CN219038188U

CN219038188U - Pyroelectric infrared protection detection device circuit

Info

Publication number: CN219038188U
Application number: CN202223063855.8U
Authority: CN
Inventors: 蔡陈松; 聂文龙; 孙旭涛; 廖志祥
Original assignee: Foxstar Technology Co ltd; Henan Costar Group Co Ltd
Current assignee: Foxstar Technology Co ltd; Henan Costar Group Co Ltd
Priority date: 2022-11-18
Filing date: 2022-11-18
Publication date: 2023-05-16
Anticipated expiration: 2032-11-18

Abstract

The utility model discloses a pyroelectric infrared protection detection device circuit which comprises two optical components, two pyroelectric infrared PIR detection sensors, two amplifying circuit modules, two signal processing circuits, a signal channel switching module, an SOC module, an A/D analog-to-digital conversion module and a projector, wherein the optical components are arranged as a Fresnel lens for effectively concentrating infrared rays of a detection space on the sensors, the Fresnel lens is positioned at one side of the two pyroelectric infrared PIR detection sensors, the amplifying circuit modules and the signal processing circuits are sequentially connected, and the two signal processing circuits are connected to the signal channel switching module.

Description

Pyroelectric infrared protection detection device circuit

Technical Field

The utility model relates to the technical field of pyroelectric infrared detection, in particular to a pyroelectric infrared protection detection device circuit.

Background

The requirements of high-specification and high-brightness projectors, particularly laser ultra-short focal projectors, are increasing, and the requirements of safe use of the projectors are also increasing, because the projectors throw pictures on curtains or wall surfaces in a light imaging mode, the higher the brightness of the projection is, the higher the intensity of the thrown light is, and when an object (particularly a child) approaches the laser ultra-short focal projectors, eyes are easily injured and eyesight is affected when eyes are closer to a light source of the projector.

The pyroelectric infrared detection technology uses a pyroelectric infrared sensor as a probe to detect infrared signals with specific wavelengths emitted by a human body, and performs non-contact detection with a long distance. The technology has the characteristics of wide measurement range, high response speed, high sensitivity, strong anti-interference capability, safety, reliability and the like. Therefore, the pyroelectric infrared-based protection detection device has wide application in laser ultra-short focal projection.

The existing pyroelectric infrared protection detection device has a plurality of defects, such as higher false alarm rate, and the reason is mainly that the detection device is easily interfered by various external light sources, internal circuits and heat source noise, and finally the pyroelectric infrared protection detection device system cannot effectively identify an invaded object. The application scene of the pyroelectric infrared protection detection device is limited to occasions with low requirements on the protection performance.

As shown in fig. 1, in the circuit scheme of the conventional pyroelectric infrared protection detection device, after infrared rays radiated by a human body are modulated by a fresnel lens, the infrared rays are focused on a pyroelectric PIR detection sensor, the sensor converts an infrared radiation change value into a weak analog voltage signal, the analog signal is amplified by an operational amplifier and then transmitted to a voltage comparator to be compared with a set reference threshold, when the analog signal exceeds the threshold, a corresponding switch signal is triggered, and then a mechanism such as turning off a projector light source or turning off reminding is executed by a control circuit of an SOC.

As shown in fig. 2, when the above-mentioned conventional pyroelectric infrared protection detection device scheme is operated, an analog waveform is generated after a target enters a detection zone of a sensor and is amplified by an operational amplifier, and as shown in part (a) of fig. 2, the analog waveform generally includes a useful analog signal and interference noise. As shown in part (b) of fig. 2, it is seen that this analog waveform, when compared in the comparator with a set threshold, will produce the "high" and "low" level signals of irregular, magnitude intervals shown, which ultimately become false trigger signals. When no object passes through the detection area, the detection area is also judged to be passed by a person, and a mechanism such as turning off a projector light source or turning off a reminding is executed.

In order to solve the false triggering defect caused by interference, a pyroelectric infrared protection detection device circuit is designed, and the interference problem is solved based on corresponding measures adopted in the novel scheme circuit.

Disclosure of Invention

The utility model aims to provide a circuit of a pyroelectric infrared protection detection device, which has better stability and stronger applicability to external and internal interference noise, thereby better solving the problem of false triggering of equipment with the pyroelectric infrared protection detection device and solving the problem in the background technology.

