Maker's fun : a home made speaker
We learn from high school that when electric current pass a metal wire, it generates magnetic field. Electromagnetic theory can make a lot of fun. A round metal coil will vibrate according to a music's electrical signal passing it, use a magnet with size about 1 cm (in diameter), put together with such a vibrating coil. The coil will vibrate according with music electrical signal, if glue a piece of thin paper by sticking the coil with paper, it will vibrates to push more air to generate sound may listen, it become louder speaker. Its fun! Enjoy your songs!
It is usually not success at the first, several methods has been tried, a lot of materials and design could share here. First we bought a silver paste pen, it use to repair broken PCB, prepare a rectangular plastic sheet, draw a coil with 4 to 5 turns, it become a coil with two end.
However, the resistance measure by a multi-meter is larger than 2 kohm. Then, we try conductive ink, the resistance is also relative high, the black coil below has 5 kohm.
We then purchase a Japan brand conductive pen, the measure resistance is much better, but still about 800 ohm, it is not good enough until it could become 1-10 ohm range. The paper is special purchase with the conductive pen supplied from Japan, it is special design, shinny and flat to optimize a best resistance.
A more direct method is use metal wire to glue it on paper. This is also a workable method in below figure.
Of same idea, aluminum foil could use to stick on a paper or plastic sheet instead of use metal wire, beware that aluminum is very easy to oxidize when in touch with air, it is the reason a foil fresh come from a roil has good conductance, when it was glue on paper, and wait for sometime, the surface is not that conductive as copper. It is also because that aluminum has an easy oxide nature to aluminum oxide.
