The touch screen of soymilk machine doesn't work, just wipe it with alcohol. That's because the touch screen is too dirty, and the human body's induction signal can't trigger the circuit to work. After cleaning with alcohol, the dirt on the surface is removed, the resistance between the human body and the circuit is reduced, and the capacitance between the finger and the internal circuit is restored, and the sensing ability is correspondingly enhanced.

The principle of induction circuit:

The inductive key circuit includes two parts: signal generation and signal shaping. Firstly, the signal generation part generates a high-level signal with a duty cycle of several hundred KHz of about 50%. Then the signal shaping part shapes the generated signal; Finally, the signal is sent to the AD port of the microcontroller. When the human body is close to the induction key, it will form a capacitance to the ground, which will shunt part of the current at the high level of signal shaping, so that the shaped signal will drop and remain at the falling potential until the human body leaves the key. When the human body leaves and presses the key, the rectified signal will rise to the original potential level. Due to circuit coupling and parasitic capacitance, the falling edge and rising edge are generally used to identify the response action of the inductive key.