Voltmeter and Ammeter

I. Design Background:
1. The LCSC CW32F030C8T6 development board is used as the main controller, with complete documentation and easy-to-use features.
2. This project provides a good understanding of PCB design, ADC usage, and digital tube driver operation.
II. Hardware Design: 1.
The power supply circuit uses an SE8550K2 linear regulator (LDO), with a maximum input voltage of 40V, output of 5V, short-circuit protection, low ESR, thermal protection (TSD), undervoltage lockout, and enable function.
2. Voltage and Current Acquisition Circuit:
Voltage:

The maximum designed voltage to be measured. For safety reasons, this project uses 30V (the actual maximum display value can be 99.9V or 100V);
ADC Reference Voltage: 1.5V in this project. This reference voltage can be configured through the program;
Power Consumption: To reduce the power consumption of the sampling circuit, the low-side resistor (R7) is usually selected as 10K based on experience;

Current:

The maximum designed measured current. In this project, it is
the voltage difference caused by the 3A current sensing resistor. It is generally not recommended to exceed
the power consumption of the current sensing resistor by more than 0.5V. A suitable package should be selected based on this parameter. Considering the power consumption (temperature) problem under high current, a 1W packaged metal wire-wound resistor was selected in this project
. Voltage Amplification Factor on the Current Sensing Resistor: No operational amplifier was used to build the amplification circuit in this project, so the factor is 1.

3. Digital Tube

Driving Method:

Segment Selection: The required numbers or characters are displayed by controlling the on/off state of each segment of the digital tube. Each segment corresponds to a control signal. When the control signal is turned on, the segment will light up, and vice versa. (a, b, c, d, e, f, g, dp)
Bit Selection: The desired display segment is selected by controlling the bit lines of the LED display. Bit line control sets the bit line of the desired segment to a high level and the bit lines of other segments to a low level. By continuously switching the state of the bit lines, display switching between multiple LEDs can be achieved.


Driving Circuit:

The LED display driving circuit can be implemented using hardware circuits, such as integrated circuits like digital signal processors (DSPs), microcontrollers (MCUs), or shift registers to generate control signals suitable for the LEDs.
These control signals can be in the form of pulse width modulation (PWM) signals, serial data signals, etc. By controlling the frequency, width, and amplitude of these signals, the brightness of the LEDs can be controlled, thereby displaying the desired numbers or letters.