PSN-L Email List Message
Subject: Re: School project
From: Mauro Mariotti mariotti@.........
Date: Wed, 29 Nov 2006 16:05:17 +0100
i might suggest to use the spring in a triangle
configuration with a vertical axis and horizontal
moving axis that sustain the mass.
The priciple is called "Lacoste suspension"
you can have a look here.
this is a very rude seismometer but it has a
free period of 1.2 seconds.
It is not so big.
The same sensor can be built in wood
(i have made one for a scientific exibition)
I have some pictures but not in a web site
if you want i can send them to the interested people.
As transducer i used a powerful magnet from the
SuperMag kids toy and the coils is stolen by
a old relay. Such instrument can induce enough current
to drive (not much) a microampmeter.
kids like it very much.
Using a small preamplifier you can get a huge signal.
Damping was made using a plastic polycarbonate strip
bended at U like a springleaf and made stiffy with
wooden axis can be made that can be easily
assembled and disassembled without any tool
i hope it helps
At 23:10 2006/11/28, you wrote:
>Hi Folks, Some discussion on a simple vertical seismometer got me
>to thinking about a possible school project for the kids. At one
>time, I found a simple vertical sensor on the internet, it used pvc
>pipe and a small 9"? spring. I built it but never tested it because
>I had an idea the coil and magnet were just too undersized. It
>probably works but would require some strong amplification, further
>more, I have no idea what the period would be.
>I wonder if one could use a "Slinky" a toy spring used by kids?
>They are about 3" in dia. and collapsed about 5" tall. I think I
>will get one and suspend it vertically, to check its suspended
>length and its natural resonance. I have no idea how long the
>spring would expand under its own weight? But let's say under 8
>feet. If so, maybe it could be hung from the ceiling and the coil
>and mass would be near the floor?
>It just might be something kids would enjoy.
>Q. 1. If I pull down on a spring and release it, it will move up
>and down, until it come to rest, if each cycle is 1 sec, (say a very
>long spring), is that its natural period?
>Q. 2. If I put a mass on the end of the spring, will it move
>slower? If so, is that, now its period? Maybe 2 or 3 seconds?
>Q. 3. If I could work out the construction details, what period
>should I target for a vertical sensor?
>Q. 4. Are there any websites or information on using long vertical
>springs? Many thanks, Ted
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