[Image] Application of AT89C2051 in multi-function window

This multifunctional window has the following 5 functions:

1. Prevent harmful gas leakage: Automatically detect the concentration of harmful gases such as gas, smoke, alcohol, etc. in the room. When the set threshold is reached, the window will be opened automatically, and ventilation such as exhaust fan or air conditioner will be started;
2. Anti-theft alarm: The pyroelectric human infrared probe detects the human body approaching from outside the window, closes the window and locks it in time, and sends out an alarm signal;
3. Anti-humidity: Automatically close the window when it rains or fogs, and the air humidity is high;
4. Automatically close the window when it is dark (can be set to ON or OFF);
5. Timer switch: Open or close the window according to the set time.

Working principle: See the attached figure for the multifunctional window circuit.

The single-chip microcomputer adopts the interrupt query working mode. The signal of the gas sensor is amplified by IC4A, which flips IC4B and isolates the high level input to N3 and N1 through the optical coupler. After inversion, N3 triggers interrupt 0. After the single-chip microcomputer finds that P31 is at a low level, it outputs the window opening instruction to P10 and P11. After isolation, Q1~Q4 drives the motor M1 to open the window; P2 port turns from high to low, Q5 is turned on, and the normally open contact of J1 is closed to start the exhaust fan or air conditioner. C2 can eliminate certain interference to avoid false triggering. To simplify the circuit, only one sensor input is drawn in the figure. P34, P35, and P37 receive signals from pyroelectric, hygroscopic, and photosensitive probes respectively. SW2 is a multi-function button. When SW1 is not pressed, SW2 is a manual window opening/closing button. Press SW1 to trigger interrupt 1 and enter the time setting mode. Each time SW2 is pressed, the setting time increases by half an hour. After stopping the button for 30 seconds, the setting ends and the timer starts working. After the anti-theft alarm is triggered, press SW2 to stop the sound of the speaker. K1 and K2 are the window opening and closing detection switches, and J2 is the window lock electromagnet coil. After the window is closed, the window is locked. LED is a multi-function indicator: after power-on, the LED lights up, indicating that it is in the initial delay (due to the initial instability of the sensor, a longer delay is required); when setting the time, each time SW2 is pressed, the LED flashes once, confirming that the key input is valid; when the gas detection is activated, the LED also lights up, and it is off at other times.

In the figure, N1 and others are triodes, N3 is a non-OR gate composed of five diodes and one triode, and the amplification and comparison of the signals of the four sensors are completed by two quad op amps. In order to ensure stable operation, the microcontroller is completely isolated from the peripheral circuit and powered separately. The entire circuit is installed in the aluminum alloy window frame, and a detection hole is opened on the outside of the window frame for the sensor. Another wire of the gas-sensitive probe is installed at the position to be detected. M1 is installed on the movable window leaf together with the mechanical transmission mechanism, and is connected to the drive circuit in a special way (the entire mechanical transmission part has been patented). In order to prevent M1 from burning due to the blockage of the mechanical part, the program needs to detect the opening and closing process of the window. When the movable window leaf is blocked, it can automatically retreat and try again. If the switch cannot be opened and closed normally after three attempts, the action stops and an alarm signal is issued. A forced reset button is added to the RST end.