Optimal microclimate in the greenhouse: installation of thermostats. Thermostats for heating: principles of operation and basics of proper installation

I would like to talk about the creation of a simple device that has made life much easier for homeowners - an automatic gas water heater temperature regulator. Similar devices have already been created and described here on Habré, I wanted to make a slightly more advanced device and describe in detail the entire creation process from idea and measurement to implementation, without using ready-made modules Arduino type. The device will be assembled on a breadboard, the programming language is C. This is my first development of a completed (and working!) device.

1. Initial data

HSV model: Vector lux eco 20-3 (China)
Water pressure: about 1.5 kgf/cm² (the pressure is low, the heater operates slightly above the permissible limit)

Solution requirements

• Simplicity
• PID controller or similar
• Possibility to select the maintained temperature
• Display of current settings
• Solving device security issues

System architecture

• Servo drive (directly in the body of the HSV)
• Standard HSV temperature sensor
• Temperature sensor signal amplification unit and servo drive power supply stabilizer (directly in the HSV body)
• Control unit (external)

2. Servo drive

Having disassembled the column and looked around, I found places to install the TowerPro MG995 servo machine, which I had long ago ordered “for delivery” on aliexpress.

To eliminate play in the rod drive, I made one rod spring-loaded. The backlash was completely eliminated, but another problem became clear - a servo with a torque > 10 kg*cm turned out to be too daring for the HSV. When turned on, transient processes in the electronics of the machine cause a jerk to a random position and after a couple of idle starts, the rod turned out to be bent! Silumin speakers will definitely not withstand such treatment. The geometry of the rocker, which was not on the axis of the regulator, also caused criticism - which led to nonlinearity of the adjustment. Final view of the throttle drive assembly:

The unit has been redone - springs from a VAZ were used (from a carburetor - purchased at an auto parts store) and the rocker is now on the geometric axis of the shaft. This design has a slight backlash, but is linear in adjustment and can dampen the steering wheel's rage. The angles are set to optimal values ​​for adjustment in the most popular positions of the regulator.

3. HSV sensor block

The R2 divider and the column temperature sensor generates a signal with a voltage of 1.4..4.96 V in the full measurement range (in practice - 20..60 degrees Celsius). Initially, I developed a bridge circuit - which could compensate for the loss of the power source, but was discarded due to the fact that the power source had little effect, and the first point of the “TK” was “simplicity”. The operational amplifier provides decoupling between the divider and the load. Zener diode D1 limits the output voltage to 5.1 V in cases where the sensor is disconnected (otherwise the output would be 12 V - which is deadly for the controller) - which will be considered an absolute error by the controller circuit. The 7805 integral stabilizer powers the servo - this is an unsuccessful solution; when the machine is stopped, it heats up terribly and I think it may fail when the drive wedges (if the built-in protection does not work). I won’t focus any more attention on this block.

4. Controller

Clocking - internal oscillator at 8 MHz. Power supply - another 7805 on the board. Indication via standard LCD1602 display. Block diagram:

The power supply of the unit is controlled from the column through a transistor - using a small-sized relay. The temperature sensor signal (Pin No. 4 of the connector) has a pull-up to ground and when the sensor is disconnected during operation it will show very high temperature- which will lead to a decrease in the regulator and will not cause dangerous situations. Assembled block:

4. Testing and adjustment

The tests revealed the following:

• Very high inertia of HSV from the beginning of exposure to the reaction on the temperature sensor - about 30 seconds
• Rounding to the nearest degree in controller firmware is a bad idea, the algorithm could be more accurate

Results of measurement and calibration of the temperature sensor. The dependence can be considered conditionally linear:

First runs in the program for drawing telemetry from the column:

(I forgot to add a legend to the graphs. Here and further - red- sensor temperature, green dotted- throttle position, blue- temperature desired by the user)

Almost successful adjustment

Successful odds options

Not a bad start

The first runs showed the main parameters of the system, then it was no longer difficult to measure them and adjust them using an accelerated formula; selecting the parameters was long and painful. It was not possible to completely get rid of fluctuations, but fluctuations within 1 degree are considered acceptable. Accepted option:

During the selection process, the integral coefficient had to be completely turned off, I think this is due to the large inertia of the system. Final odds:

Float Pk = 0.2; float Ik = 0.0; float Dk = 0.2;

5. Packaging

And in this form it works.

