Colored lamp control circuit

Abstract

The utility model belongs to the technical field of colored lamp flicker control, and particularly relates to a colored lamp control circuit, which comprises a clock module, a frequency division module, a state machine module, a colored lamp driving module, a current limiting module and a voltage stabilizing module, and is used for generating a stable clock signal so as to provide a reference time sequence required by circuit operation. According to the utility model, through high-precision clock signals and frequency division processing, the colored lamps are ensured to flicker according to a set rhythm, the control precision is improved, different colored lamp modes (such as a flowing water lamp and a gradual change lamp) are designed by adopting a state machine, the display diversity of the colored lamps is increased, different application requirements are met, and correct data transmission is ensured through storing and transmitting signals through the colored lamp driving module; signal loss is avoided, the reliability of colored lamp control is improved, the current limiting module can effectively prevent surge current from damaging the circuit and prolong the service life of the circuit and elements, and the voltage stabilizing module can filter power supply noise, ensure voltage stability, prevent circuit abnormity caused by voltage fluctuation and improve the anti-interference capability.

Description

Technical Field

[0001] The utility model belongs to the technical field of color light flickering control, and in particular relates to a color light control circuit. Background Art

[0002] With the development of modern electronic technology and lighting technology, colored lights are widely used in advertising, stage, decoration, festivals and celebrations. Existing colored light control circuits generally use simple pulse generation circuits or designs based on single control logic. Although they can achieve the basic flashing function of colored lights, they still have shortcomings in practical applications.

[0003] The oscillation or timing circuits used in traditional circuits often have problems such as unstable clock signals, large frequency drift, and difficulty in accurately controlling the flashing frequency in different modes. They cannot meet the timing accuracy requirements of various color light flashing modes (such as flowing lights, gradient flashing, fixed frequency flashing, etc.). Most of them rely on fixed logic or simple counters for state switching, and it is difficult to achieve complex color light display effects. At the moment the circuit is powered on, the impact of surge current can easily cause component damage or generate voltage spikes, which in turn affects the normal operation of key modules such as counters and logic circuits. Utility Model Content

[0004] The utility model aims to provide a colored light control circuit, which can realize accurate control of diversified flashing modes of colored lights and effectively improve the stability, reliability and anti-interference ability of the circuit.

[0005] The technical solution adopted by the utility model is as follows:

[0006] A colored light control circuit, comprising:

[0007] The clock module is used to generate a stable clock signal to provide the reference timing required for circuit operation;

[0008] The frequency division module is connected to the clock module and is used to divide the clock signal to adapt to the control requirements of the colored lights in different working modes;

[0009] The state machine module is connected to the frequency division module and is used to generate control signals of different states according to the preset color light control logic.

[0010] A colored light driving module is connected to the state machine module and is used to store and transmit colored light driving signals to realize colored light flashing control;

[0011] The current limiting module is connected to the power supply end of the clock module, the frequency division module, the state machine module and the colored light driving module to suppress the power-on surge current;

[0012] The voltage stabilizing module is connected between the power supply terminal and the ground terminal of the frequency dividing module and the state machine module to stabilize the voltage.

[0013] Furthermore, the clock module includes a resistor R1, a sliding resistor R2, a resistor R3, a diode VD2, a diode VD1, a capacitor C1, a capacitor C2 and a chip U1. One end of the resistor R1 is connected to pin 4, pin 8, a frequency division module, a state machine module, a colored light driving module, a current limiting module and a voltage stabilizing module of the chip U1. The other end of the resistor R1 is connected to pin 1 of the sliding resistor R2. Pin 2 of the sliding resistor R2 is connected to one end of the resistor R3. Pin 3 of the sliding resistor R2 is connected to one end of the diode VD2 and pin 5 of the chip U1. The other end of the resistor R3 is connected to one end of the diode VD1. The other end of the diode VD1 is connected to the other end of the diode VD2, one end of the capacitor C1, pins 2 and 6 of the chip U1. The other end of the capacitor C1 is connected to one end of the capacitor C2 and pin 1 of the chip U1 and is grounded. The other end of the capacitor C2 is connected to pin 7 of the chip U1. Pin 3 of the chip U1 is connected to the frequency division module and the colored light driving module.

