CN210136549U

CN210136549U - Remote monitoring alarm system based on single chip microcomputer

Info

Publication number: CN210136549U
Application number: CN201920293915.4U
Authority: CN
Inventors: 雷熠凡
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-03-08
Filing date: 2019-03-08
Publication date: 2020-03-10
Anticipated expiration: 2029-03-08

Abstract

The utility model provides a remote monitoring alarm system based on a single chip microcomputer, which comprises a telephone interface, a ringing detection and simulation off-hook circuit, a dual-audio decoding circuit, a single chip microcomputer and a signal acquisition and processing circuit; the telephone interface is respectively connected with the ringing detection and simulation off-hook circuit and the dual-audio decoding circuit, the ringing detection and simulation off-hook circuit and the dual-audio decoding circuit are also respectively connected with the single chip microcomputer, and the single chip microcomputer is connected with the signal acquisition and processing circuit.

Description

Remote monitoring alarm system based on single chip microcomputer

Technical Field

The utility model relates to a remote monitoring field especially relates to a remote monitoring alarm system based on singlechip.

Background

The modern residential pattern makes the safety problem of family life very important. Currently, a safety precaution and alarm system is an important guarantee for ensuring the safety of residences and residents. The best method for preventing burglary is to send out voice warning when a lawbreaker attempts to invade, increase the psychological pressure of the lawbreaker, enable the lawbreaker to leave, and inform the owner in time.

Content of reality

In view of the above shortcomings in the prior art, an object of the present invention is to provide a remote monitoring and alarming system based on a single chip microcomputer.

In order to achieve the above and other related objects, the present invention provides a remote monitoring alarm system based on a single chip microcomputer, which comprises a telephone interface, a ring detection and analog off-hook circuit, a dual-tone decoding circuit, a single chip microcomputer and a signal acquisition and processing circuit; the telephone interface is respectively connected with the ringing detection and simulation off-hook circuit and the dual-audio decoding circuit, the ringing detection and simulation off-hook circuit and the dual-audio decoding circuit are also respectively connected with the single chip microcomputer, and the single chip microcomputer is connected with the signal acquisition and processing circuit.

Optionally, the signal acquisition and processing circuit includes a processing chip BISS0001, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, and a pyroelectric infrared sensor, a D-pole of the pyroelectric infrared sensor is connected to one end of the first resistor, a eleventh pin of the processing chip BISS0001, and a power VCC, respectively, and the other end of the first resistor is connected to the ninth pin of the processing chip BISS 0001; the tenth pin of the processing chip BISS0001 is grounded through a second resistor; a twelfth pin of the processing chip BISS0001 is connected with one end of a fourth resistor, the other end of the fourth resistor is connected with one end of a third resistor, one end of the third resistor is connected with one end of a second capacitor, the other end of the second capacitor is connected with a sixteenth pin of the processing chip BISS0001, the first capacitor is connected in parallel with two ends of the fourth resistor, a fourteenth pin of the processing chip BISS0001 is respectively connected with an S pole of the pyroelectric infrared sensor, one end of a sixth resistor and one end of a fourth capacitor, the other end of the sixth resistor and the other end of the fourth capacitor are grounded, a fifteenth pin of the processing chip BISS0001 is connected with one end of a third capacitor, the other end of the third capacitor is connected with the other end of the second capacitor, a fifth resistor is connected in parallel with two ends of the third capacitor, one end of the third capacitor is connected with one end of a seventh resistor, and the other end of the seventh resistor is connected with one end of the fifth capacitor, the other end of the fifth capacitor is grounded; a thirteenth pin of the processing chip BISS0001 is connected with one end of the third resistor; the eighth foot of processing chip BISS0001 is connected with power VCC, and the seventh foot of processing chip BISS0001 is grounded, the sixth foot of processing chip BISS0001 is connected with the one end of eighth resistance, and the other end of eighth resistance is connected with the one end of seventh electric capacity, and the other end of seventh electric capacity is grounded, the fifth foot of processing chip BISS0001 is connected with the one end of seventh electric capacity, the fourth foot of processing chip BISS0001 is grounded through sixth electric capacity, and the third foot of processing chip BISS0001 is connected with the one end of sixth electric capacity through ninth resistance, and the second foot of processing chip BISS0001 connects tenth resistance, and tenth resistance is connected with the singlechip as the output, and the first foot of processing chip BISS0001 is connected with power VCC.

