Level controller based on LM324

Liquid level control is an important and indispensable part of the daily industrial production work process, which plays an extremely important role in saving resources and safe production.

What is a liquid level controller?

The liquid level controller is in industrial production and daily life, fire fighting, and other water supply systems, there are many environments that need to monitor the liquid level (or water level, oil level), accurately indicate the liquid level, and automatically control the replenishment of the liquid level medium.

In industrial production and daily life, fire-fighting, and other water supply systems, there are many environments that need to monitor the liquid level (or water level, oil level), accurately indicate the liquid level, and automatically control the replenishment of the liquid level medium, such as the water level of the water tank (pool, water tower), the oil level of the oil tank, etc.

Structure and principle

The liquid level display and control instrument is a continuous digital display, key setting of liquid level point, relay switch output, computer communication, return difference protection, fault self-test, liquid specific gravity correction, electronic parameter lock.

Continuous digital display: It can visually indicate the depth of the liquid being detected, which is more in line with the viewing habit. Unit: 0.01m.

　　-Any setting of the liquid level point: you can set any value of the liquid level parameter required at the site on the display controller panel, which is easier to use. -

　　Relay switch output: normally open/normally closed, easily meet various automatic control requirements.

　　-Output direction definition: you can make each liquid level point output by rising or falling, in line with the conventional custom.

　　-Computer communication (XMG-Y31): It can form a centralized computer monitoring and management system.

　　-Return difference protection: Avoid misoperation caused by liquid level fluctuation and protect the safety of the control system.

　　-Fault self-test: When the liquid depth transmitter signal exceeds the range, or the connection line is open and short-circuited, the fault code is displayed, which is convenient for maintenance.

　　-Display translation correction: when the installation position of the liquid depth transmitter is lower or higher than the bottom of the container being detected (see liquid depth transmitter installation), it can be corrected so that the liquid depth display value is the same as the actual value of liquid depth, which is more intuitive.

　　-Liquid specific gravity correction: When detecting the depth of liquid with different specific gravity, it can be corrected to make the liquid depth display value match with the actual value of liquid depth, which is more intuitive.

　　-Electronic parameter lock: avoiding mis-setting and mis-operation by non-professional technicians.

Design and implementation of LM324-based liquid level control system

The liquid level controller uses LM324 as the core to realize the control, the production principle is simple, using the metal strip to sense the height of the liquid level, when the predetermined value is exceeded or not reached, the main control board will control the relay to take corresponding actions, such as alarm, increase liquid, etc. In addition, LED lights are used to intuitively display the position of the liquid level, according to the height of the liquid level, LED shows different lights on, finally a responsive liquid level controller is made to simulate the whole liquid level controller system.

Liquid level control is an important and indispensable part of the daily industrial production work process, which plays an extremely important role in saving resources and safe production. This design uses liquid height sensors to form a control system to monitor the water level in all aspects. The liquid level change is monitored by the indicator of the circuit, so as to control the opening and closing of the pump or electric bell in a certain combination sequence, and the liquid level height is monitored, thus realizing the safety alarm in the process of liquid control.

The design and operation principle of the system

System structure

The system is mainly composed of the main controller circuit (main control board), measurement circuit (height sensor), display circuit (LED), and external working circuit (pump).

Main controller circuit module circuit principle

The main controller circuit in the system is the core of the whole intelligent controller.

Its electrical principle is shown in the figure. The four op-amps of LM324 in the figure are UA, UB, UC, UD.

The voltage at the input of the op-amp is UA+, UA-, UB+, UB-, UC+, UC-, UD+, UD-, and the voltage at the output is UAO, UBO, UCO, UDO. LED1, LED2, LED3, LED4 are red, yellow, green and blue lights respectively.