A curtain drive system

Abstract

The utility model discloses a curtain driving system of drawing, its voltage transformation module is through the rectifier bridge cooperation with transformer and converts alternating current into direct current, phase sequence protection module is used for detecting the phase sequence of three -phase power supply, when the phase sequence is correct, the direct current of output voltage transformation module conversion, when the phase sequence is wrong, do not output the direct current, and send out the alarm prompt to improve security, control module is connected with the output end of phase sequence protection module, control module includes a plurality of relays, forms interlocking structure, can form the control signal of three -phase motor, and power output module includes a plurality of power relays, realizes three -phase motor and three -phase power supply connection through a plurality of power relays, and power output module carries out control action according to the control signal of control module. Control module and power output module all carry out control to three -phase motor through a plurality of relay combinations, and it is favorable to simplify circuit, saves the cost.

Description

Technical Field

[0001] This utility model relates to the field of greenhouse curtain pulling equipment technology, and in particular to a curtain pulling drive system. Background Technology

[0002] The operation of opening and closing the shade net in a greenhouse is achieved by a three-phase motor driving the shade net to retract or expand via a transmission mechanism, thereby regulating the light inside the greenhouse. The power terminals of the three-phase motor are connected to a three-phase power supply. Typically, a phase sequence detection module is installed to detect the phase sequence. When an incorrect phase sequence is detected, the power supply to the three-phase motor is directly disconnected via a switch. This structure lacks an alarm unit.

[0003] Furthermore, the current control circuits for forward and reverse rotation of three-phase motors are quite complex, which is not conducive to cost reduction. Utility Model Content

[0004] The purpose of this utility model is to provide a curtain-pulling drive system. The phase sequence protection module is used to detect the phase sequence. When the phase sequence is incorrect, the back-end circuit is disconnected and an alarm is issued to improve safety. In addition, both the control module and the power output module control the three-phase motor through a combination of multiple relays, which helps to simplify the circuit and save costs.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] A curtain-pulling drive system, comprising:

[0007] The transformer module converts AC power into DC power through transformer T1 and rectifier bridge D4.

[0008] The phase sequence protection module is used to detect the phase sequence of the three-phase power supply. When the phase sequence is correct, it outputs DC power converted by the transformer module. When the phase sequence is incorrect, it does not output DC power and issues an alarm.

[0009] The control module is connected to the output of the phase sequence protection module; the control module includes multiple relays forming an interlocking structure, capable of generating control signals for the three-phase motor; and

[0010] The power output module includes multiple power relays, which connect the three-phase motor to the three-phase power supply. The power output module is also connected to the output terminal of the control module.

[0011] In some implementations, the primary winding of the transformer is connected to a three-phase power supply, and the secondary winding of the transformer outputs a 12V AC voltage.

[0012] The rectifier bridge D4 is equipped with four diodes, forming a full-bridge rectifier structure;

[0013] The output terminal of the transformer module is equipped with a capacitor C4.

[0014] In some embodiments, the phase sequence protection module includes a detection unit and a relay K1;

[0015] The detection unit is electrically connected to the three phases of the three-phase power supply; the relay K1 is connected to both the detection unit and the transformer module.

[0016] When the phase sequence is correct, relay K1 is in the energized state and outputs 12V DC voltage;

[0017] When the phase sequence is incorrect, relay K1 is in the open state and does not output 12V DC voltage.

[0018] In some embodiments, the detection unit includes resistors R1, R5, and R6;

[0019] The resistors R1, R5, and R6 are connected to phase A, phase B, and phase C of the three-phase power supply, respectively.

[0020] The output terminal of the resistor R1 is connected to the relay K1;

[0021] The output terminal of resistor R1 is connected to the input terminal of resistor R5 via capacitor C2 and resistor R4.

[0022] The output terminal of resistor R5 is grounded;

[0023] A capacitor C3 is connected between the output terminals of resistor R6 and resistor R5.

[0024] In some embodiments, the phase sequence protection module further includes a neon tube B1, a transistor Q2, and a transistor Q1 connected in sequence; the input terminal of the neon tube B1 is connected to phase A;

[0025] Pin 1 of transistor Q2 is connected to neon tube B1, pin 2 of transistor Q2 is connected to pin 1 of transistor Q1, and pin 3 of transistor Q2 is grounded.

