Terminal resistance detection circuit of fire protection product and fire protection product

Abstract

The utility model relates to a terminal resistance detection circuit of a fire protection product and a fire protection product, comprising a power supply, a first voltage-dividing resistor connected to the power supply, the first voltage-dividing resistor being connected to a terminal connection end, the detection circuit also comprising a judgment module connected to the first voltage-dividing resistor, the judgment module is driven to be turned on according to the voltage of the first voltage-dividing resistor after being connected to the terminal connection end, the judgment module is connected to an optical coupler, the conduction state of the judgment module drives the conduction of the optical coupler, the optical coupler is connected to Open and Test and connected to the I / O port of the MCU, Open and Test are also connected to a pull-up resistor and a constant voltage source, the optical coupler or the pull-up resistor and the constant voltage source drive the output level state of Open and Test, and the access condition of the terminal connection end is judged according to the output level state. The circuit can judge three different states of two bus terminals without using ADC voltage detection, thus saving MCU resources; at the same time, since the I / O port is directly used for high and low level detection, the reliability of the detection is also improved.

Description

Technical Field

[0001] The utility model relates to the field of terminal resistance detection of fire protection products, in particular to a terminal resistance detection circuit of fire protection products and a fire protection product. Background Art

[0002] At present, there are three possible states for the two bus terminals of fire protection products: open circuit, short circuit, and connected terminal resistance. Most terminal detection circuits can only detect two of these states. If ADC voltage detection is used, it will occupy additional MCU resources, and external interference received on the bus will also affect the accuracy of ADC voltage detection.

[0003] Chinese patent announcement number CN205862552U discloses a wireless sound and light alarm with line detection function, which has a base and a sound and light alarm connected to the base, and a control circuit connected to the sound and light alarm is arranged inside the base, and the control circuit detects whether the sound and light alarm is online. If the sound and light alarm is offline, the control circuit sends an alarm signal to the wireless fire alarm controller through a wireless communication module; compared with the prior art, the utility model is based on radio signal transmission technology, which can perform real-time detection. Once the sound and light alarm has an offline fault, it can be discovered and eliminated in time to ensure the stability and reliability of the fire alarm system; at the same time, the device is installed in a bottom box, and the old sound and light alarm can be connected to the bottom box, which is convenient for upgrading and transforming the old fire protection system, and has a broad market prospect. The patent uses MCU for judgment, occupies MCU resources, and the detection accuracy is prone to deviation. Utility Model Content

[0004] The technical problem to be solved by the utility model is that most terminal detection circuits can only detect two of the states. If ADC voltage detection is used, it will occupy additional MCU resources, and the external interference received on the bus will also affect the accuracy of ADC voltage detection. In view of the above defects of the prior art, a terminal resistance detection circuit and a fire protection product are provided.

[0005] In order to solve the above technical problems, the technical solution adopted by the utility model is:

[0006] A terminal resistance detection circuit of a fire protection product is constructed, comprising a power supply, a first voltage-dividing resistor connected to the power supply, the first voltage-dividing resistor being connected to a terminal connection end, the detection circuit also comprising a judgment module connected to the first voltage-dividing resistor, the judgment module being driven to conduct according to the voltage of the first voltage-dividing resistor after being connected to the terminal connection end, the judgment module being connected to an optical coupler, the conduction state of the judgment module driving the conduction of the optical coupler, the optical coupler being connected to Open and Test and connected to an I / O port of an MCU, the Open and Test being further connected to a pull-up resistor and a constant voltage source, the optical coupler or the pull-up resistor and the constant voltage source driving the output level state of Open and Test, and the access status of the terminal connection end being judged according to the output level state.

[0007] Preferably, the optocoupler is further connected to the power supply via a second voltage-dividing resistor, and the optocoupler is further connected to the power supply via an anti-interference resistor or a current-limiting resistor.

[0008] Preferably, the judgment module includes a first transistor and a first adjustable parallel regulator, the first transistor and the first adjustable parallel regulator are connected to the power supply through a voltage-dividing resistor, the optocoupler includes a first optocoupler and a second optocoupler, the first transistor is connected to the first optocoupler and connected to Open, and the first adjustable parallel regulator is connected to the second optocoupler and connected to Test.

