DIY mechanical temperature controller. How to make a thermostat for heating with your own hands

Thermostats are widely used for various purposes: in cars, heating systems of various types, refrigerators and furnaces. Their job is to turn off or turn on devices after reaching a certain temperature. It’s not difficult to make a simple mechanical thermostat with your own hands. Modern designs have a more complex design, but with some experience it is possible to make analogues of such structures.

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Mechanical thermostat

Today, the newest models of thermostats are controlled using touch buttons, while older models are controlled by mechanical ones. Most of these devices have a digital panel that displays the temperature of the coolant in real time, as well as the required maximum degree.

The production of such devices is not complete without programming them, so their price is very high. They allow you to adjust the temperature according to different parameters, for example, by hour or day of the week. The temperature will change automatically.

If we talk about thermostats for industrial steel furnaces, it will be difficult to make them yourself, since they have a complex design and require the attention of more than one specialist. These are mostly made in factories. But making a simple temperature controller with your own hands for an autonomous heating system, incubators, etc. is not a difficult task. The main thing is to adhere to all drawings and production recommendations.

In order to understand how, you can disassemble a simple mechanical structure. It works on the principle of opening and closing the door (damper) of the boiler, thereby reducing or increasing the access of air to the combustion chamber. The sensor reacts, of course, to temperature.

To produce such a device you will need the following components:

• return spring;
• two levers;
• two aluminum tubes;
• adjusting unit (looks like a crane axle box);
• a chain that connects two parts (thermostat and door).

All components must be assembled and mounted on the boiler.

The device works thanks to the property of aluminum to expand under the influence of temperature. In this regard, the damper closes. If the temperature decreases, the aluminum pipe cools and decreases in size, so the damper opens slightly.

But this scheme also has its significant disadvantages. The problem is that it is difficult to determine when the damper will operate this way. To approximately adjust the mechanism, precise calculations are needed. It is impossible to determine exactly how much an aluminum pipe will expand. Therefore, in most cases, devices with electronic sensors are now preferred.

Homemade mechanical thermostat for a mine boiler



Simple electronic device

For more precise work, you cannot do without electronic components. The simplest thermostats operate using a relay-based circuit.





The main elements of such a device are:

• threshold circuit;
• indicator device;
• temperature sensor.

The homemade thermostat circuit must respond to an increase (decrease) in temperature and turn on the actuator or suspend its operation. To implement the simplest circuit, bipolar transistors should be used. The thermal relay is made according to the Schmidt trigger type. The thermistor will act as a temperature sensor. It will change resistance depending on the temperature, which is adjusted in the general control unit.

But in addition to a thermistor, a temperature sensor can be:

• thermistors;
• semiconductor elements;
• resistance thermometers;
• bimetallic relays;
• thermocouples.

When using diagrams and drawings from unknown sources, it is worth keeping in mind that they often do not correspond to the attached description. In this regard, it is necessary to carefully study all the material before proceeding with the manufacture of the device.

Before starting work, you need to decide on the temperature range of the device, as well as its power. It must be taken into account that some components will be used for the refrigerator, and others for heating equipment.



A device consisting of three components

A simple DIY electronic thermostat can be assembled for use on fans and personal computers. Thus, you can understand the principle of its operation. A breadboard is used as the basis.

The tools you will need are a soldering iron, but if you don’t have one or don’t have enough experience, you can also use a solderless board.

The scheme consists of three elements:

• power transistor;
• potentiometer;
• a thermistor that will act as a temperature sensor.

The temperature sensor (thermistor) reacts to an increase in degrees, and therefore the fan will turn on.

To adjust the device, you must first set the data for the fan to the off position. Then you need to turn on the computer and wait until it warms up to a certain temperature in order to record the moment the fan turns on. The setup is done several times. This will ensure the effectiveness of the work.

Today, modern manufacturers of various elements and microcircuits can offer a large selection of spare parts. They all differ in technical characteristics and appearance.

DIY thermostat



Temperature controllers for heating systems

When making and installing a thermostat with an air temperature sensor with your own hands for heating systems, it is necessary to accurately calibrate the upper and lower lines. This will avoid overheating of the equipment, which can lead to failure of the entire system at best. At worst, overheating equipment can cause it to explode and possibly be fatal.




For these purposes, you will need a device to measure current strength. Using drawings and diagrams, you can make external equipment for adjusting the temperature of a solid fuel boiler. For work, you can use the K561LA7 circuit. The principle of operation lies in the same ability of a thermistor to reduce or increase resistance under certain temperature conditions. The desired parameters can be set using an AC resistor. First, the voltage is supplied to the inverter, and then transmitted to the capacitors, which are connected to the triggers and control their operation.

