The electric breast pump adopts the "piston suction type". The rotation of the motor drives the pulley speed reduction mechanism. After deceleration, the screw rotates. The screw is covered with a nut and fixed with the two pistons. The reciprocating movement of the nut drives the two pistons to move back and forth in their respective gas chambers. In order to form the "negative pressure" and "positive pressure" of the air chamber, the process of simulating the "suction" and "release" of the baby when sucking breast milk is realized.
The reason why the nut can reciprocate is because a magnetic steel is fixed above it to indicate the position of the piston. The Hall element on the fixed plate of the Hall switch is used to accurately judge the position of the magnet, so that the electric signal can be used to indirectly control the back and forth movement of the piston, that is, the purpose of adjusting the negative pressure is achieved.
Under the premise that the mechanical structure is determined, the working frequency is adjusted by adjusting the angular velocity of the motor. The molecular beam epitaxy motor has a slow rotation speed and a low working frequency, and the motor rotation speed is fast and the working frequency is high. The magnitude of negative pressure depends on the volume increase of the air chamber and the degree of tightness. In the design, the airtightness of the air chamber is not changed. By changing the parking position of the piston, the volume increment of the air chamber is changed to adjust the negative pressure range.
The hardware control part of the breast pump consists of the switching power supply, the main control circuit board of the vein display, the DC motor, the DC motor drive module, the LCD liquid crystal display, the Hall switch module, the frequency adjustment button, the negative pressure adjustment button, and the radio frequency card (non-contact Type IC card) card reader.
The DC motor drive module adopts a full-bridge drive chip plus NMOS tube IRF3205, which can quickly realize the positive and negative reversal of the motor; the single-chip model is ATMEGA32A. The chip has an advanced RISC structure and non-volatile program and data memory. An 8-bit timer / counter with independent prescaler and comparator function, a 16-bit timer / counter with prescaler, comparison function and capture function, a real-time counter RTC with independent oscillator, with independent Programmable watchdog timer of on-chip oscillator; LCD LCD screen model is HF12232F, which is used to display additional information such as operating frequency and negative pressure level and version number; power module input is 220V, output is 24V, rated current is 5.0A, 24V enters the main control board after the 5V step-down module; the Hall switch module is composed of 4 groups of a total of 28 model TP4913 Hall switches; the RF card reader is used to read the non-contact IC card, so that Authorized users can use the breast pump safely and standardizedly; the active buzzer provides sound effects and alarm functions.
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