[0009] Preferably, the voltage-dividing resistor includes a third resistor, a fourth resistor, a sixth resistor and a ninth resistor, one end of the third resistor is connected to the power supply, and the other end is connected to the terminal connection end, one end of the fourth resistor is connected to the first transistor, and the other end is connected to the terminal connection end, the anti-interference resistor includes the tenth resistor, the current-limiting resistor includes the seventh resistor, and the pull-up resistor includes the first resistor and the eighth resistor.

[0010] Preferably, the third resistor is connected to the ninth resistor via the second capacitor, the fourth resistor is connected to the ninth resistor via the third capacitor, and the fourth resistor is connected to the ninth resistor via the sixth resistor.

[0011] Preferably, the fourth resistor is connected to the base of the first transistor, the base and collector of the first transistor are connected through a fifth resistor and a first capacitor arranged in parallel, the collector of the first transistor is grounded, the ninth resistor and the sixth resistor are connected to the reference electrode of the first adjustable parallel regulator, a fourth capacitor is connected between the reference electrode and the anode of the first adjustable parallel regulator, and the anode of the first adjustable parallel regulator is grounded.

[0012] Preferably, the emitter of the first transistor is connected to the first optocoupler, the first optocoupler is connected to the power supply through the second resistor, the first optocoupler is connected to Open and is connected to the constant voltage source through the first resistor, the cathode of the first adjustable parallel regulator is connected to the second optocoupler, the second optocoupler is connected to the power supply through the seventh resistor, and the second optocoupler is connected to Test and is connected to the constant voltage source through the eighth resistor.

[0013] Preferably, the second optocoupler is connected to the seventh resistor via a tenth resistor, and one pin of the secondary transistor of the first optocoupler and the second optocoupler is grounded.

[0014] Preferably, when the Open output is a high level and the Test output is a low level, the terminal connection end is in a short-circuit state; when the Open and Test outputs are both low levels, the terminal connection end is in a load-connected state; when the Open output is a low level and the Test output is a high level, the terminal connection end is in an open-circuit state.

[0015] A fire protection product is constructed, which includes a terminal resistance detection circuit of the fire protection product as described above.

[0016] The beneficial effects of the utility model are: the three different states of the two bus terminals can be judged by the circuit without using ADC voltage detection, thus saving MCU resources; at the same time, since the I / O port is directly used for high and low level detection, the reliability of the detection is also improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the utility model will be further described below in conjunction with the accompanying drawings and embodiments. The drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work:

[0018] Figure 1 A frame diagram of a detection circuit of a preferred embodiment of the utility model;

[0019] Figure 2 A specific circuit diagram of the detection circuit of a preferred embodiment of the utility model;

[0020] Figure 3 This is a truth table for determining a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the embodiments of the utility model clearer, the following will be described clearly and completely in combination with the technical solution in the embodiments of the utility model. Obviously, the described embodiments are partial embodiments of the utility model, not all embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the utility model.

[0022] A terminal resistance detection circuit of a fire protection product in a preferred embodiment of the utility model; Figure 1 As shown, it includes a power supply, and a first voltage-dividing resistor and a second voltage-dividing resistor connected to the power supply, wherein the first voltage-dividing resistor is connected to the terminal connection end so that the terminal is connected to the detection circuit, and the voltage value of the first voltage-dividing resistor after connection is judged and output to the optocoupler, and the optocoupler drives the voltage value of the Open end and the Test end and transmits the voltage value to the I / O end of the MCU to judge the access status of the terminal connection end. The optocoupler is also directly connected to the power supply through the second voltage-dividing resistor, and the optocoupler can also be connected to the optocoupler through the power supply and the anti-interference resistor, or the current-limiting resistor to output the voltage high and low. Open and Test are both connected to the constant voltage source through a pull-up resistor, and the level signal of the I / O end connected to the Open end or the Test end is used to judge whether the terminal connection end is in a short-circuit state, an open-circuit state, or a terminal resistor state.

