Testing device of brushless axial flow fan controller

Abstract

The utility model relates to the technical field of brushless axial flow fan controller testing, and discloses a brushless axial flow fan controller testing device which comprises a control unit, a power supply unit, a PWM output unit, a testing voltage output unit, at least one direct current signal transmission unit and at least one electronic switch branch. In actual use, the control unit outputs a PWM signal through the PWM output unit and outputs a test voltage through the test voltage output unit, and the PWM signal and the test voltage can be input into the brushless axial flow fan controller through the electronic switch branch for function test. And the control unit inputs the direct current signal to the brushless axial flow fan controller through the direct current signal transmission unit for direct current testing, so that the direct current testing and function testing of the brushless axial flow fan controller can be met by one device, and the working efficiency is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of brushless axial flow fan controller testing, in particular to a testing device for a brushless axial flow fan controller. Background Art

[0002] At present, brushless axial flow fans have been widely used in various places that require ventilation due to their advantages of high performance, low noise and easy maintenance. During the use of brushless axial flow fans, their specific rotation process is controlled by the brushless axial flow fan controller.

[0003] The brushless axial flow fan controller needs to be tested after production, including DC parameter test and function test of the brushless axial flow fan controller. However, currently these two tests are performed separately and respectively by two test devices, which is inefficient. Utility Model Content

[0004] In view of the shortcomings of the background technology, the utility model provides a test device for a brushless axial flow fan controller, and the technical problem to be solved is that the DC parameter test and the function test of the brushless axial flow fan controller are currently performed separately, which is inefficient.

[0005] In order to solve the above technical problems, the utility model provides the following technical solutions: a test device for a brushless axial flow fan controller, comprising a control unit, a power supply unit, a PWM output unit, a test voltage output unit, at least one DC signal transmission unit and at least one electronic switch branch;

[0006] The power supply unit provides working voltage for the control unit respectively; the control unit is electrically connected to the PWM output unit, and outputs PWM signal through the PWM output unit; the control unit is electrically connected to the test voltage output unit, and outputs test voltage through the test voltage output unit; the control unit is electrically connected to the input end of all DC signal transmission units;

[0007] The output ends of all DC signal transmission units, the PWM signal output ends of the PWM output units, and the test voltage output ends of the test voltage output units are electrically connected to the first connection ends of different electronic switch branches, and the control unit is electrically connected to the control end of the electronic switch branch, and is used to input a switch control signal to the control end of the electronic switch branch, and the switch control signal is used to control the on and off of the electronic switch branch.

[0008] In some implementations, the control unit includes a single chip microcomputer of model STM8S903K3.

[0009] In a certain embodiment, the present invention includes five DC signal transmission units.

[0010] In a certain embodiment, the DC signal transmission unit includes resistors R7, R8, R9 and capacitor C1, one end of the resistor R9 is the input end of the DC signal transmission unit and is grounded through the capacitor C1; the other end of the resistor R9 is electrically connected to one end of the resistor R7 and one end of the resistor R8 respectively, the other end of the resistor R8 is grounded, and the other end of the resistor R7 is the output end of the DC signal transmission unit.

[0011] In a certain embodiment, seven electronic switch branches are included, and the seven electronic switch branches are provided by five relays, and the five relays are respectively a first relay, a second relay, a third relay, a fourth relay and a fifth relay;

[0012] Two of the five DC signal transmission units' output ends are electrically connected to two common ends of the first relay respectively;

[0013] The other two outgoing ends of the five DC signal transmission units are electrically connected to the two common ends of the second relay respectively;

[0014] The remaining one of the five DC signal transmission units' output ends is electrically connected to a common end of the third relay;

[0015] The PWM signal output terminal of the PWM output unit is electrically connected to a common terminal of the fourth relay;

[0016] The test voltage output terminal of the test voltage output unit is electrically connected to a common terminal of the fifth relay.