[0026] Pin 2 of transistor Q1 is connected to pin 12 of relay K1, and pin 3 of transistor Q1 is grounded.

[0027] In some embodiments, pins 4 and 9 of the relay K1 are both connected to the output terminal of the transformer module;

[0028] Pins 5 and 8 of the relay K1 are both output terminals;

[0029] The fault indicator light is connected to pin 3 of the relay K1.

[0030] In some embodiments, the phase sequence protection module further includes diode D3, diode D1, and diode D2;

[0031] The diode D3 is connected to pin 1 of transistor Q2, and the diode D1 is connected to pin 2 of transistor Q2;

[0032] The diode D2 is connected to pin 2 of the transistor Q1;

[0033] The phase sequence protection module also includes a resistor R3 and a capacitor C1, which are connected in parallel between transistor Q1 and transistor Q2.

[0034] The beneficial effects of this utility model are as follows: the phase sequence protection module is used to detect the phase sequence. When the phase sequence is incorrect, it disconnects the back-end circuit and issues an alarm, thereby improving safety. Furthermore, both the control module and the power output module control the three-phase motor through a combination of multiple relays, which helps to simplify the circuit and save costs. Attached Figure Description

[0035] Figure 1 This is a structural diagram of a curtain-pulling drive system according to the present invention;

[0036] Figure 2 This is a circuit diagram of the transformer module of this utility model;

[0037] Figure 3 This is a circuit diagram of the phase sequence protection module of this utility model;

[0038] Figure 4 This is a circuit diagram of the control module of this utility model;

[0039] Figure 5 This is a circuit diagram of the power output module of this utility model;

[0040] Among them: 1-Three-phase power supply; 2-Transformer module; 3-Phase sequence protection module; 4-Control module; 5-Power output module; 6-Three-phase motor. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings.

[0042] refer to Figures 1 to 5 A curtain-pulling drive system is used to pull the shading net of a greenhouse to retract and expand, thereby regulating light and ventilation.

[0043] The system includes:

[0044] Transformer module 2, through transformer T1 and rectifier bridge D4, converts AC power into unidirectional pulse DC power; transformer T1 is used to step down the voltage, and rectifier bridge D4 is used to rectify the voltage output by transformer T1. For example, transformer T1 reduces the three-phase power supply 1 of 380V to 12V, and rectifier bridge D4 rectifies the 12V voltage and outputs it to provide voltage for the downstream circuit.

[0045] Phase sequence protection module 3 is connected to the three phases of the three-phase power supply 1 and also to the output terminal of transformer module 2. Phase sequence protection module 3 is used to detect the phase sequence of the three-phase power supply 1. When the phase sequence is correct, it outputs a unidirectional pulse DC voltage converted by transformer module 2. When the phase sequence is incorrect, it does not output the unidirectional pulse DC voltage and issues an alarm. For example, when the phase sequence of the three-phase power supply 1 is correct, it outputs a 12V voltage. When the phase sequence is incorrect, it does not output a 12V voltage, thereby improving the safety of the circuit.

[0046] Control module 4 is connected to the output terminal of phase sequence protection module 3; control module 4 includes multiple relays, which form an interlocking structure and can generate control signals for three-phase motor 6; such as forward rotation, reverse rotation, travel limit and stop control signals, which can be understood as control actions;

[0047] as well as

[0048] The power output module 5 includes multiple power relays, which connect the three-phase motor 6 to the three-phase power supply 1. The power output module 5 is also connected to the output terminal of the control module 4. The power output module 5 executes control actions on the three-phase motor 6, such as forward and reverse rotation, according to the control signals from the control module 4.

[0049] The output end of the three-phase motor 6 is connected to the shaft of the shade net, thereby pulling the shade net to close and unfold. A speed reducer can be installed at the output end of the three-phase motor 6 to increase the torque.

[0050] Therefore, by setting up a phase sequence protection module 3 to detect the phase sequence of the three-phase power supply 1, when the phase sequence is incorrect, the phase sequence protection module 3 will not output voltage, causing the control module 4 and power output module 5 to be in a de-energized state, thus disconnecting the three-phase power supply 1 from the three-phase motor 6, and issuing an alarm prompt at the same time, which is beneficial for protecting the circuit and improving safety and service life; that is, when the phase sequence is incorrect, the phase sequence protection module 3 disconnects the downstream control module 4 and power output module 5, which not only protects the control module 4 and power output module 5, but also protects the three-phase motor 6;

[0051] Furthermore, the control module 4 generates control signals such as forward rotation, reverse rotation, travel limit, and stop through multiple interlocked relays, which helps to simplify the circuit and save costs.