The principle of operation is simple. As the degrees drop, the voltage in the relay increases. If the value is less than the lower limits, the fan automatically turns off.

It is better to solder the elements on a mole rat. As a power supply, you can use a device that operates within 3-15 V.

Any homemade device installed on the heating system can lead to its failure. In addition, such actions may be prohibited by government control services. For example, if a gas boiler is installed in the house, then such additional equipment may be removed by the gas service. In some cases, fines are even issued.

Do-it-yourself thermostat for heating elements: diagram and instructions

Digital equipment

To manufacture a modern device with precise adjustment of the required degrees, you cannot do without digital components.

The main chip is PIC16F628A. Using such a circuit, you can control various electronic devices.

The operating principle is also not very complicated. The values ​​of the set (required) temperature and the current temperature are supplied to a three-charge indicator with a common cathode.

To set the desired temperature, the microcircuit has two elements sb1 and sb2, to which mechanical buttons are subsequently soldered. The first element serves to reduce the temperature, and the second to increase it.

Setting the hysteresis value is performed by simultaneously pressing the sb3 button when setting.

When making homemade devices, it is important not only to solder and manufacture the circuit correctly, but also to place the device on the equipment in the right place. The board itself must be protected from moisture and dust to avoid short circuits and, accordingly, failure of the device. Isolation of all contacts also plays a very important role.

There are three types of internal signals:

1. 1. Data is taken directly from the coolant. It is not very popular in everyday life, since its effectiveness is insufficient. The operating principle is based on an immersion sensor or other similar device. Although there are problems with efficiency, it belongs to the expensive segment of such devices on the market.
2. 2. Internal air waves. This option is the most popular because it is considered reliable and economical. It takes data not from the temperature of the coolant, but directly from the air. This allows for higher accuracy. What degree will be set in the control unit will be the air temperature. Connects to the heating system using a cable. Such models are constantly being improved by manufacturers, which makes them more convenient and functional.
3. 3. External air waves. Operates on the basis of a street sensor. It is triggered by any changes in weather conditions and reacts immediately by changing the settings of the heating equipment.

Such devices can be either electrical or electronic. Thermostats can receive signals in automatic or semi-automatic mode. Operation and temperature changes can occur by monitoring the temperature of radiators and main lines or by recording changes in boiler power.

Today on the market there is many popular models from top manufacturers who have already secured their position. These primarily include E 51.716 and IWarm 710. The body itself is small in size and made of plastic polymer, which does not burn. Despite this, it has many useful functions. The display is quite large for such small sizes. It displays all existing data. Such devices cost between 2500-3000 rubles.

The functional features of the first model include the ability to mount it into a wall in any position, the temperature is controlled simultaneously from the floor itself, as well as the presence of a 3 m long cable. During installation, you need to think about whether there will be free access to the device for unhindered control.

To the above advantages, you can add some disadvantages. These include a small set of functions that are found in analogues of these devices. This sometimes causes discomfort when used. In addition, these models do not have an automatic heating function. But if you wish, you can finish it yourself.

Thus, making a thermostat yourself or purchasing and installing a ready-made model will not be difficult if you strictly adhere to all diagrams, drawings and instructions for manufacturing and installation. This equipment will save owners time on manually adjusting the temperature of certain devices.

From early spring to mid-summer - it's time for incubators. Almost everyone who has birds in their backyard uses incubators. With it, it is convenient to breed the required amount of any breed of bird at any time. There is no need to wait for the hen to sit on the nest.

An integral part of any incubator - It's a thermostat! The hatching of the bird also depends on its reliability and accuracy.

It is not necessary to use a programmable digital expensive thermostat. The thermostat proposed in this article does its job perfectly.

on one simple and inexpensive chip K561LA7 is proposed below. Simple

, because a bunch of transistors were replaced by one microcircuit. Reliable

1. , because the scheme uses some points:
2. To drop the voltage from 220V to 9V, a resistor is used, not a capacitor (as is often the case in other circuits). It's much more reliable.
3. The lamps are connected in series-parallel, which is also more reliable than just parallel connection.
4. If the contact of the variable resistor “temperature” is poor, the lamps will turn off, and not vice versa.

The K561LA7 microcircuit (as practice has shown) is more reliable than an op-amp or PIC. a threshold element is assembled, which changes its output position from 1 to 0 at a given temperature. Regulator "Temperature" this threshold changes.