[0023] Specifically, Figure 2 As shown, the voltage-dividing resistors include a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6 and a ninth resistor R9, the power supply is connected to a 24V voltage, the constant voltage source is connected to a 3.3V voltage, the optical coupling module is provided with two groups of optical couplers, the judgment module adopts a first transistor Q1 and a first adjustable parallel regulator U1, the pull-up resistors include a first resistor R1 and an eighth resistor R8, the anti-interference resistors include a tenth resistor R10, and the current limiting resistors include a seventh resistor R7.

[0024] Furthermore, if Figure 2As shown, the 24V power supply is connected through one end of the third resistor R3, the other end of the third resistor R3 is connected to the first end ALM+ of the terminal connection end, and is connected to the second capacitor C2, the other end of the second capacitor C2 is connected to the third capacitor C3 and the ninth resistor R9, the other end of the ninth resistor R9 is connected to the sixth resistor R6, the other end of the sixth resistor R6 is connected to the other end of the third capacitor C3, and is connected to the second end ALM- of the terminal connection end. For the convenience of subsequent description, the connection end of the sixth resistor R6 and the third capacitor C3 is recorded as the A end, and the connection end of the ninth resistor R9 and the sixth resistor R6 is recorded as the B end, wherein the A end is also connected to the fourth resistor R4 and connected to the first The base of the first transistor Q1 is connected, and a fifth resistor R5 and a first capacitor C1 arranged in parallel are connected between the base and the collector of the first transistor Q1. At the same time, the collector of the first transistor Q1 is grounded, and the emitter of the first transistor Q1 is connected to the first optical coupler OPQ1, specifically connected to the cathode of the primary diode of the first optical coupler, and the anode of the primary diode of the first optical coupler is connected to the 24V power supply through the second resistor R2. One end of the secondary transistor of the first optical coupler is grounded, and the other end is connected to the Open connection end, and is connected to the 3.3V constant voltage source through the first resistor R1, and the Open connection end is connected to the I / O port of the MCU. The B end is connected to the reference end of the first adjustable parallel regulator U1, the anode of the first adjustable parallel regulator U1 is connected to the ninth resistor R9 and grounded, and a fourth capacitor is connected between the anode and the reference end, the cathode of the first adjustable parallel regulator U1 is connected to the second optical coupler OPQ2, specifically connected to the cathode of the primary diode of the second optical coupler, the anode of the primary diode of the second optical coupler is connected to the 24V power supply through the seventh resistor R7, and a tenth resistor R10 is connected between the anode and cathode of the primary diode of the second optical coupler, one end of the secondary transistor of the second optical coupler is grounded, and the other end is connected to the Test connection end, and is connected to the 3.3V constant voltage source through the eighth resistor R8. The Test connection end is connected to the I / O port of the MCU. The different levels of Open and Test can be judged through the I / O port to determine which state the bus is in. The specific judgment truth table is as follows Figure 3 shown.

[0025] Furthermore, Open and Test are connected to the I / O ports of the MCU respectively, and ALM+ and ALM- are short-circuited directly. At this time, the terminal state is in a short-circuit state, and the voltage U at point A is A The calculation method is as follows:

[0026]

[0027] The base voltage U of the first transistor Q1 is b1 The calculation method is as follows:

[0028]

[0029] Since the first transistor Q1 is not turned on, it is equivalent to an open circuit. At this time, no current flows through the first transistor Q1, and no voltage drop occurs across the second resistor R2. The primary diode voltage drop of the first optical coupler OPQ1 is about 1.2V, so the emitter voltage U of the first transistor is e1 =24-1.2=22.8V, that is, by properly configuring the resistance values ​​of the voltage divider resistors R3-R6 and R9, the emitter voltage of the first transistor and the base voltage U e1 -U b1 <0.7V, this voltage difference cannot drive the first PNP transistor to conduct. Since the first transistor is not conducting, it cannot drive the first optical coupler OPQ1, so that the secondary transistor of the first optical coupler is not conducting, and the Open end can be pulled up to 3.3V through the first resistor R1, and Open is at a high level. The voltage at point B U B The calculation method is as follows:

