Timing socket with metering function

Abstract

The utility model provides a timing socket with a metering function, which relates to the technical field of sockets and is characterized in that a zero line output end is electrically connected with a zero line input end, a circuit board is electrically connected between a live line output end and a live line input end, and a power supply circuit, a main control circuit, a switching circuit and a metering circuit are arranged in the circuit board; the switching circuit comprises a relay, one end of a relay coil is electrically connected with the output end of the power supply circuit, the other end is electrically connected with the main control circuit, one end of a relay contact is electrically connected with the live wire input end through a resistor R6, and the other end is electrically connected with the live wire output end; the metering circuit comprises a metering chip, an analog input port of a voltage channel of the metering chip is electrically connected with the zero line input end by connecting a plurality of resistors in series, an analog input port of a current channel of the metering chip is electrically connected with the two ends of a resistor R6, and the metering chip is electrically connected with the main control circuit. The switching circuit is controlled to be switched on according to the actual switching-on charging amount counted by the metering circuit, and it is ensured that charging equipment can be switched off after being fully charged.

Description

Technical Field

[0001] This utility model relates to the field of socket technology, and more specifically, to a timer socket with metering function. Background Technology

[0002] A socket is a receptacle with one or more electrical connections that can be inserted. With technological advancements, some electrical devices, especially charging devices, require timed start-up and shutdown to effectively prevent overcharging and potential safety hazards.

[0003] In existing technologies, these types of sockets typically use a timer within the main control chip to time and control their start and stop. However, in actual use, simply using timed start and stop is insufficient to ensure that the charging device receives the preset charge. If the charging device is plugged into the socket for an extended period and an external object causes poor contact, the device may experience insufficient charging within a specific timeframe. Utility Model Content

[0004] The technical problem to be solved by this utility model is that the existing timer sockets cannot guarantee that the device is fully charged during the charging process. In order to overcome the above-mentioned defects of the existing technology, this utility model provides a timer socket with metering function.

[0005] This utility model provides a timer socket with metering function, including a live wire input terminal, a neutral wire input terminal, a live wire output terminal, and a neutral wire output terminal, wherein the neutral wire output terminal is electrically connected to the neutral wire input terminal.

[0006] A circuit board is electrically connected between the live wire output terminal and the live wire input terminal. The circuit board contains a power supply circuit, a main control circuit, a switch circuit, a metering circuit, a display circuit, and a button circuit. The input terminal of the power supply circuit is electrically connected to the live wire input terminal and the neutral wire input terminal. The output terminal of the power supply circuit is electrically connected to the power supply terminal of the main control circuit. The display circuit and the button circuit are both electrically connected to the main control circuit.

[0007] The switching circuit includes a relay K1. One end of the coil of the relay K1 is electrically connected to the output terminal of the power supply circuit, and the other end of the coil of the relay K1 is electrically connected to the main control circuit. One end of the contact of the relay K1 is electrically connected to the live wire input terminal through a resistor R6, and the other end of the contact of the relay K1 is electrically connected to the live wire output terminal.

[0008] The metering circuit includes a metering chip U3. The analog input port of the voltage channel of the metering chip U3 is electrically connected to the neutral input terminal through a series of several resistors. The analog input port of the current channel of the metering chip U3 is electrically connected to both ends of the resistor R6. The metering chip U3 is electrically connected to the main control circuit.

[0009] Compared with the prior art, the timer socket with metering function proposed in this application has the following advantages: the metering circuit counts the actual charging amount after the circuit is turned on, and the main control circuit controls the switching circuit to turn on based on the actual charging amount after the circuit is turned on. This ensures that the charging device can be turned off only after it is fully charged, based on the timer socket. At the same time, the display circuit displays the actual charging amount, and the button circuit adjusts the display content and the preset charging amount.

