Pulse modulation circuit of photoelectric sensor

Abstract

The utility model discloses a photoelectric sensor pulse modulation circuit which comprises an RC charging and discharging circuit, a Schmitt trigger U2 and a photoelectric device driving circuit. The Schmitt trigger U2 is connected with the RC charging and discharging circuit, the Schmitt trigger U2 and the RC charging and discharging circuit are connected with the photoelectric device driving circuit, the RC charging and discharging circuit is used for generating oscillation time, and the photoelectric device driving circuit is used for driving a large-current device to operate. According to the utility model, the RC charging and discharging circuit is used for generating oscillation time; the arranged Schmitt trigger U2 is a NOT gate circuit and can realize level inversion; the photoelectric device driving circuit can be used for driving large-current devices such as a photoelectric sensor and the like; by means of the arrangement, the frequency and duty ratio modulation function of the photoelectric sensor is achieved, and frequency modulation is stable.

Description

Technical Field

[0001] The utility model relates to the technical field of industrial measurement and control equipment, in particular to a photoelectric sensor pulse modulation circuit. Background Art

[0002] An electrical sensor is a device that converts light signals into electrical signals. Its working principle is based on the photoelectric effect. The photoelectric effect refers to the phenomenon that when light shines on certain substances, the electrons of the substance absorb the energy of photons and produce corresponding electrical effects. According to the different photoelectric effect phenomena, the photoelectric effect is divided into three categories: external photoelectric effect, internal photoelectric effect and photovoltaic effect.

[0003] Since photoelectric sensors usually use visible red light with wavelengths of 650nm, 660nm, 680nm, etc., which are more common in nature, they are easily disturbed by ambient light, causing the sensor to malfunction. A common solution is to modulate the emitted light to a specific frequency, so that the sensor will only trigger an action when it receives this specific frequency signal, thereby reducing the impact of ambient light on it.

[0004] There are many traditional optical frequency modulation methods, but most of them have disadvantages such as being complex to implement or being costly.

[0005] The following are three common measurement methods:

[0006] 1. MCU modulation: PWM modulation (pulse width modulation) is performed using the built-in timer of the MCU. This method has the characteristics of high stability, but it is expensive because it requires the use of a microcontroller chip (single-chip microcomputer); 2. Crystal oscillator modulation: A crystal oscillator is used to generate a specific frequency, and the generated signal is amplified to drive the subsequent photoelectric device to work. This method can generate a stable frequency signal, but it cannot modulate the pulse width, and the circuit is complex; 3: Oscillation circuit modulation: The Wien bridge oscillator, double-T oscillator, square wave oscillator, etc. composed of operational amplifiers are characterized by simple circuit principles, but the circuit is complex, the stability is poor, and the frequency is greatly affected by temperature. For this reason, we propose a photoelectric sensor pulse modulation circuit. Utility Model Content

[0007] The utility model aims to provide a photoelectric sensor pulse modulation circuit to solve the problems raised in the background technology.

[0008] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: a photoelectric sensor pulse modulation circuit, including an RC charge and discharge circuit, a Schmitt trigger U2 and a photoelectric device driving circuit; the Schmitt trigger U2 is connected to the RC charge and discharge circuit, the Schmitt trigger U2 and the RC charge and discharge circuit are connected to the photoelectric device driving circuit, the RC charge and discharge circuit is used to generate an oscillation time, and the photoelectric device driving circuit is used to drive a large current device to operate.

[0009] Furthermore, the RC charge and discharge circuit includes a diode D1, a diode D2, a resistor R2, a resistor R5, and a capacitor C2, the A pin of the Schmitt trigger U2 is connected to the positive electrode of the diode D1, the diode D2 is connected between the A pin of the Schmitt trigger U2 and the diode D1, the cathode of the diode D1 is connected to the resistor R2, the positive electrode of the diode D2 is connected to the resistor R5, the resistor R2 and the resistor R5 are connected to the photoelectric device driving circuit, the A pin of the Schmitt trigger U2 is connected to the capacitor C2, the Y pin of the Schmitt trigger U2 is connected to the resistor R2 and the resistor R5, and the VCC pin of the Schmitt trigger U2 is connected to the capacitor C1.