6. Safety of use

Galvanic isolation of column and regulator circuits

Disconnection or detachment of the sensor inside the HSV

Disabling or separating the sensor from the controller

Electronic and mechanical protection of HSV

Temperature is an indicator of the thermodynamic state of an object and is used as an output coordinate when automating thermal processes. The characteristics of objects in temperature control systems depend on the physical parameters of the process and the design of the apparatus. Therefore, it is impossible to formulate general recommendations for choosing ACP temperatures and a careful analysis of the characteristics of each specific process is required.

Temperature regulation in engineering systems is carried out much more often than regulation of any other parameters. The range of adjustable temperatures is small. The lower limit of this range is limited by the minimum outside air temperature (-40 °C), the upper limit by the maximum coolant temperature (+150 °C).

The general features of temperature ASR include significant inertia of thermal processes and temperature meters (sensors). Therefore, one of the main tasks when creating a temperature control system is to reduce the inertia of sensors.

Let us consider, as an example, the characteristics of the most common manometric thermometer in a protective case in engineering systems (Fig. 5.1). Block diagram such a thermometer can be represented as a series connection of four thermal containers (Fig. 5.2): a protective cover /, an air gap 2 , thermometer walls 3 and working fluid 4. If we neglect the thermal resistance of each layer, then the equation heat balance for each element of this device can be written in the form

G,Cpit, = a p? Sjі ( tj _і - tj) - a i2 S i2 (tj -Сн), (5.1)

Where Gj- the mass of the cover, air gap, wall and liquid, respectively; C pj - specific heat; tj- temperature; a,i, a/2 - heat transfer coefficients; S n , S i2 - heat transfer surfaces.

Rice. 5.1. Schematic diagram manometric thermometer:

• 1 - protective cover; 2 - air gap; 3 - thermometer wall;
• 4 - working fluid

Rice. 5.2.

As can be seen from equation (5.1), the main directions for reducing the inertia of temperature sensors are;

• increased heat transfer coefficients from the medium to the cover as a result of the correct choice of the sensor installation location; in this case, the speed of movement of the medium should be maximum; all other things being equal, it is more preferable to install thermometers in the liquid phase (compared to the gaseous phase), in condensing steam (compared to condensate), etc.;
• reducing the thermal resistance and thermal capacity of the protective cover as a result of the choice of its material and thickness;
• reducing the time constant of the air gap due to the use of fillers (liquid, metal shavings); for thermocouples, the working junction is soldered to the body of the protective cover;
• selection of the type of primary converter: for example, when choosing, it is necessary to take into account that the low-inertia thermocouple has the least inertia, and the manometric thermometer has the greatest inertia.

Each temperature control system in engineering systems is created for a very specific purpose (regulating the temperature of indoor air, heating or cooling fluid) and, therefore, is designed to operate in a very small range. In this regard, the conditions for using one or another ACP determine the device and design of both the sensor and the temperature controller. For example, when automating engineering systems, direct-acting temperature controllers with pressure measuring devices are widely used. So, to regulate the air temperature in administrative and public buildings When using ejection and fan coils of a three-pipe heating and cooling circuit, a direct-acting regulator of the RTK direct type is used (Fig. 5.3), which consists of a thermal system and a control valve. The thermal system, which proportionally moves the control valve rod when the temperature of the recirculation air at the inlet to the closer changes, includes a sensing element, a set point and an actuator. These three nodes are connected by a capillary tube and represent a single sealed volume filled with a heat-sensitive (working) fluid. A three-way control valve controls the supply of hot or cold water to the ejection heat exchanger

Rice. 5.3.

a - regulator; b - control valve; c - thermal system;

