Circuit diagram of automatic water level controller for two new applications

At present, most water level controllers on the market do not have water tower (pool) water inflow indication, protection, and alarm functions. When the water source is empty or the water pump fails, the pump cannot automatically stop, which wastes electric energy and easily burns the motor. When the water level is lower than the lower water level and there is no water in the pump, the pump cannot be stopped in time to alarm and remind the user. Therefore, its safety and reliability are still insufficient. The two automatic water level controllers introduced in this article are designed to solve the above problems.

Figure 1 is the electrical schematic diagram of the SZK-II automatic water level controller . Inverters IC 3 and IC4 form a large hysteresis Schmitt trigger. R12 and C4 are integrating circuits, which can effectively eliminate the interference introduced by the AC power supply. R14 and R13 make the IC4 output exhibit Schmitt characteristics. By sequentially contacting the ground electrode of the water tower and the lower and upper water level electrodes with the water, the IC3 input voltage is changed to achieve automatic water level control.

The outputs of IC1, IC2, and IC3 jointly control transistor VT1. When VT1 is turned on, C3 is discharged and the output of IC5 is negative. When VT1 is cut off, VD7 is reverse biased, the power supply charges C3 through R10, and the delay begins. After the delay time is reached, the output of IC5 becomes positive and the circuit enters the protection or alarm state. The delay time should be adjusted to be slightly longer than the time required from starting the pump to water entering the water tower. There are two situations when VT1 is cut off: ① The outputs of IC1 and IC2 are both positive, that is, the water level is above the upper water level electrode and there is still water flow at the water inlet. This is an alarm designed specifically for environments where the tap water pressure is abnormal and a pressure pump must be installed or tap water is used together with well or river water. When the tap water pressure can flow up the water tower by itself, the water full alarm will sound, reminding the user to close the water valve. If the water tower is equipped with a water level float valve and the float valve closing water line is above the upper water level electrode, it can be automatically controlled without alarm. At this time, VD5 and VD6 should be removed, and the VT1 emitter should be connected to the negative pole of the power supply to open the IC2 output to eliminate this alarm. ②The outputs of IC1, IC2, and IC3 are all negative, which is the state when the water level is below the upper water level electrode, the water pump is working, and the water is not (not) pumped to the water tower. At this time, during the delay time, if there is water flow at the water inlet of the water tower, the IC1 output becomes positive and VT1 is turned on; if there is still no water flow, the IC5 output becomes positive due to the increase in C4 charging voltage. VD8 and R15 can accelerate IC5 flipping and eliminate the influence of power supply fluctuations. The output of IC5 is divided into two channels. One channel provides the base current for VT2 to generate a bird chirping alarm; the other channel is added to the input terminal of IC4 through VD9 to make its output positive and the water pump stops. At the same time, it acts on the input terminal of IC3 through R11. At this time, if the water level is above the lower water level electrode, the Schmidt circuit flips to positive, VT1 is turned on, the alarm stops, and the circuit returns to the normal state. If the water level is below the lower water level electrode, the IC3 output is still negative due to the open circuit of the water resistance, and the pump stop alarm state is locked. To start the water pump, the controller must be powered off for a few seconds and then powered on again. In the picture, LED1 is the power indicator, LED2 is the water inlet indicator, and LED3 is the pump start indicator.

The birdsong sound circuit composed of R16, R17, VD10, C5, B, VT2 and buzzer has the characteristics of simplicity, stability, large volume and good sound quality, and can work stably under the power supply voltage of 1~20V. When the voltage is low, VD10 can be used. Oscillation transformer B uses a 6mm I-shaped core, first wind T1 with 0.03mm enameled wire, and then wind T2 with 0.09mm enameled wire.

The SUK-Ⅱ water level display controller has more complete functions than the SZK-Ⅱ water level automatic controller . Figure 2 is its electrical schematic diagram. It uses light-emitting diodes to display the water storage volume of the water tower on the controller in five levels. On the basis of automatically controlling the pump water, it also adds self-stop start, manual stop start and pump stop buttons. The automatic stop-start can start the pump at any time, it will automatically stop when the water is full, and it has an alarm protection locking state reset function. The manual start button has no self-stop function and is designed for pumping water for other purposes (not for filling water towers). Please pay attention to manually stopping the pump after starting it. String 3IC1 is a four-operational amplifier, which together with VT1 forms a level one to five level water level display circuit. After the positive power supply is filtered by R5 and C3, one channel is divided by R6~R10 and used as the reference voltage for input at all levels of IC1. The other channel is connected to the ground electrode at the bottom of the water tower and connected to the water level electrodes at all levels through water. It forms a different series with R1~R4. After that, it is divided with R13 and R14 to obtain voltage signals representing different water levels and added to the other input end of each stage of IC1. After comparing it with each reference voltage, it outputs the water level indication of the second to fifth levels. The first The level water level indication is output by VT1. LED1~LED5 indicate the first to fifth level water levels respectively. IC2 is a Schmitt trigger. IC2a is used to amplify water ingress, and LED6 is used to indicate water intrusion. IC2b forms a delay protection, and the delay time is set by R25 and C9. It should be slightly longer than the time required from starting the pump to water entering the water tower. IC2c and IC2d form a bistable circuit, which has automatic control and protection functions. The input is controlled by four channels: ① When the water level is lower than the first-stage electrode, the VT1 collector is positive, and the bistable is in the pump-on state through R20 and VD7, realizing automatic pump-on when the water level is low. ②Press the auto-stop start button K1, and the bistable pump is on. ③When the IC2b output is negative, the bistable is in the pump-off state. That is, when the water level reaches the fifth level or above, the output of IC1d is positive, and VD6 acts on IC2b to realize self-stop when the water is full; or when the pump is out of water and the delay time is reached, the output of IC2b becomes negative to realize the self-stop when there is no water. . ④Press the pump stop button K3, and the bistable is in the pump-off state. LC2e and IC2f form a manual bistable circuit. The manual stop button K2 turns on the pump and K3 turns off the pump, which is equivalent to an ordinary switch. The two-stage bistable parallel control VT2 switches the water pump on and off through a relay. LED7 and LED8 are the indicator lights for self-stop start and manual stop start respectively.

In the picture, VD5, R11, and C6 can ensure that the fifth-level water level electrode is continuously immersed in water for about 10 seconds before IC1d is turned over, preventing the fifth-level water level indicator from not indicating full water after turning off the pump due to water surface fluctuations. VD11 prevents C9 from discharging to the output terminal of IC2d, so that the water level is lower than the first-level water level electrode and there is no water in the pump. After stopping the pump, the voltage charged by C9 and the Schmitt hysteresis can keep IC2b locked for a long time. Pump off state. VD12, R28, C10, C8, R32 play the role of reset. When the self-stop start button is pressed, the output of IC2d becomes positive, causing IC2a ​​to output a negative pulse to quickly discharge the charge on C9, and IC 2b locks the pump off state to reset.