How to use this invisible earphones?
First you need to put a tiny magnet in one of your ears or put two in both of your ears. Then you need to wear a coil necklace which is connected with an amplifier. Next connect your mp3 player to the amplifier. Cover the coil necklace and the amplifier properly with your clothes.Turn it on. Now you can enjoy music without being noticed by other people. You can use another small magnet to get it out. This sort of Invisible headphones is sold on ebay.
(Warning : Don't put the magnet deeply in your ear. Although there is no medical proof that says magnets will cause trouble to your ear , it's better not to use this device for a long time. Magnetic fields can disrupt the operation of some internal medical devices such as pacemakers.Neodymium magnets are made with special powders and coatings, so they are very fragile. They are often plated with a metal such as nickel. The magnets can fracture at temperatures over 150 °C, or under impact as a result of their own acceleration. When this happens, in some cases the magnets may break apart so suddenly that flying pieces can cause injury.
Make sure that there are no magnets around you, when you use this device. These magnets can move with surprising force when exposed to another magnet or magnetic field.)
If you don't know what you can do with this device. please watch this video. (Just for Fun
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Step 1: How Invisible Earphones Work
As you know, in a normal speaker. The magnet stays still. The coil vibrates producing sound. Unlike the normal speaker, when this device is working , the coil necklace which is around your neck stays still. The magnet vibrates in your ear producing sound.
Step 2: Find the Proper Magnet for Your Project
I' ve tested magnets of different sizes. And I might find the best size for this project. You can buy this sort of magnets on ebay by searching the key word " Neodymium magnet" . Actually, there is a resonance frequency. The bigger the magnet is, the lower resonance frequency you'll get.
Step 3: How to Make the Coil Necklace Part.1
What you will need: 1. cardboard
2.enamelled wire ( Length=50meters Diameter=0.25millimeter )
Enamelled wire is a kind copper wire which is coated with Polyurethane. I use a cardboard to wind the coil necklace. Make sure the diameter of this coil necklace is larger than the diameter of your head. The resistance of the coil I made is about 23ohm.
Step 4: How to Make the Coil Necklace Part.2
Cover the coil necklace with tape to protect it. In order to connect the wire to the amplifier., you need to solder on the tip of the wire. So you need to use a knife to get rid of the plastic layer on the tip of the wire.
Step 5: The Amplifier
The LM386 is the power amplifier. The power supply consists of two 9 volts battery. Actually , there are there types of LM386. According to the datasheet, only LM386-4 can work with 18 volts power supply. I find out that LM386-1 can also work for at least 10 minutes with 18 volts power supply. But I am not sure how long it will work.
Component List :
Capacitors 220uF X 1
10uF X 1
100nF X 1
47nF X 1
resistors 10 ohm X 1
1k ohm X 1
LM386 X 1
9 volts battery X 2
Step 6: Final Assembly
Put the tiny magnet in one of your ear. Connect the coil necklace to the amplifier . Put on the coil necklace. Turn it on.
If you succeed in making this device , you can send me a e-mail with the picture of your work. I'll put the picture at the end of this tutorial.
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