Detailed explanation of the voltage calculation method of resistor voltage division of single chip microcomputer

In microcontroller applications, voltage measurement and signal conditioning are very important links. Due to the limited input voltage range of the ADC (analog-to-digital converter) of the microcontroller, directly measuring high-voltage signals may damage the microcontroller or lead to inaccurate measurements. at this time,resistanceA voltage divider circuit becomes an easy and effective solution. This article will introduce in detail the method of calculating the voltage by dividing the resistor of the microcontroller, and help readers master the core skills of voltage dividing circuit design and voltage calculation.

A resistor divider circuit usually consists of two resistors connected in series to divide the input voltage into a lower voltage output in proportion to the resistance. According to Ohm's law and the principle of voltage distribution, the calculation formula of the divided voltage V_out is:

\[ V_{out} = V_{in} \times \frac{R_2}{R_1 + R_2} \]

Among them, V_in is the input voltage, R1 and R2 are the resistance values ​​of two series resistors, and V_out is the output voltage after voltage division.

When selecting the resistor value, the current size, power consumption and measurement accuracy need to be considered comprehensively. Generally speaking, the resistance of the resistor should not be too small to avoid excessive current and increased power consumption; nor should it be too large to avoid noise and interference at the ADC input end. Commonly used resistor values ​​range from 1kΩ to 100kΩ.

When calculating the voltage divider, first determine the input voltage range, and then invert the resistor value ratio based on the required output voltage range (usually the maximum input voltage of the microcontroller ADC). The formula is transformed into:

\[ \frac{R_2}{R_1 + R_2} = \frac{V_{out}}{V_{in}} \]

Use this ratio to select appropriate R1 and R2.

Manufacturing tolerances in resistors can affect the accuracy of the divided output voltage. It is recommended to choose a resistor with higher accuracy (such as 1% or higher accuracy), or to compensate for the error through calibration software.

The voltage divider circuit will produce a certain quiescent current, and the power consumption calculation formula is:

\[ P = \frac{V_{in}^2}{R_1 + R_2} \]

In order to save energy, a larger resistance combination should be selected, but the stability of the signal must be taken into consideration.

When multiple analog signals are input, it is necessary to design an independent voltage dividing network for each signal to avoid interference between signals. Reasonably arrange the resistor value and grounding method to ensure accurate measurement.

The output of the voltage divider circuit should be connected to the ADC input of the microcontroller, taking care to avoid floating ground and common mode interference. When measuring, it is recommended to use an oscilloscope or multimeter to verify whether the divided voltage complies with the calculated value.

The ADC value read by the microcontroller is usually a digital quantity, which needs to be converted into an actual voltage through software. The conversion formula is:

\[ V_{in} = V_{adc} \times \frac{R_1 + R_2}{R_2} \]

where V_adc is the voltage value measured by the ADC.

单片机电阻分压计算电压方法是嵌入式系统中常用的电压测量方案。通过合理选择电阻阻值、精确计算分压电压，并结合软件校准，可以有效实现高精度电压测量，保护单片机输入端口，提升系统稳定性。掌握以上分压设计要点，将为单片机项目的电压采集提供坚实基础。