[0017] In a certain embodiment, one end of the control coils of all relays is electrically connected for inputting a driving voltage V_R, the other end of the control coil of the first relay is electrically connected to the other end of the control coil of the second relay and the other end of the control coil of the third relay, respectively, and the other end of the control coil of the first relay, the other end of the control coil of the fourth relay, and the other end of the control coil of the fifth relay are respectively connected to a driving circuit;

[0018] The driving circuit includes a resistor R1, a resistor R2 and a transistor Q1, the collector of the transistor Q1 is electrically connected to the other end of the control coil, the base of the transistor Q1 is electrically connected to one end of the resistor R1 and one end of the resistor R2 respectively, the other end of the resistor R1 is electrically connected to the control unit for inputting the switch control signal, and the other end of the resistor R2 and the emitter of the transistor Q1 are both grounded.

[0019] In a certain embodiment, the utility model further comprises a switch power supply unit, wherein the switch power supply unit comprises a first power supply chip of model LM317;

[0020] Pin No. 3 of the first power chip is grounded through capacitors C5 and C7 respectively, and is used for inputting voltage VCC;

[0021] Pin 1 of the first power chip is grounded through capacitor C8, capacitor R22 and resistor R23, and is electrically connected to one end of resistor R24;

[0022] Pin No. 2 of the first power chip is grounded through capacitors C9 and C10, and is electrically connected to the other end of resistor R24 ​​and one end of resistor R25, respectively, for outputting a driving voltage V_R. The other end of resistor R25 is grounded through resistor R26.

[0023] In some embodiments, the power supply unit includes a second power chip of model LM317 and a third power chip of model 78L05;

[0024] Pin No. 3 of the second power chip is grounded through capacitor C17 and capacitor C18 respectively, and is used for inputting voltage VCC; Pin No. 1 of the second power chip is grounded through capacitor C19 and resistor R56 respectively, and is electrically connected to one end of resistor R57; Pin No. 2 of the second power chip is grounded through capacitor C20 and capacitor C21 respectively, and is electrically connected to the other end of resistor R57 and pin No. 3 of the third power chip respectively; Pin No. 2 of the third power chip is grounded, and pin No. 1 of the third power chip is grounded through capacitor C22 and capacitor C23 respectively, and is used for outputting the working voltage.

[0025] In a certain embodiment, the PWM output unit includes a transistor Q6, the emitter of the transistor Q6 is electrically connected to one end of the resistor R30, and is used to input the voltage VCC, the base of the transistor Q6 is electrically connected to the other end of the resistor R30 and one end of the resistor R29, respectively, the collector of the transistor Q6 is electrically connected to one end of the resistor R31 and one end of the capacitor C11, respectively, and is the PWM signal output end, and the other end of the resistor R31 and the other end of the capacitor C11 are both grounded;

[0026] The other end of resistor R29 is electrically connected to the collector of transistor Q5, the base of transistor Q5 is electrically connected to one end of resistor R27 and one end of resistor R28 respectively, the other end of resistor R27 is electrically connected to the control unit, and the other end of resistor R28 and the emitter of transistor Q5 are both grounded.

[0027] In a certain embodiment, the test voltage output unit includes a resistor R38, one end of the resistor R38 is electrically connected to one end of the resistor R39 for inputting the voltage VCC, the other end of the resistor R38 is electrically connected to the cathode of the voltage zener diode Z1, the cathode of the voltage zener diode Z2, the collector of the transistor Q10 and the base of the transistor Q9, the other end of the resistor R39 is electrically connected to the collector of the transistor Q9, the anode of the voltage zener diode Z1 is grounded, the anode of the voltage zener diode Z2 is electrically connected to the collector of the transistor Q8, and the base of the transistor Q9 is electrically connected to the collector of the transistor Q10. The base of transistor Q8 is electrically connected to one end of resistor R36 and one end of resistor R37 respectively, the other end of resistor R36 is electrically connected to the control unit, the other end of resistor R37 and the emitter of transistor Q8 are both grounded; the emitter of transistor Q9 is electrically connected to the base of transistor Q10 and one end of resistor R40 respectively, the emitter of transistor Q10 is electrically connected to one end of resistor R41, one end of capacitor C12 and the other end of resistor R40 respectively, which is the test voltage output end, the other end of resistor R41 and the other end of capacitor C12 are both grounded.