In order to achieve the above purpose, the present utility model provides the following technical solutions: the utility model provides a pyroelectric infrared protection detection device circuit, includes two optical components and parts, two pyroelectric infrared PIR detection sensors, two amplifier circuit modules, two signal processing circuit, signal path switching module, SOC module, AD analog-to-digital conversion module and projecting apparatus, optical components and parts set up to be used for concentrating the infrared ray in detection space effectively to the fei nier lens on the sensor, fei nier lens is located one side of two pyroelectric infrared PIR detection sensors, amplifier circuit module and signal processing circuit connect gradually, two signal processing circuit all connect on signal path switching module, SOC module and projecting apparatus connect gradually, AD analog-to-digital conversion module installs the inside at the SOC module.

Preferably, the pyroelectric infrared PIR detection sensor is an energy conversion device, and the core device of the pyroelectric infrared PIR detection sensor is a pyroelectric infrared sensor capable of detecting infrared rays radiated by a human body in a non-contact manner.

Preferably, the signal processing circuit is configured as a second-order band-pass filter circuit including a low-pass filter circuit composed of C1 and R1 and a high-pass filter circuit composed of C2 and R2.

Preferably, the low-pass filter circuit and the high-pass filter circuit are connected in series, that is, when the cut-off frequency ωh of the low-pass filter circuit is greater than the cut-off frequency ωl of the high-pass filter circuit, the low-pass filter circuit and the high-pass filter circuit are connected in series to form a second-order band-pass filter circuit.

Preferably, the amplifying circuit module is set as an operational amplifier, and the operational amplifier is powered by a 5V power supply.

Preferably, the signal channel switching module is configured as a miniaturized two-channel analog switch with high integration and patch installation.

Preferably, the signal channel switching module is connected to a signal input end of the a/D analog-to-digital conversion module, and a core device of the a/D analog-to-digital conversion module is set as an a/D converter.

Preferably, the signal channel switching module comprises an analog switch chip U2, a C77 and a C80 which are arranged in parallel are connected on a pin five of the U2, one end of the C80 is connected with an R81, and a pin six of the U2 is connected with an R82 and an R83 respectively.

Preferably, the resistance of R81 is set to 10 ohms, the resistance of R82 is set to 1 kiloohm, and the resistance of R83 is set to 100 kiloohms.

Compared with the prior art, the utility model has the beneficial effects that:

the utility model has better stability and stronger applicability to external and internal interference noise, thereby better solving the problem of false triggering of equipment with a pyroelectric infrared protection detection device.

Drawings

FIG. 1 is a structural frame diagram of a circuit of a conventional pyroelectric infrared protection detection device;

FIG. 2 is a schematic diagram of a waveform of a sampling signal of a circuit of a conventional pyroelectric infrared protection detection device;

FIG. 3 is a schematic view of a structural framework of the present utility model;

FIG. 4 is a schematic diagram of the frequency response principle of the band-pass filter of the present utility model;

FIG. 5 is a schematic view of an application scenario incorporating an ultra-short focal projector according to the present utility model;

FIG. 6 is a circuit diagram of a pre-amplification circuit of the present utility model;

FIG. 7 is a diagram of a second order bandpass filter circuit of the utility model;

fig. 8 is a circuit diagram of a signal channel switching module according to the present utility model.

Detailed Description

The following description of the embodiments of the present utility model will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.

The same reference numbers in different drawings identify the same or similar elements; it should be further understood that terms such as "first," "second," "third," "upper," "lower," "front," "rear," "inner," "outer," "end," "section," "width," "thickness," "region," and the like are merely convenient for a viewer to construct with reference to the drawings and are merely used to facilitate the description of the utility model, and are not limiting of the utility model.

Referring to fig. 3-8, the present utility model provides a technical solution: the utility model provides a pyroelectric infrared protection detection device circuit, includes two optical components and parts, two pyroelectric infrared PIR detection sensors, two amplifier circuit modules, two signal processing circuit, signal path switching module, SOC module, AD analog-to-digital conversion module and projecting apparatus, optical components and parts set up to be used for concentrating the infrared ray in detection space effectively on the sensor's chenille lens, and its main effect is just concentrating the infrared ray in detection space effectively on the sensor. The narrow bands (windows) distributed on the lens are used for realizing the collection of infrared rays, which is equivalent to the action of a convex lens, and the narrow bands are mainly designed and made of lens materials.

