Some useful information about electret microphones.
Today electret microphones have practically taken the place of microphones of other assemblies. This is due to the fact that at a low cost, they have a flat frequency response, low weight and a high degree of reliability. Since the scheme of operation of such a device is quite simple - anyone can make a microphone.
An electret microphone is a condenser, one of the plates of which is made of the thinnest plastic film stretched over a ring. It is irradiated with a group of electrons entering at a shallow depth, which provides a space charge that persists for a long time.
A thin film of metal is applied to the film, which serves as one of the electrodes. As another electrode, a metal cylinder is used.
Acoustic waves cause the film to vibrate, which creates electricity between the electrodes. For the interaction of the high impedance of the microphone with the low input impedance of the amplifier, a matching stage is used, which is made on a field-effect transistor located in the housing of the microphone capsule. It also houses the microphone itself.
To check if the microphone amplifier is suitable, you need to connect a multimeter to the input jack. If it shows 2-3 Volts, then the amplifier can work with a microphone. These amplifiers can be found in computer audio cards. In order to make a microphone, we need:
- Capsule. Can be found in an old Chinese radio, phone, or purchased on the market.
- Thin shielded wire.
- Plug type Jack 3, 5mm.
- Syringe for 2 grams.
- Paper clip
- Thick foam for the windproof cap.
Let's get to work.
Cut off part of the syringe from the side of the needle near the 1 g mark and remove all markings from the syringe using acetone. Then, along the trimmed edge, you need to walk with a finely coated sandpaper. Insert a shielded cable into the needle hole and tie it in a knot. Now you need to solder the capsule so that the cable sheath is connected to the body. Insert the capsule into the body and snap the place on the body where the needle holder used to be, using a paper clip. Solder the plug on the back of the cable. Now, for the windshield, we cut off a piece of foam rubber and cut a recess in it in the form of a cylinder. Next, we remove all unnecessary in order to get something that looks like a sphere. The microphone is ready to use!
