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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Automatic water pump. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Home, household, hobby Our magazine has already published descriptions of various devices that allow you to automate the operation of a pump when pumping water from a basement or pumping it from a well into a reservoir. However, all of them made it possible to control the water level in only one place - either in its source or in a reservoir for its storage. The author of the article brought to the attention of readers tells how to make an automaton that simultaneously controls levels in two places. With a limited flow of water into the well, it is desirable to automate the operation of the pump in such a way that it can be used to pump out the maximum possible amount of water, without, of course, overflowing the reservoir. The scheme of the machine that provides the necessary mode of operation of the pump is shown in fig. 1.
Four level sensors lowered into the water are connected to contacts 1-5. The sensors connected to pins 1 and 2 are installed respectively 10 and 100 mm below the upper edge of the receiving tank. Similarly, the sensors connected to pins 4 and 3 are located at the bottom of the well: the first one is about 50, and the second one is 150 mm above the level of the intake holes of the vibration pump or centrifugal valve. Contact 5 is connected to the body of the receiving tank and to a metal pipe through which water is pumped out of the well. If the sensors are dry, through the resistors R1-R8, the corresponding inputs of the DD1 microcircuit are supplied with +9 V power supply voltage, but as soon as they are immersed in water, the voltage at the inputs of the microcircuit due to the conductivity of water approaches zero. Consider the operation of the machine from the moment it is connected to the network. Suppose there is enough water in the well, and the receiving tank is empty. In this case, at the inputs 1 and 2 of the element DD1.1 there is a high logic level, and at the inputs 3 and 4 of the element DD1.2 - low. These elements are the majority valves [1], the output signal of which corresponds to the majority of the input. Therefore, the output of the element DD1.1 will be high, the output of DD1.2 will be low. The two inputs of the DD2.1 element are high, so its output is low, and the output of DD2.3 is high. This level opens the transistor VT1, which turns on the trinistor optocoupler U1, which connects the anode and the control electrode of the triac VS1 to each other through the resistor R13. The triac turns on and supplies voltage to the pump motor M1. Since the author used a three-phase motor, voltage is applied to one of its outputs through a phase-shifting capacitor C8. When the machine is connected to the network, the capacitor C5 is discharged. The low logic level present at the output of the DD2.1 element is transmitted through the capacitor C5 to the input of the DD2.4 element, and a high logic level appears at its output, opening the transistor VT2. After that, the optocoupler U2 is turned on and the triac VS2 connects the starting capacitor C8 in parallel with the capacitor C9, which ensures a quick start of the M1 engine. The voltage on the lower plate of the capacitor C5 according to the scheme is increased due to the current flowing through the resistor R10. After about 3 seconds, it will rise to the switching threshold of the DD2.4 element, a low logic level will appear at its output and the starting capacitor C9 will turn off. The voltage rise time on the capacitor C5 is chosen with a large margin, which guarantees the engine start. At the same time, it is not enough to overheat it. There are two options for the operation of the device. Assume that there is enough water in the well to fill the receiving tank. Then, some time after the start, the water will approach the sensor connected to pin 2, a low level will appear at the input 2 of the DD1.1 element. The output of this element, however, will not change, since its inputs 13 and 1 are high. When the tank is full, a low level will appear at the input 1 of the element DD1.1. Now, since the two inputs of this element are low, the same signal will appear at its output, as a result of which the motor M1 will stop. When water is taken from the tank, a high level will first appear at inlet 1 of element DD1.1. However, this will not change its state, since its inputs 13 and 2 are low. Only when the water level is below the sensor connected to pin 2, the two inputs of this element will be high and the pump motor will turn on again. Thus, the DD1.1 element performs the functions of a trigger, which is