enterprise out of Space Dock, "For everything, there is a first time."

This is a sucker bet. I've never seen the inside of your garage and don't expect to. ;-p

If winding coils is giving you pains in the neck, you might need some kind of spool or fixture to manage the lengths of wire. Once, I needed to wind a fairly large toroid (1.5" OD) with some teflon-insulated wire. I made a shuttle out of a stick about 2' long, with notches in the ends. Loaded it with a passel of wire, and it only took a couple of hours to get it wound. But winding on a cylinder should be trivial.

If the PITA you're having has to do with getting the exact length of wire wound on the coil, let that whole idea go. Go by number of turns, and let the length of the wire be whatever it needs to be. I used to hold a pencil between my knees to mount the source spool on, but the point kept sticking into my knee, until I figured out that I should use something blunt.

When do I get the opportunity to say, "Elementary, ..." ;-P

(what did Mr. Holmes say about the digestive system? "Alimentary, my dear Watson".)

Good Luck! Rich

If you can get to the ends of that half, you can just cut it and swap the ends.

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Google? What's Google? :-) Suppose I had virtually no knowledge of electricity and magnetism. Would you make the same suggestion? Then too I'll bet you've never seen the inside of my garage and the exciting time I had unwinding the coil and rewinding it. I'll bet ... Oh, well.

I tried 5-6 LEDs. Sounds right to me. Thanks. Weather permitting, I think I'll do the rewinding outside. I just had to check before facing the confines of my garage again. It takes about an hour in my garage. Alice-in-Wonderland would feel happy there.

Yes, I'm familiar with those demos. Eddie's currents. :-) I always liked that guy. Fun stuff.

It's too late at night here, but a suggestion. Before you rewind try reversing the end connections of one of windings! Might work? Logic being that if one coil is reversed in winding direction to the other reversing connections to one of them MIGHT put the induced voltage back in series? Terry in Canada.