[0052] Furthermore, the power output module 5 is designed with multiple circuit breakers, which simplifies the circuit and saves costs.

[0053] refer to Figure 2 The primary winding of the transformer T1 is connected to the three-phase power supply 1, and the secondary winding of the transformer T1 outputs a 12V AC voltage.

[0054] The rectifier bridge D4 is equipped with four diodes to form a full-bridge rectifier structure; the rectifier bridge D4 is composed of four diodes to achieve full-wave rectification and output DC voltage;

[0055] Transformer T1 works by stepping down the input 380V AC voltage to 12V AC voltage. Through electromagnetic induction, the primary winding connects to 380V AC, while the secondary winding outputs 12V AC, achieving voltage level conversion to meet the low-voltage requirements of subsequent circuits.

[0056] Rectifier bridge D4 working principle: Diode model: KBP206. Four diodes form a rectifier bridge, which performs full-wave rectification of the 12V AC voltage output from transformer T1. Utilizing the unidirectional conductivity of the diodes, the negative half-cycle of the AC voltage is flipped to the positive half-cycle, and a unidirectional pulsating DC voltage is output.

[0057] The output terminal of the transformer module 2 is equipped with a capacitor C4.

[0058] The function of capacitor C4 is to filter the rectified unidirectional pulsating DC voltage. Capacitors have the characteristic of "passing AC and blocking DC," storing and releasing electrical energy, smoothing voltage fluctuations, making the output 12V DC voltage more stable, reducing ripple, and providing a stable DC voltage for downstream circuits.

[0059] refer to Figure 2 The phase sequence protection module 3 includes a detection unit 31 and a relay K1;

[0060] The detection unit 31 is electrically connected to the three phases of the three-phase power supply 1; the relay K1 is connected to both the detection unit and the transformer module 2.

[0061] When the phase sequence is correct, relay K1 is in the energized state and outputs 12V DC voltage;

[0062] When the phase sequence is incorrect, relay K1 is in the open state and does not output 12V DC voltage.

[0063] Furthermore, the detection unit includes resistors R1, R5, and R6;

[0064] The resistors R1, R5 and R6 are respectively connected to phase A, phase B and phase C of the three-phase power supply 1;

[0065] The output terminal of the resistor R1 is connected to the relay K1;

[0066] The output terminal of resistor R1 is connected to the input terminal of resistor R5 via capacitor C2 and resistor R4.

[0067] The output terminal of resistor R5 is grounded;

[0068] A capacitor C3 is connected between the output terminals of resistor R6 and resistor R5.

[0069] Therefore, the phase sequence of the three-phase power supply 1 is detected by resistors R1, R5, R6, capacitor C2, and resistor R4.

[0070] Furthermore, the phase sequence protection module 3 also includes a neon tube B1, a transistor Q2 and a transistor Q1 connected in sequence; the input terminal of the neon tube B1 is connected to A;

[0071] Pin 1 of transistor Q2 is connected to neon tube B1, pin 2 of transistor Q2 is connected to pin 1 of transistor Q1, and pin 3 of transistor Q2 is grounded.

[0072] Pin 2 of transistor Q1 is connected to pin 12 of relay K1, and pin 3 of transistor Q1 is grounded.

[0073] Therefore, neon tube B1 is configured to trigger corresponding indicators. When the phase sequence of the three-phase power supply 1 is correct, the voltage across neon tube B1 is normal, and neon tube B1 does not light up. When the phase sequence of the three-phase power supply 1 is incorrect, the voltage across neon tube B1 increases, and neon tube B1 lights up. The downstream transistors Q2 and Q1, through the indication of neon tube B1, trigger the state of the control relay K1. Both transistors Q1 and Q2 are model S8050; the relay K1 is model TX2-12V.

