Humidifier and aromatherapy machine are small household appliances that we often use. Their principle is very simple. As the main control, THE MOS tube is driven by the triode push-pull circuit through PWM, so that the atomizing plate works near the resonant frequency.

Many MCU manufacturers encapsulate this part of the code, so many small friends are not clear about the basic scheme of water detection and frequency pursuit through the atomized chip. Here is a simple analysis for small friends.

Frequency chasing principle:

The humidifier based on single chip microcomputer can automatically follow the frequency to the resonant point. Its implementation principle is as follows:

The relationship between the voltage at both ends of the atomizing plate and its oscillation frequency is normal distribution, as shown in the figure below:

Through the relationship between voltage and frequency, the software algorithm can be used to track the frequency point, so that the atomizer always works at the frequency point.

Water detection principle:

The humidifier based on single chip microcomputer is used to detect whether there is water or not by the change of voltage characteristics of atomized sheet when there is water or not. In normal operation, the shock voltage of atomizing plate is stable in a normal range, and there is little change. When the water amount is reduced to a certain degree or there is no water, the voltage at both ends of the oscillating plate will increase or rise suddenly. Through such a change rule to determine whether the humidifier has water.