Preface
Growatt has purchased a wireless current transformer from Growatt, which uses a current transformer to detect the AC current in the circuit, and transmits the collected current information to the central control device for power calculation through wireless communication. The wireless flow sensor is housed in an IP65 waterproof metal enclosure and is powered by 220Vac.
The module adopts RF433 wireless communication, and is equipped with a power cable, a current transformer interface and a wireless antenna interface on the shell. The package is equipped with mounting screws inside for hanging mounting. The following charging head network will bring the disassembly of Growatt SP-CT wireless current sensor, and take a look at the internal scheme and design.
Unboxing of Growatt SP-CT wireless flow sensor
The product is packaged in a kraft paper box, and the top surface is printed with the GROWATT brand and the English name of the product.
There is an information sticker pasted on the side of the package, which indicates the power supply parameters, specifications and serial number information of the equipment.
The package contains accessories such as a sensor unit, a current transformer and an antenna.
Close-up of a current sensor with the sensor probe and socket connected by wires.
The current sensor is from LEM, model TOP 90-S10/SP2, with a maximum current of 90A.
The transformer core can be opened and placed in the conductor to be measured, without the need to cut the conductor or reassemble the conductor.
Close-up of the current sensor plug.
The plug is secured by a screw.
The measured current sensor wire length is about 1.3 meters.
Close-up of the suction cup antenna.
The antenna feeder length is about 1 meter.
Close-up of gold-plated SMA connectors.
Close-up of cable ties, expansion screws and antennas included inside the package.
A list of wireless flow sensor hosts, with the power supply wires tied to the left side.
There is a Growatt brand in the upper left corner of the main fuselage, a working indicator in the black area in the middle, and the product name of the SP-CT wireless flow sensor printed in the lower right corner.
There is a product nameplate on the back, and the yellow, green and blue three-color logo on the upper right indicates that the product has passed the Hi-Pot, ATE, and QC tests.
There is a tamper-evident sticker on the top of the main unit.
At the bottom are the power wiring, pairing button, sensor interface and antenna interface.
Close-up of the working indicator and fault indicator.
Close-up of the waterproof sealed terminal of the power cord.
Power cord crimp terminals for easy installation.
The measured length of the power cord is about 1.5 meters.
Close-up of the interface to which the sensor is connected.
Close-up of the interface to connect the wireless antenna.
Using vernier calipers, the length of the main body is about 113.9mm.
The width of the main body is about 114.4mm.
The thickness of the fuselage is about 38.4mm.
The weight of the whole machine is about 637.5g.
Growatt SP-CT wireless flow sensor disassembly
After looking at the appearance of this wireless flow sensor, let's disassemble it and take a look at the internal scheme and design.
First, unscrew the fixing screws of the cover plate and disassemble the box.
The box cover is connected with a yellow-green grounding wire.
The inside of the cover is illuminated by an indicator light, and the grounding wire is secured with screws.
There is a PCBA module inside the shell, and the power cord and the current transformer wiring are connected through connectors, which is convenient for assembly.
The edge of the housing is provided with a sealing strip.
The PCBA module is fixed by screws.
The power cord is secured by a connector.
The grounding wire is secured by screws.
Close-up of the code switch used to wirelessly connect to the host.
The current transformers are connected using plug-ins.
Wirelessly connected feeder glue fixing.
Unscrew the fixing screws, disconnect the wires, and take out the internal PCBA module.
The front of the PCBA module is at a glance, the bottom and left side are the switching power supply part, soldered terminals, rectifier bridges, NTC thermistors, high-voltage filter capacitors and power main control chips. Welded transformer on the left side, filter capacitor. The wireless connection module is soldered in the upper right corner, and the main control MCU is soldered in the middle position.
There are no soldering elements on the back of the PCBA module.
Close-up of the AC input connector.
The two blue Y capacitors are from Murata.
The common mode inductor core is fixed with a stainless steel sheet.
The SMD rectifier bridge is from onsemi, model DF04S, specification is 400V 1.5A.
The green NTC thermistor is used to suppress the inrush current at power-up.
The high-voltage filter capacitor is from Manyu and is specified at 10μF 450V.
The two blue Y capacitors are from Murata.
The power supply master controller is from PI, model TNY280PN, is the TinySwitch3 family, is a high-efficiency offline switching power supply chip, with enhanced flexibility and enhanced power range. TNY280P at 230Vac input, the adapter environment supports 8.5W output power.
The filter capacitor that powers the main control chip is 10μF 16V.
Diodes, chip resistors, and chip absorption capacitors for RCD absorption circuits are close-up.
The power transformer is produced by Huizhou Baohui Electronic Technology.
The LTV-817 optocoupler is used for output voltage feedback.
The rectifier diode model UF2G has a specification of 2A 400V.
The two filter capacitors are 100μF 25V.
Close-up of 10μH filter inductor.
The 431 is used for output voltage feedback.
Close-up of a three-terminal regulator.
The output filter capacitor specification is 100μF 25V.
The main MCU is an 8-bit MCU from STMicroelectronics, model number STM8S005K6T6, clocked at 16MHz. Integrated 32KB Flash and 128B E2PROM, 2KB RAM. It is used for parameter acquisition and whole machine control.
Close-up of two 10KΩ resistors.
Close-up of the indicator light used to indicate the working status.
The STMicroelectronics TL074I low-noise quad op amp is used for signal acquisition amplification.
Close-up of the current transformer interface.
Close-up of current transformer load resistance.
Close-up of wireless communication board, soldering MCU and communication module.
The wireless communication board is welded in the air.
STMicroelectronics STM8S003F3P6 MCUs are used for communication control.
The wireless transceiver chip is from Silicon Labs, model Si4432, and is used for the host wireless communication function.
Close-up of an external chip clock crystal oscillator.
Close-up of antenna switch chip of silkscreen G4C.
Close-up of the antenna connector.
A working indicator light is welded underneath.
Close-up of reserved communication terminals.
Close-up of the pushbutton switch for pairing.
A list of all dismantling and a family photo.
Summary of the dismantling of the charging head network
Growatt SP-CT is a wireless current transformer that detects the current information of the external current transformer and transmits it wirelessly to the central control equipment to collect current information in the photovoltaic system. It is equipped with a Lyme current transformer, which has an open design and is easy to install. The main unit adopts a waterproof metal shell and is equipped with two antennas for use in different occasions.
Through the dismantling of the charging head network, it is learned that the wireless current transformer is equipped with a PCBA module inside the metal shell, a switching power supply, a main control MCU and a communication module. The switching power supply uses the PI TNY285PG power supply chip, the main control MCU uses STMicroelectronics STM8S005K6T6, and the wireless communication module uses STMicroelectronics STM8S003F3P6 MCU and Silicon Si4432 wireless transceiver chip. The communication information collected by the transformer is processed by the host computer and transmitted wirelessly.