The Fresnel lens has two functions, namely a focusing function, namely, a pyroelectric infrared signal is refracted (reflected) on the pyroelectric infrared PIR detection sensor, and a second function is to divide a detection area into a plurality of bright areas and dark areas, so that a moving object entering the detection area can generate a variable pyroelectric infrared signal on the PIR in a temperature change mode.

The Fresnel lens is located on one side of two pyroelectric infrared PIR detection sensors, the amplifying circuit module and the signal processing circuit are sequentially connected, the two signal processing circuits are connected to the signal channel switching module, the SOC module and the projector are sequentially connected, and the A/D analog-to-digital conversion module is installed inside the SOC module.

The SOC module is a core part of the whole system, mainly completes overall control of the system and coordinated operation among all functional modules, and is a main control module of the system. The functions realized by the method are as follows: control the functions of the display part of the projector, man-machine interaction input, A/D conversion in the data acquisition processing module, audio/video encoding and decoding, multimedia playing, propagation and the like.

The A/D analog-to-digital conversion module carries out analog-to-digital conversion on the signal conditioned by the pyroelectric infrared module, and realizes the conversion of the analog signal quantity into the digital signal quantity. According to the characteristics of the system, when the signals are digitized, the speed and the precision of the A/D conversion are required to meet the corresponding requirements, and because the system SOC has strong functions and rich resources, the A/D conversion function module built in the SOC is adopted for analog-to-digital conversion.

The A/D sampling circuit converts the analog signal output by the channel switching module into a digital signal. The core device of the sampling circuit is an A/D converter, and the performance of the sampling circuit directly influences the accuracy and the integrity of noise signal extraction. Considering various reasons such as performance, price, sampling precision and the like, an A/D conversion module built in the SOC is finally selected.

The pyroelectric infrared PIR detection sensor is an energy conversion device for converting heat change into electric quantity change, and the core device of the pyroelectric infrared PIR detection sensor is a pyroelectric infrared sensor capable of detecting infrared rays radiated by a human body in a non-contact mode. When the alternating infrared rays irradiate the surface of the crystal, the temperature of the crystal is changed rapidly due to the thermal effect of the infrared rays, and the charges are changed at the moment, so that an obvious external electric field is formed, and the pyroelectric crystal inside the pyroelectric infrared sensor is polarized and changed along with the change of the temperature.

If the infrared radiation is constantly irradiated on the probe of the detector, the temperature of the pyroelectric crystal is not changed, the crystal is electrically neutral to the outside, and the detector is not output by an electric signal, so that the constant infrared radiation cannot be detected. In the scheme, the pyroelectric infrared PIR sensor detects alternating infrared radiation signals, when the temperature of infrared radiation of a human body is changed, charge balance is lost, charges are released outwards, the signals are converted into weak voltage signals, and after amplification and processing, a system can monitor and control the mechanisms such as a projector light source switch or shutdown reminding in real time, so that the purpose of using the projector safely is achieved.

The signal processing circuit is mainly used for conditioning the sensor signal with the amplified front end, the filter can not only extract the frequency component wanted by people from the complex signal, but also effectively remove the frequency point of the specific frequency or the frequency outside the frequency point, and the signal is filtered to eliminate the interference noise, so that a pure signal is obtained, the signal is better processed by the microcontroller, the misjudgment condition of the system is reduced, and the anti-interference capability of the system is improved.

A(s) =vo (s)/Vi(s) according to the amplitude-frequency characteristic of the filter circuit; when s=jω, then:

the transmission capacity of the filter circuit to signals with different frequencies can be reflected, and the transmission capacity is an important index for selecting a proper filter circuit. The scheme needs to filter out high-frequency and low-frequency clutter output by the sensor, and simultaneously amplifies noise signals of the characteristics of the sensor, so that the band-pass filter circuit is selected for filtering.

The signal processing circuit is arranged as a second-order band-pass filter circuit, the second-order band-pass filter circuit comprises a low-pass filter circuit formed by C1 and R1 and a high-pass filter circuit formed by C2 and R2, the low-pass filter circuit and the high-pass filter circuit are connected in series, namely when the cut-off frequency omega H of the low-pass filter circuit is larger than the cut-off frequency omega L of the high-pass filter circuit, the low-pass filter circuit and the high-pass filter circuit are connected in series to form the second-order band-pass filter circuit. The band-pass frequency band can be designed according to the requirements, and high-frequency and low-frequency clutter can be filtered. Its function is to attenuate signals with frequencies greater than ωh and less than ωl by signals with frequencies in the range from ωl to ωh.