Optionally, the ringing detection and analog off-hook circuit includes a first bridge, a first zener diode, a second zener diode, an eighth capacitor, a ninth capacitor, a tenth capacitor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, and a first optocoupler; two input ends of the first electric bridge are respectively connected with a telephone line, the eighth capacitor is connected between the two input ends of the first electric bridge in parallel, the first voltage stabilizing diode is connected between the two output ends of the first electric bridge in parallel, the ninth capacitor is connected with the first voltage stabilizing diode in parallel, one end of the eleventh resistor is connected with one end of the ninth capacitor, the other end of the ninth capacitor is grounded, the other end of the eleventh resistor is connected with the cathode of the second voltage stabilizing diode, the anode of the second voltage stabilizing diode is grounded, the tenth capacitor is connected with the two ends of the second voltage stabilizing diode in parallel, one end of the twelfth resistor is connected with one end of the tenth capacitor, the other end of the twelfth resistor is connected with the anode of the light emitting diode of the first optical coupler, the cathode of the light emitting diode of the first optical coupler is grounded, the collector electrode of the triode of the first optical coupler is connected with a power supply, and the emitter electrode of the triode of the first, meanwhile, an emitting electrode of a triode of the first optocoupler is connected with the singlechip;

the ringing detection and simulation off-hook circuit further comprises a second bridge, a tenth capacitor, an eleventh capacitor, a twelfth capacitor, a fourteenth resistor, a fifteenth resistor, a second optical coupler and a transformer; two input ends of the second bridge are respectively connected with a telephone line, a positive output end of the second bridge is connected with a collector of a triode of the second optocoupler, an emitter of the triode of the second optocoupler is grounded through a fifteenth resistor, meanwhile, an emitter of the triode of the second optocoupler is connected with a positive electrode of a tenth capacitor, a negative electrode of the tenth capacitor is connected with one end of a primary side of the transformer, one end of an eleventh capacitor is grounded, and the other end of the eleventh capacitor is connected with the other end of the primary side of the transformer; the positive pole of the light emitting diode of the second optocoupler is connected with one end of a fourteenth resistor, the other end of the fourteenth resistor is connected with the single chip microcomputer, one end of the secondary side of the transformer is connected with the positive pole of a twelfth capacitor, the negative pole of the twelfth capacitor is grounded, and the other end of the secondary side of the transformer is connected with a DTMF input signal.

Optionally, the dual tone decoding circuit includes an MT8880 module, a fourteenth capacitor, a fifteenth capacitor, a sixteenth capacitor, a seventeenth capacitor, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a twentieth resistor, and a crystal oscillator; one end of a fourteenth capacitor is used as DTMF input, the other end of the fourteenth capacitor is connected with one end of a sixteenth resistor, the other end of the sixteenth resistor is respectively connected with one end of a seventeenth resistor and a second pin of the MT8880 module, the other end of the seventeenth resistor is connected with a third pin of the MT8880 module, a first pin of the MT8880 module is connected with a fourth pin, a fifth pin of the MT8880 module is grounded, and a crystal oscillator is connected between the sixth pin and the seventh pin of the MT8880 module; an eighth pin of the MT8880 module is respectively connected to one end of a fifteenth capacitor and one end of an eighteenth resistor, and the other end of the fifteenth capacitor and the other end of the eighteenth resistor are respectively grounded; the twentieth pin of the MT8880 module is respectively connected with a power supply, one end of a sixteenth capacitor and one end of a seventeenth capacitor, the other end of the sixteenth capacitor is grounded, the other end of the seventeenth capacitor is respectively connected with one end of a nineteenth resistor and a nineteenth pin of the MT8880 module, the other end of the nineteenth resistor is connected with an eighteenth pin of the MT8880 module, the seventeenth pin, the sixteenth pin, the fifteenth pin, the fourteenth pin, the thirteenth pin, the twelfth pin and the eleventh pin of the MT8880 module are respectively connected with the single chip microcomputer, and the thirteenth pin of the MT8880 module is connected with the power supply through a twentieth resistor; and a ninth pin and a tenth pin of the MT8880 module are connected with the singlechip, and an eighth pin of the MT8880 module is used as DTMF output.