[0010] In one possible implementation, the power supply circuit includes voltage regulator chip U1 and voltage regulator chip U2; the neutral input terminal is electrically connected to the positive terminal of diode D1 through a series resistor R1 and capacitor C1, the negative terminal of diode D1 is electrically connected to the input terminal of voltage regulator chip U1, a resistor R3 is connected in parallel across capacitor C1, the live input terminal is electrically connected to the positive terminal of diode D3, the negative terminal of diode D3 is electrically connected to the positive terminal of diode D1, the positive terminal of diode D3 is grounded, and the input terminals of voltage regulator chip U1 are grounded through electrolytic capacitor E1 and capacitor C2 respectively. The input terminal of voltage regulator chip U1 is electrically connected to the negative terminal of Zener diode Z1, and the positive terminal of Zener diode Z1 is grounded. The output terminal of voltage regulator chip U1 is grounded through electrolytic capacitor E2, and the output terminal of voltage regulator chip U1 is electrically connected to the input terminal of voltage regulator chip U2. The input terminal of voltage regulator chip U2 is grounded through capacitor C3, and the output terminal of voltage regulator chip U2 is grounded through capacitor C4 and electrolytic capacitor E3, respectively. The output terminal of voltage regulator chip U2 is electrically connected to the positive terminal of diode D2 through series resistor R2, and the negative terminal of diode D2 is electrically connected to the power supply terminal of the main control circuit.

[0011] Compared with existing technologies, this method first uses diodes D1 and D3 to achieve semi-current rectification, converting AC power into DC power. Then, voltage regulator chips U1 and U2 are used to provide stable DC power to various circuits by outputting different stable voltages.

[0012] In one possible implementation, the circuit board is further provided with a voltage detection circuit for detecting whether the voltage is abnormal. The voltage detection circuit includes resistors R21, R23, R29, and R30, and a transistor Q3. The input terminal of the voltage regulator chip U1 is connected to ground via resistors R23 and R30 in series. The connection terminal of resistors R23 and R30 is electrically connected to the base of transistor Q3 through resistor R29. The collector of transistor Q3 is grounded. The emitter of transistor Q3 is electrically connected to the output terminal of voltage regulator chip U2 through resistor R21. The emitter of transistor Q3 is electrically connected to the main control circuit.

[0013] Compared with existing technologies, a voltage detection circuit is used to detect whether the voltage of the power supply circuit is abnormal, thus ensuring the stability of the working power supply.

[0014] In one possible implementation, the switching circuit further includes a transistor Q10 and a diode D4. One end of the relay K1 coil is electrically connected to the negative terminal of the diode D4, the positive terminal of the diode D4 is electrically connected to the other end of the relay K1 coil, the other end of the relay K1 coil is electrically connected to the collector of the transistor Q10, the emitter of the transistor Q10 is grounded, and the base of the transistor Q10 is electrically connected to the main control circuit through a resistor R40.

[0015] Compared with existing technologies, the transistor Q10 is used to achieve conduction and cutoff, ensuring the stability of the energization and de-energization of the relay K1 coil, thereby controlling the relay K1 to work stably; at the same time, the diode D4 is used to prevent the current from flowing back across the relay K1 coil, thus protecting the relay K1.

[0016] In one possible implementation, the metering chip U3 is electrically connected to the main control circuit via a voltage conversion circuit, which includes transistors Q1 and Q2. The signal receiving terminal of the metering chip U3 is electrically connected to the collector of transistor Q1, which is grounded through resistor R22. The emitter of transistor Q1 is electrically connected to the output terminal of the power supply circuit. The base of transistor Q1 is electrically connected to the collector of transistor Q2 through resistor R19, which is grounded. The base of transistor Q2 is electrically connected to the main control circuit through resistor R20, and the collector of transistor Q2 is electrically connected to the output terminal of the power supply circuit through resistor R18. The signal transmitting terminal of the metering chip U3 is electrically connected to the main control circuit through resistor R31.

[0017] Compared with existing technologies, voltage conversion circuits are used to ensure stable serial communication and prevent interference.

[0018] In one possible implementation, the display circuit is an LCD display circuit, and the LCD display circuit is electrically connected to the main control circuit.

[0019] Compared with existing technologies, setting the display circuit to an LCD screen circuit can display more information and facilitate identification.