• 1 - bellows; 2 - set point; 3 - tuning knob; 4 - frame;
• 5, 6 - regulators of hot and cold water respectively; 7 - rod; 8 - actuating mechanism; 9 - sensing element

closer and consists of a housing and regulatory bodies. As the air temperature rises, the working fluid of the thermal system increases its volume and the valve bellows moves the rod and the regulator, closing the passage of hot water through the valve. When the temperature increases by 0.5-1 °C, the regulating bodies remain motionless (the hot and cold water passages are closed), and at a higher temperature only the cold water passage opens (the hot water passage remains closed). The set temperature is ensured by rotating the adjustment knob connected to the bellows, which changes the internal volume of the thermal system. The regulator can be adjusted to temperatures ranging from 15 to 30 °C.

When regulating the temperature in water and steam heaters and coolers, RT type regulators are used, which differ slightly from RTK type regulators. Their main feature is the combined design of a thermal cylinder with a set pointer, as well as the use of a double-seat valve as a regulating body. Such pressure regulators are available in several 40-degree ranges ranging from 20 to 180 °C with a nominal diameter from 15 to 80 mm. Due to the presence of a large static error (10 °C) in these controllers, they are not recommended for high-precision temperature control.

Manometric thermal systems are also used in pneumatic P-regulators, which are widely used for temperature control in engineering air conditioning and ventilation systems (Fig. 5.4). Here, when the temperature changes, the pressure in the thermal system changes, which, through the bellows, acts on the levers that transmit force to the pneumatic relay rod and membrane. When the current temperature is equal to the set one, the entire system is in equilibrium, both pneumatic relay valves, supply and bleed, are closed. As the pressure on the rod increases, the supply valve begins to open. Pressure is supplied to it from the compressed air supply network, as a result of which a control pressure is formed in the pneumatic relay, increasing from 0.2 to 1 kgf/cm2 in proportion to the increase in the temperature of the controlled environment. This pressure activates the actuator.

For automatic regulation indoor air temperatures, thermostatic valves from an American company began to be widely used Honeywell and radiator thermostats (thermostats) RTD produced by the Moscow branch

Rice. 5.4.

with manometric thermosystem:

• 1 - pneumatic relay rod; 2 - unevenness node; 3, 9 - levers;
• 4, 7 - screws; 5 - scale; 6 - screw; 8 - spring; 10 - bellows;
• 11 - membrane; 12 - pneumatic relay; 13 - thermal cylinder; 14 - nourishing

valve; 15 - bleed valve

Danish company Danfoss, the required temperature is set by turning the adjusted handle (head) with a pointer from 6 to 26 °C. Lowering the temperature by 1 °C (for example, from 23 to 22 °C) allows you to save 5-7% of the heat consumed for heating. Thermostats RTD allow you to avoid overheating of premises during the transitional and other periods of the year and ensure minimal required level heating in rooms with occasional occupancy. In addition, radiator thermostats RTD provide hydraulic stability for a two-pipe heating system and the possibility of its adjustment and coordination in case of errors during installation and design without the use of throttle washers and other design solutions.

The thermostat consists of a control valve (body) and a thermostatic element with a bellows (head). The connection between the body and the head is made using a threaded union nut. For ease of installation on the pipeline and connection of the thermostat to the heating device, it is equipped with a union nut with a threaded nipple. The room temperature is maintained by changing the water flow through heating device(radiator or convector). The change in water flow occurs due to the movement of the valve stem by a bellows filled with a special mixture of gases that change their volume even with a slight change in the temperature of the air surrounding the bellows. The elongation of the bellows as the temperature rises is counteracted by an adjustment spring, the force of which is regulated by turning the handle with an indicator of the desired temperature value.

To better suit any heating system, two types of regulator housings are available: RTD-G with low resistance for single-pipe systems and RTD-N with increased resistance for two-pipe systems. Housings are manufactured for straight and angle valves.

Thermostatic elements of the regulators are manufactured in five versions: with a built-in sensor; with remote sensor (capillary tube length 2 m); with protection against inept use and theft; with the setting range limited to 21 °C. In any design, the thermostatic element ensures that the set temperature range is limited or fixed at the required air temperature in the room.

