Liquid level controller circuit design

Liquid level controller refers to the control of high and low liquid levels through mechanical or electronic methods. It can control solenoid valves, water pumps, etc. to achieve semi-automation or full automation. There are many methods, which vary according to the different products selected. Next, Guangdong Liangde Electronic Technology Co., Ltd. will introduce the circuit working principle of the liquid level automatic controller. The circuit is simple and easy to make, no debugging is required, and it can be used for liquid level detection and control of various industrial and mining liquid storage tanks. Circuit working principle

The liquid level automatic controller circuit consists of a power supply circuit and a liquid level detection control circuit, as shown in the figure.

The power circuit is composed of knife switch Q, fuse FU1, FU2, power switch S1, power transformer T, rectifier bridge UR and filter capacitor C. Rectifier bridge plays an important role in many circuits. The

liquid level detection control circuit is composed of reed switch SA1, SA2, relay K1, 0, thyristor VT, resistor R, AC contactor KM, thermal relay KR, control button S2, S4 and manual/automatic control switch S3.

HL1 and HL2 are power indicator and working indicator respectively.

When the knife switch Q and power switch S1 are turned on, the AC 220V voltage between the phase line L1 end and the neutral line N end is reduced by T to generate AC 12V voltage as the working voltage of HL1 and HL2. At the same time, after UR rectification and C filtering, it provides 12V DC working voltage for the liquid level detection control circuit.

SA1 is a reed switch for low liquid level detection and control, and SA2 is a reed switch for high liquid level detection and control.

When the controlled liquid level drops to the low level, the permanent magnet installed on the float approaches SA1, and the contact of SA1 is connected under the magnetic force of the permanent magnet, so that VT is triggered to conduct, K1 is energized and attracted, and its normally open contacts K1-1 and K1-2 are connected, so that HL2 lights up, KM is energized and attracted, and the motor M is energized to work, driving the liquid pump to add liquid to the liquid storage tank.

The float rises with the rise of the liquid level, causing the permanent magnet to leave SA1, and the contact of SA1 is disconnected, but VT remains in the conducting state. Until the liquid level rises to the set high level and the permanent magnet approaches SA2, the contact of SA2 is connected, K2 is energized and attracted, and the normally closed contact of K2 is disconnected, so that K1 is released, VT is cut off, and the normally open contacts K1-1 and K1-2 of K1 are disconnected, HL2 is extinguished, KM is released, and M is powered off and stops working.

When the liquid level drops and the permanent magnet drops below SA2, the contact of SA2 is disconnected, K2 is released, and the normally closed contact of K2 is connected again, but K1 and KM are still in the cut-off state until the liquid level drops to SAI again and the contact of SA1 is connected, VT is turned on again, K1 and KM are attracted, and M is powered on again.

The above working process is repeated, so that the controlled liquid level can be kept between the high liquid level and the low liquid level, thereby realizing the automatic control of the liquid level.

Component selection R uses a metal film resistor or a carbon film resistor.

C uses an aluminum electrolytic capacitor with a withstand voltage of 16V.

UR uses a 1A, 50V rectifier bridge stack or uses 4 lN4007 silicon rectifier diodes connected in bridge form to replace it.

VT uses a thyristor with a voltage of more than 1A and 50V, such as MCR100-6 and other models.

SA1 and SA2 both use glass-encapsulated normally open reed switches.

K1 uses JQX-10F 12V DC relay; K2 uses JRX-13F 12V DC relay.

HLI and HL2 both use 12V indicator lights.

S1 uses SA, 220V power switch; S2 uses break button; S3 uses bipolar double-position switch (two sets of contacts are used in parallel); S4 uses close button.

T uses 3~5W, secondary voltage 12V power transformer.

Q, FU1, KM and KR should be reasonably selected according to the rated power of M.