set to a single state when a high level is applied to its two inputs and to a zero state when a low level is applied to them [2]. The water level hysteresis prevents the motor from starting too often. Similarly, the machine controls the operation of the pump in the case when the water in the well is not enough to fill the tank. It turns it off when the water level is below the sensor connected to pin 4 and turns it on when the water rises above the sensor connected to pin 3. Resistors R5-R8 and capacitors C1-C4 protect the inputs of the DD1 chip from static electricity and noise induced in wires and sensors. Resistor R9 limits the output current of the element DD2.2 when recharging capacitor C5. Resistors R11 and R12 set the current through the LEDs of the optocouplers U1 and U2, and R13 and R14 limit the current through their dinistors and the control electrodes of the triacs VS1 and VS2 at the moment of switching on. Resistor R16 ensures the discharge of capacitor C9 after it is disconnected from capacitor C8, and R15 limits the current through the triac VS2 at the moment it is turned on again when capacitor C9 is not completely discharged. The device uses an unstabilized power supply, since the K561 series microcircuits used in it remain operational when the supply voltage changes from 3 to 15 V. When a single-phase motor is installed in the pump, which does not require an additional capacitor to be connected at the time of start-up, as well as in the case of a vibration pump, all elements, from resistor R9 to resistor R16, can be excluded. It is only necessary to connect the inputs of the unused element DD2.4 to a common wire or pin 14 of this microcircuit. The device is assembled in the form of a bookcase and covered with a cap made from a polyethylene canister for automotive oil. Capacitors C6 and C8 are installed on the bottom board, made of textolite 9 mm thick, resistor R16 is soldered to the terminals of the latter. The top board is printed with dimensions 80x180 mm made of fiberglass 1,5 mm thick. It contains all the other parts of the machine. A drawing of a fragment of the board is shown in fig. 2.
The board is designed for the installation of MLT resistors of the appropriate power, capacitors KM-6 (C1-C4, C6), K50-16 (C5) and K50-35 (C7). K7-50 or K6-50 can also be used as C16, but then when manufacturing a printed circuit board, it should be taken into account that the distance between their leads is 7,5 mm. Instead of KT315G transistors, you can install any transistors of the npn structure of low or medium power with a base current transfer coefficient of at least 40 (at a collector current of 30 ... 50 mA). The K561LP13 microcircuit can be replaced by the K561IK1 [3], provided that its control inputs (pins 7 and 9) are connected to a common wire. Instead of diode bridges, you can use any diodes with an operating current of at least 100 mA; diodes with an operating voltage of at least 1 V are suitable for replacing VD2 and VD300. Trinistor optocouplers of the AOU103 series can have letter indices B and C, and triacs KU208 - B and G. The power transformer T1 is TPP220, all its secondary windings are connected in series. It is permissible to install any transformer that provides a voltage of 7 ... 9 V on the secondary winding at a current of up to 100 mA, for example, a transformer from any adapter. By the way, you can take a capacitor from the adapter to replace C7 and diodes to replace the VD3 bridge. Resistor R15 - vitrified wire, with a resistance of 20 ... 33 ohms. The capacitance of capacitors C8 and C9 is indicated for the case of using an AOL22-43F motor with a power of 400 W, the windings of which are connected in a triangle. When using an engine of a different power, their capacity must be proportionally changed. Capacitors C8 and C9 - metal-paper MBGO, MBGT, MBGP for a voltage of at least 400 V or MBGCH, K42-19 for 250V. The sensors are flat spirals with an outer diameter of about 25 mm, tightly twisted from the bare ends of a copper or aluminum lighting wire in double insulation with a cross section of 2x1,5 or 2x2,5 mm2. On fig. 3 shows a possible variant of their installation. Here: 1 - a pipe through which water is pumped out of the well; 2 - vibration pump or centrifugal pump valve; 3 - spiral sensors; 4 - wire in isolation.
To reduce the shunting of the sensors, the length of the wires and insulation from the place of their separation to the sensors must be at least 200 mm. If the flow of water into the well is large enough, the distance between the sensors can be significantly increased, which will reduce the frequency of switching on the pump. Literature
Author: S. Biryukov, Moscow
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