On the second element DD1.2 a pulse shaper has been assembled for proper operation of the thyristor.

Third element DD1.3— adder.

Fourth element DD1.4- is free and can be used (as a last resort) to replace one of the remaining elements in the event of its failure.

Microcircuit K561LA7 you can replace it with an imported analogue CD4011B.

The current consumption of the 9V circuit is 5 mA, the temperature of R13 is approximately 60 - 70 degrees. - this is the normal mode of the resistor.

Pulses arriving at the transistor open it, which subsequently contributes to the opening of the thyristor.

Thyristor (T122 or KU202N,M,L)- a powerful switching element of the circuit. A thyristor (if KU202N,M,L is used) without a radiator is capable of switching a load up to 300 W. Usually this is enough. If your load exceeds this value, then the thyristor must be placed on the radiator. Maximum value 1000 W. You can also install a more powerful thyristor - T122.

Calculate load easy for incubator. We turn on the heaters (lamps) through this temperature regulator to full. And we control the temperature with a thermometer. Even at full (the lights do not turn off), the temperature in the incubator should not rise above 50 degrees.

Since, during operation, the lamp filaments sag greatly and burn out. There is a danger of the thyristor failing. Therefore, it is recommended to connect the lamps in series-parallel, as indicated in the diagram, for a longer service life of the lamps and the circuit.

Since the incubator has very high humidity at temperature sensor - thermistor you need to put on a piece of tube and fill it with waterproof glue or sealant on both sides. It is better to do this several times with a period of several hours after drying. The end of the thermistor can be left on the surface for greater sensitivity.

The circuit is universal for the choice of thermistors. The value of the thermistor is suitable within a wide range. I tried from 1 kOhm to 15 kOhm that I had available. Others will do too. The correct operating mode must be selected by dividing by R2, R3. You can select R3 using the table below.

Should be considered: The greater the resistance of the thermistor or the greater the resistance of R1 - R5, the smaller the range of regulation by variable resistors.

You can use thermistors with both negative and positive TCR. With a negative TKS, as now in the diagram, and with a positive thermistor, the thermistor should be installed at the bottom of the divider (for example, in the gap between R3 and R4).

The thermostat circuit is built on a logic chip, and between logic levels 0 and 1 there is an indeterminate state (see figure), so this circuit has a certain hysteresis (delay between turning on and off).

Hysteresis depends very much on the type of thermistor used.

If you do not need the circuit to respond quickly to temperature, use a thermistor in a metal case. Type MMT-4. The hysteresis in this case is 2.5 - 3 g.

If you need a quick response of the circuit to temperature, then use thermistors in a non-metallic case. Hysteresis 0.1 - 0.5 g. Light bulbs turn on and off several times more often.

Table of DC voltages of the K561LA7 microcircuit

(measured with a digital multimeter in the working circuit)

Photo of the assembled board

Note: The marking of some parts according to the diagram has changed.

Photo of the printed circuit board

Thanks to the use of a resistor (R13, not a capacitor) to lower the voltage, stabilize and filter the voltage supplying the microcircuit, as well as other “chips,” this thermostat circuit has been used in the incubator for more than 10 years and has never failed!

A. Zotov. Volgograd region

P.S. If you decide to make the above thermostat, but you do not have a board or some electronics. components, then you can purchase from us KIT FOR SELF ASSEMBLY OF TEMPERATURE REGULATOR FOR INCUBATOR.

Photo of the finished board assembled from the kit

When equipping a cellar, it is necessary to create a temperature regime at which all reserves will be stored for as long as possible. And to maintain it, you will need a thermostat - a device that helps maintain the set temperature. This device is used in many household appliances: irons, refrigerators, soldering irons. How to make a thermostat for a cellar with your own hands?

Quality materials to get the job done

You will need:

• potentiometer;
• integral stabilizer;
• network adapter;
• output device;
• thermostat.

Currently, any device can be bought in a store, but sometimes it is cheaper to make it yourself. Naturally, it is not worth soldering spare parts for electrical appliances, but it is quite possible to make an individual device suitable for the parameters of your cellar. The circuit diagram of such a device is simple. A certain temperature is maintained by turning on/off the heating element (heating element).

The temperature rises to a predetermined level, a special device - a comparator - is activated, and the heating element is turned off. In theory, such a device is easy to make, but when it comes to practical implementation, it becomes clear that not everything is so simple. Previously, calibration was performed as follows: the temperature sensor was immersed first in ice, then in boiling water.