[0020] In one possible implementation, the button circuit includes several buttons for controlling the display circuit to display different information. One end of each button is grounded, and the other end of each button is electrically connected to the output terminal of the power supply circuit through a resistor. A capacitor is connected in parallel with each button.

[0021] Compared with existing technologies, this method uses multiple buttons for easy adjustment, and each button is connected in parallel with a capacitor to eliminate sparks at the moment the switch is turned on, thereby improving circuit stability and suppressing interference.

[0022] In one possible implementation, the circuit board is provided with an output indicator circuit for indicating whether there is output. The output indicator circuit includes resistor R32, resistor R33, transistor Q4, and light-emitting diode LED1.

[0023] The power supply terminal of the main control circuit is electrically connected to the positive terminal of LED1 through resistor R32. The negative terminal of LED1 is electrically connected to the collector of transistor Q4. The emitter of transistor Q4 is grounded. The base of transistor Q4 is electrically connected to the main control circuit through resistor R33.

[0024] Compared with existing technologies, the output indicator circuit makes it easy to identify whether the socket has an output. Attached Figure Description

[0025] Figure 1 This is a circuit diagram of a timer socket with metering function according to this utility model. Detailed Implementation

[0026] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of this application and are not intended to limit the scope of protection of the embodiments of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0027] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0028] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0029] See Figure 1 As shown in the figure, this application discloses a timer socket with metering function, including a live wire input terminal, a neutral wire input terminal, a live wire output terminal and a neutral wire output terminal, wherein the neutral wire output terminal is electrically connected to the neutral wire input terminal.

[0030] A circuit board is electrically connected between the live wire output terminal and the live wire input terminal. The circuit board contains a power supply circuit, a main control circuit, a switch circuit, a metering circuit, a display circuit, and a keypad circuit. The input terminal of the power supply circuit is electrically connected to the live wire input terminal and the neutral wire input terminal, and the output terminal of the power supply circuit is electrically connected to the power supply terminal of the main control circuit. The display circuit and the keypad circuit are both electrically connected to the main control circuit.

[0031] The switching circuit includes a relay K1. One end of the relay K1 coil is electrically connected to the output terminal of the power supply circuit, and the other end of the relay K1 coil is electrically connected to the main control circuit. One end of the relay K1 contact is electrically connected to the live wire input terminal through a resistor R6, and the other end of the relay K1 contact is electrically connected to the live wire output terminal.

[0032] The metering circuit includes a metering chip U3. The analog input port of the voltage channel of the metering chip U3 is electrically connected to the neutral input terminal through several resistors in series. The analog input port of the current channel of the metering chip U3 is electrically connected to both ends of the resistor R6. The metering chip U3 is electrically connected to the main control circuit.

[0033] A metering circuit tracks the actual charging amount after connection, and the main control circuit then uses this data to control the switching circuit. This ensures that charging devices are fully charged before disconnecting, building upon the existing timed socket design. A display circuit shows the actual charging amount, and buttons allow users to adjust the display and preset charging amounts. Real-time monitoring of the charging amount on the display circuit helps determine if the socket is functioning correctly, enhancing its early warning capabilities.

[0034] The timer socket with metering function in this embodiment allows you to know exactly how much electricity your electrical equipment has consumed. For example, when charging an electric bicycle, the charging location may be different from your home, resulting in different costs. This socket allows you to know how much electricity was used within a certain period (e.g., one month).

[0035] The metering chip U3 calculates the actual charging amount after the circuit is turned on; this is done by the internal program of the metering chip U3 and is existing technology. The main control circuit displays the actual charging amount obtained from the metering chip U3 after it is turned on through the display circuit; its program is also existing technology.

[0036] The metering chip U3 is a BL6523GX chip. However, in actual designs, other metering chips can be used, as long as they can perform power consumption statistics. The main control circuit only needs to use chips capable of data processing, such as STM32 series chips.

