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When operating a greenhouse, one of the most important tasks is to maintain an optimal temperature at a natural level of humidity. The easiest way to solve the problem is to ventilate the room.
However, doing it manually is most often problematic due to lack of time. Therefore, it makes sense to arrange automatic adjustment of the leaf position using a thermal drive.
How to make an automatic machine for ventilating greenhouses with your own hands? What is the best way to organize automatic ventilation in the greenhouse? How to make a polycarbonate window pan for a greenhouse?
The principle of operation of the thermal drive
Regardless of the design of the thermal actuator, the essence of its work is to open the leaf of the window when the temperature rises. When the air in the greenhouse cools down, the thermal actuator automatically closes the window to its original position.
There are two main elements in the device:
- actuating mechanism.
Wherein the design of the sensors and actuators themselves can be completely arbitrary. Additionally, the devices can be equipped with door closers and locks that ensure a tight closing of the transom.
There is also division into volatile and nonvolatile devices... Electric drives operating from the power supply network are most often volatile.
To their merits include great power and extensive programming behavior.
To the disadvantages - if the power supply is lost, there is a risk of either chilling the plants due to the vents left open for the night, or boiling them on a hot day with the ventilation unopened.
Scope of application
Where can you install a do-it-yourself thermal drive for greenhouses?
Installation of thermal drives (photo on the right) can be done absolutely to any greenhouses: film, polycarbonate and glass.
In the latter case, to the choice of the drive you need to be especially careful, since the glass vent has a significant mass and a sufficiently powerful device may be required to work with it.
Besides, the size of the greenhouse matters... It makes little sense to install such a device in a greenhouse with an area of one and a half square meters. m. There is simply not enough space, and the frames of such structures are often not capable of carrying an additional load.
In very large greenhouses, some problems can also arise. This is due to the need to simultaneously open several vents at once, often also differing in considerable size. The power of a homemade thermal drive is simply not enough to do such a hard job.
The most harmonious thermal actuators fit into the construction of greenhouses made of cellular polycarbonate. The vents made of this material are light enough that even a home-made device can operate them. At the same time, polycarbonate is reliable enough to make a durable window, suitable for repeated opening and closing cycles.
By the mechanism of action there are several main groups of thermal drives. How to arrange automatic opening of vents in a greenhouse with your own hands?
As the name suggests, in these devices the actuator is driven electric motor... The command to turn on the motor is given by the controller, which is guided by the information from the temperature sensor.
To the merits electric drives include high power and the ability to create programmable intelligent systems that include a wide variety of sensors and allow the most correct determination of the greenhouse ventilation mode.
Main disadvantages electric thermal drives - dependence on power supply and not the lowest cost for a simple gardener. In addition, the humid atmosphere of the greenhouse does not contribute to the long-term operation of any electrical appliances.
The principle of their work is based on different coefficients of thermal expansion for different metals. If two plates of such metals are somehow fastened together, then when heated, one of them will necessarily become larger in size than the other. The resulting skew is used as a source of mechanical work when opening the window.
Dignity such a drive is its simplicity and autonomy, disadvantage - not always sufficient power.
The operation of pneumatic thermal actuators is based on on the supply of heated air from a sealed container to the drive piston... When the container heats up, the expanded air is fed through a tube to the piston, which starts to move and opens the transom. When the temperature drops, the air inside the system is compressed and pulls the piston in the opposite direction, closing the window.
With all the simplicity of this design, it is rather difficult to make it yourself. It will be necessary to ensure a serious sealing not only of the container, but also inside the piston. It complicates the task and the property of air is easily compressed, which leads to a loss in the efficiency of the entire system.
Hydraulic Thermal Actuator Mechanism driven by a change in balance in the weight of a pair of containers, between which the liquid moves. In turn, the liquid begins to move between the vessels due to the change in air pressure during heating and cooling.
The advantage of hydraulics is its relatively high power with complete non-volatility. In addition, assembling such a structure with your own hands is much easier and cheaper than for other drives.
How to independently organize automatic ventilation of greenhouses (thermal drive, which one to choose)?
How to make a device for airing greenhouses with your own hands? For self-production, the simplest and most effective option for a thermal drive for greenhouses is hydraulic.
To assemble it you will need:
- 2 glass jars (3 l and 800 g);
- brass or copper tube 30 cm long and 5-7 mm in diameter;
- 1 m long plastic tube from a medical dropper;
- a piece of timber with a length equal to the width of the opening transom. The cross-section of the bar is selected taking into account the weight of the vents, since it will be used to manufacture a counterweight;
- metal rigid wire;
- two lids for cans: polyethylene and metal;
- nails 100 mm - 2 pcs.
The assembly sequence will be as follows:
- 800 gr is poured into a three-liter jar;
- the can is tightly sealed with a metal lid using a seaming machine;
- a hole is punched or drilled in the lid, into which the brass tube is inserted. It is necessary to lower the tube until 2-3 mm remains to the bottom;
- the joint between the tube and the lid is sealed with a sealant;
- one end of the plastic tube is pushed onto the metal tube.
Then they work with a jar of 800 grams, only it is left empty, closed with a plastic lid and a plastic tube is inserted with the second end. 2-3 mm are also left from the tube cut to the bottom of the jar.
The final stage place banks at workplaces. To do this, a three-liter one with a nail and a metal wire is suspended next to the rotating window so that, in any position of the window, the length of the plastic tube is enough for it.
A small jar is also fixed on a nail and wire on the upper part of the frame of a horizontally rotating window. To balance the mass of the can, a counterweight bar is nailed from the street side of the window to the lower part of its frame.
Now, if the temperature rises in the greenhouse, then the air heated in a large jar will begin to squeeze water through a plastic tube into a small jar. As water is collected in a small jar, due to the increased weight of the upper part of the window, it will begin to rotate around its axis, i.e., it will begin to open.
As the air in the greenhouse cools down, the air in a three-liter jar will begin to cool and compress. The resulting vacuum will pull the water back in from the small can. The latter will lose weight and the window frame will drop to the “closed” position under the weight of the counterweight.
Not the most tricky design of the hydraulic thermal drive allows you to independently assemble a device that seriously facilitates the care of the greenhouse. With its help, the need to control the air temperature in the greenhouse completely disappears.
To your attention informative videos about thermal drives for greenhouses.
And here is a video about a do-it-yourself thermal drive for greenhouses from a shock absorber.
Read about other options for automating greenhouse maintenance here.
And here read about thermostats for greenhouses.