[0014] Furthermore, the frequency division module includes chip U2 and logic gate chip U5A, pins 3, 4, 5 and 6 of chip U2 are all connected to the voltage stabilizing module and grounded, pin 7 of chip U2 is connected to pin 10 of chip U2, pin 1 of chip U2, pin 2 of logic gate chip U5A, one end of resistor R1, state machine module, color light driving module, current limiting module and voltage stabilizing module, pin 9 of chip U2 is connected to pin 3 of logic gate chip U5A, pin 2 of chip U2 is connected to pin 3 of chip U1 and the color light driving module, and pin 14 of chip U2 is connected to pin 1 of logic gate chip U5A and the state machine module.

[0015] Furthermore, the state machine module includes a chip U3 and a logic gate chip U6A, pins 3, 4 and 6 of chip U3 are all connected to the voltage stabilizing module and grounded, pin 5 of chip U3 is connected to pin 7 of chip U3, pin 10 of chip U3, pin 1 of chip U3, pin 2 of logic gate chip U6A, one end of resistor R1, a colored light driving module, a current limiting module and a voltage stabilizing module, pin 9 of chip U3 is connected to pin 3 of logic gate chip U6A, pin 2 of chip U3 is connected to pin 14 of resistor R3 and pin 1 of logic gate chip U5A, pins 11, 12, 13 and 14 of chip U3 are all connected to the colored light driving module, and pin 15 of chip U3 is connected to pin 1 of logic gate chip U6A.

[0016] Furthermore, the colored light driving module includes a logic gate chip U7A, a logic gate chip U8A and a chip U4, pin 2 of the logic gate chip U7A is connected to pin 2 of the logic gate chip U8A, pin 1 of the chip U4, one end of the resistor R1, a current limiting module and a voltage stabilizing module, pin 1 of the logic gate chip U7A is connected to pin 14 of the chip U3, pin 1 of the logic gate chip U8A is connected to pin 13 of the chip U3, pin 9 of the chip U4 is connected to pin 12 of the chip U3, pin 1 of the chip U4 is connected to pin 11 of the chip U3, pin 11 of the chip U4 is connected to pin 3 of the chip U1, pins 3, 4, 5 and 6 of the chip U4 are all connected to pin 3 of the logic gate chip U7A, and pins 2 and 7 of the chip U4 are all connected to pin 3 of the logic gate chip U8A.

[0017] Furthermore, the current limiting module includes an NTC thermistor RT1, one end of the NTC thermistor RT1 is connected to the power supply end, and the other end of the NTC thermistor RT1 is connected to one end of the resistor R1 and the voltage stabilizing module.

[0018] Furthermore, the voltage stabilizing module includes capacitor C3 and capacitor C4, one end of capacitor C3 is connected to one end of resistor R1, the other end of capacitor C3 is connected to pin 3 of chip U2, one end of capacitor C4 is connected to one end of resistor R1, and the other end of capacitor C4 is connected to pin 3 of chip U3.

[0019] The technical effects achieved by the utility model are:

[0020] The utility model ensures that the colored lights flash according to the set rhythm through high-precision clock signals and frequency division processing, improves the control accuracy, adopts a state machine to design different colored light modes (such as flowing lights, gradient lights), increases the diversity of colored light displays, and adapts to different application requirements. The colored light drive module stores and transmits signals to ensure correct data transmission, avoid signal loss, and improve the reliability of colored light control.

[0021] The utility model can effectively prevent the damage of the circuit by the surge current in the current limiting module, thereby prolonging the service life of the circuit and the components.

[0022] The utility model can filter out power supply noise in the voltage stabilizing module, ensure voltage stability, prevent circuit abnormality caused by voltage fluctuation, and improve anti-interference capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a circuit diagram of the utility model;

[0024] Figure 2 It is a schematic diagram of controlling four colored lights of the utility model. DETAILED DESCRIPTION

[0025] In order to make the purpose and advantages of the utility model more clear, the utility model is specifically described in combination with the following embodiments. It should be understood that the following text is only used to describe one or several specific implementation methods of the utility model, and does not strictly limit the scope of protection of the specific request of the utility model.