To measure the readings, we took a voltmeter and a thermometer and set the desired response temperature. The process took a lot of time and did not give the best results. Today, buying a temperature sensor is not a problem. They are calibrated during manufacture, so there is no need to conduct any experiments. Modern technologies have made it possible to create a temperature sensor that transmits digital information. With the help of these devices, it is possible to measure the temperature at various points in the apartment - you control the temperature not only outside the window, but also inside the house.

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Indoor control

It is possible to control the thermostat in several rooms.

Typical thermostat circuit for a cellar.

Devices are designated by Latin letters and numbers. For example, LM135. In order not to make a mistake in your choice, remember: 1 - application in military equipment, 2 - application in production apparatus and devices, 3 - application in household appliances. The Russian analogue is the designation of transistors - 2T (military) and KT (mass). The operating principle of such a sensor is as follows: as the temperature rises, the stabilization voltage increases, that is, it is a zener diode. You can make sure you made the right choice by reading the technical specifications of the device. The calibration point is indicated in Kelvin. The temperature scale is indicated in degrees Celsius.

Remembering the school physics course, translate 0C = 0+273 = 273K. The operating range of the sensor is from -40 to 100°C. If such a sensor is used, there is no need for questionable experiments. It is enough to calculate the voltage at the output of the zener diode, and then indicate this value to the master at the input of the comparator (comparing device). The LM335 temperature sensor is inexpensive - about 35-40 rubles. Using this temperature sensor as a basis, draw a diagram of a temperature regulator for the cellar.

Schematic diagram of the thermostat.

In practice, it will be supplemented with an output device for turning on the heater, a power supply and an operation indicator.

The next important element is a comparator, for example LM311. It has two inputs - direct (2), designated “+”, and inverse (3), designated “-”, and one output. In the diagram, the comparator output is indicated by the number 7. This device works like this: the voltage at input 2 is greater than at input 3, and we get a high level at the output. The transistor opened and connected the load. A potentiometer connected to the direct input sets the temperature - sets the response threshold of the comparator. In the opposite situation (the voltage at input 2 is less than at input 3), the output level decreases. The temperature rises, the thermal relay is triggered, the comparator goes to a low level, the transistor closes, the heating element turns off. This cycle repeats continuously.

Among the numerous assortment of useful devices that bring comfort to our lives, there are a large number of those that you can make with your own hands. This number also includes a thermostat, which turns heating and cooling equipment on or off in accordance with the specific temperature at which it is set. This device is perfect for periods of cold weather, for example for a basement where you need to store vegetables. So how to make a thermostat with your own hands, and what parts will be needed for this?

DIY thermostat: diagram

About the design of the thermostat, we can say that it is not particularly complicated, it is for this reason that most radio amateurs begin their training with this device, and also hone their skills and craftsmanship on it. You can find a very large number of device circuits, but the most common is a circuit using a so-called comparator.

This element has several inputs and outputs:

• One input responds by supplying a reference voltage that corresponds to the required temperature;
• The second receives voltage from the temperature sensor.

The comparator itself receives all incoming readings and compares them. If it generates a signal at the output, it will turn on the relay, which will supply current to the heating or refrigerating unit.

What parts will you need: DIY thermostat

For a temperature sensor, a thermistor is most often used; this is an element that regulates electrical resistance depending on the temperature reading.

Semiconductor parts are also often used:

• Diodes;
• Transistors.

Temperature should have the same effect on their characteristics. That is, when heated, the transistor current should increase and at the same time it should stop working, despite the incoming signal. It should be taken into account that such parts have a big drawback. It is too difficult to calibrate, or more precisely, it will be difficult to associate these parts with some temperature sensors.

However, at the moment the industry does not stand still, and you can see devices from the 300 series, this is the LM335, which is increasingly recommended by experts and the LM358n. Despite the very low cost, this part occupies the first position in the markings and is oriented towards combination with household appliances. It is worth mentioning that modifications of this part LM 235 and 135 are successfully used in the military and industrial sectors. Including about 16 transistors in its design, the sensor is capable of working as a stabilizer, and its voltage will completely depend on the temperature indicator.

The dependency is as follows:

1. For each degree there will be about 0.01 V, if you focus on Celsius, then at 273 the output result will be 2.73V.
2. The operating range is limited to -40 to +100 degrees. Thanks to such indicators, the user completely gets rid of adjustments by trial and error, and the required temperature will be ensured in any case.

Also, in addition to the temperature sensor, you will need a comparator, it is best to purchase LM 311, which is produced by the same manufacturer, a potentiometer to generate a reference voltage and an output setting to turn on the relay. Don't forget to purchase a power supply and special indicators.