As above, the utility model discloses a remote monitoring alarm system based on singlechip has following beneficial effect:

the device has the function of sound and light alarm locally, and has the function of warning the family personnel.

Possess long-range cell-phone alarming function, when nobody in the house, the accessible SMS transmits alarm information for householder's cell-phone, plays the warning effect, lets outside householder know. Before family members such as householders enter the door, the alarm can be controlled by the mobile phone in a remote way so as not to give an alarm.

Drawings

FIG. 1 is a schematic block diagram of a remote monitoring alarm system based on a single chip microcomputer in the embodiment of the present invention;

FIG. 2 is a circuit diagram of a signal acquisition and processing circuit according to an embodiment of the present invention;

fig. 3 is a circuit diagram of a ring detection and analog off-hook circuit in an embodiment of the present invention;

FIG. 4 is a circuit diagram of a dual audio decoding circuit according to an embodiment of the present invention;

fig. 5 is a schematic diagram of a single chip microcomputer in the embodiment of the invention.

Detailed Description

The following description is provided for illustrative purposes, and other advantages and features of the present invention will become apparent to those skilled in the art from the following detailed description.

It should be understood that the structure, ratio, size and the like shown in the drawings attached to the present specification are only used for matching with the content disclosed in the specification, so as to be known and read by those skilled in the art, and are not used for limiting the limit conditions that the present invention can be implemented, so that the present invention has no technical essential meaning, and any structure modification, ratio relationship change or size adjustment should still fall within the scope that the technical content disclosed in the present invention can cover without affecting the function that the present invention can produce and the purpose that the present invention can achieve. Meanwhile, the terms such as "upper", "lower", "left", "right", "middle" and "one" used in the present specification are for convenience of description, and are not intended to limit the scope of the present invention, and changes or adjustments of the relative relationship thereof may be made without substantial technical changes, and the present invention is also regarded as the scope of the present invention.

As shown in fig. 1, the utility model provides a remote monitoring alarm system based on a single chip microcomputer, which comprises a telephone interface, a ringing detection and simulation off-hook circuit, a dual-audio decoding circuit, a single chip microcomputer and a signal acquisition and processing circuit; the telephone interface is respectively connected with the ringing detection and simulation off-hook circuit and the dual-audio decoding circuit, the ringing detection and simulation off-hook circuit and the dual-audio decoding circuit are also respectively connected with the single chip microcomputer, and the single chip microcomputer is connected with the signal acquisition and processing circuit.

In this embodiment, the single chip microcomputer is PIC16F 877A.