Regulator service life RTD 20-25 years, although at the Rossiya Hotel (Moscow) the service life of 2000 regulators is registered for more than 30 years.

Regulating device (weather compensator) ECL(Fig. 5.5) ensures maintenance of the coolant temperature in the supply and return pipelines of the heating system depending on the outside air temperature according to the corresponding specific repair and specific object heating schedule. The device acts on a control valve with an electric drive (if necessary, also on circulation pump) and allows you to perform the following operations:

• maintaining settlement heating schedule;
• nightly decrease in temperature schedule according to weekly (2-hour intervals) or 24-hour (15-minute intervals) programmable clocks (in the case of electronic clocks, 1-minute intervals);
• flooding the room for 1 hour after an overnight drop in temperature;
• connection via relay outputs of a control valve and a pump (or 2 control valves and 2 pumps);

Rice. 5.5. EU weather compensator/. with setting,

available to the consumer:

1 - programmable clock with the ability to set periods of operation at a comfortable or reduced temperature on a daily or weekly cycle: 2 - parallel movement of the temperature graph in the heating system depending on the outside air temperature (heating graph): 3 - operating mode switch; 4 - space for operating instructions: 5 - power-on signaling, current operating mode,

emergency modes;

O - heating is turned off, the temperature is maintained to prevent freezing of the coolant in the heating system;) - work with low temperature in the heating system; © - automatic switching from mode comfortable temperature to a mode with a reduced temperature and back in accordance with the task on the programmable clock;

O - work without lowering the temperature on a daily or weekly cycle; - manual control: the regulator is turned off, the circulation pump is constantly on, the valve is controlled manually

• automatic transition from summer mode in winter and back according to a given outside temperature;
• stopping night temperature reduction when outside temperatures drop below a set value;
• protection of the system from freezing;
• correction of the heating schedule based on indoor air temperature;
• transition to manual control of the valve drive;
• maximum and minimum restrictions on supply water temperature and the possibility of fixed or proportional

on-line limitation of return water temperature depending on the outside air temperature;

• self-testing and digital indication of temperature values ​​of all sensors and states of valves and pumps;
• setting the dead band, proportional band and accumulation time;
• the ability to work using temperature values ​​accumulated over a given period or current values;
• setting the thermal stability coefficient of the building and setting the influence of the return water temperature deviation on the supply water temperature;
• protection against scale formation when working with gas boiler. Automation schemes for engineering systems use

also bimetallic and dilatometric thermostats, in particular electric two-position and pneumatic proportional.

The electrical bimetallic sensor is intended mainly for two-position temperature control in rooms. The sensitive element of this device is a bimetallic spiral, one end of which is fixedly fixed, and the other is free and meets moving contacts that close or open with a fixed contact depending on the current and set temperature values. The set temperature is set by turning the setting scale. Depending on the setting range, thermostats are available in 16 modifications with a total setting range from -30 to + 35 °C, and each regulator has a range of 10, 20 and 30 °C. Operation error ±1 °С at the middle mark and up to ±2.5 °С at the extreme marks of the scale.

The pneumatic bimetallic regulator, as a converter-amplifier, has a nozzle-flap, which is acted upon by the force of the bimetallic measuring element. These regulators are available in 8 modifications, direct and reverse acting, with a total adjustment range from +5 to +30 °C. The setting range for each modification is 10 °C.

Dilatometric regulators are designed using the difference in the linear expansion coefficients of an Invar (iron-nickel alloy) rod and a brass or steel tube. These thermostats, in terms of the operating principle of the control devices, do not differ from similar regulators using a manometric measuring system.

Thermostats are small in size, but very practical devices for controlling heat transfer in everyday life. Depending on the actual need, temperature regulators for radiators increase or reduce the volume of coolant. Agree, this is useful both for the well-being of the owners of the house/apartment and for their wallets.