[0037] In this embodiment, the display circuit is an LCD screen circuit, and the LCD screen display circuit is electrically connected to the main control circuit. Setting the display circuit as an LCD screen circuit enables the display of more information and facilitates identification.

[0038] The button circuit includes several buttons for controlling the display circuit to display different information. One end of each button is grounded, and the other end of each button is electrically connected to the output of the power supply circuit through a resistor. A capacitor is connected in parallel with each button. By setting multiple buttons, adjustment is convenient, and the capacitor connected in parallel with each button eliminates sparks at the moment of switch conduction, improving circuit stability and suppressing interference.

[0039] The button circuit includes at least a setting button for setting a fixed timeout duration, a switching button for switching the timeout display and the power consumption during conduction, a reset button for resetting the preset timeout and resetting the power consumption during conduction to zero, a menu button for switching the main menu display, and an increment button for adjusting the timeout duration.

[0040] In actual use, firstly, pressing the setting button activates the main control circuit, which closes the switch circuit to achieve timed power-on of the socket. During this process, the timer duration can be adjusted using the additional button; each press increases the timer duration by a fixed amount (e.g., 30 minutes). After the socket is powered on, the amount of electricity passing through the live wire input and output terminals is measured by the metering chip U3 and sent to the main control circuit. The main control circuit then displays the information through the display circuit. Users can check the charging information displayed on the LCD screen to determine if the socket is properly connected. In case of poor contact, the timer duration can be manually increased; alternatively, the main control circuit can be set to turn off the switch circuit only after a preset charging amount has been reached, independent of the timer.

[0041] In this embodiment, the power supply circuit includes voltage regulator chip U1 and voltage regulator chip U2.

[0042] The neutral input terminal is electrically connected to the positive terminal of diode D1 through a series resistor R1 and capacitor C1. The negative terminal of diode D1 is electrically connected to the input terminal of voltage regulator chip U1. A resistor R3 is connected in parallel across capacitor C1. The live input terminal is electrically connected to the positive terminal of diode D3. The negative terminal of diode D3 is electrically connected to the positive terminal of diode D1. The positive terminal of diode D3 is grounded. The input terminals of voltage regulator chip U1 are grounded through electrolytic capacitor E1 and capacitor C2. The input terminal of voltage regulator chip U1 is electrically connected to the negative terminal of Zener diode Z1. The positive terminal of Zener diode Z1 is grounded. The output terminal of voltage regulator chip U1 is grounded through electrolytic capacitor E2. The output terminal of voltage regulator chip U1 is electrically connected to the input terminal of voltage regulator chip U2.

[0043] The input terminal of the voltage regulator chip U2 is grounded through capacitor C3, and the output terminal of the voltage regulator chip U2 is grounded through capacitor C4 and electrolytic capacitor E3 respectively. The output terminal of the voltage regulator chip U2 is electrically connected to the positive terminal of diode D2 through series resistor R2, and the negative terminal of diode D2 is electrically connected to the power supply terminal of the main control circuit.

[0044] First, half-current rectification is achieved through diodes D1 and D3 to convert AC power into 12V DC power. Then, voltage regulator chips U1 and U2 are used to provide stable DC power to various circuits by outputting different stable voltages.

[0045] Among them, voltage regulator chip U1 is an AMS1117-5.0 chip, which outputs 5V DC power; voltage regulator chip U2 is an XC6206P302MR chip, which outputs 3V DC power.

[0046] In this embodiment, the circuit board is also provided with a voltage detection circuit for detecting whether the voltage is abnormal. The voltage detection circuit includes resistors R21, R23, R29, and R30, transistor Q3, and the input terminal of the voltage regulator chip U1 is connected to ground through series resistors R23 and R30. The connection terminal of resistors R23 and R30 is electrically connected to the base of transistor Q3 through resistor R29. The collector of transistor Q3 is grounded. The emitter of transistor Q3 is electrically connected to the output terminal of voltage regulator chip U2 through resistor R21. The emitter of transistor Q3 is electrically connected to the main control circuit.

[0047] A voltage detection circuit is used to detect whether the voltage of the power supply circuit is abnormal, ensuring the stability of the working power supply.