[0030]

[0031] The voltage U at point B can be calculated by the distribution of the above-mentioned voltage divider resistance values. B The voltage exceeds the reference voltage 2.5V of the R pin of the reference source of the first adjustable parallel regulator U1 TL431, so the K pin and A pin of the first adjustable parallel regulator U1 TL431 are turned on, and the cathode voltage of the primary light-emitting diode of the second optical coupler OPQ2 is pulled down. At the same time, the 24V power supply provides a bias voltage for the anode of the primary diode of the second optical coupler through the seventh resistor R7, and plays a current limiting role to drive the secondary transistor of the second optical coupler to turn on, and pull Test down to GND. At this time, Test is displayed as a low level. The tenth resistor R10 set at both ends of the primary diode of the second optical coupler also improves the anti-interference ability.

[0032] In summary, in the short-circuit state, Open is a high level and Test is a low level.

[0033] Connect Open and Test to the I / O ports of the MCU respectively, and connect ALM+ and ALM- to the load. At this time, the terminal state is connected to the terminal resistor R X state, and at this time the voltage at point A is U A The calculation method is as follows:

[0034]

[0035] Since the first transistor Q1 is not turned on, it is equivalent to an open circuit. At this time, no current flows through the first transistor Q1, and no voltage drop occurs across the second resistor R2. The primary diode voltage drop of the first optical coupler OPQ1 is about 1.2V, so the emitter voltage U of the first transistor is e1=24-1.2=22.8V, that is, by properly configuring the resistance values ​​of the voltage divider resistors R3-R6 and R9, the emitter voltage of the first transistor and the base voltage U e1 -U b1 >0.7V, this voltage difference drives the first PNP transistor to turn on. Since the first transistor Q1 is turned on, the primary light-emitting diode of the first optical coupler OPQ1 is pulled down to GND to drive the secondary transistor of the first optical coupler to turn on, and Open is pulled down to GND. At this time, Open is displayed as a low level. It should be noted that although the first resistor and the constant voltage source still exist at this time, after the secondary transistor of the first optical coupler is turned on, there is only one conducting PN junction from the Open end to GND, and the voltage drop of this PN junction is about 0.5V, which is equivalent to the voltage of the Open end being clamped at 0.5V. When the voltage of the I / O port is lower than 0.8V, the MCU will determine that the I / O is at a low level, so the first pull-up resistor does not affect the performance of the Open low level.

[0036] At this time, the voltage at point B is U B The calculation method is as follows:

[0037]

[0038] The voltage U at point B can be calculated by the distribution of the above-mentioned voltage divider resistance values. B It exceeds the reference voltage of 2.5V of the R pin of the reference source TL431 of the first adjustable parallel regulator U1, so the K pin and A pin of the TL431 of the first adjustable parallel regulator U1 are turned on, and the cathode voltage of the primary light-emitting diode of the second optical coupler OPQ2 is pulled down to drive the secondary transistor of the second optical coupler to turn on, and pull Test down to GND. At this time, Test shows a low level.

[0039] In summary, when the terminal resistor or load is connected, Open is a low level and Test is a low level.

[0040] Connect Open and Test to the I / O port of MCU respectively, and disconnect ALM+ and ALM-. At this time, the terminal state is in an open circuit state. Point A will have no voltage, the base of the first transistor Q1 will be pulled down to GND through the fifth resistor, and the collector will be connected to the 24V power supply through the primary light-emitting diode of the first optical coupler and the second resistor, so that the first transistor is turned on to drive the first optical coupler OPQ1 to pull Open down to GND. At this time, Open is displayed as a low level.

[0041] Since there is no voltage at point A, there is no voltage at point B either. Therefore, the K pin and A pin of the first adjustable parallel regulator U1 TL431 are not conducting, and the secondary transistor of the first optocoupler OPQ2 cannot be driven to conduct. At this time, Test is pulled up to 3.3V through the eighth resistor and the 3.3V constant voltage source, and Test is at a high level.

[0042] In summary, in the open circuit state, Open is a low level and Test is a high level.