[0074] Furthermore, pins 4 and 9 of the relay K1 are both connected to the output terminal of the transformer module 2;

[0075] Pins 5 and 8 of the relay K1 are both output terminals;

[0076] Pin 3 of relay K1 is connected to a fault indicator light;

[0077] Therefore, when the phase sequence is correct, circuit breaker K1 is energized and outputs 12V voltage. When the phase sequence is incorrect, circuit breaker K1 is de-energized and does not output 12V voltage. At this time, the fault indicator light illuminates to issue an alarm. Circuit breaker K1, as a switching structure, outputs 12V voltage according to the phase sequence, which is beneficial for circuit protection.

[0078] Furthermore, the phase sequence protection module 3 also includes diode D3, diode D1, and diode D2;

[0079] The diode D3 is connected to pin 1 of transistor Q2, and the diode D1 is connected to pin 2 of transistor Q2;

[0080] The diode D2 is connected to pin 2 of the transistor Q1;

[0081] The model numbers of diodes D3, D1, and D2 are all 1N4007.

[0082] Among them, diode D3 mainly serves to rectify or prevent reverse voltage, protecting downstream electronic components such as transistor Q2; diode D1 prevents reverse voltage from affecting components such as transistor Q1; and diode D2 is used for freewheeling when the coil of relay K1 is de-energized, protecting transistor Q1.

[0083] Furthermore, the phase sequence protection module 3 also includes a resistor R3 and a capacitor C1, which are connected in parallel between transistor Q1 and transistor Q2.

[0084] Therefore, resistor R3 and capacitor C1 form a filter or delay circuit, which helps to stabilize the output signal of transistor Q2. At the same time, resistor R3 is connected to pin 1 of transistor Q1, and the base of transistor Q1 is pulled up to a high level through resistor R3.

[0085] Working principle of phase sequence protection module 3:

[0086] The circuit breaker K1 is configured to achieve electrical isolation and signal conversion of the circuit, and to control the switching of the +12V voltage of the back-end circuit (e.g., control module 4).

[0087] When the phase sequence is normal, the base (pin 1) of transistor Q2 is at a low level, and the emitter (pin 3) of transistor Q1 has no output. At this time, the base (pin 1) of transistor Q1 is pulled up to a high level through resistor R3, and the emitter (pin 3) and collector (pin 2) of transistor Q1 are connected. The collector (pin 2) is connected to the negative terminal, so the emitter (pin 3) of transistor Q1 outputs the negative terminal. Since pin 12 of relay K1 is connected to the emitter of transistor Q1 and pin 12 of relay K1 is connected to the positive terminal, the coil of relay K1 receives 12V voltage, the contacts close and output 12V voltage, which powers the control module 4. Thus, the control module 4 can control the forward and reverse rotation of the three-phase motor 6.

[0088] When the phase sequence is incorrect, the base (pin 1) of transistor Q2 is at a high level, so the emitter (pin 3) and collector (pin 2) of transistor Q1 cannot conduct, the 12V voltage is disconnected, and the fault light outputs a fault alarm through the normally closed contact of the circuit breaker K1.

[0089] The FAULT terminal is connected to the fault indicator light. Resistor R7 limits the current of the fault indicator light. When a fault occurs in the circuit (such as the relay not engaging properly), the fault indicator light will illuminate to indicate the fault.

[0090] Working principle of control module 4:

[0091] refer to Figure 4 The control module 4 consists of a circuit with interlocking function and interlocking control with the travel limit switch, composed of five small electrical relays (K2 to K6), used for motor forward and reverse rotation, travel limit, stop and other controls.

[0092] Interlocking is typically achieved by connecting the contacts of other relays to the coil or contact circuit of a relay. For example, in a motor forward / reverse control circuit, the forward and reverse relays need to be interlocked. When the forward relay coil is energized, its normally closed contact will disconnect the coil circuit of the reverse relay, ensuring that the reverse relay cannot be energized simultaneously, thus preventing damage to the motor from starting in both forward and reverse directions at the same time.

[0093] Forward rotation: Relay K2 (Model: TX2-12V)

[0094] Working principle: When the LEFT VCC ON signal is high (+12V), the coil of relay K2 is energized and the contacts actuate, resulting in a LEFT OUT output, thus enabling the forward rotation function of the three-phase motor 6. LEFT VCC and LEFT GND supply power to the control terminals of relay K2, while LEFT ZS can be used to provide feedback on the forward rotation status.

