KR960004255B1 - Sensing temperature compensating circuit - Google Patents

Abstract

The infrared sensor is for detecting the infrared energy radiated in a human body. The infrared sensor includes a pyroelectric infrared sensor(12) for detecting infrared energy, a first amplifier(30) for amplifying output signal of the pyroelectric infrared sensor(12), a first thermistor(32) for varying the amplification of the first amplifier(30), a second amplifier(34) for amplifying output signal of the first amplifier(30), and a second thermistor(36) for varying the amplification gain of the first amplifier(30).

Description

Temperature compensation hot wire detection sensor circuit

1 is a block diagram of a conventional hot wire detection sensor,

2 is a circuit diagram of a conventional hot wire detection sensor,

3 is a circuit diagram of an amplification unit of a heat ray detection sensor for temperature compensation of the present invention;

4 is a thermistor characteristic curve of the present invention.

The present invention relates to a hot wire detection sensor that outputs a signal by detecting infrared energy emitted from the human body, and in particular, a hot wire detection sensor circuit that accurately detects the movement of the human body and outputs an alarm signal even when the temperature is similar to or slightly larger than the temperature of the human body. It is about.

Nowadays, the reverse line sensor is useful in many aspects of living spaces such as flashing lights, passenger chime signals and anti-theft bells. In the present invention, the chime is output by detecting the movement of the human body to prevent theft. In addition, the application of the field of use is widely applied to many other fields.

In general, all objects, including the human body, walls, floors, buildings, and the like radiate energy in their own region with respect to each surface temperature. Pyroelectric Infrared Sensor is a sensor that detects infrared energy emitted according to the temperature of the human body. Typically, the intrinsic bandwidth of the wavelength sensed by the pyroelectric sensor is about 7-14 μm. The reason for having the inherent bandwidth as described above is to allow the pyroelectric sensor to respond only to temperature changes near the human body temperature.

1 is a block diagram of a conventional hot wire detection sensor. The heat ray detection sensor includes a light collector 10 for collecting infrared energy according to a temperature of an object through a reflector, and a pyroelectric element for converting and outputting only infrared energy according to a human body temperature among the energy collected by the light collector 10. Comparing a sensor 12, an amplifier 14 for amplifying and outputting an electric signal output from the pyroelectric sensor 12 by a predetermined amount, and comparing the voltage output from the amplifier 14 with a preset reference voltage Comparing unit 16 for outputting a signal when the set value or more, and the transmitting unit 18 for outputting an alarm signal by the signal output from the comparing unit 16.

The amplifier 14 and comparator 16 in FIG. 1 are shown as a specific circuit in FIG.

First, in the description of the operation of the conventional hot wire detection sensor with reference to FIGS. 1 and 2, it will be described under the assumption that the ambient temperature is not less than the temperature of the human body.

Reference is first made to FIG. The infrared energy radiated according to the temperature of the object has a region of a natural frequency, and is condensed by the light collector 10 through a reflector. The light collector 10 focuses the infrared energy of the near area around the sensor through the reflector to focus the optical filter of the pyroelectric sensor 12. In the pyroelectric sensor 12 composed of an optical filter and a FET, the optical filter detects only an infrared region emitted from the human body and outputs a signal, and the FET inputs a signal passing through the optical filter to change the input signal, that is, temperature It operates when there is a change of (calorie change), and outputs it as an electrical signal.

Here, since the ambient temperature of the pyroelectric sensor 12 is assumed to be similar to the temperature of the human body, the change in the signal input to the pyroelectric sensor 12 is weak, and the amount of the signal converted into the electrical signal is also reduced. The amplifier 14 amplifies and outputs a weak signal output from the pyroelectric sensor 12 with a constant amplification coefficient.

The amplifier 14 of FIG. 1 is composed of two stages as the first amplifier 14a and the second amplifier 14b, as specifically shown in FIG. The reason why the amplifier is implemented in two stages as described above is that the signal output from the pyroelectric sensor 12 is input regardless of the input terminal of the inverting terminal (-) of the OP amplifier or the non-inverting terminal (+) and has the same sign as the input signal. This is to amplify and output the signal of, and to prevent oscillation that can occur when amplifying a large voltage at once.

The comparator 16 compares the amplified signal Vmaf output from the amplifying unit 14 with the reference set voltage Vref preset as an input and outputs a signal Vack when the reference set voltage Vref is greater than or equal to the reference set voltage Vref. Here, the reference set voltage Vref is a value of the minimum amount of heat generated in the human body. At this time, since the signal Vamf output from the amplifier 14 is smaller than the reference set voltage Vref, the signal Vack is not output. Therefore, the transmitter 18 does not output the alarm signal ALRM because the signal Vack is not output from the comparator 16.

As described above, when the temperature around the sensor is equal to or greater than the temperature of the human body, a change in the amount of heat inputted into the pyroelectric sensor (change in temperature) decreases and a signal value converted into an electrical signal decreases. In the case of a conventional hot wire detection sensor, when the temperature around the sensor is near the human body temperature, the alarm is not generated because the signal is not output because the sensor's temperature is less than the reference set value even though the human body's temperature is detected, converted, and amplified and output. Has been a problem.

Accordingly, an object of the present invention is to provide a hot wire detection sensor circuit that outputs an alarm signal by detecting the motion of the human body even when the temperature of the human body is similar to or slightly larger than the human body temperature.