In calculating the parameters, we let r1=r3=r, r2=2r, c1=c2=c, resulting in a transfer function:

where G is the voltage gain of the in-phase proportional amplifying circuit, which is calculated by the formula g=1+r4/R5. G <3 is required depending on the conditions under which the circuit needs to operate stably. According to the design of the requirement, selecting the values of R and C, and setting the center frequency Fm as follows:

the gain Am at the center frequency Fm is:

the center angular frequency ωm is:

the filter quality factor Q is:

the passband width BW of the bandpass filter circuit is:

based on the above equation, and bringing s=jω into the transfer function of the second order bandpass filter circuit, there is a transfer function that can be deformed as:

the above equation shows that when ω=ωm, the band-pass filter circuit has the maximum voltage gain, then:

is the passband voltage gain of the bandpass filter.

From the above solving process, it is known that the second-order band-pass filter circuit has an advantage that the configuration tone quality Q can be changed by the internal gain G without changing the center frequency fm. The amplitude-frequency response can be obtained from the formula of the transfer function, and therefore, it can be known that the larger the value of Q is, the smaller the value of a is, i.e., the narrower the passband of the filter is. When the absolute value of the denominator imaginary part of the transfer function is 1, then there are:

thus, use is made of

And taking a positive root to obtain two cut-off angular frequencies of the band-pass filter.

From bw=fm/Q, Q can be found as:

from Q, am can be found as:

since g=1+r4/R5, the ratio between R4 and R5 can be obtained after substitution.

The band width of the band-pass filter is: bw=ωh- ωl. The quality factor is q=ω0/BW, ω0 being the center frequency. When the Q value is high, the passband bandwidth is narrow, the filtering effect is good, but the response time is slow, and when the Q value is low, the passband bandwidth is wide, the filtering effect is poor, but the response time is fast. The choice of the appropriate passband bandwidth is critical to the bandpass filter to exhibit good characteristics, depending on the implementation of the device.

The amplifying circuit module is used for amplifying the weak voltage signal output by the pyroelectric infrared PIR detection sensor into an analog signal which can be identified by a subsequent circuit. In general, the amplified signal also contains system noise, and thus a signal processing circuit is required to perform processing such as filtering and denoising.

Because the pyroelectric infrared sensor can monitor the changed output detection signal, the voltage is very weak (usually in mV level), the circuit identification at the rear end is inconvenient, and the amplifying circuit module is set as an OPA2313 operational amplifier, the operational amplifier has the advantages of wide frequency band, low noise, low disturbance and high speed, and the operational amplifier is powered by a 5V power supply and only needs 20mA power supply current.

The signal channel switching module is set to be a miniaturized double-channel analog switch with high integration and patch installation, and the miniaturized double-channel analog switch has the following characteristics: having an input channel select control signal, ch0 is available when the select control signal is 1, and Ch1 is available when the select control signal is 0;

the typical value of the low on-resistance is only 2.7 omega at normal temperature, so that the measurement error caused by the resistance is negligible;

low off current, single channel typical value only 10pA; all address options have very low static dissipation power, typically only 0.2 μw, under all power supply conditions; the static power consumption is low, the power supply burden is reduced, the heating value is greatly reduced, and the service life of the equipment is prolonged;

a wide power supply range and a high cut-off frequency typical value, the power supply range is: the direct current is 1.8V-5.5V, which can meet the requirement of the circuit; the cut-off frequency is typically greater than or equal to 10MHz, and is far higher than the frequency value of the sensor characteristic noise.

The signal channel switching module is connected to the signal input end of the A/D analog-to-digital conversion module, when one sensor has a short circuit fault, the normal operation of other sensors is not affected, and the filtered signals are output to the signal input ends Ch0 to Ch1 of the channel switching IC.

The signal channel switching module comprises an analog switch chip U2, a C77 and a C80 which are arranged in parallel are connected to a pin five of the U2, one end of the C80 is connected with an R81, and a pin six of the U2 is respectively connected with an R82 and an R83.