[0026] like Figure 1 to Figure 2 As shown, a colored light control circuit comprises:

[0027] The clock module is used to generate a stable clock signal to provide the reference timing required for circuit operation;

[0028] The frequency division module is connected to the clock module and is used to divide the clock signal to adapt to the control requirements of the colored lights in different working modes;

[0029] The state machine module is connected to the frequency division module and is used to generate control signals of different states according to the preset color light control logic.

[0030] A colored light driving module is connected to the state machine module and is used to store and transmit colored light driving signals to realize colored light flashing control;

[0031] The current limiting module is connected to the power supply end of the clock module, the frequency division module, the state machine module and the colored light driving module to suppress the power-on surge current;

[0032] The voltage stabilizing module is connected between the power supply terminal and the ground terminal of the frequency dividing module and the state machine module to stabilize the voltage.

[0033] It should be noted that, depending on the number of controlled colored lights, an appropriate number of colored lights are connected to the output end of the colored light driving module.

[0034] The clock module generates a high-precision clock signal as the reference timing of the entire circuit to ensure that each module runs synchronously. For example, a crystal oscillator or an internal oscillation circuit is used to provide a stable reference clock. The frequency division module receives the clock signal and divides it as needed to adapt to different flashing modes of colored lights. For example, a 1MHz clock signal is divided into 1Hz, 10Hz or 100Hz to control different flashing rates of colored lights. The state machine module presets different colored light control logics, such as flowing lights, gradual flashing, fixed frequency flashing, etc., and generates corresponding control signals. The colored light driving module receives the control signal generated by the state machine, stores and transmits it to the colored lights to make them flash according to the set mode. The current limiting module is connected to the power supply end of the entire circuit to prevent the generation of current at the moment of power-on. The surge current impact, the voltage stabilizing module, is connected between the power supply and ground terminals of the frequency division module and the state machine module to ensure voltage stability and avoid abnormal operation caused by voltage fluctuations. Through high-precision clock signals and frequency division processing, the colored lights are ensured to flash according to the set rhythm and improve control accuracy. Different colored light modes (such as flowing lights and gradient lights) are designed using a state machine to increase the diversity of colored light displays and adapt to different application requirements. The colored light driver module stores and transmits signals to ensure correct data transmission, avoid signal loss, and improve the reliability of colored light control. The current limiting module can effectively prevent surge current from damaging the circuit and extend the service life of the circuit and components. The voltage stabilizing module can filter out power supply noise, ensure voltage stability, prevent circuit abnormalities caused by voltage fluctuations, and improve anti-interference capabilities.

[0035] In a preferred embodiment, the clock module includes a resistor R1, a sliding resistor R2, a resistor R3, a diode VD2, a diode VD1, a capacitor C1, a capacitor C2 and a chip U1, one end of the resistor R1 is connected to pin 4, pin 8, a frequency division module, a state machine module, a colored light driving module, a current limiting module and a voltage stabilizing module of the chip U1, the other end of the resistor R1 is connected to pin 1 of the sliding resistor R2, pin 2 of the sliding resistor R2 is connected to one end of the resistor R3, pin 3 of the sliding resistor R2 is connected to one end of the diode VD2 and pin 5 of the chip U1, the other end of the resistor R3 is connected to one end of the diode VD1, the other end of the diode VD1 is connected to the other end of the diode VD2, one end of the capacitor C1, pins 2 and 6 of the chip U1, the other end of the capacitor C1 is connected to one end of the capacitor C2, pin 1 of the chip U1 and grounded, the other end of the capacitor C2 is connected to pin 7 of the chip U1, and pin 3 of the chip U1 is connected to the frequency division module and the colored light driving module.

[0036] As mentioned above, the resistor R1, the sliding resistor R2 and the resistor R3 jointly determine the charging rate of the capacitor C1. The capacitor C1 is charged through these resistors, and the voltage gradually rises. When the voltage of the capacitor C1 reaches the threshold voltage of the chip U1 (such as the 555 timer), the internal discharge tube of the chip U1 is turned on, and the capacitor C1 is discharged through the resistor R3 and the diode VD1 until the voltage drops to the trigger voltage. The chip U1 re-enters the charging state, and this cycle forms an oscillation. The sliding resistor R2 can be used to adjust the time constant of the charging and discharging of the capacitor C1, thereby changing the frequency of the output pulse signal, that is, adjusting the clock signal. cycle, can change the charge and discharge time constant, flexibly adjust the frequency of the output clock signal to adapt to different system requirements, resistor R3 and diode VD1 are responsible for controlling the discharge rate, affecting the signal duty cycle, making the pulse signal more stable, and pin 3 of chip U1 outputs a stable clock pulse. This pulse signal is used as the clock input of the subsequent frequency division module, state machine module, and colored light drive module, providing a synchronization signal for the entire system, and can generate an adjustable clock signal. It optimizes the frequency and duty cycle through the sliding resistor R2 and diodes VD1 and VD2 to ensure the stable operation of the subsequent circuits.

