Circuit capable of detecting simultaneous touch of human body on blade and trigger of electric scissors

Abstract

The utility model relates to a circuit capable of detecting that a human body simultaneously touches a blade and a trigger of electric scissors, which utilizes the characteristics of human body resistance and biological alternating current to output sinusoidal waveform signals which are smaller than power supply voltage and have the frequency of 50HZ through an operational amplifier when two hands of the human body respectively touch the blade and the trigger. And the two hands of the person are judged to respectively touch the blade and the trigger through the waveform and the intensity of the signal, so that the detection accuracy is greatly improved. Meanwhile, the circuit is simple in structure, the detection voltage enters the operational amplifier only through the divider resistor and the current-limiting resistor, then the detection result is output from the output end of the operational amplifier, and the corresponding speed is higher.

Description

Technical Field

[0001] The utility model belongs to the technical field of emergency protection circuit devices, and in particular relates to a circuit capable of detecting that a human body touches a blade and a trigger of electric scissors at the same time. Background Art

[0002] At present, electric scissors are selling very well in the market and are widely used in various gardening places. In the process of using electric scissors, if people accidentally touch the blades of the scissors, there is a risk of cutting their hands. Most electric scissors with human touch recognition on the market use "capacitive touch" technology to identify human touch, such as the technical solution disclosed in the utility model patent with patent number 2020221778146 and the name "Anti-hand cutting circuit and scissors". "Capacitive touch" technology identifies human touch by using the human body's own capacitance. This technology has the risk of not being able to identify when there is water on the human hand. At the same time, when the human hand touches the blade, this technology has a certain delay in detection. Therefore, this technology cannot be reliably identified, and the recognition response is slow, posing a safety hazard.

[0003] In view of the above shortcomings, it is necessary to develop a human body touch recognition protection circuit that is safer, more reliable and more responsive. Utility Model Content

[0004] The technical problem to be solved by the utility model is: a circuit that can detect when a human body touches the blade and the trigger of an electric scissors at the same time, thereby solving the technical problems of low detection reliability and slow recognition response of a traditional human body touch recognition circuit based on "capacitive touch" technology.

[0005] In order to solve the above technical problems, the technical solution adopted by the utility model is: a circuit that can detect when a human body touches the blade and trigger of an electric scissors at the same time, including an operational amplifier, the positive power pin and the negative power pin of the operational amplifier are connected to a power supply, the positive input terminal of the operational amplifier is connected in parallel with a second diode and a current limiting resistor, the other end of the current limiting resistor is connected in parallel with a voltage divider resistor, the blade of the electric scissors and a first diode, the positive electrode of the first diode is connected to the trigger of the electric scissors and grounded, the cathode of the first diode is connected to the current limiting resistor, the other end of the voltage divider resistor is connected to a detection voltage, the cathode of the second diode is connected to a positive voltage, the negative input terminal of the operational amplifier is connected to an output terminal, the output terminal is used to connect to the main control chip of the electric scissors, and the voltage of the power supply is the same as the detection voltage and the positive voltage connected to the cathode of the second diode.

[0006] As a preferred solution, a first filter capacitor is also connected in parallel to the positive input terminal of the operational amplifier, and the other end of the first filter capacitor is grounded.

[0007] As a preferred solution, a second filter capacitor is also connected in parallel to the positive power supply pin of the operational amplifier, and the other end of the second filter capacitor is grounded.

[0008] As a preferred solution, the voltage-dividing resistor has a resistance value greater than the resistance value between two hands of a human body.

[0009] As a preferred solution, the voltage-dividing resistor has a resistance value of 1 MΩ to 3 MΩ.

[0010] As a preferred solution, the power supply is 5V.

[0011] The beneficial effects of the utility model are as follows: the utility model utilizes the characteristics of human body resistance and biological alternating current, and when a person's two hands touch the blade and the trigger respectively, the operational amplifier outputs a sine waveform signal with a frequency of 50HZ and a voltage lower than the power supply voltage, and determines whether the person's two hands touch the blade and the trigger respectively by the waveform and strength of the signal, thereby greatly improving the detection accuracy. At the same time, the utility model has a simple circuit structure, and the detection voltage enters the operational amplifier only through the voltage divider resistor and the current limiting resistor, and then the detection result is output from the output end of the operational amplifier, and the response speed is faster. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The specific implementation of the utility model is further described in detail below with reference to the accompanying drawings, wherein:

[0013] Figure 1 The utility model is a circuit diagram of a circuit capable of detecting that a human body touches a blade and a trigger of electric scissors at the same time. DETAILED DESCRIPTION

[0014] The specific implementation scheme of the utility model is described in detail below in conjunction with the accompanying drawings.

[0015] like Figure 1 A circuit that can detect that a human body touches the blade and trigger of an electric scissors at the same time is shown, including an operational amplifier U2, the positive power supply pin 5 and the negative power supply pin 2 of the operational amplifier are connected to a power supply, the positive input terminal 3 of the operational amplifier U2 is connected in parallel with a second diode D2 and a current limiting resistor R3, the other end of the current limiting resistor R3 is connected in parallel with a voltage divider resistor R1, the blade of the electric scissors BJ and a first diode D1, the positive electrode of the first diode D1 is connected to the trigger of the electric scissors BJ-Gnd and grounded, the negative electrode of the first diode D1 is connected to the current limiting resistor R3, the other end of the voltage divider resistor R1 is connected to the detection voltage, the negative electrode of the second diode D2 is connected to the positive voltage, the negative input terminal 4 of the operational amplifier U2 is connected to the output terminal 1, and the output terminal 1 is used to connect the main control chip of the electric scissors, and the voltage of the power supply is the same as the detection voltage and the positive voltage connected to the negative electrode of the second diode D2, and in this embodiment, they are all 5V. In practical applications, the voltage of the power supply, the detection voltage, and the positive voltage connected to the negative electrode of the second diode can be increased or decreased according to the actual needs of the operational amplifier U2.

