Circuit diagram of water level controller

The water level controller is to control the high and low water level by mechanical or electronic methods. It can control the solenoid valve, water pump, etc., and become the water level automatic controller or water level alarm, so as to realize semi-automatic or full automation. As shown in the figure below:


In the pool water supply control system, the main engine is installed in the pool, and the slave machine is installed in the water source pump room. During the operation, the main engine detects the water depth signal of the pool in real time, and commands the slave machine to control the pump by SMS, start the pump at the upper limit and stop the pump at the lower limit. If the water level of the pool exceeds the upper limit or lower limit, the host will send a message to the administrator. If the water pump fails, the slave will send a message to the administrator. The administrator can check on the spot, or edit and send short message instructions to force the water pump to start and stop.

Water level controller is widely used in industrial boilers, civil building pools, water towers, water tanks, as well as petrochemical, papermaking, food, sewage treatment and other industries in open or closed storage tanks, underground tanks liquid level measurement, the detected medium can be divided into water, oil, acid, alkali, industrial sewage and other conductive and non-conductive liquids. With the electric valve to form a set of advanced liquid level display and control equipment, automatically open and close the electric valve.

Automatic water level control circuit

The circuit is very simple and very easy to make. SW1 (normally closed) and SW2 (normally open) in Figure 1 are miniature reed switches in sealed PVC pipes. Both ends of the pipe are made waterproof and sealed with waterproof sealant.


One magnet is mounted on a hot porous sheet that floats on the water surface. The magnet can move up and down with the water surface and drive the reed switch. When the pool is completely empty, the magnet is placed on the brake (as shown in Figure 1), and SW2 is closed. The 12V power supply is connected to the coil of RL relay through SW1 and SW2. The relay is energized and connected to the pump motor via a common end of the relay.

When the pump starts to fill the pool, the magnet moves up with the water. When the magnet leaves the support, SW2 is open, but the power supply is still connected to the coil of the relay through the second common end of the relay RL. When the magnet reaches SW1, it turns on the SW1 switch, and the second path of power to the relay coil is also disconnected. The relay removes the excitation and turns off the water pump. When draining water from the pool, SW1 is closed again, but the power supply cannot reach the relay coil. The water is further drained, SW2 is closed, and the relay is activated again, thus starting the pump again. This process is repeated over and over again.

The pump is not continuous operation, but interval operation. The interval time depends on the distance between the reed switches, however, the water pump can be started by manually pressing the instantaneous switch SW3.

RL is a DPDT relay (one pole for logic control and one pole for on / off motor). The coil voltage is 12VDC, and the point load depends on the negative voltage.

Circuit diagram of automatic water level controller

Figure 1 is the electrical schematic diagram of SZK – Ⅱ automatic water level controller. The homophasor IC3 and iC4 constitute a Schmitt trigger with large return difference. R12 and C4 are integral circuits, which can effectively eliminate the interference caused by AC power supply. R14 and R13 make the output of iC4 present Schmidt characteristic. The water level can be controlled automatically by changing the input voltage of IC3 through the sequential contact between the ground electrode of water tower and the lower and upper water level electrodes.

The output of IC1, IC2 and IC3 jointly controls the transistor VT1. When VT1 is on, C3 is discharged and IC5 output is negative. When VT1 is cut off, vd7 is reversed, the power supply is charged to C3 via R10, and the delay starts. When the delay time is reached, the output of IC5 becomes positive, and the circuit enters protection or alarm state. The delay time should be adjusted to be slightly longer than the time required to start the pump until there is water in the water tower.


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