[0037] In a preferred embodiment, the frequency division module includes chip U2 and logic gate chip U5A, pins 3, 4, 5 and 6 of chip U2 are all connected to the voltage stabilizing module and grounded, pin 7 of chip U2 is connected to pin 10 of chip U2, pin 1 of chip U2, pin 2 of logic gate chip U5A, one end of resistor R1, state machine module, color light driving module, current limiting module and voltage stabilizing module, pin 9 of chip U2 is connected to pin 3 of logic gate chip U5A, pin 2 of chip U2 is connected to pin 3 of chip U1 and the color light driving module, and pin 14 of chip U2 is connected to pin 1 of logic gate chip U5A and the state machine module.

[0038] As mentioned above, pin 2 of chip U2 receives the clock pulse signal output from pin 3 of chip U1 of the clock module. The signal is usually a square wave with a fixed frequency. Chip U2 is a binary divider (such as a 74LS161D counter). Its function is to count the input clock signal and generate a low-frequency clock signal. Pin 9 of chip U2 outputs the divided clock signal, which is sent to pin 3 of logic gate chip U5A for further logic processing. Pin 1 of logic gate chip U5A outputs the final clock signal, which is used in the state machine module to ensure synchronous operation of the system.

[0039] In a preferred embodiment, the state machine module includes a chip U3 and a logic gate chip U6A, pins 3, 4 and 6 of chip U3 are all connected to the voltage stabilizing module and grounded, pin 5 of chip U3 is connected to pin 7 of chip U3, pin 10 of chip U3, pin 1 of chip U3, pin 2 of logic gate chip U6A, one end of resistor R1, a colored light driving module, a current limiting module and a voltage stabilizing module, pin 9 of chip U3 is connected to pin 3 of logic gate chip U6A, pin 2 of chip U3 is connected to pin 14 of resistor R3 and pin 1 of logic gate chip U5A, pins 11, 12, 13 and 14 of chip U3 are all connected to the colored light driving module, and pin 15 of chip U3 is connected to pin 1 of logic gate chip U6A.

[0040] As mentioned above, chip U3 is a counter (such as a 74LS161D counter) used to store current state information and perform state transitions according to input signals. Pins 11, 12, 13, and 14 of chip U3 are connected to the colored light driver module. These pins control the display mode of the colored light driver module. In different state machine states, different output pins will be high level, thereby driving the colored lights to display corresponding modes.

[0041] In a preferred embodiment, the colored light driving module includes a logic gate chip U7A, a logic gate chip U8A and a chip U4, pin 2 of the logic gate chip U7A is connected to pin 2 of the logic gate chip U8A, pin 1 of the chip U4, one end of the resistor R1, a current limiting module and a voltage stabilizing module, pin 1 of the logic gate chip U7A is connected to pin 14 of the chip U3, pin 1 of the logic gate chip U8A is connected to pin 13 of the chip U3, pin 9 of the chip U4 is connected to pin 12 of the chip U3, pin 1 of the chip U4 is connected to pin 11 of the chip U3, pin 11 of the chip U4 is connected to pin 3 of the chip U1, pins 3, 4, 5 and 6 of the chip U4 are all connected to pin 3 of the logic gate chip U7A, and pins 2 and 7 of the chip U4 are all connected to pin 3 of the logic gate chip U8A.

[0042] It should be noted that, depending on the number of controlled colored lights, for example, to control 4 colored light cycles, the 11th, 12th, 13th and 14th pins of the chip U4 are connected to a colored light respectively. If 8 colored light cycles are to be controlled, two colored light driver modules need to be connected in parallel after the state machine module, and each colored light driver module controls 4 colored lights.

