Why won't our generator work??

Questions about Shaking Up Some Energy project and kit. (http://www.sciencebuddies.org/science-f ... ml?fromAAE)

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Why won't our generator work??

Postby Najwa Ahmed » Sun Feb 26, 2012 10:13 am

Hello, My son is in 2nd grade and has chosen "Shaking Up Some Energy", creating a simple generator, as his science fair project. We've done two trial runs. We followed the directions exactly, yet the LED won't light up! We are very confused. What could we be doing wrong? We wound the coil wire around the canister 1000 times (we also did another generator with 350 turns of a thicker coil wire), connected the wires to the LED, put in the magnet, shook it up...No electricity. Please help!!! The fair is this thursday March 1st. Thank You! :) P.S. we ordered the advanced kit that correlated with the experiment.
Najwa Ahmed
 
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Project Question: Shaking up some energy! How is electricity generated?
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Project Status: I am conducting my experiment

Re: Why won't our generator work??

Postby rmarz » Sun Feb 26, 2012 12:34 pm

Nahwa - There are a few things that you could be interfering with your experiment success. First, the beginning of the article talks about a commercial flashlight that uses a rechargeable battery as a storage element. The experiment and kit do not include a storage element. Even better than a rechargeable battery for this experiment would be a "super capacitor" (and appropriate rectifier) that charges quickly and will provide excellent storage for the high efficiency LED. Without the storage element, you will only get flashes of light when the magnet is actually passing through the coil. Have you observed this? I guess as long as you shake it quickly, the pulsating light may appear to the eye to be continuous. With a storage element you can probably store enough energy to have the light sustained for a long period. The kit seems to include several LED's. I would use the red LED first, because it will likely have a lower voltage requirement (than the green LED) to light.

Rick Marz
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Re: Why won't our generator work??

Postby Najwa Ahmed » Sun Feb 26, 2012 2:37 pm

Hi Rick and thank you for replying so quickly! We haven't observed ANY light :( So are you essentially saying that this generator will not produce a steady light while the magnet is passing through the coil? Only flashes? Is there any way to create a simple storage unit here? We were so excited about creating electricity. Also, with our kit we received a voltmeter. Any ideas on how to use this to gauge if we are actually producing electricity?
Najwa Ahmed
 
Posts: 3
Joined: Sun Feb 26, 2012 9:59 am
Occupation: Asst. Pre-K teacher
Project Question: Shaking up some energy! How is electricity generated?
Project Due Date: March 1st!!!!!
Project Status: I am conducting my experiment

Re: Why won't our generator work??

Postby rmarz » Sun Feb 26, 2012 6:37 pm

Najwa - I think you understand the experiment a little better now. The original author of the paper, from which this project was created, explains in excellent detail what is happening in the experiment. As he states, the generator will only produce power as the coil passes through the flux field of the magnet. Therefore it will only illuminate for a brief period as the magnet moves past the coil. In addition, he describes how to build a storage device that will enable constant illumination of the LED. Here are the links to these pages:

http://www.creative-science.org.uk/gensimple1.html

Toward the bottom of his paper there is a link to building a storage device. Click on that for details. He has described a rectifier circuit with a high value (10,000 microfarad) electrolytic capacitor to provide a power storage unit. He correctly recommends the use of germanium diodes for the rectifier, but I think you may have problems finding them at a Radio Shack. Rather than a 4 diode 'full wave bridge' I would suggest a simple half wave rectifier using a single Schottky diode that has a low forward voltage drop. These seem to be available at Radio Shack as their part number NTE584 for only $0.68. If you can find a germanium diode (1N270 series, for example, it's probably even better). At Radio Shack you can try to find the lowest cost, highest value electrolytic capacitor, with under 10 volt rating. I found their part number NTE VHT3300M10 a 3300uF, 10V part, for $1.52. It should work fine.

I've attached a sketch on how to wire it up. Because we are now dealing with DC, you will have to be mindful of which way the LED is connected, also the polarities of the diode and electrolytic capacitor must be connected properly. It is probably difficult to tell the polarity of the LED so just try it in one direction to see if it lights. If it doesn't, reverse the leads. There is no danger of harming the LED with these low voltages.

Rick Marz
Attachments
Generator Storage.pdf
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Re: Why won't our generator work??

Postby Najwa Ahmed » Fri Apr 13, 2012 11:38 am

Firstly Id like to apologize for letting so much time pass before I updated you. Now, I'd like to sincerely thank you for your help. Your suggestions brought my son and I to the realization that we must've done something wrong when initially creating the generator. I was all set to go to Radio Shack to get what we need to build the storage unit when we decide to make the generator ONE MORE TIME, this time focusing on the neatness of the coil wire. When we got to the step of connecting the wire to LED, we would then connect the ends of the wires to TO EACH OTHER!! This was our mistake! The connection of the coil wires canceled out the production of the electricity!!! Once we disconnected them, the generator worked exactly how you described; flashes of light as the magnets passed back and forth past the coil. My son gained honorable mention and was 2 points away from 2nd place. I will definitely use this site again. I want to thank you again, because it was your fast and thorough responses that gave us the hope we need to make the generator work. Thank You VERY much!!! :D

Warmest Regards,

Najwa (and my son too)
Najwa Ahmed
 
Posts: 3
Joined: Sun Feb 26, 2012 9:59 am
Occupation: Asst. Pre-K teacher
Project Question: Shaking up some energy! How is electricity generated?
Project Due Date: March 1st!!!!!
Project Status: I am conducting my experiment

Re: Why won't our generator work??

Postby rmarz » Fri Apr 13, 2012 4:05 pm

Najaw Ahmed - Thank you for your feedback, and congratulations to your son for winning the honorable mention. Science Buddies was glad to assist.

Rick Marz
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