Voltmeter and Ammeter

1. Describe
a simple digital voltmeter and ammeter based on the LCSC CW32 microcontroller.
It adopts a core board plus expansion board design concept, using plug-in components to simplify learning and deepen exploration.
The core board uses the domestic Wuhan Xinyuan Semiconductor CW32 as the main controller, while also being compatible with other similar development boards; however, the CW32 has advantages.
The project is highly integrated, practical, and compact, and can be used as a desktop instrument after completion.
A physical image is shown below:
2. Hardware Introduction
1. DC Input Circuit
LDO (Low Dropout Linear Regulator) Selection
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 selected the SE8550K2, which has a maximum input voltage of up to 40V, as the power supply.
2. Voltage Sampling Circuit
1. A common battery voltage sampling circuit is similar to the low-side voltage circuit on the right, using two 10K resistors to divide the external voltage. 2. The high-side voltage sampling circuit uses a 220K+10K resistor for voltage division. U =
(R/Rtotal)xUSource-->U_ADC=10K/(220K+10K)×VMeasurement. Given a reference voltage of 1.5V, the maximum measurable voltage is 34.5V.
3. Through diode forward clamping, when the measured voltage is too high, the pin voltage is forced to be clamped to a 5V+ voltage drop, preventing damage to the chip pins.