LCSC Training Camp Voltage and Ammeter

1. Project Function Introduction
System Overview
This system is designed to measure 0-30V voltage and 0-3A current. It uses the LCSC CW32F030C8T6 development board (core board) as the main controller, and displays voltage and current through two 3-digit LED displays. Additionally, the board includes one analog voltage and one analog current line for learning purposes.

2. Project Attributes
This project is a study and replication of the official LCSC open-source project, not my original work. The circuit design follows the official training camp, and the program is basically modeled after the open-source code from the training camp tutorial. It is only open-sourced on the LCSC open-source platform.

3. Open Source License
GPL3.0

4. Hardware Part
4.1 Power Supply Circuit

![WeChat image_20240825002601.png] This project uses an LDO as the power supply. Considering that most voltmeter products are used in industrial scenarios with 24V or 36V power supplies, this project chose the SE8550K2 with a maximum input voltage of up to 40V as the power supply.
4.2 Voltage Sampling Circuit

![05761368422a4c9000a5a3c2ae00746.png] Two voltage input ranges are selectable: 0~30V and 0~3V, with the 3V range offering higher accuracy.
Both ranges use two series resistors for voltage division sampling. Since the ADC's internal reference voltage of 1.5V is used (which can be replaced),
the voltage division ratio is 1.5V/30V = 0.05. A 10KΩ resistor is chosen for voltage division sampling, so the total resistance R = 10 / 0.05 = 200KΩ. Therefore, the high-side resistance value = 200 - 10 = 190KΩ. A more common 200KΩ resistor was chosen here. The same logic applies to the 3V range.
4.3 Current Sampling Circuit

![image.png] The sampling current designed for this project is 3A, and the selected sampling resistor (R0) is 100mΩ. According to the formula, 3A * 100mΩ = 300mV, 900mW. See the schematic diagram for other details.

5. Software:
The program is basically modeled after the open-source code in the training camp tutorial. The source code is attached.

6. BOM List:
See the attached BOM list.

7. Defects
: The schematic diagram has a maximum voltage range of 3V and a section using TL431 as the reference voltage, but these were not implemented due to time constraints. The calibration function was also not added.

8. Finished Product Demonstration:


Simulated voltage measurement


![image.png]

Simulated current measurement
![image.png]

Recording table

![image.png] The results are quite close.

Video link
(【LCSC Training Camp: Voltage and Current Meter Based on CW32 (Replica)】 https://www.bilibili.com/video/BV184WBeGEn7/?share_source=copy_web&vd_source=05b0b175ba8cb9c0cdc3770ec87bc6c6)))