[0016] The positive input terminal 3 of the operational amplifier U2 is also connected in parallel with a first filter capacitor C6, and the other end of the first filter capacitor C6 is grounded. The first filter capacitor C6 can stabilize the voltage input to the operational amplifier U2 and improve the accuracy of the signal output from the output terminal 1 of the operational amplifier U2.

[0017] The positive power supply pin of the operational amplifier U2 is also connected in parallel with a second filter capacitor C13, and the other end of the second filter capacitor C13 is grounded. The second filter capacitor C13 can stabilize the power supply voltage of the operational amplifier U2, so that the maximum output voltage of the operational amplifier U2 remains stable, and improves the accuracy of the final output signal of the output terminal 1 of the operational amplifier U2.

[0018] In this embodiment, the resistance of the voltage divider resistor R1 is greater than the resistance between the human hands. This can significantly increase the drop in the output voltage of the output terminal 1 of the operational amplifier U2 when the human hands touch the blade and the trigger respectively, further improving the detection accuracy.

[0019] Since the resistance between the human hands fluctuates within a certain range, the greater the resistance of the voltage-dividing resistor R1 is than that between the human hands, the more it can weaken the difference in detection signals caused by the resistance change between the hands. Therefore, it is preferable that the resistance of the voltage-dividing resistor R1 is greater than the resistance between the hands.

[0020] In this embodiment, the resistance of the voltage divider resistor R1 is preferably set to 1MΩ-3MΩ, and more preferably to 2MΩ.

[0021] When the circuit capable of detecting that the human body touches the blade and trigger of the electric scissors at the same time is used for contact detection, the electric scissors main control chip is used to detect the signal HB having a sinusoidal waveform and a voltage less than the power supply voltage to determine whether the human body touches the blade and trigger of the electric scissors with both hands at the same time. Such a detection result is more accurate.

[0022] The working principle of the utility model is: combining Figure 1 When the human hand does not touch BJ or BJ_Gnd, the output terminal 1 of the operational amplifier U2 outputs a 5V straight line signal. When the human hand touches BJ or BJ_Gnd alone, the detection signal HB detects a sine wave signal with an upper rail of 5V. When the human hand touches the blade and the trigger at the same time, a resistor is formed between BJ and BJ_Gnd, which lowers the voltage at the BJ end. The output terminal 1 of the operational amplifier U2 outputs a voltage below 5V. At the same time, due to the characteristics of the human body's own 50HZ physiological alternating current, the detection signal HB output by the output terminal 1 of the operational amplifier U2 is a 50HZ sine signal. When the main control chip MCU of the electric scissors detects a voltage below 5V and a 50HZ sine signal, it quickly controls the blade to pop open, thereby preventing the user from being cut by the blade of the electric scissors.

[0023] The above embodiments are only illustrative of the principles and effects of the invention, as well as some embodiments of its application, and are not intended to limit the invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the invention, and all of these belong to the protection scope of the invention.

Claims

1. A circuit capable of detecting a human body touching a blade and a trigger of electric scissors simultaneously, characterized in that: The utility model comprises an operational amplifier, wherein the positive power supply pin and the negative power supply pin of the operational amplifier are connected to a power supply, a second diode and a current limiting resistor are connected in parallel to the positive input terminal of the operational amplifier, a voltage divider resistor, an electric scissors blade and a first diode are connected in parallel to the other end of the current limiting resistor, the positive electrode of the first diode is connected to the trigger of the electric scissors and grounded, the negative electrode of the first diode is connected to the current limiting resistor, the other end of the voltage divider resistor is connected to a detection voltage, the negative electrode of the second diode is connected to a positive voltage, the negative input terminal of the operational amplifier is connected to an output terminal, the output terminal is used to connect to a main control chip of the electric scissors, and the voltage of the power supply is the same as the detection voltage and the positive voltage connected to the negative electrode of the second diode.

2. The circuit capable of detecting a human body touching the blade and trigger of electric scissors at the same time according to claim 1, characterized in that: The positive input terminal of the operational amplifier is also connected in parallel with a first filter capacitor, and the other end of the first filter capacitor is grounded.

3. The circuit capable of detecting a human body touching the blade and trigger of electric scissors at the same time according to claim 1, characterized in that: The positive power supply pin of the operational amplifier is also connected in parallel with a second filter capacitor, and the other end of the second filter capacitor is grounded.

4. The circuit capable of detecting a human body touching the blade and trigger of electric scissors at the same time according to claim 1, characterized in that: The voltage-dividing resistor has a resistance value greater than the resistance value between two hands of a human body.

5. The circuit capable of detecting a human body touching the blade and trigger of electric scissors simultaneously according to claim 4, characterized in that: The voltage divider resistor has a resistance value of 1MΩ to 3MΩ.

6. The circuit capable of detecting a human body touching the blade and trigger of electric scissors simultaneously according to claim 1, characterized in that: The power supply is 5V.

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