Another object of the present invention is to provide a hot wire detection sensor circuit for accurately detecting the temperature emitted from the human body to the ambient temperature change of the hot wire detection sensor to alert.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The condenser 10, the pyroelectric sensor 12, the comparator 16, and the transmitter 18 of FIG. 1 of the conventional heat ray detection sensor are the same as the circuit configuration of the present invention, and thus, these components are omitted in FIG. It should be noted that

Therefore, Figure 3 shows in detail the amplifier of the temperature compensation recessive detection sensor of the present invention. The configuration of FIG. 3 includes a first amplifier 30 for amplifying a small amount of electrical signal output from the pyroelectric sensor 12 as an input, and a first negative amplifier variable near the human body temperature to a large negative temperature resistance value. A first thermistor 32 for varying the degree of amplification of 30, a second amplifier 34 for amplifying and outputting a signal output from the first amplifier 30 again, a first thermistor 32, It consists of the 2nd thermistor 34 which shows the same characteristic. It becomes a means for varying so that the amplification gain of the said 1st, 2nd thermistor 32,34 may become large.

4 shows the temperature characteristic curves of the first and second thermistors 32 and 34.

Referring now to FIGS. 3 and 4, the small amount of electrical signal Vp output from the pyroelectric sensor 12 of FIG. 1 is input to the first amplifier 30. The first and second thermistors (THRI) 2 and 32 and 36 have negative temperature characteristics. Referring to the embodiment of the negative temperature characteristic with reference to the temperature characteristic curve of FIG. When the temperature is lower than the human body's temperature (about 30 ° C), it has a low value of swelling. The first amplifier 30 is the first amplification of a sufficiently large voltage when near the human body temperature due to the change in resistance to the temperature change of the first thermistor 32 in response to the input of the minute amount of the electrical signal (Vp) Output the signal VAF1. The second amplifier 34 also outputs the second amplified signal VAF2 in the same operation as that of the first amplifier 30 and the first thermistor 32.

The reason why the amplifier is implemented in two stages is that the electrical signal Vp output from the pyroelectric sensor (12 in FIG. 1) is input to either the input terminal of the inverting terminal of the amplifier or the input terminal of the non-inverting terminal. Even if the signal VAF2 having the same sign as the input signal is amplified and output.

The amplified signal VAF2 output from the second amplifier 34 is input to the comparator (16 in FIG. 1).

When the appearance of the human body is detected, the comparator (16 in FIG. 1) becomes a transmitter (18 in FIG. Output the signal with). The transmitter (18 in FIG. 1) outputs an alarm signal ALRM by the signal output from the comparator 16. FIG.

Hereinafter, the operation of controlling the amplification gain in the amplifier of FIG. 3 when the temperature around the pyroelectric sensor 12 is near the human body temperature will be described in more detail. In the following description of the operation, the thermistors 32 and 34 connected to the inverting terminals (-) of the amplifiers 30 and 32 are the same device and have the same characteristics, so only the thermistor 32 will be referred to. However, it should be noted that the application is also applied to the thermistor 34.

The signal output from the pyroelectric sensor 12 is input to the non-inverting terminal (-) of the OPD amplifier which is the amplifier 30.

Since the thermistor 32 hardly operates when the ambient temperature is below the basic room temperature (25 ° C.), the first amplifier 30 performs the same amplification operation as the conventional amplifier 30 shown in FIG. However, when the ambient temperature is between 25 ° C and 35 ° C, that is, when the ambient temperature is similar to that of the human body, the first thermistor 32 has a large gradient with respect to the temperature as shown in the characteristic curve of FIG. Negative resistance characteristics are shown, and lower resistance values are obtained at room temperature (25 ° C). Since the resistance value THR1 of the first thermistor 32 is maintained at a much larger value than the value of the resistance R2, the resistance value of the resistance R2 compared to the resistance value THR1 of the first thermistor 32 is negligible. to be.

Therefore, due to the decrease in the resistance value THR1 of the first thermistor 32, the first amplifier 30 exhibits a higher degree of amplification than at room temperature. The second amplifier 34 connected to the next stage also amplifies again with the same amplification degree as the first amplifier 30.

The calculation formulas of the amplification degrees Av1 and Av2 of the first and second amplifiers 30 and 34 are as follows.

Amplification degree Av1 = 1 + (R3 / R2 + THR1) of the first amplifier 30

Amplification degree Av2 = 1 + (R6 / R5 + THR2) of the second amplifier 34

Looking at the fraud calculation formula, it can be easily seen that the amplification degree increases as the resistance value THR1 of the first thermistor 32 and the resistance value THR2 of the first thermistor 32 decrease.

Since the amplified value is sufficiently larger than the reference set value Vref of the comparison unit 16 shown in FIG. 2, the comparison unit 16 outputs a signal Vack to the transmitter 18. As a result, the transmitter 18 outputs an alarm ALRM.

As described above, the present invention outputs a signal by accurately detecting the amount of heat of the human body by increasing the degree of amplification by the voltage variation of the temperature compensation circuit even if the signal value output from the pyroelectric sensor is small due to the increase in the ambient temperature.

The present invention as described above can prevent the malfunction of the sensor due to the temperature rise has the advantage of bringing a stable operation of the hot wire detection sensor.

Claims (2)

A hot wire detection sensor circuit for notifying the appearance of a human body, comprising: a pyroelectric sensor for detecting a change in temperature of a human body due to the movement of a human body and outputting the detected body position temperature change as a motion detection signal, and a motion output from the pyroelectric sensor An amplifier for amplifying the sensed signal with a predetermined amplification gain, and an amplifying gain variable portion for varying the amplification gain by using the negative temperature characteristic of the internal resistance such that the amplification gain of the amplifier is increased in the vicinity of the human body temperature. Circuit. The method of claim 1, wherein the amplification gain variable portion, the resistance of the variable variable gain gain has a negative temperature characteristic, when the ambient temperature of the pyroelectric sensor is similar to the human body temperature, the value of the resistance is lowered and the ambient of the earth sensor And a negative temperature characteristic thermistor in which the resistance is high when the temperature is at least lower than the human body temperature.