Automation of irrigation systems and soil moisture control in greenhouses

Automatic humidity regulator: 1 — chamber; 2 — membrane; 3 — siphon chamber; 4 — hinge; 5 — lever; 6 — flexible hose; 7 — spring; 8 — adjustment screw; 9 — gate valve;

10 — cylinder; 11 — piston; 12, 13 — lower and upper cavities; 14, 15 — overflow pipes; 16 — pressure line;

17, 18 — overflow pipes; 19 — valve for closing pipe 17, moving piston 11 to the upper position, and closing the gate valve. The adjustment screw 8 is used to set the soil moisture control limits.

An electronic humidity regulator can be used. One of the diagrams for such a regulator is shown in the figure. Two carbon rods from a 3336L battery with a depolarizer act as the humidity sensor (only the zinc casing needs to be removed from the cells).

Schematic diagram of the soil moisture regulator: K1=47

K; B2=21 K; B3=47 K; B4=1 K; O — humidity sensor; K —

Container with solenoid valve: 1 — solenoid; 2 — barrel; 3 — linkage; 4 — 2 valve. The rods should be inserted into the soil at a distance of 20 cm. At reduced soil moisture, the resistance between them is about 1500 Ohms. The circuit is set to the desired trigger threshold of the regulator using variable resistor K1; variable resistor B2 is used to set the initial humidity. The regulator uses MP16B, MP25, MPA42 transistors or their equivalents, and an RES-10 type output relay.

When using an electronic regulator to supply water to the irrigation system, it is necessary to install a solenoid valve, an electrically operated gate valve, or an SVM-type solenoid valve with a diameter of 20-25 mm. A solenoid valve can be made by oneself. One of the designs is shown in the figure.

The valve itself is an outlet valve from a standard toilet flush tank, connected by a stainless steel wire linkage to an actuating solenoid. A magnetic starter can be used as a solenoid, its coil being rewound to 36 V for safety reasons.

As tempting as it is to control an irrigation system using electronics, one must remember that high reliability is provided by the simplest device. An uncomplicated programmed irrigation device can be made with one's own hands without the use of electronic circuits and solenoid valves. The diagram of such a device is shown in the figure.

The device consists of a 200-250 L barrel, where the irrigation water supply is poured. If there is a water supply inlet, a float valve 1 is installed. Water flows from the barrel 2 through a dispenser 3 into the dosing container 4, which serves to fill the capacity 8 and trigger the siphon 9. The starter container 4 must have a capacity of 2-3 L, and the working container — 8-10 L. In the initial position, the starter container 4 is held by a weight 6 and a linkage 5; after filling the container through the dispenser 3, the system equilibrium is disturbed, and the container tips over. For stable emptying of the container, it is equipped with support strips 7 that shift the center of gravity at the initial moment of tipping. After the working container 8 is filled and the siphon 9 triggers, the irrigation cycle begins.

Setting up the automatic irrigation system and calculations

Setting the automatic irrigation mode

By adjusting the flow of the dispenser 3, various irrigation programs can be set. For example, if the barrel 2 has a capacity of 250 L, the working container 8 has a capacity of 10 L, and the dispenser is set to a flow rate of 2 L/hour, the irrigation period for the plants will be 125 hours, or 5 days.

In this case, the irrigation process indicators will be as follows:

If more intensive irrigation is required, the dispenser performance is increased, but it must be taken into account that the total water reserve must be increased if there is no water supply inlet.

Diagram and calculation of the total water reserve

The irrigation device diagram includes the following elements:

• 1 — float valve;
• 2 — water barrel;
• 3 — dispenser;
• 4 — dosing container;
• 5 — block;
• 6 — weight;
• 7 — support strip;
• 8 — charging container;
• 9 — siphon.

If we assume a water consumption of 5 L/m² per day for mature plants, then for a 10 m² greenhouse, the total water reserve for five days must be 250 L, and for a 15 m² greenhouse, it will be necessary to install a container with a capacity of 375 L or two 200 L barrels.

The described designs for heating, ventilation, and irrigation of greenhouses and hotbeds do not exhaust the entire spectrum of possible solutions and are not mandatory to replicate without any changes. Undoubtedly, everyone can choose the most acceptable elements from different designs for themselves, using the descriptions provided here.