[0010] Furthermore, the photoelectric device driving circuit includes a MOS tube U1, a resistor R1, a resistor R3, a resistor R4, and a photoelectric device LD1. The resistor R1 is connected to the RC charge and discharge circuit, the resistor R1 is connected to the MOS tube U1, the MOS tube U1 is connected to the resistor R4, and the resistor R4 is connected to the photoelectric device LD1.

[0011] Furthermore, a resistor R3 is connected between the MOS tube U1 and the resistor R1.

[0012] Furthermore, the diode D1 is connected to the gate of the MOSFET U1, and the drain of the MOSFET U1 is connected to the resistor R4.

[0013] Compared with the prior art, the utility model has the following beneficial effects: the utility model sets an RC charging and discharging circuit to generate oscillation time; the Schmitt trigger U2 is a NOT gate circuit, which can realize level inversion; and the photoelectric device driving circuit can drive large current devices such as photoelectric sensors; such a setting realizes the frequency and duty cycle modulation function of the photoelectric sensor, and the frequency modulation is stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the system principle of the utility model;

[0015] Figure 2 This is a circuit diagram of the utility model;

[0016] Figure 3This is a schematic diagram of the RC charging and discharging circuit of the utility model;

[0017] Figure 4 This is a schematic diagram of a driving circuit for a photoelectric device of the utility model. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0019] See also Figure 1-Figure 4 The utility model provides a technical solution: a photoelectric sensor pulse modulation circuit, including an RC charging and discharging circuit, a Schmitt trigger U2 and a photoelectric device driving circuit; the Schmitt trigger U2 is connected to the RC charging and discharging circuit, the Schmitt trigger U2 and the RC charging and discharging circuit are connected to the photoelectric device driving circuit, the RC charging and discharging circuit is used to generate an oscillation time, and the photoelectric device driving circuit is used to drive a large current device to operate.

[0020] Among them, an RC charging and discharging circuit is set up to generate oscillation time; the Schmitt trigger U2 is set as a NOT gate circuit, which can realize level inversion; and the photoelectric device driving circuit can drive large current devices such as photoelectric sensors; such a setting realizes the frequency and duty cycle modulation function of the photoelectric sensor, and the frequency modulation is stable.

[0021] See also Figure 1 , Figure 2 and Figure 3 The RC charge and discharge circuit includes a diode D1, a diode D2, a resistor R2, a resistor R5, and a capacitor C2. The A pin of the Schmitt trigger U2 is connected to the positive electrode of the diode D1. The diode D2 is connected between the A pin of the Schmitt trigger U2 and the diode D1. The cathode of the diode D1 is connected to the resistor R2. The positive electrode of the diode D2 is connected to the resistor R5. The resistor R2 and the resistor R5 are connected to the photoelectric device driving circuit. The A pin of the Schmitt trigger U2 is connected to the capacitor C2. The Y pin of the Schmitt trigger U2 is connected to the resistor R2 and the resistor R5. The VCC pin of the Schmitt trigger U2 is connected to the capacitor C1.

[0022] Among them, Schmitt trigger U2 is a non-gate inverting circuit composed of Schmitt, resistor R4 is a current limiting resistor of the photoelectric device, capacitor C1 is a bypass capacitor of Schmitt trigger U2, when the circuit is started, the A pin of Schmitt trigger U2 is low level, Schmitt trigger U2 is a non-gate inverter, the Y pin of Schmitt trigger U2 outputs a high level at this time, the right end of resistor R5 is high level, the current charges capacitor C2 through resistor R5 and diode D2, the voltage at the end of capacitor C2 gradually increases, and when it reaches the positive threshold voltage of the A pin of Schmitt trigger U2, the Y pin of Schmitt trigger U2 outputs a low level. Capacitor C2 is discharged through diode D1 and resistor R2, and when the voltage at the A pin of Schmitt trigger U2 reaches the negative threshold voltage, it enters the next cycle, and thus a square wave signal oscillates back and forth.