As shown in fig. 2, the signal collecting and processing circuit includes a processing chip BISS0001, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, and a pyroelectric infrared sensor, wherein a D-pole of the pyroelectric infrared sensor is respectively connected to one end of the first resistor, a tenth pin of the processing chip BISS0001, and a power VCC, and the other end of the first resistor is connected to a ninth pin of the processing chip BISS 0001; the tenth pin of the processing chip BISS0001 is grounded through a second resistor; a twelfth pin of the processing chip BISS0001 is connected with one end of a fourth resistor, the other end of the fourth resistor is connected with one end of a third resistor, one end of the third resistor is connected with one end of a second capacitor, the other end of the second capacitor is connected with a sixteenth pin of the processing chip BISS0001, the first capacitor is connected in parallel with two ends of the fourth resistor, a fourteenth pin of the processing chip BISS0001 is respectively connected with an S pole of the pyroelectric infrared sensor, one end of a sixth resistor and one end of a fourth capacitor, the other end of the sixth resistor and the other end of the fourth capacitor are grounded, a fifteenth pin of the processing chip BISS0001 is connected with one end of a third capacitor, the other end of the third capacitor is connected with the other end of the second capacitor, a fifth resistor is connected in parallel with two ends of the third capacitor, one end of the third capacitor is connected with one end of a seventh resistor, and the other end of the seventh resistor is connected with one end of the fifth capacitor, the other end of the fifth capacitor is grounded; a thirteenth pin of the processing chip BISS0001 is connected with one end of the third resistor; the eighth foot of processing chip BISS0001 is connected with power VCC, and the seventh foot of processing chip BISS0001 is grounded, the sixth foot of processing chip BISS0001 is connected with the one end of eighth resistance, and the other end of eighth resistance is connected with the one end of seventh electric capacity, and the other end of seventh electric capacity is grounded, the fifth foot of processing chip BISS0001 is connected with the one end of seventh electric capacity, the fourth foot of processing chip BISS0001 is grounded through sixth electric capacity, and the third foot of processing chip BISS0001 is connected with the one end of sixth electric capacity through ninth resistance, and the second foot of processing chip BISS0001 connects tenth resistance, and tenth resistance is connected with the singlechip as the output, and the first foot of processing chip BISS0001 is connected with power VCC.

In this embodiment, the second pin of the processing chip BISS0001 is connected to the nineteenth pin of the single chip microcomputer PIC16F 877A.

In the present embodiment, the pyroelectric infrared sensor usually employs a 3-pin metal package, and the pin diagram is shown in the following figure. The power supply end (D pole-DRAIN of the internal switch tube), the signal output end (S pole-SOURCE of the internal switch tube) and the grounding end (GROUND).

The working principle and the characteristics of the passive pyroelectric infrared probe are as follows: generally, a human body has a constant body temperature, generally 37 degrees, and thus emits infrared rays having a specific wavelength of about 10UM, and a passive infrared probe operates by detecting infrared rays having a wavelength of about 10UM emitted from the human body. The infrared rays of about 10UM emitted by the human body are concentrated on the infrared induction source after being enhanced by the Fresnel filter. The infrared induction source usually adopts a pyroelectric element, the pyroelectric element loses charge balance when receiving the change of the infrared radiation temperature of a human body, charges are released outwards, and an electric subsequent circuit can generate an alarm signal after being checked and processed.

Such probes are targeted at detecting body radiation. The pyroelectric element must be very sensitive to infrared radiation having a wavelength of around 10 UM. In order to be sensitive only to infrared radiation of the human body, the radiation exposure surface is usually covered with a special Fresnel filter, so that the environmental interference is controlled significantly. The sensor of the passive infrared probe comprises two pyroelectric elements which are mutually connected in series or in parallel. And the two manufactured electric polarization directions are just opposite, the environmental background radiation almost has the same effect on the two pyroelectric elements, so that the pyroelectric effects generated by the two pyroelectric elements are mutually counteracted, and then the detector has no signal output.

Once a person invades the detection area, the infrared radiation of the human body is focused through a part of mirror surface and is received by the pyroelectric elements, but the heat received by the two pyroelectric elements is different, the pyroelectric elements are also different and cannot be counteracted, and the alarm is given out through signal processing.

BISS0001 is a sensing signal processing integrated circuit with higher performance. It is matched with pyroelectric infrared sensor and a small quantity of external components to form passive pyroelectric infrared switch. The automatic control device can automatically and quickly turn on various incandescent lamps, fluorescent lamps, buzzers, automatic doors, electric fans, dryers, automatic hand washing pools and other devices, and is particularly suitable for sensitive areas such as aisles, corridors and the like of enterprises, hotels, shopping malls, storehouses and families, or is used for automatic lighting, illumination and alarm systems of safe areas.

