The microphone is a subminiature receivertogether with a speaker and a battery. It is so small that it is located in the auricle and is completely invisible to others. When passing any exams, this thing is absolutely indispensable.
Of course, this device can be bought.But it is also very cheap! However, craftsmen say: you can make a micro-earpiece with your own hands. And you will always get it if you have at least superficial knowledge in radio engineering.
To the question: "How to make a micro-headphone?" The answer will be one: "It's easy, but this work is extremely thin, and, naturally, great care is required."
The whole set consists of several parts: a mobile phone, headphones from an old mobile phone and the microphone itself.
This system works as follows:
- The assistant sends the necessary information to your mobile phone.
- The headphones are connected to the tube. This structure plays the role of a transmitting antenna.
- The receiving antenna is placed with the device in the auricle.
How to make a micro-earphone with your own hands? First, remake the headphones. To do this, we cut them at the branch point. Then remove and disassemble the microphone. It will be needed for feedback from the subscriber.
We solder to the microphone a thin two-wire wire of the necessary length so that the microphone can be taken out to a place that is inconspicuous and convenient for you, for example, by a collar or by a tie.
The wires of the left and right channels of the headphones are connected together.
Now we have two points: the channel point and the common wire. They will be soldered to the inductance (loop of a thin wire), which will be the transmitting antenna.
During the work of the phone, the inductance will bea modulated magnetic field is produced. It will be received by the inductive antenna of the microphone, and you will hear the voice of your interlocutor. Everything works on the principle of the action of an ordinary transformer.
We continue to make a micro-earpiece with our own hands,if the hands are not tired, of course. To make the transmission loop, you will need any round object that will be used as a template for winding. A glass jar is suitable. It will also require a PEL wire of 0.08 - 0.1 mm.
On the jar very carefully reel the inductor. The resistance should be approximately 40 ohms. The finished coil is lubricated with PVA glue and removed from the frame. It can be wrapped around the perimeter with electrical tape.
Now you need to solder the stranded wires to the ends of the coil, insulate and fix the soldering points. The second ends are soldered to the points "channels" and "common".
The transmitting part is ready.It remains to make a micro-earpiece with your own hands. To do this, you need: an operational amplifier TDA 7052, a miniature TEM 1956 or any other (the smaller it is, the better), a resistor of 1 to 5.1 Kom, two smallest 1.5 V batteries (LR 41 or 361 A) , wire PEL 0,08 - 0,1 mm. And a very important addition: a micro-earpiece to make very difficult, without having the most simple tester.
Now the last, most important stage of the work.The chip is glued to the speaker housing. Above it, we reel up the receiving inductive antenna to the maximum of the turns, if only the winding does not protrude beyond the edges of the speaker.
We connect the solderings 1 and 3 pins. Then we connect 2,4 and 5 - this is minus the supply (ground).
Solder one end of the coil to point 1.3.
The second end passes through the resistor to the ground. Initially put a 1 Kom resistor, if necessary, select its value.
To terminals 6 and 7 we solder the speaker.
Output 8 is a power supply + 3 volts.
Before the first start, carefully inspect the installation for a short circuit.
Between 8 output and + batteries we connect the tester. We measure the current consumed. Ideally, it should be about 3.5 mA. But it is permissible and up to 5 mA.
Turn on the power, we catch on the mobile phone any FM-station. In the microphone, we need to hear it. We select the resistor to the maximum volume. Think about fixing the batteries.
We put the finished product into a tube of heat shrink and crimp it with heating. The work is done.
