Not so long ago, this miracle of Chinese industry entered our lives, but immediately won our hearts with its simplicity and cheapness. And its simplicity lies in the following: I bought a bell, turned it on, threw it on the closet, and glued the button to the door. That's it, no wires for you, drilling holes for fastenings, etc. . . .
But still, let's look into it and look at the circuit diagram.
Button. Three transistors, 12 volt battery. The high-frequency generator is assembled according to a capacitive three-point circuit, an amplifier-converter. Converts from a frequency of about 433 MHz. What surprised me was the parallel connection of two circuits, one is tuned to the primary frequency of the generator, and the second catches somewhere around the 10th harmonic and is excited at a frequency of 433 MHz. Our Chinese friends again found an original, and most importantly simple solution to the problem using a minimum of details.
The most interesting thing is that the transmitter does not have a transmitting antenna, of course it is inside, i.e. the outline itself is her. Thanks to the use of ultra-shortwave range, this is quite enough.
Call. The receiver is assembled on a single transistor according to a regenerative detector circuit. The signal received from it goes to the operational amplifier. Next, the signal enters the SOUND CHIP. It is not difficult to guess that he is the shaper of the melodies that we hear. From it to a power amplifier, assembled on one transistor, and into a dynamic head. That's it, I just want to note the relatively small current consumption in standby mode.
They took it apart, looked at it, sorted out the work. All? No, not all! The bell is an almost universal transmitter-receiver circuit. Based on it, you can assemble many other interesting devices.
As an example. The bell controls the light.
We take our call and connect the circuit shown below.
This is a common trigger. When it receives an impulse from a bell, it switches to one of the fixed positions. The output of the trigger is a relay, and a controlled device is connected to the relay, in our case it is an incandescent lamp.
An example of the location of the bell and button.
Printed circuit board.
Location of parts on the printed circuit board.
PS: I was tormented by the question: where can I get power for this circuit? Shouldn't we run a separate line? Here's where you can find a way out - it's in double wiring. If your wiring in the ceiling is designed for two lamps, and the switch has two buttons, the answer came by itself - one button controls the device, and from the second it is powered, say, through charging from a mobile phone (it is economical).