[0095] Limit switch for open travel: Relay K3 (Model: HFD4 / 12)

[0096] Working principle: When the equipment reaches the open travel limit position, a corresponding signal is triggered, causing a change in LEFT ZS and an output of LEFT VCC OUT. This can be used to cut off the forward rotation control circuit or issue a limit signal. LEFT GND and LEFT VCC power relay K3, while +B 12V is an external power supply.

[0097] Limit switch for travel: Relay K5 (Model: HFD4 / 12)

[0098] Working principle: Similar to the open travel limit switch, when the equipment reaches the closed travel limit position, the RIGHT ZS signal changes, and the RIGHT VCC OUT output is triggered, cutting off the reverse control circuit or issuing a limit signal. RIGHT GND and RIGHT VCC power relay K5, and +B 12V is the external power supply.

[0099] Reverse: Relay K4 (Model: TX2-12V)

[0100] Working principle: When the RIGHT VCC ON signal is high (+12V), the coil of relay K4 is energized and the contacts actuate, resulting in a RIGHT OUT output, thus realizing the reverse function of the three-wheeled motor. RIGHT VCC and RIGHT GND supply power to the control terminals of relay K4, while RIGHT ZS can be used to provide feedback on the reverse state.

[0101] Stop: Relay K6 (Model: HFD4 / 12)

[0102] Working principle: When the STOP signal is valid (high level +12V), the relay K6 is energized, cutting off the power supply to the forward and reverse control circuit of the three-phase motor 6 (by cutting off the +12V power supply), thus stopping the three-phase motor 6 from running.

[0103] The following explanation uses relays K2 and K3 as examples:

[0104] Pin 1 of relay K3 is 12V. Pin 8 is connected in series with the normally closed switch of the limit switch and the negative power supply (GND) (leading out from the external terminal CN2). At this time, relay K3 is energized, and the contacts of pins 5 and 6 are connected. Because the normally closed switch of the limit switch is connected in series with the negative power supply (GND), the LEFT ZS state of pin 5 is also connected to the negative power supply (GND). At the same time, LEFT VCCOUT of pin 3 is also connected to LEFT-VCC of pin 4. LEFT VCC is connected through the normally closed contacts of pins 9 and 10 of relay K4. Therefore, LEFT VCC of pin 1 of relay K2 is also connected to the 12V power supply. When the external manual switch is pressed (leading out from the CN1 external terminal), pin 1 "GND" and pin 4 "LEFT" of CN1 terminal are connected. At this time, the LEFT pin of relay K2 is also connected to GND, relay K2 is energized and engaged, pins 8 and 9 of relay K2 are engaged and conducting, and the LEFT OUT of pin 8 outputs 12V power. Therefore, LEFT OUT simultaneously supplies 12V power to relays K7, K8, and K9, relays K7, K8, and K9 are engaged at the same time, and the three-phase motor starts to rotate forward. When relay K2 is energized, the LEFT contacts at pins 4 and 5 close, forming a self-locking connection. Relays K7, K8, and K9 are continuously powered, maintaining the three-phase motor's forward rotation. When the limit switch reaches its position, the normally closed switch opens, and pins 1 (GND) and 4 (LEFT) of the CN2 external terminal disconnect. The LEFT GND of pin 8 of relay K3 also disconnects from GND, causing relay K3 to de-energize and reset. The LEFT VCC of pin 4 is also de-energized. At this time, relay K2 also de-energizes and resets, and relays K7, K8, and K9 are also de-energized simultaneously, stopping the three-phase motor from operating.

[0105] Working principle of power output module 5:

[0106] refer to Figure 5 The power output module 5 includes multiple power relays (K7 to K12), all of which are model number HF115F / 012-H33A. The power relays are used to realize the forward and reverse rotation output of the motor.

[0107] Forward rotation output section (relays K7 to K9):

[0108] Working principle: When the LEFT OUT signal is valid, the coils of the corresponding relays (K7 to K9) are energized and closed, the contacts actuate, and the A, B, and C phases of the three-phase power supply are connected in the forward sequence for output, realizing the forward rotation of the motor. Relay K7 is equipped with diode D5, which plays a freewheeling protection role, preventing the back electromotive force generated when relay K7 is de-energized from damaging the circuit.