As shown in fig. 3, the ringing detection and analog off-hook circuit includes a first bridge, a first zener diode, a second zener diode, an eighth capacitor, a ninth capacitor, a tenth capacitor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, and a first optocoupler; two input ends of the first electric bridge are respectively connected with a telephone line, the eighth capacitor is connected between the two input ends of the first electric bridge in parallel, the first voltage stabilizing diode is connected between the two output ends of the first electric bridge in parallel, the ninth capacitor is connected with the first voltage stabilizing diode in parallel, one end of the eleventh resistor is connected with one end of the ninth capacitor, the other end of the ninth capacitor is grounded, the other end of the eleventh resistor is connected with the cathode of the second voltage stabilizing diode, the anode of the second voltage stabilizing diode is grounded, the tenth capacitor is connected with the two ends of the second voltage stabilizing diode in parallel, one end of the twelfth resistor is connected with one end of the tenth capacitor, the other end of the twelfth resistor is connected with the anode of the light emitting diode of the first optical coupler, the cathode of the light emitting diode of the first optical coupler is grounded, the collector electrode of the triode of the first optical coupler is connected with a power supply, and the emitter electrode of the triode of the first, meanwhile, an emitting electrode of a triode of the first optocoupler is connected with the singlechip; the ringing detection and simulation off-hook circuit further comprises a second bridge, a tenth capacitor, an eleventh capacitor, a twelfth capacitor, a fourteenth resistor, a fifteenth resistor, a second optical coupler and a transformer; two input ends of the second bridge are respectively connected with a telephone line, a positive output end of the second bridge is connected with a collector of a triode of the second optocoupler, an emitter of the triode of the second optocoupler is grounded through a fifteenth resistor, meanwhile, an emitter of the triode of the second optocoupler is connected with a positive electrode of a tenth capacitor, a negative electrode of the tenth capacitor is connected with one end of a primary side of the transformer, one end of an eleventh capacitor is grounded, and the other end of the eleventh capacitor is connected with the other end of the primary side of the transformer; the positive pole of the light emitting diode of the second optocoupler is connected with one end of a fourteenth resistor, the other end of the fourteenth resistor is connected with the single chip microcomputer, one end of the secondary side of the transformer is connected with the positive pole of a twelfth capacitor, the negative pole of the twelfth capacitor is grounded, and the other end of the secondary side of the transformer is connected with a DTMF input signal.

According to the provisions of the national standard GB3380, telephone line signal analysis provides a dc voltage of approximately 48V before future ringing of the telephone line by the telephone exchange. When a subscriber is called, the telephone exchange sends a ringing signal. The ringing signal is a sine wave of 25 +/-3 volts, the harmonic ring distortion is not more than 10 percent, and the effective voltage value is 90 +/-15V. Ringing takes 5 seconds as a period, namely 1 second for sending and 4 seconds for cutting off. Ringing current enters a bridge B1 through a DC blocking capacitor C5, after full-wave rectification, the ringing current is subjected to two-stage voltage stabilization by VD3 and VD4, and finally rectified into 12V DC level to drive an optical coupler U2 to work, the single chip microcomputer detects ringing times by recording the working times of U2, when the preset ringing times of off-hook are reached, the single chip microcomputer controls the optical coupler U3 to work, and an off-hook resistor R10 is connected into a telephone loop to realize automatic off-hook.

Because the response of the SPC telephone exchange to the telephone going off-hook is that the telephone line loop current suddenly increases to a current of about 30mA, the exchange detects the increase in loop current and assumes that the telephone has gone off-hook. When the subscriber goes off-hook, the telephone picks up a load of about 200 Ω through the hook switch, causing a current of about 30mA to flow through the entire telephone line loop. The exchanger stops ringing current transmission after detecting the current, and changes the line voltage into direct current of tens of volts to complete the connection.

In this embodiment, an emitter of a triode of the first optocoupler is connected to a fifteenth pin of the single chip microcomputer PIC16F877A, and a nineteenth resistor is connected to a fourteenth pin of the single chip microcomputer PIC16F 877A.