The resistance of R81 is set to 10 ohms, the resistance of R82 is set to 1 kiloohm, and the resistance of R83 is set to 100 kiloohms.

The signal channel switching module is used for enabling the sampling circuit to multiplex the two paths of signals in a time-sharing mode, the amplified output signals of the two sensors correspond to a special signal processing circuit, the input signals are in two groups in total, each group of signals is subjected to gating switching measurement by using a multi-path analog switch, and only one path of output signals is finally connected to the signal input end of the A/D sampling functional module of the SOC. That is, when one sensor has a short circuit fault, the normal operation of other sensors is not affected. The filtered signals are output to the signal input terminals Ch0 to Ch1 of the channel switching IC. The channel selection end is output by a control signal, any one channel of Ch0 to Ch1 can be gated, and an output signal corresponding to the channel is connected to a detection pin of the A/D analog-to-digital conversion module for sampling processing.

In order to better improve the system precision and eliminate the influence of noise, software filtering is also required to be added in the actual design to optimize the system. When the scheme is designed, the front-end signal is processed by adopting a mode of combining the amplitude limiting filtering algorithm and the anti-shake filtering algorithm, and the specific implementation process is not repeated here because the software part is not important in the scheme.

To sum up, the working process of the scheme is as follows: when the infrared rays radiated by the two pyroelectric infrared PIR detection sensors are focused on the detecting element of the pyroelectric infrared PIR sensor through the Fresnel lens, the pyroelectric infrared PIR sensor outputs a weak signal with a certain voltage, the weak signal is amplified by the signal amplifying module and then sent into the signal processing circuit, and the processed filtering signal is subjected to the multipath switching circuit to output a path of signal which is connected to the signal input end of the A/D sampling functional module of the SOC module. The analog signals are converted into digital signals through the A/D analog-to-digital conversion module, the digital signals are judged by the SOC module according to the rules set by the system, and corresponding mechanisms such as turning off the projector light source or turning off reminding are executed.

Although embodiments of the present utility model have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the utility model, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The pyroelectric infrared protection detection device circuit is characterized by comprising two optical components, two pyroelectric infrared PIR detection sensors, two amplifying circuit modules, two signal processing circuits, a signal channel switching module, an SOC module, an A/D analog-to-digital conversion module and a projector;

the optical component is arranged as a Fresnel lens for effectively concentrating infrared rays of a detection space on the sensor, the Fresnel lens is positioned on one side of the two pyroelectric infrared PIR detection sensors, the amplifying circuit module and the signal processing circuit are sequentially connected, the two signal processing circuits are both connected to the signal channel switching module, the SOC module and the projector are sequentially connected, and the A/D analog-to-digital conversion module is arranged inside the SOC module.

2. The pyroelectric infrared protection detection device circuit of claim 1, wherein: the pyroelectric infrared PIR detection sensor is an energy conversion device.

3. The pyroelectric infrared protection detection device circuit of claim 1, wherein: the signal processing circuit is configured as a second-order band-pass filter circuit comprising a low-pass filter circuit consisting of C1 and R1 and a high-pass filter circuit consisting of C2 and R2.

4. A pyroelectric infrared protection detection device circuit as recited in claim 3 wherein: the low-pass filter circuit and the high-pass filter circuit are connected in series.

5. The pyroelectric infrared protection detection device circuit of claim 1, wherein: the amplifying circuit module is arranged as an operational amplifier, and the operational amplifier is powered by a 5V power supply.

6. The pyroelectric infrared protection detection device circuit of claim 1, wherein: the signal channel switching module is arranged as a miniaturized double-channel analog switch with high integration and surface mounted.

7. The pyroelectric infrared protection detection device circuit of claim 1, wherein: the signal channel switching module is connected to the signal input end of the A/D analog-to-digital conversion module, and the core device of the A/D analog-to-digital conversion module is set as an A/D converter.

8. The pyroelectric infrared protection detection device circuit of claim 1, wherein: the signal channel switching module comprises an analog switch chip U2, a C77 and a C80 which are arranged in parallel are connected to a pin five of the U2, one end of the C80 is connected with an R81, and a pin six of the U2 is respectively connected with an R82 and an R83.

9. The pyroelectric infrared protection detection device circuit of claim 8, wherein: the resistance of R81 is set to 10 ohms, the resistance of R82 is set to 1 kiloohm, and the resistance of R83 is set to 100 kiloohms.