[0023] By changing the resistance values ​​of resistors R2 and R5, the pulse width can be adjusted (duty cycle). When the resistance R5 increases, the pulse duty cycle increases, and when the resistance R2 decreases, the pulse duty cycle decreases. By adjusting the resistance values ​​of resistors R2 and R5, the pulse frequency can be changed. When the resistance values ​​of resistors R2 and R5 decrease, the modulation frequency increases. Therefore, the resistance values ​​of resistors R2 and R5 are inversely proportional to the modulation frequency.

[0024] Frequency adjustment can also be achieved by changing the size of capacitor C2. As the capacitance of capacitor C2 decreases, the modulation frequency increases. Therefore, the capacitance of capacitor C2 is inversely proportional to the modulation frequency.

[0025] See also Figure 1 , Figure 2 and Figure 4 The photoelectric device driving circuit includes a MOS tube U1, a resistor R1, a resistor R3, a resistor R4, and a photoelectric device LD1. The resistor R1 is connected to the RC charge and discharge circuit, the resistor R1 is connected to the MOS tube U1, the MOS tube U1 is connected to the resistor R4, the resistor R4 is connected to the photoelectric device LD1, the photoelectric device LD1 is a photoelectric sensor, the diode D1 is connected to the gate of the MOS tube U1, and the drain of the MOS tube U1 is connected to the resistor R4.

[0026] Among them, the PWM signal modulated by the RC charge and discharge circuit is input to the MOS tube U1 through the resistor R1. The MOS tube U1 adopts an N-type MOSFET, and the gate of the MOS tube U1 is controlled to realize the conduction and cutoff of the MOS tube U1. The resistor R1 is the gate resistor of the MOS tube U1, which is used to eliminate the ringing effect of the MOS tube U1 and prevent the MOS tube U1 from breaking down due to the ringing effect; the resistor R4 is the current limiting resistor of the photoelectric device LD1, which protects the photoelectric device LD1;

[0027] When the PWM signal is at a high level, the gate of the MOSFET U1 is at a high level, at which time the MOSFET U1 is cut off, no current flows through the resistor R4, and the photoelectric device LD1 is in an off state; when the PWM signal is at a low level, the gate of the MOSFET U1 is at a low level, at which time the MOSFET U1 is turned on, and the current flows to the photoelectric device LD1 through the resistor R4, and the photoelectric device LD1 is in a light-emitting state.

[0028] See also Figure 4 A resistor R3 is connected between the MOS tube U1 and the resistor R1, wherein the resistor R3 is a gate pull-down resistor of the MOS tube U1 to reduce the distortion of U1.

