On the pages of popular publications repeatedly published describing various acoustic options switches.
Propose another scheme, which I has developed and manufactured more than nine years ago, and since then she works flawlessly in the hallway of my apartment. The circuit has a relay time. After the filing of a short beep, the light in the hallway turns on for about four minutes, then automatically turns off. The scheme itself is imbedded in the wall, walls wallpapered.
No switches in the hallway no, Wallpaper clean, which rarely happens when there is a switch, and children I always use them.
The scheme works as follows. Sound the signal perceived electret microphone WM comes the chip DA1 (microphone amplifier with special frequency response), used in radio type "FLAX".
With the circuit output signal is supplied to the driver rectangular pulses collected at two inverters chip DD1, and further to the base of transistor VT1, which, opening that discharges the timing capacitor (NW) trigger Schmitt. Thus on the output element of the trigger DD1.4 appears logical "On" and turns on the multivibrator, made on the chip DD2. At the output of the multivibrator is pulse amplifier (VT2, VT3), the output of which through a blocking capacitor C7, the signal is sent to a control the electrode of the triac VS1. The triac is opened and includes load. When the capacitor Sz charged to the level of logical 1, the Schmitt trigger switches to another stable state, the output DD1.4 appears logical "1", multivibrator off, closes the triac and the light bulb goes off.
The exposure time is selected depending on the specific the scheme is applied. When the nominal value of the capacitance C s, specified in the scheme, burning time of lamps is 4 minutes. Led VD5 you can apply any.
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