As shown in fig. 4, the dual tone decoding circuit includes an MT8880 module, a fourteenth capacitor, a fifteenth capacitor, a sixteenth capacitor, a seventeenth capacitor, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a twentieth resistor, and a crystal oscillator; one end of a fourteenth capacitor is used as DTMF input, the other end of the fourteenth capacitor is connected with one end of a sixteenth resistor, the other end of the sixteenth resistor is respectively connected with one end of a seventeenth resistor and a second pin of the MT8880 module, the other end of the seventeenth resistor is connected with a third pin of the MT8880 module, a first pin of the MT8880 module is connected with a fourth pin, a fifth pin of the MT8880 module is grounded, and a crystal oscillator is connected between the sixth pin and the seventh pin of the MT8880 module; an eighth pin of the MT8880 module is respectively connected to one end of a fifteenth capacitor and one end of an eighteenth resistor, and the other end of the fifteenth capacitor and the other end of the eighteenth resistor are respectively grounded; the twentieth pin of the MT8880 module is respectively connected with a power supply, one end of a sixteenth capacitor and one end of a seventeenth capacitor, the other end of the sixteenth capacitor is grounded, the other end of the seventeenth capacitor is respectively connected with one end of a nineteenth resistor and a nineteenth pin of the MT8880 module, the other end of the nineteenth resistor is connected with an eighteenth pin of the MT8880 module, the seventeenth pin, the sixteenth pin, the fifteenth pin, the fourteenth pin, the thirteenth pin, the twelfth pin and the eleventh pin of the MT8880 module are respectively connected with the single chip microcomputer, and the thirteenth pin of the MT8880 module is connected with the power supply through a twentieth resistor; and a ninth pin and a tenth pin of the MT8880 module are connected with the singlechip, and an eighth pin of the MT8880 module is used as DTMF output.

Wherein, DTMF input receives signal through short message, DTMF output is also output to mobile phone in short message form

In this embodiment, the seventeenth pin, the sixteenth pin, the fifteenth pin, the fourteenth pin, the thirteenth pin, the twelfth pin, the eleventh pin, the tenth pin, and the ninth pin of the MT8880 module are respectively connected to the fifth pin, the fourth pin, the third pin, the second pin, the twenty-first pin, the twenty-second pin, the twenty-third pin, the twenty-fourth pin, and the twenty-fifth pin of the single chip PIC16F 877A.

MT8880 is a single-chip DTMF signal transceiver with call processing filters. The receiving part of the DTMF signal adopts the industrial manufacturing standard of a DTMF signal receiving singlechip MT 8870; the transmitting part adopts a switched capacitor to carry out D/A conversion and transmits DTMF signals with high precision and low distortion. The internal register provides a group pattern. In dual tone cluster mode, DTMF signals can be transmitted with precise timing. The call processing filter may be selected to allow a microprocessor to process the call audio signal. MT8880C also has a standard microprocessor bus that connects directly to the 6800 family of microprocessors.

The MT8880 module integrates the structure of an MT8880C singlechip of a transceiving function, and comprises a high-performance receiver with an internal amplifier with variable gain and a transmitter with a pulse counter. A standard microprocessor interface that can access registers within the MT 8880. The internal registers of the MT8880 include 1 status register, 2 data registers, and 2 control registers.

The MT8880 has an interface connected with a microcontroller (singlechip), and must be matched with the singlechip for use, and the pin has the following functions:

IN +, IN-: the input end is the non-inverting input end and the inverting input end of the internal amplifier, namely the input end for receiving DTMF signals; GS: the output end of the internal amplifier is externally connected with a negative feedback resistor to the IN _ end; UREF: an internal reference voltage output, the reference voltage equal to UDD/2; UDD, USS: the power supply is respectively the positive end and the negative end of the power supply, and the power supply voltage is 5V; OSCl, OSC 2: externally connecting a 4MHz crystal to form a crystal oscillator; TONE: a dual audio signal output; R/W is a read/write control terminal which reads the MT8880 when applied with a high level and writes the MT8880 when applied with a low level; RS 0: and a control terminal for selecting each internal register, the control terminal selecting the control register or the status register when a high level is applied, and selecting the transmission data register or the reception data register when a low level is applied.