For those wishing to purchase thermostats for equipping radiators, we suggest that you familiarize yourself with detailed description types of heat transfer control devices. We have presented and compared their control methods, operating principles, cost, and installation specifics. Our recommendations will help you choose the optimal variety.

We supplemented the information presented for consideration, collected and systematized for future buyers of heat regulators, with visual photo collections, diagrams, regulatory tables, and videos.

It is known that the temperature in different rooms of the house cannot be the same. It is also not necessary to constantly maintain one or another temperature regime.

For example, in the bedroom at night it is necessary to lower the temperature to 17-18 o C. This has a positive effect on sleep and allows you to get rid of headaches.

Image gallery

The optimal temperature in the kitchen is 19 o C. This is due to the fact that there are a lot of heating equipment in the room, which generates additional heat. If the temperature in the bathroom is below 24-26 o C, then the room will feel damp. Therefore, it is important to ensure high temperature here.

If the house has a children's room, then its temperature range may vary. For a child under one year old, a temperature of 23-24 o C will be required; for older children, 21-22 o C will be sufficient. In other rooms, the temperature can vary from 18 to 22 o C.

A comfortable temperature background is selected depending on the purpose of the room and partly on the time of day

At night, you can lower the air temperature in all rooms. It is not necessary to maintain a high temperature in the home if the house will be empty for some time, as well as during sunny warm days, when some electrical appliances are operating that generate heat, etc.

In these cases, setting the thermostat has a positive effect on the microclimate - the air does not overheat and does not dry out.

From the table it is clear that in living rooms in the cold season, the temperature should be 18-23 o C. landing, in the pantry low temperatures are allowed - 12-19 o C

The thermostat solves the following problems:

• allows you to create a certain temperature regime in rooms for different purposes;
• saves boiler life, reduces the amount of consumables for system maintenance (up to 50%);
• It becomes possible to perform an emergency battery shutdown without shutting down the entire riser.

It should be remembered that using a thermostat it is impossible to increase the efficiency of the battery or increase its heat transfer. Save on consumables People with individual heating systems will be able to. Residents apartment buildings Using a thermostat, they can only regulate the temperature in the room.

Let's figure out which ones exist and how to make the right choice of equipment.

Types of thermostats and principles of operation

Thermostats are divided into three types:

• mechanical, with manual adjustment of coolant supply;
• electronic controlled by an external temperature sensor;
• semi-electronic, controlled by a thermal head with a bellows device.

The main advantage of mechanical devices is their low cost, ease of operation, clarity and consistency in work. During their operation there is no need to use additional energy sources.

The modification allows manual mode regulate the amount entering the radiator, thereby controlling the heat transfer of the batteries. The device is distinguished by high precision in adjusting the degree of heating.

A significant drawback of the design is that it does not have markings for adjustment, so the unit will have to be adjusted exclusively empirically. We will look at one of the balancing methods below.

The main elements of a mechanical type regulator are a thermostat and a thermostatic valve

A mechanical thermostat consists of the following elements:

• regulator;
• drive;
• bellows filled with gas or liquid;

Electronic thermostats - more complex designs, which is based on a programmable microprocessor. With it, you can set a certain temperature in the room by pressing several buttons on the controller. Some models are multifunctional, suitable for controlling a boiler, pump, or mixer.

Structure, principle of operation electronic device practically no different from its mechanical counterpart. Here the thermostatic element (bellows) has the shape of a cylinder, its walls are corrugated. It is filled with a substance that reacts to fluctuations in air temperature in the home.

As the temperature rises, the substance expands, resulting in pressure being generated on the walls, which promotes the movement of the rod, which automatically closes the valve. As the stem moves, the conductivity of the valve increases or decreases. If the temperature decreases, the working substance is compressed, as a result the bellows does not stretch, but the valve opens, and vice versa.

Bellows have high strength, long service life, and can withstand hundreds of thousands of compressions over several decades.