[0043] A fire protection product of a preferred embodiment of the utility model contains a terminal resistance detection circuit as described above for detecting the terminal resistance to determine the status of the two bus terminals. The specific detection circuit structure is the same as described above and will not be repeated here.

[0044] It should be understood that the present invention is described by some embodiments, and those skilled in the art are aware that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. A terminal resistance detection circuit for a fire protection product, comprising a power supply, a first voltage-dividing resistor connected to the power supply, the first voltage-dividing resistor being connected to a terminal, characterized in that: The detection circuit also includes a judgment module connected to the first voltage-dividing resistor, which drives the judgment module to turn on according to the voltage of the first voltage-dividing resistor after the terminal is connected. The judgment module is connected to an optocoupler, and the on-state of the judgment module drives the optocoupler to turn on. The optocoupler is connected to Open and Test and connected to the I / O port of the MCU. Open and Test are also connected to a pull-up resistor and a constant voltage source. The optocoupler or the pull-up resistor and the constant voltage source drive the output level state of Open and Test, and the access status of the terminal connection end is judged according to the output level state.

2. The detection circuit according to claim 1, characterized in that: The optical coupler is also connected to the power supply through a second voltage-dividing resistor, and the optical coupler is also connected to the power supply through an anti-interference resistor or a current-limiting resistor.

3. The detection circuit according to claim 2, characterized in that: The judgment module includes a first transistor and a first adjustable parallel regulator, the first transistor and the first adjustable parallel regulator are connected to a power supply through a voltage-dividing resistor, the optocoupler includes a first optocoupler and a second optocoupler, the first transistor is connected to the first optocoupler and connected to Open, and the first adjustable parallel regulator is connected to the second optocoupler and connected to Test.

4. The detection circuit according to claim 3, characterized in that: The voltage-dividing resistor includes a third resistor, a fourth resistor, a sixth resistor and a ninth resistor, one end of the third resistor is connected to the power supply, and the other end is connected to the terminal, one end of the fourth resistor is connected to the first transistor, and the other end is connected to the terminal, the anti-interference resistor includes the tenth resistor, the current-limiting resistor includes the seventh resistor, and the pull-up resistor includes the first resistor and the eighth resistor.

5. The detection circuit according to claim 4, characterized in that: The third resistor is connected to the ninth resistor via the second capacitor, the fourth resistor is connected to the ninth resistor via the third capacitor, and the fourth resistor is connected to the ninth resistor via the sixth resistor.

6. The detection circuit according to claim 4, characterized in that: The fourth resistor is connected to the base of the first triode, the base and collector of the first triode are connected through the fifth resistor and the first capacitor arranged in parallel, the collector of the first triode is grounded, the ninth resistor and the sixth resistor are connected to the reference electrode of the first adjustable parallel regulator, the fourth capacitor is connected between the reference electrode and the anode of the first adjustable parallel regulator, and the anode of the first adjustable parallel regulator is grounded.

7. The detection circuit according to claim 3, characterized in that: The emitter of the first transistor is connected to the first optocoupler, the first optocoupler is connected to the power supply through the second resistor, the first optocoupler is connected to Open and is connected to the constant voltage source through the first resistor, the cathode of the first adjustable parallel regulator is connected to the second optocoupler, the second optocoupler is connected to the power supply through the seventh resistor, and the second optocoupler is connected to Test and is connected to the constant voltage source through the eighth resistor.

8. The detection circuit according to claim 7, characterized in that: The second optical coupler is connected to the seventh resistor via the tenth resistor, and the first pin of the secondary transistor of the first optical coupler and the second optical coupler is grounded.

9. The detection circuit according to claim 1, characterized in that: When the Open output is high and the Test output is low, the terminal connection end is in a short-circuit state; when both the Open and Test outputs are low, the terminal connection end is in a load-connected state; when the Open output is low and the Test output is high, the terminal connection end is in an open-circuit state.

10. A fire protection product, characterized in that: The fire protection product includes a terminal resistance detection circuit of a fire protection product as described in any one of claims 1-9.

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