[0109] Among them, ports U, A, and W are the power supply terminals for the three-phase motor 6.

[0110] Inverting output section (relays K10 to K12):

[0111] Working principle: Similar to forward rotation, when the RIGHT OUT signal is valid, the coils of the corresponding relays (K10 to K12) are energized and closed, the contacts actuate, and the three-phase power sequence is changed, thus reversing the motor. Relay K10 is equipped with diode D6, which provides freewheeling protection to prevent the back electromotive force generated when relay K10 is de-energized from damaging the circuit.

[0112] The above description only discloses some embodiments of this utility model. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of this utility model, and these all fall within the protection scope of this utility model.

Claims

1. A curtain-pulling drive system, characterized in that, include: The transformer module (2) converts AC power into DC power through the transformer T1 and the rectifier bridge D4. The phase sequence protection module (3) is used to detect the phase sequence of the three-phase power supply (1). When the phase sequence is correct, it outputs the DC power converted by the transformer module (2). When the phase sequence is incorrect, it does not output the DC power and issues an alarm. The control module (4) is connected to the output terminal of the phase sequence protection module (3); the control module (4) includes multiple relays, which form an interlocking structure and can generate control signals for the three-phase motor (6); The phase sequence protection module (3) includes a detection unit (31) and a relay K1; The detection unit (31) is connected to the three-phase power supply (1); the relay K1 is connected to the detection unit (31) and the transformer module (2) respectively; The phase sequence protection module (3) also includes a neon tube B1, a transistor Q2 and a transistor Q1 connected in sequence; the input terminal of the neon tube B1 is connected to phase A; Pin 1 of transistor Q2 is connected to neon tube B1, pin 2 of transistor Q2 is connected to pin 1 of transistor Q1, and pin 3 of transistor Q2 is grounded. Pin 2 of transistor Q1 is connected to pin 12 of relay K1, and pin 3 of transistor Q1 is grounded. The phase sequence protection module (3) also includes diode D3 and diode D1. One end of diode D3 is connected to pin 1 of transistor Q2, and the other end of diode D3 is grounded. One end of diode D1 is connected to pin 2 of transistor Q2, and the other end of diode D1 is connected to pin 1 of transistor Q1. The phase sequence protection module (3) also includes a resistor R3 and a capacitor C1, which are connected in parallel between transistor Q1 and transistor Q2. The model number of the relay K1 is TX2-12V; the model numbers of the transistors Q1 and Q2 are both S8050. The power output module (5) includes multiple power relays, which connect the three-phase motor (6) to the three-phase power supply (1). The power output module (5) is connected to the output terminal of the control module (4). The power output module (5) performs control actions according to the control signal of the control module (4).

2. The curtain-pulling drive system according to claim 1, characterized in that, The primary winding of the transformer is connected to a three-phase power supply (1), and the secondary winding of the transformer outputs a 12V AC voltage. The rectifier bridge D4 is equipped with four diodes, forming a full-bridge rectifier structure; The output terminal of the transformer module (2) is equipped with a capacitor C4.

3. The curtain-pulling drive system according to claim 1, characterized in that, When the phase sequence is correct, relay K1 is in the energized state and outputs 12V DC voltage; When the phase sequence is incorrect, relay K1 is in the open state and does not output 12V DC voltage.

4. The curtain-pulling drive system according to claim 1, characterized in that, The detection unit includes resistors R1, R5, and R6; The resistors R1, R5 and R6 are respectively connected to phase A, phase B and phase C of the three-phase power supply (1); The output terminal of the resistor R1 is connected to the relay K1; The output terminal of resistor R1 is connected to the input terminal of resistor R5 via capacitor C2 and resistor R4. The output terminal of resistor R5 is grounded; A capacitor C3 is connected between the output terminals of resistor R6 and resistor R5.

5. The curtain-pulling drive system according to claim 1, characterized in that, Pins 4 and 9 of the relay K1 are both connected to the output terminal of the transformer module (2); Pins 5 and 8 of the relay K1 are both output terminals; The fault indicator light is connected to pin 3 of the relay K1.

6. The curtain-pulling drive system according to claim 1, characterized in that, The phase sequence protection module (3) also includes diode D2; The diode D2 is connected to pin 2 of the transistor Q1.

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