[0028] Compared with the prior art, the utility model has the following beneficial effects: in actual use, the control unit of the utility model outputs a PWM signal through the PWM output unit and outputs a test voltage through the test voltage output unit, the PWM signal and the test voltage can be input into the brushless axial flow fan controller through the electronic switch branch for functional testing, and the control unit inputs a DC signal into the brushless axial flow fan controller for DC testing through the DC signal transmission unit, thereby one device can meet the DC test and functional test of the brushless axial flow fan controller, thereby improving work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of the utility model in the embodiment;

[0030] Figure 2 A circuit diagram of a control unit in an embodiment

[0031] Figure 3 is a circuit diagram of five DC signal transmission units in the embodiment;

[0032] Figure 4 is a circuit diagram of five relays in the embodiment;

[0033] Figure 5 is a circuit diagram of a switch power supply unit in an embodiment;

[0034] Figure 6 is a circuit diagram of a power supply unit in an embodiment;

[0035] Figure 7 is a circuit diagram of a PWM output unit in an embodiment;

[0036] Figure 8 is a circuit diagram of a test voltage output unit in an embodiment. DETAILED DESCRIPTION

[0037] Now the utility model is further described in detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the utility model in a schematic manner, and therefore only show the components related to the utility model.

[0038] like Figure 1 As shown, a test device for a brushless axial flow fan controller includes a control unit 1, a power supply unit 2, a PWM output unit 3, a test voltage output unit 4, at least one DC signal transmission unit 6 and at least one electronic switch branch 5;

[0039] The power supply unit 2 provides working voltage to the control unit 1 respectively; the control unit 1 is electrically connected to the PWM output unit 3, and the PWM signal is output through the PWM output unit 3; the control unit 1 is electrically connected to the test voltage output unit 4, and the test voltage is output through the test voltage output unit 4; the control unit 2 is electrically connected to the input end of all DC signal transmission units 6;

[0040] The output ends of all DC signal transmission units 6, the PWM signal output ends of the PWM output unit 3, and the test voltage output ends of the test voltage output unit 4 are electrically connected to the first connection ends of different electronic switch branches 5, and the control unit 1 is electrically connected to the control end of the electronic switch branch 5, and is used to input a switch control signal to the control end of the electronic switch branch 5, and the switch control signal is used to control the on and off of the electronic switch branch 5.

[0041] In actual use, the control unit 1 of the utility model outputs a PWM signal through the PWM output unit 3 and outputs a test voltage through the test voltage output unit 4. The PWM signal and the test voltage can be input into the brushless axial flow fan controller through the electronic switch branch 5 for functional testing. The control unit 1 inputs the DC signal into the brushless axial flow fan controller for DC testing through the DC signal transmission unit 6, thereby allowing one device to meet the DC test and functional test of the brushless axial flow fan controller, thereby improving work efficiency.

[0042] Specifically, in this embodiment, assuming that the number of all electronic switch branches is A and the number of DC signal transmission units 6 is B, A and B need to satisfy the following relationship: A is greater than or equal to B+2.

[0043] Specifically, in this embodiment, the circuit of the control unit 1 is as follows: Figure 2 As shown, the control unit 1 includes a single chip microcomputer U4 of model STM8S903K3.

[0044] Specifically, in this embodiment, Figure 3 As shown, the utility model includes five DC signal transmission units 6, and the circuits of the five DC signal transmission units 6 are the same. Taking the top DC signal transmission unit 6 as an example, the DC signal transmission unit 6 includes resistors R7, resistors R8, resistors R9 and capacitor C1. One end of the resistor R9 is the input end of the DC signal transmission unit 6 and is grounded through the capacitor C1; the other end of the resistor R9 is electrically connected to one end of the resistor R7 and one end of the resistor R8 respectively, the other end of the resistor R8 is grounded, and the other end of the resistor R7 is the output end of the DC signal transmission unit 6.

[0045] Specifically, in this embodiment, the utility model includes seven electronic switch branches 5, such as Figure 4 As shown, the seven electronic switch branches 5 are provided by five relays, and the five relays are respectively a first relay K1_1, a second relay K1_2, a third relay K1_3, a fourth relay K4 and a fifth relay K5;

[0046] Two of the five DC signal transmission units 6 are electrically connected to two common terminals of the first relay K1_1 respectively;

[0047] The other two outgoing ends of the five DC signal transmission units 6 are electrically connected to the two common ends of the second relay K1_2 respectively;

[0048] The remaining one of the five DC signal transmission units 6 is electrically connected to a common terminal of the third relay K1_3;

[0049] The PWM signal output terminal of the PWM output unit 3 is electrically connected to a common terminal of the fourth relay K4;

[0050] The test voltage output terminal of the test voltage output unit 6 is electrically connected to a common terminal of the fifth relay K5 .