[0048] The switching circuit also includes a transistor Q10 and a diode D4. One end of the relay K1 coil is electrically connected to the negative terminal of the diode D4, the positive terminal of the diode D4 is electrically connected to the other end of the relay K1 coil, the other end of the relay K1 coil is electrically connected to the collector of the transistor Q10, the emitter of the transistor Q10 is grounded, and the base of the transistor Q10 is electrically connected to the main control circuit through a resistor R40.

[0049] Transistor Q10 is used to turn the relay on and off, ensuring the stability of the relay K1 coil's energization and de-energization, thereby controlling the relay K1 to work stably; at the same time, diode D4 is used to prevent the current from flowing back across the relay K1 coil, thus protecting the relay K1.

[0050] In this embodiment, the metering chip U3 is electrically connected to the main control circuit through a voltage conversion circuit, which includes transistors Q1 and Q2. The signal receiving end of the metering chip U3 is electrically connected to the collector of transistor Q1, the collector of transistor Q1 is grounded through resistor R22, the emitter of transistor Q1 is electrically connected to the output of the power supply circuit, the base of transistor Q1 is electrically connected to the collector of transistor Q2 through resistor R19, the emitter of transistor Q2 is grounded, the base of transistor Q2 is electrically connected to the main control circuit through resistor R20, and the collector of transistor Q2 is electrically connected to the output of the power supply circuit through resistor R18. The signal transmitting end of the metering chip U3 is electrically connected to the main control circuit through resistor R31.

[0051] A voltage conversion circuit is used to ensure stable serial communication and prevent interference.

[0052] In this embodiment, the circuit board is provided with an output indicator circuit for indicating whether there is output. The output indicator circuit includes resistor R32, resistor R33, transistor Q4 and light-emitting diode LED1. The power supply terminal of the main control circuit is electrically connected to the positive terminal of LED1 through resistor R32, the negative terminal of LED1 is electrically connected to the collector of transistor Q4, the emitter of transistor Q4 is grounded, and the base of transistor Q4 is electrically connected to the main control circuit through resistor R33.

[0053] The output indicator circuit makes it easy to identify whether the socket has an output.

[0054] In the description of the embodiments of this application, it should be noted that the terms "inner" and "outer" and other terms indicating direction or positional relationship are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this application.

[0055] In the description of this application, the references to terms such as "an embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0056] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A timer socket with metering function, comprising a live wire input terminal, a neutral wire input terminal, a live wire output terminal, and a neutral wire output terminal, wherein the neutral wire output terminal is electrically connected to the neutral wire input terminal, characterized in that, A circuit board is electrically connected between the live wire output terminal and the live wire input terminal. The circuit board contains a power supply circuit, a main control circuit, a switch circuit, a metering circuit, a display circuit, and a button circuit. The input terminal of the power supply circuit is electrically connected to the live wire input terminal and the neutral wire input terminal. The output terminal of the power supply circuit is electrically connected to the power supply terminal of the main control circuit. The display circuit and the button circuit are both electrically connected to the main control circuit. The switching circuit includes a relay K1. One end of the coil of the relay K1 is electrically connected to the output terminal of the power supply circuit, and the other end of the coil of the relay K1 is electrically connected to the main control circuit. One end of the contact of the relay K1 is electrically connected to the live wire input terminal through a resistor R6, and the other end of the contact of the relay K1 is electrically connected to the live wire output terminal. The metering circuit includes a metering chip U3. The analog input port of the voltage channel of the metering chip U3 is electrically connected to the neutral input terminal through a series of several resistors. The analog input port of the current channel of the metering chip U3 is electrically connected to both ends of the resistor R6. The metering chip U3 is electrically connected to the main control circuit.