The main element of the electronic regulator is a temperature sensor. Its functions include transmitting information about the ambient temperature, as a result of which the system generates required amount heat

Electronic thermostats are conventionally divided into:

• Closed thermostats for heating radiators do not have an automatic temperature detection function, so they are adjusted manually. It is possible to adjust the temperature that will be maintained in the room and the permissible temperature fluctuations.
• Open thermostats can be programmed. For example, if the temperature drops by several degrees, the operating mode may change. It is also possible to set the response time of a particular mode and adjust the timer. Such devices are used mainly in industry.

Electronic regulators are powered by batteries or a special battery that comes with a charger. Semi-electronic regulators are ideal for domestic purposes. They come with a digital display that shows the room temperature.

The operating principle of semi-electronic devices for adjusting heat transfer by a radiator is borrowed from mechanical models, so its adjustment is carried out manually

Gas-filled and liquid thermostats

When developing a regulator, a substance in a gaseous or liquid state (for example, paraffin) can be used as a thermostatic element. Based on this, devices are divided into gas-filled and liquid.

Paraffin (liquid or gaseous) has the property of expanding under the influence of temperature. As a result, the mass presses on the stem to which the valve is connected. The rod partially blocks the pipe through which the coolant passes. Everything happens automatically

Gas-filled regulators have high term service (from 20 years). The gaseous substance allows you to more smoothly and accurately regulate the air temperature in your home. The devices come with a sensor that determines the air temperature in the home.

Gas bellows respond faster to fluctuations in room temperature. Liquid ones are distinguished by higher accuracy in transmitting internal pressure to the moving mechanism. When choosing a regulator based on a liquid or gaseous substance, they are guided by the quality and service life of the unit.

Liquid and gas regulators can be of two types:

• with built-in sensor;
• with remote

If the radiator is connected to working system heating, then the water should be drained from it. You can do this using ball valve, shut-off valve or any other device that blocks the flow of water from the common riser.

After this, open the battery valve, located in the area where water enters the system, and turn off all taps.

After the water has been removed from the battery, it must be purged to remove air. This can also be done using a Mayevsky crane

The next step is to remove the adapter. Before the procedure, the floor is covered with material that absorbs moisture well (napkins, towels, soft paper, etc.).

A thermometer is placed in the room, then the valve is turned off until it stops. In this position, the coolant will fill the radiator completely, which means that the heat transfer of the device will be maximum. After some time, it is necessary to record the resulting temperature.

Next, you need to turn the head until it stops reverse side. The temperature will begin to drop. When the thermometer shows optimal values ​​for the room, the valve begins to open until the sound of water is heard and sudden heating occurs. In this case, the rotation of the head is stopped, fixing its position.

Conclusions and useful video on the topic

The video clearly shows how to set up a thermostat and implement it into the heating system. As an example, take the Living Eco automatic electronic controller from the Danfoss brand:

You can choose a thermostat based on your own wishes and financial capabilities. For domestic purposes, a mechanical and semi-electronic unit is ideal. Fans of smart technology may prefer functional electronic modifications. It is also possible to install devices without the involvement of specialists.

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As you know, in order to efficiently heat any room, it is necessary to correctly adjust the temperature indicators so that the heating corresponds to optimally comfortable conditions and ensures a favorable microclimate in the home. Therefore, we should consider in more detail the features of such a device as a temperature controller for a heating radiator, which is designed to perform all these functions. In addition, you should understand how to regulate the temperature of the heating battery in various buildings, including private and apartment buildings.

The need to install thermostats

• saving heat produced by heating;
• maintaining a comfortable temperature in the home.

It is very important to remember that during installation it is extremely necessary to have a special jumper located directly in front of the heating device. If it is not there, then the coolant flow will not be able to be regulated through the radiator, since this will have to be done through a common riser.

Speaking of savings, this factor is relevant for those owners whose living space is equipped with an autonomous heating system, as well as for housing and communal services that use metering devices to pay for heat supplied from its producers.

Installation of temperature controllers in apartment buildings

The supply and return pipelines are equipped with special retaining washers, before and after each of which pressure-regulating sensors are located. Due to the fact that the diameter of these sensors is known, it becomes possible to calculate the flow rate of the coolant circulating through the sensors. As a result, the difference obtained between the water flow in the supply and return pipelines will reflect the volume of water consumed by residents.

