Magnetic Pendulum

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dbodnar
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Magnetic Pendulum

Post by dbodnar » Wed Sep 02, 2009 1:36 pm

Good day - I just wanted to thank Tony Gasparovic for an excellent article in the September issue, Magnetic Pendulum.

I got 2000' of magnet wire in the mail today and have two pendulums (pendula?) working.

When I got the first one going I couldn't resist making a quick video:

http://trainelectronics.com/Pendulum/

As you can see it almost goes 360 degrees in the video --- well, a few minutes later it got going well enough to make it all the way around - what a hoot! I now have a full blown rotary motor!

Thanks again, Tony!

dave

metracom
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Re: Magnetic Pendulum

Post by metracom » Wed Sep 02, 2009 2:59 pm

Dave, I'm glad to see your having with the pendulum !!

Tony Gasparovic :grin:

metracom
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Re: Magnetic Pendulum

Post by metracom » Wed Sep 02, 2009 5:03 pm

If you build a Magnetic Pendulum please take a video and post the link on this thread.

Here's my video. http://www.youtube.com/watch?v=4xTjIzzbXTQ

Tony

dbodnar
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Re: Magnetic Pendulum

Post by dbodnar » Thu Sep 03, 2009 2:00 am

I just updated the web page and added a second video of the latest pendulum.

http://trainelectronics.com/Pendulum/

Tony, have you tried using caps to stop the oscillation of the circuit - that is on my list of things to try... Perhaps a 5 pf from the base of Q1 to ground?


dave

metracom
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Re: Magnetic Pendulum

Post by metracom » Thu Sep 03, 2009 5:04 am

Dave, thanks for the additional pictures. If you use a NTE290A transistor will give you more pendulum arc. I tried connecting a cap on the base of Q1 but that caused the transistor to not switch properly. I think it shunts the feedback from the coil. Just solider a few unused circuit board traces to the base of Q1. This fixes the oscillation problem.

Tony

mosimpson
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Re: Magnetic Pendulum

Post by mosimpson » Thu Sep 17, 2009 2:36 pm

Hi Tony,

I built my first pendulum with fishing line holding the magnet and it worked great. I then made a rigid arm pendulum like that shown in the second set of pictures in your article and also shown on your YouTube video. My arm doesn't swing nearly as high as yours. I'm curious how long your rigid pendulum arm is? Is there something else that would cause yours to swing so high?

Also, my nine year old son is studying magnetism is his class. I was thinking of having him take the pendulum in for a demo. Is there a simplied version of explaining electrically what's happening that you can provide besides what is in you article? Something on the level for 10yr olds with no electronics background.

Thanks for the article it was a fun and fast project. My kids really enjoy the Pendulum.

Robert Reed
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Re: Magnetic Pendulum

Post by Robert Reed » Thu Sep 17, 2009 2:45 pm

Dbodnar
Maybe a ferrite bead for oscillation problem. These things have worked wonders for me in the past for annoying parasitics.

metracom
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Re: Magnetic Pendulum

Post by metracom » Thu Sep 17, 2009 8:36 pm

mosimpson

I'm glad to see that you and your son are enjoying the Magnetic Pendulum project.

You will find that upholstery thread works better than fishing line. Fishing line will work, but with added drag. Remember the less drag the better.

The arm on my pendulum is 8 inches long. There are lots of factors that will determine the over height of the pendulum arc. Try adjusting the gap between the coil and magnet. In my testing I found that 1/8 inch gap worked the best.

Science kits are a great way to help youngsters understand magnetism. Check out this link:
http://www.sciencestoreforthestars.com/ ... iakit.aspx

I posted a new video on youtube. With new batteries, my pendulum will swing 360.

http://www.youtube.com/watch?v=5tFGIQrKgBc

Tony

dbodnar
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Re: Magnetic Pendulum

Post by dbodnar » Mon Sep 21, 2009 8:50 am

Tony - I took the pendulum idea and used it to create two animated acrobats for a train layout that we (The Pittsburgh Garden Railway Society) set up during a local weekend Oktoberfest.

I put some videos on my web page at:

http://trainelectronics.com/Pendulum/

The coil, battery and electronics are hidden under the figure. The two brass supports and piano wire cross bar give a very low friction system that allows the acrobats to do 360's from time-to-time depending on the wind!

I also put the bases on a rotating turntable to add to the animation. It was very well received!

dave

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