Voltmeter and Ammeter

LCSC Diwenxing CW32F030 Digital Voltage and Current Meter Expansion Board
 
Function Introduction:
    DC power input, supporting up to 40V. Voltage and current measurement
    via 2mm banana plugs (T_V, T_GND). Multimeter or high-precision benchtop digital multimeter probes can be inserted to verify the board's measurement accuracy. Alternatively, 2mm banana plug multimeter probes can be inserted to replace the CH1 port for handheld measurements.
    The middle pin VP of the 3-pin XH2.54 terminal is the power supply pin for the development board and should not be connected when using the DC port. When not using DC power and the measured value is greater than 5V and less than 30V, the power supply under test can be connected, or it can be powered independently.
 
The LDO section
    uses an SE8550K2-HF as the main power supply, supporting a maximum input voltage of 40V and an output of 200mA.
    Diodes are used for reverse connection protection, and a 10Ω resistor is connected in series to prevent LDO overheating (for protection).
 
The MCU section
    uses the LCSC Diwenxing development board as the main controller, with the CW32F030C8T6 core.
 
The voltage sampling circuit
    uses a voltage divider circuit to achieve high voltage acquisition. It is designed to acquire 100V, but the current configuration allows for a voltage range of 0-30V. The voltage divider resistors are 220K+10K, resulting in a voltage division ratio of 22:1 (ADC_IN11).
    Auxiliary circuits for simulating voltage measurement, calibration, and measurement calibration, as well as voltage measurement terminals, are also provided.
 
The current sampling circuit
    uses a low-side current sampling circuit for current detection. The low-side of the sampling circuit shares a common ground with the development board's meter interface. **
    Note:** Do not solder the sampling resistor during learning!
    The designed sampling current is 3A, and the selected sampling resistor is a 100mΩ
    series resistor R18 (1KΩ). Its functions are: protecting the ADC pins, filtering, and noise reduction.
    Auxiliary circuits for simulating current measurement, calibration, and measurement calibration are also provided (do not solder the R0 sampling resistor when using this function. If not using this function, disconnect JP2).
 
The digital tube driver section
    uses two 0.28-inch common cathode three-digit digital tubes
    with 300Ω current-limiting resistors; the brightness can also be adjusted by changing the resistance value.
 
The indicator light section
    includes a power indicator and an I/O operation indicator.
 
The button circuit section
    has three buttons
 
for voltage measurement calibration.
    An additional TL431 circuit was added to provide a 2.5V reference voltage, which can be used to provide an external voltage reference for the chip to calibrate the AD converter.
 
[Image of the actual product ]