[0043] As mentioned above, chip U4 is a driver chip (such as 74LS194D). Chip U4 receives the signal from the state machine module and converts it. The control signal is input through pins 11, 12, 13 and 14 of chip U4 to control the on and off of the connected colored lights.

[0044] In a preferred embodiment, the current limiting module includes an NTC thermistor RT1, one end of the NTC thermistor RT1 is connected to the power supply end, and the other end of the NTC thermistor RT1 is connected to one end of the resistor R1 and the voltage stabilizing module.

[0045] As mentioned above, the resistance of NTC thermistor RT1 decreases as the temperature increases. It is connected in series on the VCC power supply line. When the circuit is powered on, the instantaneous current may be very large. It can limit the surge current at the moment of power-on to protect the circuit. As the circuit works, the NTC thermistor RT1 heats up and the resistance decreases, eventually providing a lower impedance without affecting the normal power supply. It can reduce the surge current, avoid impacting the chip when powered on, reduce the voltage spike at startup, and prevent affecting the normal operation of chips such as counters and logic circuits.

[0046] In a preferred embodiment, the voltage stabilizing module includes capacitor C3 and capacitor C4, one end of capacitor C3 is connected to one end of resistor R1, the other end of capacitor C3 is connected to pin 3 of chip U2, one end of capacitor C4 is connected to one end of resistor R1, and the other end of capacitor C4 is connected to pin 3 of chip U3.

[0047] As mentioned above, capacitor C3 and capacitor C4 are connected in parallel between VCC and GND of chip U2 and chip U3, respectively, to prevent voltage fluctuations from affecting logic chips, especially components of chip U2 and chip U3 that may be sensitive to power supply stability, thereby removing power supply ripple, reducing high-frequency noise, and improving circuit power supply stability.

[0048] The working principle of the utility model is as follows: the clock module generates a high-precision clock signal as the reference timing of the entire circuit to ensure that each module runs synchronously. For example, a crystal oscillator or an internal oscillation circuit is used to provide a stable reference clock. The frequency division module receives the clock signal and divides the frequency as needed to adapt to different flashing modes of colored lights. For example, a 1MHz clock signal is divided into 1Hz, 10Hz or 100Hz to control different flashing rates of colored lights. The state machine module presets different colored light control logics, such as flowing lights, gradual flashing, fixed frequency flashing, etc., and generates corresponding control signals. The colored light driving module receives the control signal generated by the state machine, stores and transmits it to the colored lights to make them flash according to the set mode. The current limiting module is connected to the power supply end of the entire circuit to prevent the colored lights from flashing. The surge current impact generated by the instantaneous electricity, the voltage stabilizing module, is connected between the power supply end and the ground end of the frequency division module and the state machine module to ensure voltage stability and avoid abnormal operation caused by voltage fluctuations. Through high-precision clock signals and frequency division processing, the colored lights are ensured to flash according to the set rhythm to improve control accuracy. Different colored light modes (such as flowing lights and gradient lights) are designed using a state machine to increase the diversity of colored light displays and adapt to different application requirements. The colored light driver module stores and transmits signals to ensure correct data transmission, avoid signal loss, and improve the reliability of colored light control. The current limiting module can effectively prevent surge current from damaging the circuit and extend the service life of the circuit and components. The voltage stabilizing module can filter out power supply noise, ensure voltage stability, prevent circuit abnormalities caused by voltage fluctuations, and improve anti-interference capabilities.

[0049] The above is only a preferred embodiment of the present invention. It should be noted that, for ordinary technicians in the technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the field unless otherwise specified and limited.

Claims

1. A colored light control circuit, characterized in that: include: The clock module is used to generate a stable clock signal to provide the reference timing required for circuit operation; The frequency division module is connected to the clock module and is used to divide the clock signal to adapt to the control requirements of the colored lights in different working modes; The state machine module is connected to the frequency division module and is used to generate control signals of different states according to the preset color light control logic. A colored light driving module is connected to the state machine module and is used to store and transmit colored light driving signals to realize colored light flashing control; The current limiting module is connected to the power supply end of the clock module, the frequency division module, the state machine module and the colored light driving module to suppress the power-on surge current; The voltage stabilizing module is connected between the power supply terminal and the ground terminal of the frequency dividing module and the state machine module to stabilize the voltage.