IRQ: in the dual tone mode and in the interrupt mode, the terminal changes from high level to low level when a valid DTMF signal is received or ready to send a DTMF signal; when the call processing mode detects the effective signal tone, the end outputs square waves; D0-D3: a write command or a read status data line.

The DTMF signal is amplified by the internal receiving operational amplifier determined by the value of TONE pin output IN-pin input R2/R1, the higher the ratio is, the higher the receiving sensitivity is, the higher the value of resistance R4 and capacitance C2 affect the stability of received data, the updating time of the D0-D3 data port output latch is proportional to the value of (R4.C2), if the value of (R4.C2) is smaller, the DTMF signal can be jittered after decoding to cause a receiving error.

The above embodiments are merely illustrative of the principles and effects of the present invention, and are not to be construed as limiting the invention. Modifications and variations can be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which may be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. A remote monitoring alarm system based on a single chip microcomputer is characterized by comprising a telephone interface, a ringing detection and analog off-hook circuit, a dual-audio decoding circuit, the single chip microcomputer and a signal acquisition and processing circuit; the telephone interface is respectively connected with the ringing detection and analog off-hook circuit and the dual-tone decoding circuit, the ringing detection and analog off-hook circuit and the dual-tone decoding circuit are also respectively connected with the single chip microcomputer, and the single chip microcomputer is connected with the signal acquisition and processing circuit; the signal acquisition and processing circuit comprises a processing chip BISS0001, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor and a pyroelectric infrared sensor, wherein the D pole of the pyroelectric infrared sensor is respectively connected with one end of the first resistor, the eleventh pin of the processing chip BISS0001 and a power supply VCC, and the other end of the first resistor is connected with the ninth pin of the processing chip BISS 0001; the tenth pin of the processing chip BISS0001 is grounded through a second resistor; a twelfth pin of the processing chip BISS0001 is connected with one end of a fourth resistor, the other end of the fourth resistor is connected with one end of a third resistor, one end of the third resistor is connected with one end of a second capacitor, the other end of the second capacitor is connected with a sixteenth pin of the processing chip BISS0001, the first capacitor is connected in parallel with two ends of the fourth resistor, a fourteenth pin of the processing chip BISS0001 is respectively connected with an S pole of the pyroelectric infrared sensor, one end of a sixth resistor and one end of a fourth capacitor, the other end of the sixth resistor and the other end of the fourth capacitor are grounded, a fifteenth pin of the processing chip BISS0001 is connected with one end of a third capacitor, the other end of the third capacitor is connected with the other end of the second capacitor, a fifth resistor is connected in parallel with two ends of the third capacitor, one end of the third capacitor is connected with one end of a seventh resistor, and the other end of the seventh resistor is connected with one end of the fifth capacitor, the other end of the fifth capacitor is grounded; a thirteenth pin of the processing chip BISS0001 is connected with one end of the third resistor; the eighth pin of the processing chip BISS0001 is connected with a power supply VCC, the seventh pin of the processing chip BISS0001 is grounded, the sixth pin of the processing chip BISS0001 is connected with one end of an eighth resistor, the other end of the eighth resistor is connected with one end of a seventh capacitor, the other end of the seventh capacitor is grounded, the fifth pin of the processing chip BISS0001 is connected with one end of the seventh capacitor, the fourth pin of the processing chip BISS0001 is grounded through the sixth capacitor, the third pin of the processing chip BISS0001 is connected with one end of the sixth capacitor through a ninth resistor, the second pin of the processing chip BISS0001 is connected with a tenth resistor, the tenth resistor is used as an output end and connected with a single chip microcomputer, and the first pin of the processing chip BISS0001 is connected with the power supply VCC; the ringing detection and simulation off-hook circuit comprises a first bridge, a first voltage stabilizing diode, a second voltage stabilizing diode, an eighth capacitor, a ninth capacitor, a tenth capacitor, an eleventh resistor, a twelfth resistor, a thirteenth resistor and a first optical coupler; two input ends of the first electric bridge are respectively connected with a telephone line, the eighth capacitor is connected between the two input ends of the first electric bridge in parallel, the first voltage stabilizing diode is connected between the two output ends of the first electric bridge in parallel, the ninth capacitor is connected with the first voltage stabilizing diode in parallel, one end of the eleventh resistor is connected with one end of the ninth capacitor, the other end of the ninth capacitor is grounded, the other end of the eleventh resistor is connected with the cathode of the second voltage stabilizing diode, the anode of the second voltage stabilizing diode is grounded, the tenth capacitor is connected with the two ends of the second voltage stabilizing diode in parallel, one end of the twelfth resistor is connected with one end of the tenth capacitor, the other end of the twelfth resistor is connected with the anode of the light emitting diode of the first optical coupler, the cathode of the light emitting diode of the first optical coupler is grounded, the collector electrode of the triode of the first optical coupler is connected with a power supply, and the emitter electrode of the triode of the first, meanwhile, an emitting electrode of a triode of the first optocoupler is connected with the singlechip;

