1. Real time clock PCF8563

PCF8563 is a low-power CMOS real-time clock / calendar chip. It provides a programmable clock output, an interrupt output and power down detector. All addresses and data are transmitted serially through the ci2 bus interface. The maximum bus speed is 400kbits / s. After reading and writing data each time, the embedded word address register will automatically generate increment. The working circuit of PCF8563 real-time clock chip is as follows:

Circuit combination of each module of safe smart home monitoring system

Among them, osoi is the oscillator input, OSOC is the oscillator output, / int is the interrupt output (open drain; low level is effective), SSV is grounded, SDA is the serial data I / O, SCL is the serial clock input, clkout is the clock output (open drain), and DDV is the positive power supply.

  2. Gas (smoke) detection circuit gas (smoke) detection circuit is shown in the figure

Circuit combination of each module of safe smart home monitoring system

The No. 3 terminal of the integrated comparator lm311 has a constant input voltage of 5V. Since the sensor output current is proportional to the indoor gas (smoke) concentration, I = KC (I is the sensor output current, C is the indoor gas concentration, K is the proportional constant), the concentration can be converted into a voltage signal through the sensor and potentiometer 1R and input to the No. 2 terminal of lm311 (i.e. v = KC * 1R). The voltage comparator can convert the analog signal into a binary signal. Lm311 is a general integrated comparator with low open-loop gain, large offset voltage and small common mode rejection ratio; But its response speed is fast, the transmission delay time is short, and the high-level signal can be directly input to the single chip microcomputer. From the above analysis, it can be seen that the resistance value of potentiometer can be adjusted to adjust the upper limit of indoor alarm concentration.

  3. Door magnetic detection and alarm circuit door magnetic detection and alarm circuit is as follows:

Circuit combination of each module of safe smart home monitoring system

The door magnetic switch 5c-31b can be set to normally open and normally closed. When it is set to normal start, the door will not alarm and the door will alarm; When it is set as normally closed, the door will open and alarm, and the door will not close.

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