2. The colored light control circuit according to claim 1, characterized in that: The clock module includes a resistor R1, a sliding resistor R2, a resistor R3, a diode VD2, a diode VD1, a capacitor C1, a capacitor C2 and a chip U1. One end of the resistor R1 is connected to pin 4, pin 8, a frequency division module, a state machine module, a colored light driving module, a current limiting module and a voltage stabilizing module of the chip U1. The other end of the resistor R1 is connected to pin 1 of the sliding resistor R2, pin 2 of the sliding resistor R2 is connected to one end of the resistor R3, pin 3 of the sliding resistor R2 is connected to one end of the diode VD2 and pin 5 of the chip U1, the other end of the resistor R3 is connected to one end of the diode VD1, the other end of the diode VD1 is connected to the other end of the diode VD2, one end of the capacitor C1, pins 2 and 6 of the chip U1, the other end of the capacitor C1 is connected to one end of the capacitor C2, pin 1 of the chip U1 and grounded, the other end of the capacitor C2 is connected to pin 7 of the chip U1, and pin 3 of the chip U1 is connected to the frequency division module and the colored light driving module.

3. The colored light control circuit according to claim 2, characterized in that: The frequency division module includes chip U2 and logic gate chip U5A. Pin 3, pin 4, pin 5 and pin 6 of chip U2 are all connected to the voltage stabilizing module and grounded. Pin 7 of chip U2 is connected to pin 10 of chip U2, pin 1 of chip U2, pin 2 of logic gate chip U5A, one end of resistor R1, state machine module, color light driving module, current limiting module and voltage stabilizing module. Pin 9 of chip U2 is connected to pin 3 of logic gate chip U5A. Pin 2 of chip U2 is connected to pin 3 of chip U1 and the color light driving module. Pin 14 of chip U2 is connected to pin 1 of logic gate chip U5A and the state machine module.

4. The colored light control circuit according to claim 3, characterized in that: The state machine module includes chip U3 and logic gate chip U6A. Pin 3, pin 4 and pin 6 of chip U3 are all connected to the voltage stabilizing module and grounded. Pin 5 of chip U3 is connected to pin 7 of chip U3, pin 10 of chip U3, pin 1 of chip U3, pin 2 of logic gate chip U6A, one end of resistor R1, color light driving module, current limiting module and voltage stabilizing module. Pin 9 of chip U3 is connected to pin 3 of logic gate chip U6A. Pin 2 of chip U3 is connected to pin 14 of resistor R3 and pin 1 of logic gate chip U5A. Pins 11, 12, 13 and 14 of chip U3 are all connected to the color light driving module. Pin 15 of chip U3 is connected to pin 1 of logic gate chip U6A.

5. The colored light control circuit according to claim 4, characterized in that: The colored light driving module includes a logic gate chip U7A, a logic gate chip U8A and a chip U4. Pin 2 of the logic gate chip U7A is connected to pin 2 of the logic gate chip U8A, pin 1 of the chip U4, one end of the resistor R1, a current limiting module and a voltage stabilizing module. Pin 1 of the logic gate chip U7A is connected to pin 14 of the chip U3. Pin 1 of the logic gate chip U8A is connected to pin 13 of the chip U3. Pin 9 of the chip U4 is connected to pin 12 of the chip U3. Pin 1 of the chip U4 is connected to pin 11 of the chip U3. Pin 11 of the chip U4 is connected to pin 3 of the chip U1. Pins 3, 4, 5 and 6 of the chip U4 are all connected to pin 3 of the logic gate chip U7A. Pins 2 and 7 of the chip U4 are all connected to pin 3 of the logic gate chip U8A.

6. The colored light control circuit according to claim 5, characterized in that: The current limiting module includes an NTC thermistor RT1, one end of the NTC thermistor RT1 is connected to the power supply end, and the other end of the NTC thermistor RT1 is connected to one end of the resistor R1 and the voltage stabilizing module.

7. The colored light control circuit according to claim 6, characterized in that: The voltage stabilizing module includes capacitor C3 and capacitor C4, one end of capacitor C3 is connected to one end of resistor R1, the other end of capacitor C3 is connected to pin 3 of chip U2, one end of capacitor C4 is connected to one end of resistor R1, the other end of capacitor C4 is connected to pin 3 of chip U3.

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