On 10/5/11 5:14 PM, James Hutton wrote:
Hey guys, I have an idea for a science fair I plan on entering this spring.It will involve capacitors, and a few simple car parts.I really need help with this because my knowledge of capacitors sucks...so if anyone would be able to help send me in the right direction I would really appreciate it!email me at b-u-r-t-o-n-boy@xxxxxxxxxxx if your interested!(basically my idea is when you have a half dead car battery that wont start the car, you can charge up a capacitor to send enough power to the ignition coil.... kinda like a flash in a camera) thanks! :)
Ah, Science Fairs. my favorite.. If you do a good job, maybe I'll see you in Pittsburgh at ISEF.
OK.. You're starting off right with some research. A couple things.Your topic needs to be structured so that you have a question that needs to be answered in a quantitative way. Rather than a "can I build an X" you really want something that you could say "X works 20% better than existing approaches, and here's the measurements to prove it" or something like that.
As far as your specific idea, I don't know that the limiting thing is the ignition (although it's true, I've had a car where I could try to push start it, but the battery was so dead the ignition didn't fire and the Electronic fuel injection didn't work).
Capacitor discharge experiments are interesting in many ways. Here's a sort of related set of ideas that might get you started.. The ability of an electrolytic capacitor or supercapacitor to store charge changes significantly with temperature. Water as a dielectric changes dramatically between liquid and solid.
You've probably seen supercapacitors used instead of batteries for things like backup power for a clock, or things like that.
Say you had a wildlife tracking radio beacon (or, in my specific case, a beacon on a container holding a sample on the surface of mars that you want to find.) You want the beacon powered by a battery or supercap (or something). You want it to work, even after having been cooled to below -50C (and then, warmed up). Is there a way to store energy that works for this? Supercaps might work. Some Lithium batteries might work.
So, for a project, you have to do things like control and measure temperature. You need to be able to put known amounts of charge/energy into the thing you're testing, and then measure how much charge/energy you can get out, after cooling/warming cycles, etc.
This kind of project could also be used to compare battery types, etc. (although I'm intrigued by looking at supercaps)
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