DISCLAIMER: THESE MAGNETS ARE NOT TOYS! They are extremely
strong and can cause pinching of fingers between them and magnetic
surfaces if not careful. Additionally, they are very brittle and tend
to chip easily, if impacted, leaving sharp edges and can cut fingers. DO NOT TAKE THESE NEAR ANYONE WITH A PACEMAKER! And obviously do not leave them lying around.
3.5mm Plug
A mini stereo jack (3.5mm plug) is the common headphone jack that fits one's smart phone or standard MP3 players. Most often, this can be salvaged from an old, broken headset. This will be used to hook it up to an MP3 player. If you will be running your music through an amplifier then you can connect the speaker directly to the speaker port on the amp.
30-Gauge Copper Wire
Thin copper wire should be used. The thickness of the wire is given by
the gauge and the higher the gauge, the thinner the wire. For this project, 30-gauge wire is recommended. It is not
recommended to use wire thicker than 26-gauge. This project requires at
least 30 feet of wire in order to make the voice coil for the speaker.
Wrapped Magnet
Building the Voice Coil
From a regular sheet of paper, cut two similar strips. Each should have a width of about 2 inches. Wrap one of the strips around the magnet forming a cylinder. Use a piece of sticky tape to hold the paper cylinder together. This first strip is to be used as a spacer between the magnet and the voice coil, SO you want to make sure that it it has a little thickness to it. Paper should wrap around the magnet a few times - it is not necessary to trim to size. This will be used as a form about which we will build the voice coil.
Forming the Voice Coil
We form the voice coil by wrapping the 2nd strip of paper around the
wrapped magnet. A couple of things to note here. The 2nd strip of
paper should be trimmed in length to ensure about only 1/2 inch of
overlap (unlike the 1st strip of paper which was wrapped several times
around the magnet). The 2nd strip should not wrapped too tightly around the wrapped magnet. We want to ensure that the inner diameter of the voice coil is somewhat larger than the diameter of the magnet.
Winding the Wire
The copper wire is then wound around the 2nd strip of paper. The more
coils, the louder the speaker will be. In forming the voice coil for
this project, we used 70 winds of the wire. When winding the wire, care
should be taken to keep the winding near the middle of the 2nd strip of
paper. Winding should be dense so you should move back-and-forth when
winding in order to create overlapping coils. The copper wire is
insulated so this is fine. This is where the thinner gauge wires will
allow for more dense windings of the coils.
Removing the Form
Once the winding is complete, hot glue is used to keep the wire in place. A touch of glue was also added to the seam of the paper. Upon allowing the glue to cool, the voice coil was born. Very carefully, the magnet and then the first strip of paper is removed from inside the voice coil. It is important to do this without squishing or bending the voice coil. What remains is the voice coil which is the 2nd strip of paper with the copper wire wrapped around it and hot glued.
The Voice Coil
The voice coil is trimmed to a total length (height) of about 1.25 inches. The result is a neat and even paper cylinder. If there is too much overlap, this will create excess paper that tends to clog the inside of the cylinder. This must be trimmed without deforming the paper cylinder and can be done using nail scissors. We are now ready to assemble the speaker.
Magnet Mounted on Base Plate
Speaker Assembly
One of the paper plates is placed face down on the table which will be used as the base of the speaker. The magnet is hot glued to the back of the plate in the center of the plate (this does not need to be exact - just a best guesstimate).
Voice Coil Mounted on Diaphragm
A second paper plate will be used as the diaphragm. This is the part of the speaker that moves. In order to make it move, the voice coil must be attached. In order to mark the correct placement for the voice coil, the voice coil is placed over the magnet and the the plates are placed back-back-back and the position marked on the diaphragm where the voice coil will be attached. The voice coil is then attached to the diaphragm using hot glue making sure not to clog the center of the voice coil. The voice coil must be able to slide over the magnet unobstructed.
Cardboard Springs are Added
The third paper plate is for parts. Cut out the center part of the third paper plate and from this cut two strips each of width 1 inch and length 6 inches. The strips are folded back-and-forth to create pleats. These will be used as cardboard springs to support the diaphragm while allow it to vibrate. The springs are hot glued to the back of the diaphragm on opposite edges with the voice coil in between as shown in the picture.
Removing the Insulation
Before attaching the diaphragm to the base, the last thing to do is to remove a section of insulation at each of the ends of the copper wire. This is easily achieved by simply using a lighter and burning off the insulation. The insulation burns quite readily so be ready to blow it out when enough has burnt away.
Positioning the Diaphragm
The diaphragm is placed in position over the base plate. The cardboard springs are trimmed to the correct length to ensure that the voice coil is positioned directly over the magnet and passes over the magnet unobstructed as the diaphragm is pressed down slightly. The diaphragm should be raised high enough above the base plate so that the bottom of the voice coil never touches the base plate. The diaphragm is attached to the base plate by gluing the feet of the cardboard springs to the base plate.
The Completed Speaker
The assembly is completed by bending and adjusting the springs slightly to ensure correct positioning and movement of the diaphragm on the base plate. And that's it!
All that remains is to attach the ends of the copper wire to the mini jack (3.5mm plug) and plug it in to an MP3 player and to listen to those sweet sounds.
No comments:
Post a Comment