[0051] In addition, Figure 4 In the embodiment, one end of the control coils of all relays is electrically connected for inputting a driving voltage V_R, the other end of the control coil of the first relay K1_1 is electrically connected to the other end of the control coil of the second relay K1_2 and the other end of the control coil of the third relay K1_3, respectively, and the other end of the control coil of the first relay K1_1, the other end of the control coil of the fourth relay K4 and the other end of the control coil of the fifth relay K5 are respectively connected to a driving circuit;

[0052] Taking the driving circuit electrically connected to the control coil of the first relay K1_1 as an example, it includes a resistor R1, a resistor R2 and a transistor Q1, the collector of the transistor Q1 is electrically connected to the other end of the control coil, the base of the transistor Q1 is electrically connected to one end of the resistor R1 and one end of the resistor R2 respectively, the other end of the resistor R1 is electrically connected to the control unit for inputting a switch control signal, and the other end of the resistor R2 and the emitter of the transistor Q1 are both grounded.

[0053] Specifically, in this embodiment, the utility model further includes a switch power supply unit 7, which is used to supply power to the control coil of the relay. Figure 5 As shown, the switch power supply unit 7 includes a first power supply chip U1 of model LM317;

[0054] Pin No. 3 of the first power chip U1 is grounded through capacitors C5 and C7 respectively, and is used for inputting voltage VCC;

[0055] Pin 1 of the first power chip U1 is grounded through capacitor C8, capacitor R22 and resistor R23 respectively, and is electrically connected to one end of resistor R24;

[0056] Pin No. 2 of the first power chip U1 is grounded through capacitors C9 and C10, and is electrically connected to the other end of resistor R24 ​​and one end of resistor R25, respectively, for outputting a driving voltage V_R. The other end of resistor R25 is grounded through resistor R26.

[0057] Specifically, in this embodiment, the circuit of the power supply unit 2 is as follows: Figure 6 The invention comprises a second power chip U2 of model LM317 and a third power chip U3 of model 78L05;

[0058] Pin No. 3 of the second power chip U2 is grounded through capacitor C17 and capacitor C18 respectively, and is used for input voltage VCC; Pin No. 1 of the second power chip U2 is grounded through capacitor C19 and resistor R56 respectively, and is electrically connected to one end of resistor R57; Pin No. 2 of the second power chip U2 is grounded through capacitor C20 and capacitor C21 respectively, and is electrically connected to the other end of resistor R57 and pin No. 3 of the third power chip U3 respectively; Pin No. 2 of the third power chip U3 is grounded, and pin No. 1 of the third power chip U3 is grounded through capacitor C22 and capacitor C23 respectively, and is used for outputting working voltage.

[0059] Specifically, in this embodiment, the circuit of the PWM output unit 3 is as follows: Figure 7As shown, it includes a transistor Q6, the emitter of the transistor Q6 is electrically connected to one end of the resistor R30, for inputting a voltage VCC, the base of the transistor Q6 is electrically connected to the other end of the resistor R30 and one end of the resistor R29, respectively, the collector of the transistor Q6 is electrically connected to one end of the resistor R31 and one end of the capacitor C11, respectively, for outputting a PWM signal, and the other end of the resistor R31 and the other end of the capacitor C11 are both grounded;

[0060] The other end of resistor R29 is electrically connected to the collector of transistor Q5, the base of transistor Q5 is electrically connected to one end of resistor R27 and one end of resistor R28 respectively, the other end of resistor R27 is electrically connected to the control unit, and the other end of resistor R28 and the emitter of transistor Q5 are both grounded.

[0061] In actual use, the control unit 1 outputs a PWM signal by controlling the on and off of the transistor Q5.