Temperature sensors are designed to monitor both areas. Therefore, knowing the volume of heat consumed and what its temperature is, you can easily calculate the amount of heat that remains in the room.

To make it easier to regulate the heating operation, you need to constantly monitor the temperature.

1. Installation shut-off valve . Such a device is designed to partially shut off the pipeline system if the return temperature is higher than the set one. It is a conventional solenoid valve. Similar option will be suitable for those houses where the heating system is relatively simple and does not have a large volume of coolant.
2. Three-way valve design. This device also allows you to regulate the current flow of coolant, but it functions somewhat differently: if the water temperature exceeds the norm, it is directed through open valve into the supply line more. By mixing with cooled water, the overall temperature will decrease, and the required circulation rate will be maintained.

Installation of mechanical regulators is not particularly difficult. To install such a device, you only need to connect it to the flange in the elevator assembly. It is also important that the price of such devices is significantly lower compared to electronic mechanisms.

Installation of temperature controllers in private homes

In boilers electric type electronic sensors are used that are directly connected to installed heating elements (thermal electric heating elements) or to the voltage arising on the electrodes or on the boiler winding.

Temperature sensors for radiators

Sometimes one temperature sensor has several heating radiators. This is influenced, first of all, by the installation diagram. But it is much more common to mount the regulator on each heating device separately.

It is worth noting that in order to adjust the heating temperature, you can use not only standard devices.

Common mechanisms of this type include:

• thermostatic head. Represents automatic sensor, which controls the temperature of the coolant in the battery. The principle of its operation is as follows: during the heating process, liquid and gaseous substances expand (in more detail: ""). This, as a consequence, leads to the fact that the heated product squeezes out a special rod, thereby blocking the access of the coolant;
• devices called chokes are no less often used. They are special screw-type taps, with which you can manually regulate the flow of coolant. Their cost is more affordable, and in addition, they can be used to control two-pipe heating systems;
• The least expensive and simplest mechanism to help regulate temperature is a traditional valve. Of course, exploit in in this case should only modern models, and not outdated screw devices, since in old mechanisms valves very often come off, and there is also a risk of oil seals leaking. The situation is completely different with ball valves: even in a half-open position, they function reliably and efficiently over a long period of time.

In order for the design of temperature controllers to be as convenient as possible, many experts recommend that you first study various photos these devices and detailed videos according to their correct connection.

Automatic regulation is very convenient. Using a thermostat for greenhouses, you can maintain the required air temperature in the building.

Types of thermostats and their characteristics

There are many types of thermostats. To do right choice, you need to know their features. There are 3 main types.

1. Electronic thermostat. It has a liquid crystal display, which makes it possible to obtain accurate information about the status.
2. Touch devices. They are good because you can set a work program in them, which makes it possible to create different temperatures V different time days.
3. Mechanical product. Most easy installation, allowing you to control soil temperature. In this case, the temperature is set once, and then you simply adjust it. Perfect option for small greenhouses.

How to choose a thermostat

When choosing a thermostat, you should be guided by what you ultimately want to achieve. First of all, you should pay attention to the following characteristics:

• installation features;
• control method;
• appearance;
• power;
• presence or absence of additional functions.

When choosing thermostats for greenhouses Special attention It's worth paying attention to power. It must be greater than the required ground heating power. Take plenty! In this case, all work is controlled by a sensor. He can be:

• external;
• hidden.

A circuit may consist of several elements. Appearance There are different types of thermostats too. Installation can be either mounted or hidden.

Installation Features

When installing the system with your own hands, it is worth knowing that the regulator operates from sensors - light and temperature. The temperature in the building will be higher during the day and lower at night. Depending on this, heating also changes. The parameters for the thermostat are as follows:

• illumination limit - from 500 to 2600 lux;
• deviation in the power supply of the device - up to 20%;
• temperature range - from +15 to 50 degrees;

• when crossing the illumination limit, the temperature difference is up to 12 degrees;
• accuracy is about 0.4 degrees.

