As part of my "build your own seismometer" project, I needed to winded 3 coils with #38 gauge wire (2500 turns!). I needed to build a machine that would let me do the winding and count the turns. After a lot of searching on the internet, I found and modified a design that I have finally completed and just this afternoon I wound my first coil!
The winder uses my die grinder as the motor and it is connected to a "Powerstat" that regulates the rpm (its really turned down slow. It took me about a half an hour to wind one coil)
The form that I constructed to hold the wire in a coil, slips onto a shaft that is then connected to the die grinder. The other end of the shaft has a disk with a powerful magnet glued to it. The magnet passes over a "reed switch" which allows a current to flow in wires that are connected to a pedometer set to count steps. Steps in this case are revolutions of the disk with the magnet and therefore the coil. The pedometer works only at fairly low "rpm" or step/ rate, which turned out to be OK, because even at the slow speed it took a lot of concentration to keep the wire winding smoothly on the form.
The supply of wire is in a coil on a box on the floor. It unwinds and goes over two smooth chromed tubes and then is fed through a small diameter plastic tube that I hold and use to guide the wire back and forth over the form which is spinning on the shaft attached to the die grinder.
Here is a close up:
This is right after I completed the coil winding. You can see the plastic guide tube on the floor of the winder. Note that I painted the background of the actual winding station black so I could better see the thin wire. (#38 gauge is like human hair!) The counter says I'm one turn away from my goal but actually I stopped early and wound the last turn my hand. The ends (beginning and end are attached to the form with blue painters tape.
I'm just blown away that it all worked so well!... I only had to stand in one spot for half and hour! My back is killing me!
2 more to go!
(The eventual seismometer station will have 3 seismometers, two horizontal, oriented North-South, and East-West, and one vertical seismometer, hence the need for 3 coils.)
The coils are attached to the moving part of the seismometer (or rather the part that tries to stay still when the earth moves) and the coils move between strong magnets which cause a current to flow in the winding of the coil. The fluctuation of this current is what is shown on the computer screen. When the ground moves, whether horizontally, or vertically, the resulting currents are recorded by the computer and displayed as a wiggly line:
Here is a picture of the horizontal seismometer design I am building:
The coil is attached to the bottom of the red block mounted on the swinging horizontal boom. It moves between the two metal plates to the right (they have magnets attached to the inner surfaces. The metal plate/magnet arrangement on the left-hand side are used to dampen the motion of the boom. A solid copper bar is positioned between those magnets (just like the coil) and the interaction between the copper and the magnetic field resists the motion of the boom. This keeps the boom from oscillating endlessly when the ground moves. Note that boom and it's brass weights and coil etc is the thing that tries to remain still, where as the magnets and the whole black structure moves with the ground.
Posts