[0062] Specifically, in this embodiment, the circuit of the test voltage output unit 4 is as follows: Figure 8 As shown, it includes a resistor R38, one end of the resistor R38 is electrically connected to one end of the resistor R39 for inputting a voltage VCC, the other end of the resistor R38 is electrically connected to the cathode of the voltage zener diode Z1, the cathode of the voltage zener diode Z2, the collector of the transistor Q10 and the base of the transistor Q9, the other end of the resistor R39 is electrically connected to the collector of the transistor Q9, the anode of the voltage zener diode Z1 is grounded, the anode of the voltage zener diode Z2 is electrically connected to the collector of the transistor Q8, and the base of the transistor Q8 is electrically connected to the cathode of the voltage zener diode Z1, the cathode of the voltage zener diode Z2 is electrically connected to the collector of the transistor Q8, and the base of the transistor Q8 is electrically connected to the cathode of the voltage zener diode Z2. They are respectively electrically connected to one end of resistor R36 and one end of resistor R37, the other end of resistor R36 is electrically connected to the control unit, the other end of resistor R37 and the emitter of transistor Q8 are both grounded; the emitter of transistor Q9 is respectively electrically connected to the base of transistor Q10 and one end of resistor R40, the emitter of transistor Q10 is respectively electrically connected to one end of resistor R41, one end of capacitor C12 and the other end of resistor R40, which is the test voltage output end, the other end of resistor R41 and the other end of capacitor C12 are both grounded.

[0063] In actual use, when the transistor Q8 is turned on and off, the test voltage output unit 4 outputs voltages in different intervals. When the transistor Q8 is turned on, the voltage output by the test voltage output unit 4 is between 5.1V-0.7V, and when the transistor Q8 is turned off, the voltage output by the test voltage output unit 4 is between 12V-0.7V.

[0064] The above is based on the enlightenment of this utility model. Through the above description, relevant staff can make various changes and modifications without deviating from the technical idea of ​​this utility model. The technical scope of this utility model is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A test device for a brushless axial flow fan controller, characterized in that: It includes a control unit, a power supply unit, a PWM output unit, a test voltage output unit, at least one DC signal transmission unit and at least one electronic switch branch; The power supply unit provides working voltage for the control unit respectively; the control unit is electrically connected to the PWM output unit, and outputs PWM signal through the PWM output unit; the control unit is electrically connected to the test voltage output unit, and outputs test voltage through the test voltage output unit; the control unit is electrically connected to the input end of all DC signal transmission units; The output ends of all DC signal transmission units, the PWM signal output ends of the PWM output units, and the test voltage output ends of the test voltage output units are electrically connected to the first connection ends of different electronic switch branches, and the control unit is electrically connected to the control end of the electronic switch branch, and is used to input a switch control signal to the control end of the electronic switch branch, and the switch control signal is used to control the on and off of the electronic switch branch.

2. A brushless axial flow fan controller testing device according to claim 1, characterized in that: The control unit includes a single chip microcomputer of model STM8S903K3.

3. A brushless axial flow fan controller testing device according to claim 1, characterized in that: Includes five DC signal transmission units.

4. A brushless axial flow fan controller testing device according to claim 3, characterized in that: The DC signal transmission unit includes resistors R7, R8, R9 and capacitor C1, one end of the resistor R9 is the input end of the DC signal transmission unit and is grounded through the capacitor C1; the other end of the resistor R9 is electrically connected to one end of the resistor R7 and one end of the resistor R8 respectively, the other end of the resistor R8 is grounded, and the other end of the resistor R7 is the output end of the DC signal transmission unit.

5. The test device for a brushless axial flow fan controller according to claim 3, characterized in that: The device comprises seven electronic switch branches, wherein the seven electronic switch branches are provided by five relays, and the five relays are respectively a first relay, a second relay, a third relay, a fourth relay and a fifth relay; Two of the five DC signal transmission units' output ends are electrically connected to two common ends of the first relay respectively; The other two outgoing ends of the five DC signal transmission units are electrically connected to the two common ends of the second relay respectively; The remaining one of the five DC signal transmission units' output ends is electrically connected to a common end of the third relay; The PWM signal output terminal of the PWM output unit is electrically connected to a common terminal of the fourth relay; The test voltage output terminal of the test voltage output unit is electrically connected to a common terminal of the fifth relay.