[0029] When in use, first, the Schmitt trigger U2 is a non-gate inverting circuit composed of Schmitt, the resistor R4 is the current limiting resistor of the photoelectric device, and the capacitor C1 is the bypass capacitor of the Schmitt trigger U2. When the circuit is started, the A pin of the Schmitt trigger U2 is a low level, the Schmitt trigger U2 is a non-gate inverter, and the Y pin of the Schmitt trigger U2 outputs a high level at this time. The right end of the resistor R5 is a high level, and the current charges the capacitor C2 through the resistor R5 and the diode D2. The voltage at the end of the capacitor C2 gradually increases. When it reaches the positive threshold voltage of the A pin of the Schmitt trigger U2, the Y pin of the Schmitt trigger U2 outputs a low level. Capacitor C2 is discharged through diode D1 and resistor R2. When the voltage at pin A of Schmitt trigger U2 reaches the negative threshold voltage, the next cycle is entered, and a square wave signal oscillates back and forth. By changing the resistance values ​​of resistors R2 and R5, the pulse width can be adjusted (duty cycle). When resistor R5 increases, the pulse duty cycle increases, and when resistor R2 decreases, the pulse duty cycle decreases. By adjusting the resistance values ​​of resistors R2 and R5, the pulse frequency can be changed. When the resistance values ​​of resistors R2 and R5 decrease, the modulation frequency increases. Therefore, the resistance values ​​of resistors R2 and R5 are inversely proportional to the modulation frequency. Frequency adjustment can also be achieved by changing the size of capacitor C2. When the capacitance value of capacitor C2 decreases, the modulation frequency increases. Therefore, the capacitance value of capacitor C2 is inversely proportional to the modulation frequency. The PWM modulated by the RC charge and discharge circuit The signal is input to the MOS tube U1 through the resistor R1. The MOS tube U1 adopts an N-type MOSFET. The gate of the MOS tube U1 is controlled to realize the conduction and cutoff of the MOS tube U1. The resistor R1 is the gate resistor of the MOS tube U1, which is used to eliminate the ringing effect of the MOS tube U1 and prevent the MOS tube U1 from breaking down due to the ringing effect; the resistor R4 is the current limiting resistor of the photoelectric device LD1, which protects the photoelectric device LD1; when the PWM signal is at a high level, the gate of the MOS tube U1 is at a high level, at this time the MOS tube U1 is cut off, no current passes through the resistor R4, and the photoelectric device LD1 is in an off state; when the PWM signal is at a low level, the gate of the MOS tube U1 is at a low level, at this time the MOS tube U1 is turned on, and the current flows to the photoelectric device LD1 through the resistor R4, and at this time the photoelectric device LD1 is in a light-emitting state.

[0030] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A photoelectric sensor pulse modulation circuit, characterized in that: It includes an RC charge and discharge circuit, a Schmitt trigger U2 and a photoelectric device driving circuit; the Schmitt trigger U2 is connected to the RC charge and discharge circuit, the Schmitt trigger U2 and the RC charge and discharge circuit are connected to the photoelectric device driving circuit, the RC charge and discharge circuit is used to generate an oscillation time, and the photoelectric device driving circuit is used to drive a large current device to operate.

2. A photoelectric sensor pulse modulation circuit according to claim 1, characterized in that: The RC charge and discharge circuit includes a diode D1, a diode D2, a resistor R2, a resistor R5, and a capacitor C2. The A pin of the Schmitt trigger U2 is connected to the positive electrode of the diode D1, and a diode D2 is connected between the A pin of the Schmitt trigger U2 and the diode D1. The cathode of the diode D1 is connected to the resistor R2, and the positive electrode of the diode D2 is connected to the resistor R5. The resistor R2 and the resistor R5 are connected to the photoelectric device driving circuit, the A pin of the Schmitt trigger U2 is connected to the capacitor C2, the Y pin of the Schmitt trigger U2 is connected to the resistor R2 and the resistor R5, and the VCC pin of the Schmitt trigger U2 is connected to the capacitor C1.

3. A photoelectric sensor pulse modulation circuit according to claim 2, characterized in that: The photoelectric device driving circuit includes a MOS tube U1, a resistor R1, a resistor R3, a resistor R4 and a photoelectric device LD1. The resistor R1 is connected to the RC charge and discharge circuit, the resistor R1 is connected to the MOS tube U1, the MOS tube U1 is connected to the resistor R4, and the resistor R4 is connected to the photoelectric device LD1.

4. A photoelectric sensor pulse modulation circuit according to claim 3, characterized in that: A resistor R3 is connected between the MOS tube U1 and the resistor R1.

5. A photoelectric sensor pulse modulation circuit according to claim 4, characterized in that: The diode D1 is connected to the gate of the MOSFET U1 , and the drain of the MOSFET U1 is connected to the resistor R4 .

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