2. The timer socket with metering function according to claim 1, characterized in that, The power supply circuit includes voltage regulator chip U1 and voltage regulator chip U2; The neutral input terminal is electrically connected to the positive terminal of diode D1 via a series resistor R1 and capacitor C1. The negative terminal of diode D1 is electrically connected to the input terminal of voltage regulator chip U1. A resistor R3 is connected in parallel across capacitor C1. The live input terminal is electrically connected to the positive terminal of diode D3. The negative terminal of diode D3 is electrically connected to the positive terminal of diode D1. The positive terminal of diode D3 is grounded. The input terminals of voltage regulator chip U1 are grounded via electrolytic capacitor E1 and capacitor C2. The input terminal of voltage regulator chip U1 is electrically connected to the negative terminal of Zener diode Z1. The positive terminal of Zener diode Z1 is grounded. The output terminal of voltage regulator chip U1 is grounded via electrolytic capacitor E2. The output terminal of voltage regulator chip U1 is electrically connected to the input terminal of voltage regulator chip U2. The input terminal of the voltage regulator chip U2 is grounded through capacitor C3, and the output terminal of the voltage regulator chip U2 is grounded through capacitor C4 and electrolytic capacitor E3 respectively. The output terminal of the voltage regulator chip U2 is electrically connected to the positive terminal of diode D2 through series resistor R2, and the negative terminal of diode D2 is electrically connected to the power supply terminal of the main control circuit.

3. The timer socket with metering function according to claim 2, characterized in that, The circuit board also includes a voltage detection circuit for detecting whether the voltage is abnormal. The voltage detection circuit includes resistors R21, R23, R29, and R30, and transistor Q3. The input terminal of the voltage regulator chip U1 is connected to ground via series resistors R23 and R30. The connection terminal of resistors R23 and R30 is electrically connected to the base of transistor Q3 through resistor R29. The collector of transistor Q3 is grounded. The emitter of transistor Q3 is electrically connected to the output terminal of voltage regulator chip U2 through resistor R21. The emitter of transistor Q3 is electrically connected to the main control circuit.

4. The timer socket with metering function according to claim 1, characterized in that, The switching circuit also includes a transistor Q10 and a diode D4. One end of the relay K1 coil is electrically connected to the negative terminal of the diode D4, the positive terminal of the diode D4 is electrically connected to the other end of the relay K1 coil, the other end of the relay K1 coil is electrically connected to the collector of the transistor Q10, the emitter of the transistor Q10 is grounded, and the base of the transistor Q10 is electrically connected to the main control circuit through a resistor R40.

5. The timer socket with metering function according to claim 1, characterized in that, The metering chip U3 is electrically connected to the main control circuit through a voltage conversion circuit, which includes transistors Q1 and Q2. The signal receiving end of the metering chip U3 is electrically connected to the collector of transistor Q1. The collector of transistor Q1 is grounded through resistor R22. The emitter of transistor Q1 is electrically connected to the output of the power supply circuit. The base of transistor Q1 is electrically connected to the collector of transistor Q2 through resistor R19. The emitter of transistor Q2 is grounded. The base of transistor Q2 is electrically connected to the main control circuit through resistor R20. The collector of transistor Q2 is electrically connected to the output of the power supply circuit through resistor R18. The signal transmitting end of the metering chip U3 is electrically connected to the main control circuit through resistor R31.

6. The timer socket with metering function according to claim 1, characterized in that, The display circuit is an LCD display circuit, which is electrically connected to the main control circuit.

7. The timer socket with metering function according to claim 1, characterized in that, The button circuit includes several buttons for controlling the display circuit to display different information. One end of each button is grounded, and the other end of each button is electrically connected to the output terminal of the power supply circuit through a resistor. A capacitor is connected in parallel with each button.

8. The timer socket with metering function according to claim 1, characterized in that, The circuit board is provided with an output indicator circuit for indicating whether there is output. The output indicator circuit includes resistor R32, resistor R33, transistor Q4 and light-emitting diode LED1. The power supply terminal of the main control circuit is electrically connected to the positive terminal of LED1 through resistor R32. The negative terminal of LED1 is electrically connected to the collector of transistor Q4. The emitter of transistor Q4 is grounded. The base of transistor Q4 is electrically connected to the main control circuit through resistor R33.

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