6. A brushless axial flow fan controller testing device according to claim 5, characterized in that: One end of the control coils of all relays is electrically connected for inputting a driving voltage V_R, the other end of the control coil of the first relay is electrically connected to the other end of the control coil of the second relay and the other end of the control coil of the third relay, respectively, and the other end of the control coil of the first relay, the other end of the control coil of the fourth relay and the other end of the control coil of the fifth relay are respectively connected to a driving circuit; The driving circuit includes a resistor R1, a resistor R2 and a transistor Q1, the collector of the transistor Q1 is electrically connected to the other end of the control coil, the base of the transistor Q1 is electrically connected to one end of the resistor R1 and one end of the resistor R2 respectively, the other end of the resistor R1 is electrically connected to the control unit for inputting the switch control signal, and the other end of the resistor R2 and the emitter of the transistor Q1 are both grounded.

7. A brushless axial flow fan controller testing device according to claim 6, characterized in that: It also includes a switch power supply unit, wherein the switch power supply unit includes a first power supply chip of model LM317; Pin No. 3 of the first power chip is grounded through capacitors C5 and C7 respectively, and is used for inputting voltage VCC; Pin 1 of the first power chip is grounded through capacitor C8, capacitor R22 and resistor R23, and is electrically connected to one end of resistor R24; Pin No. 2 of the first power chip is grounded through capacitors C9 and C10, and is electrically connected to the other end of resistor R24 ​​and one end of resistor R25, respectively, for outputting a driving voltage V_R. The other end of resistor R25 is grounded through resistor R26.

8. The test device for a brushless axial flow fan controller according to claim 1, characterized in that: The power supply unit includes a second power chip of model LM317 and a third power chip of model 78L05; Pin No. 3 of the second power chip is grounded through capacitor C17 and capacitor C18 respectively, and is used for inputting voltage VCC; Pin No. 1 of the second power chip is grounded through capacitor C19 and resistor R56 respectively, and is electrically connected to one end of resistor R57; Pin No. 2 of the second power chip is grounded through capacitor C20 and capacitor C21 respectively, and is electrically connected to the other end of resistor R57 and pin No. 3 of the third power chip respectively; Pin No. 2 of the third power chip is grounded, and pin No. 1 of the third power chip is grounded through capacitor C22 and capacitor C23 respectively, and is used for outputting the working voltage.

9. A brushless axial flow fan controller testing device according to claim 1, characterized in that: The PWM output unit includes a transistor Q6, the emitter of the transistor Q6 is electrically connected to one end of the resistor R30, and is used to input the voltage VCC, the base of the transistor Q6 is electrically connected to the other end of the resistor R30 and one end of the resistor R29, respectively, the collector of the transistor Q6 is electrically connected to one end of the resistor R31 and one end of the capacitor C11, respectively, and is the PWM signal output end, and the other end of the resistor R31 and the other end of the capacitor C11 are both grounded; The other end of resistor R29 is electrically connected to the collector of transistor Q5, the base of transistor Q5 is electrically connected to one end of resistor R27 and one end of resistor R28 respectively, the other end of resistor R27 is electrically connected to the control unit, and the other end of resistor R28 and the emitter of transistor Q5 are both grounded.

10. A brushless axial flow fan controller testing device according to claim 1, characterized in that: The test voltage output unit includes a resistor R38, one end of which is electrically connected to one end of a resistor R39 for inputting a voltage VCC, the other end of which is electrically connected to the cathode of a voltage zener diode Z1, the cathode of a voltage zener diode Z2, the collector of a transistor Q10 and the base of a transistor Q9, respectively, the other end of which is electrically connected to the collector of a transistor Q9, the anode of a voltage zener diode Z1 is grounded, the anode of a voltage zener diode Z2 is electrically connected to the collector of a transistor Q8, and the base of a transistor Q8 is electrically connected to the cathode of a voltage zener diode Z1. They are respectively electrically connected to one end of resistor R36 and one end of resistor R37, the other end of resistor R36 is electrically connected to the control unit, the other end of resistor R37 and the emitter of transistor Q8 are both grounded; the emitter of transistor Q9 is respectively electrically connected to the base of transistor Q10 and one end of resistor R40, the emitter of transistor Q10 is respectively electrically connected to one end of resistor R41, one end of capacitor C12 and the other end of resistor R40, which is the test voltage output end, the other end of resistor R41 and the other end of capacitor C12 are both grounded.

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