Automatic shutdown of the pump. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Automatic shutdown of the pump. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Clocks, timers, relays, load switches

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When pumping water into a container, the user often simply forgets to turn it off at the right time, which leads to such unpleasant consequences as flooding the room with water. The proposed device is designed to solve this problem. It works on the principle of "click and forget", so you do not need to worry about disconnecting the pump from the mains: when it pumps water into the tank to the required level, it will turn it off and turn itself off at the same time.

The scheme of the device is shown in fig. 1. With a short press on the SB1 button, the mains voltage of 230 V is supplied to the primary winding of the transformer T1. As a result, a reduced voltage of about 15 ... 16 V appears on its secondary winding, which, after being rectified by the diode bridge VD3-VD6, smoothed by the capacitor C1 and stabilized by the parametric stabilizer R5VD1, is converted into a constant voltage of 12 V, which feeds the DD1 chip and the relay winding K1. Chip DD1 contains four logical elements 2I-NOT. One of them is used in the described device, the inputs of the rest, in accordance with the recommendations for the use of CMOS microcircuits, are connected to a common wire.

Automatic pump shutdown
Rice. 1. Scheme of the automatic shutdown of the pump

In the absence of water or its insufficient level in the container, the contacts E1 and E2 are in the air and the resistance between them is almost equal to infinity. The upper (according to the diagram) input (pin 1) of the DD1.1 element is connected to the power line (+2 V) through the resistor R12, so the log level is maintained on it. 1, and the bottom (pin 2) through R5 to the common wire, so there is a log on it. 0. With this combination of input signals, the output voltage (pin 3) of the DD1.1 element has a log level. 1, therefore, after pressing the button, the transistor VT1 opens, the relay K1 is activated and its contacts K1.1 block the contacts of the pressed button (now it can be released), and the contacts K1.2 close the power supply circuit of the pump.

When the water level in the tank rises so much that the contacts E1 and E2 are in the water, the resistance between them will decrease, the level of the log. 0 at pin 2 DD1.1 will be replaced by the log level. 1, and the same level at its output - the log level. 0. As a result, the transistor VT1 will close, the relay will release and its contacts will disconnect both the pump and the device from the network.

The HL1 LED serves to indicate the operation of the machine, and also (together with resistors R5, R6) to discharge the capacitor C1, which eliminates the bounce of the K1 relay contacts after the device is turned off. Diode VD2 protects the transistor from the back EMF that occurs on the relay winding at the moment it is released.

A drawing of the printed circuit board of the device and the location of parts on it are shown in fig. 2. Resistors - MLT, S2-33, capacitor - imported oxide, relay K1 - RES48A version RS4.590.202 or RS4.590.202-01 (winding resistance - 85 ... 115 Ohm, actuation current - 52 mA). Transformer T1 - any small-sized one with a secondary winding of 15 ... 16 V with a current consumption of 0,2 A. The device does not require adjustment and, with proper assembly and serviceable parts, it starts working immediately after it is turned on for the first time.

Automatic pump shutdown
Rice. 2. Drawing of the printed circuit board of the device and the location of parts on the board

It is strongly recommended to use a transformer to lower the mains voltage, this will ensure galvanic isolation from the mains and safety when using the device.

Author: V. Atlasov

See other articles Section Clocks, timers, relays, load switches.

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