the ringing detection and simulation off-hook circuit further comprises a second bridge, a tenth capacitor, an eleventh capacitor, a twelfth capacitor, a fourteenth resistor, a fifteenth resistor, a second optical coupler and a transformer; two input ends of the second bridge are respectively connected with a telephone line, a positive output end of the second bridge is connected with a collector of a triode of the second optocoupler, an emitter of the triode of the second optocoupler is grounded through a fifteenth resistor, meanwhile, an emitter of the triode of the second optocoupler is connected with a positive electrode of a tenth capacitor, a negative electrode of the tenth capacitor is connected with one end of a primary side of the transformer, one end of an eleventh capacitor is grounded, and the other end of the eleventh capacitor is connected with the other end of the primary side of the transformer; the positive electrode of a light emitting diode of the second optocoupler is connected with one end of a fourteenth resistor, the other end of the fourteenth resistor is connected with the single chip microcomputer, one end of the secondary side of the transformer is connected with the positive electrode of a twelfth capacitor, the negative electrode of the twelfth capacitor is grounded, and the other end of the secondary side of the transformer is connected with a DTMF input signal; the dual-tone decoding circuit comprises an MT8880 module, a fourteenth capacitor, a fifteenth capacitor, a sixteenth capacitor, a seventeenth capacitor, a sixteenth resistor, a seventeenth resistor, an eighteenth resistor, a nineteenth resistor, a twentieth resistor and a crystal oscillator; one end of a fourteenth capacitor is used as DTMF input, the other end of the fourteenth capacitor is connected with one end of a sixteenth resistor, the other end of the sixteenth resistor is respectively connected with one end of a seventeenth resistor and a second pin of the MT8880 module, the other end of the seventeenth resistor is connected with a third pin of the MT8880 module, a first pin of the MT8880 module is connected with a fourth pin, a fifth pin of the MT8880 module is grounded, and a crystal oscillator is connected between the sixth pin and the seventh pin of the MT8880 module; an eighth pin of the MT8880 module is respectively connected to one end of a fifteenth capacitor and one end of an eighteenth resistor, and the other end of the fifteenth capacitor and the other end of the eighteenth resistor are respectively grounded; the twentieth pin of the MT8880 module is respectively connected with a power supply, one end of a sixteenth capacitor and one end of a seventeenth capacitor, the other end of the sixteenth capacitor is grounded, the other end of the seventeenth capacitor is respectively connected with one end of a nineteenth resistor and a nineteenth pin of the MT8880 module, the other end of the nineteenth resistor is connected with an eighteenth pin of the MT8880 module, the seventeenth pin, the sixteenth pin, the fifteenth pin, the fourteenth pin, the thirteenth pin, the twelfth pin and the eleventh pin of the MT8880 module are respectively connected with the single chip microcomputer, and the thirteenth pin of the MT8880 module is connected with the power supply through a twentieth resistor; and a ninth pin and a tenth pin of the MT8880 module are connected with the singlechip, and an eighth pin of the MT8880 module is used as DTMF output.