When installing the system yourself, you should know that the thermostat includes an adjustment unit and a temperature control unit. They can be performed using transistors. A switch allows you to vary the temperature. The relay can be combined with a heating device for the stove using contacts. The regulator may have an output relay that controls the heating.

The sensors include photoresistors and thermistors. They respond to various changes in environment. Settings can be made according to the instructions provided by the manufacturer.

You should set up the installation yourself, starting with calibrating the resistor scale. First, the sensors are lowered into heated water and then the temperature is determined. Next, the light sensor is calibrated. It is allowed to assemble the temperature regulator inside greenhouses. It is placed near a heating device, which can be a stove.

Thermostat review (video)

How to work with a thermostat

Thermostats, regardless of whether they are made by hand or purchased in a store, are very similar in principle of operation. Because of this, it is easy to work with them. What are the characteristics of working with the device?

• A special button helps you scroll through the menu.
• Temperature adjustment is done manually.
• You can save settings in the device's memory for quick startup.
• The use of special buttons allows you to control the operation of the boiler and stove and set heating characteristics.
• If there is a display with readings, you can find out what the heating is like at a given time.

Among other things, thermostats make it possible to control the boiler for heating the greenhouse.

1. Once power is applied to the controller, the sensors are polled for real-time information. Then the controller compares the readings and already recorded information for day or night and selects the necessary settings for the thermostat.
2. After 5 minutes, the thermostat is activated and the boiler starts working.
3. If heating is insufficient, the heater and pump begin to function. A command is given to increase the fuel supply, which increases heating.

Thermostats are multifunctional. With their help, you can heat the greenhouse and set the required temperature for the air in the building, as well as heat the soil and water.

The regulator is capable of supporting optimal conditions environment in any . Some devices turn on and work independently, which is very convenient. They are connected to the controller, heat sensors, stove and boiler. As a result, you can fully control the temperature regime.

Making a simple regulator with your own hands

You can make the regulator yourself using a standard household thermometer. However, it will have to be modified.

• First disassemble the device, but remember to proceed carefully.
• A hole is made in the scale, at the location of the area of ​​the required control limit. Its diameter should be less than 2.5 millimeters. A phototransistor is fixed opposite it. Sheet aluminum is taken, a corner is made in which a 2.8 mm hole is drilled. The phototransistor is glued to the socket using Moment glue.
• Below the hole, a corner is fixed so that if the temperature exceeds (during the day), the arrow does not have the opportunity to pass through the hole. This will prevent the heating from turning on when it is not needed.
• A 9-volt light bulb is installed on the outside of the thermometer. A hole is drilled for it in the thermometer body. A lens is placed inside between the scale and the light bulb. It is needed for the device to work accurately.
• The wires from the light bulb are routed through a hole in the housing, and the wires from the phototransistor are routed through a hole in the scale. The common tourniquet is placed in a vinyl chloride tube and secured with a clamp. A 0.4 mm hole is drilled opposite the light bulb.

• In addition to the sensor, the thermostat must have a voltage stabilizer. A photo relay is also required. The stabilizer is powered from a transformer. A modified transistor of the GT109 type serves as a photocell for the photo relay. All you need to do is remove the cap from its body and break off the base terminal.
• A mechanism made from a factory-made relay is used as a load. The work in this case follows the principle of an electromagnet, where a steel armature goes inside the coil and influences the microswitch, which is fixed with 2 brackets. And the microswitch activates the electromagnetic starter, through the contacts of which the supply voltage goes to the heating device.
• The photo relay along with the power subunits is placed in a housing made of insulating material. A thermometer is attached to it on a special rod. There is a neon light on the front side (it will signal the start of work heating elements) and toggle switch.
• In order for the regulator to work accurately, it is necessary to achieve a clear focus of the light emanating from the light bulb onto the photocell.

How to make a thermostat with your own hands (video)

Thus, despite the complexity of the work, installing a thermostat significantly simplifies maintenance. Crops that receive an optimal microclimate develop better, which means the harvest will be significantly larger.