CW32 Voltage and Current Meter

Main Functions:
This is a voltage and current meter designed based on the CW32F030C8T6, displaying voltage and current values ​​via a digital tube. The board features a 2mm jack for banana plug testing. Measurement ranges can be switched using buttons. This project can measure voltages from 0V to 30V and currents from 0A to 3A.
 
Design Considerations:
The circuit uses a step-down design. In the PCB layout, the current first passes through a 47uF capacitor and then a 100nF ceramic capacitor.
Electrolytic and ceramic capacitors are connected in parallel in a sequential manner. When the electrolytic and ceramic capacitors are connected in parallel, they can achieve a "high-low pairing," resulting in good filtering performance in both high-frequency and low-frequency regions. Electrolytic capacitors filter out low-frequency interference, while ceramic capacitors filter out high-frequency interference. Combining the two can achieve a better filtering effect.
The current flow
display circuit on the PCB uses a 0.36-inch digital tube with a small resistor in series
(the resistor in the schematic can be reduced).
The voltage calibration circuit uses the TL431, a somewhat old chip
from Youtai Semiconductor, which has a maximum output voltage of 36V.
Applications and testing circuits are discussed. For further information on other uses of this chip
, please refer to the chip datasheet. The current sampling circuit doesn't have many key points; the main thing to note is the PCB layout
. The sampling resistor traces use a Kelvin connection.
In power electronics applications, the Kelvin connection also has its applications. For example, in high-precision current measurement, when using a shunt (a small resistor) for current measurement, PCB routing and soldering can affect the current measurement. To solve this problem, a Kelvin connection can be implemented through PCB routing, or a shunt with four terminals can be used to implement a Kelvin connection internally within the device to improve measurement accuracy.
In summary, the PCB Kelvin connection is an important circuit design technique. By optimizing the measurement methods of current and voltage, it significantly improves the accuracy and reliability of measurements, especially in applications requiring high-precision measurements. (From Baidu)
You don't necessarily have to strictly follow this design; as long as the signal flow is complete, interference-free, and doesn't affect functionality, you can design it according to your own ideas.
The remaining simple circuits will not be elaborated on further; feel free to use your creativity. In
conclusion:
1. The program source code, images, and other instructions are all in the attachments and can be downloaded directly.
2. When measuring, pay attention to electrical safety and clearly mark the positive and negative terminals in the design.
As a newcomer to open source, please be kind; please point out any errors!