Liquid level control circuit diagram of towerless booster water supply device composed of NE555

As shown in the figure, it is the liquid level control circuit of the towerless booster water supply device. The control circuit is composed of a capacitor step-down rectifier circuit, an electric contact pressure gauge, a 555 trigger circuit, a thyristor control circuit, etc. Among them, the step-down rectifier circuit provides a DC voltage for the entire control circuit.

For the electric contact pressure gauge P, when there is no water in the water supply device, the internal pressure is low, and the moving contact "1" in the gauge is closed with the lower limit contact "3", making the IC (555) pin ② low level, and the corresponding 555 is set, and the high level output by pin 3 triggers the thyristor SCR to conduct, CJ is energized, and the water pump D pumps water into the water supply device, and the air pressure in the pressure gauge rises. When the moving contact "1" rises to disengage from "3" and engages with the upper limit contact "2", 555 is reset due to the high level of pin ⑥, so that the SCR is cut off, and the water pump D stops working due to the lack of electricity. After that, due to the use of water, the water level drops, the air pressure in the gauge drops, and the moving contact "1" engages with the lower limit contact "3" again, so that 555 is set and the SCR is turned on. The water pump pumps water. This cycle is repeated. The control of the liquid level of the water supply device is achieved.

In the circuit, CJ adopts CJ-40A AC contactor, and 3A/400V bidirectional SCR can be directly driven to work.

The control circuit can realize the automatic control of the liquid level of the water supply device, and can also prevent the contacts of the electric contact pressure gauge from being burnt or sintered, thereby extending its service life.