DIY temperature controller: power and load

As for the connection of LM 335, it must be serial. All resistances must be selected so that the total current that passes through the temperature sensor corresponds to values ​​from 0.45 mA to 5 mA. The mark should not be exceeded, as the sensor will overheat and show distorted data.

The thermostat can be powered in several ways:

• Using a power supply oriented at 12 V;
• Using any other device whose power supply does not exceed the above figure, but the current flowing through the coil should not exceed 100 mA.

Let us remind you once again that the current in the sensor circuit should not exceed 5 mA; for this reason, you will have to use a high-power transistor. KT 814 is best. Of course, if you want to avoid using a transistor, you can use a relay with a lower current level. It can operate on a voltage of 220 V.

Homemade thermostat: step-by-step instructions

If you have purchased all the necessary components for assembly, all that remains is to review the detailed instructions. We will consider the example of a temperature sensor designed for 12V.

A homemade temperature controller is assembled according to the following principle:

1. We prepare the body. You can use old shells from the meter, for example from the Granit-1 installation.
2. You select the circuit that you like best, but you can also focus on the board from the meter. The forward stroke marked “+” is required to connect the potentiometer. The inverse input marked “–” will be used to connect the temperature sensor. If it so happens that the voltage at the direct input is higher than required, the output will be set to a high level and the transistor will begin to supply power to the relay, and it, in turn, to the heating element. As soon as the output voltage exceeds the permissible level, the relay will turn off.
3. In order for the thermostat to operate on time and temperature differences to be ensured, you will need to make a negative connection using a resistor, which is formed between the direct input and output of the comparator.
4. As for the transformer and its power supply, you may need an induction coil from an old electric meter. In order for the voltage to correspond to 12 volts, you will need to make 540 turns. It will only be possible to fit them if the diameter of the wire is no more than 0.4 mm.

That's all. These small steps are where all the work of creating a thermostat with your own hands lies. It may not be possible to do it yourself without certain skills right away, but with the help of photo and video instructions you will be able to test all your skills.

Thanks to its simple design, a self-created thermal controller can be used anywhere.

For example:

• For heated floors;
• For the cellar;
• Can adjust air temperature;
• For the oven;
• For an aquarium where the water temperature will be controlled;
• In order to control the temperature value of the electric boiler pump (its switching on and off);
• And even for a car.

It is not necessary to use a digital, electronic or mechanical commercial thermal switch. Having bought an inexpensive thermal relay, adjust the power on the triac and thermocouple and your homemade device will work no worse than the purchased one.

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

In our article on creating a thermostat yourself, all the main points were indicated, from the necessary details for the design to step-by-step instructions. Don’t rush to start creating right away, study the literature and advice from experienced craftsmen. Only with the right approach can you get a perfect result on the first try.

The Russian winter is distinguished by its severity and extreme cold, as everyone knows. Therefore, the rooms in which people are located must be heated. Central heating is the most common option, and if this is not available, you can use an individual gas boiler. However, it often happens that neither one nor the other is accessible, for example, in an open field there is a small room of a water pumping station, in which drivers are on duty around the clock. This could be a room in some large uninhabited building or a guard tower. There are plenty of examples.

Way out

All these cases force the installation of electric heating. For small rooms, it is quite possible to get by with a conventional electric oil radiator, but in large rooms, water heating using a radiator is most often installed. If you do not monitor the temperature of the water, sooner or later it may boil, causing the entire boiler to fail. To protect against such cases, thermostats are used.

Device Features

In functional terms, the device can be divided into several separate units: a comparator, as well as load control devices. All these parts will be described below. This information is necessary in order to make a thermostat with your own hands. In this case, a design is proposed in which a conventional bipolar transistor serves as a temperature sensor, so that the use of thermistors can be eliminated. This sensor operates on the basis that the parameters of the transistors of all semiconductor devices depend to a greater extent on the temperature of the medium.

Important nuances

Creating a thermostat with your own hands must take into account two points. Firstly, we are talking about the tendency of automatic devices to self-generate. If the connection between the actuator and the thermal relay sensor is too strong, after operation the relay immediately turns off and then turns on again. This will occur in cases where the sensor is in close proximity to a cooler or heater. Secondly, all sensors and electronic devices have a certain accuracy. For example, you can track a temperature of 1 degree, but smaller values ​​are much more difficult to track. In this case, simple electronics often begin to make mistakes and make mutually exclusive decisions, especially when the temperature is almost equal to the one set for operation.

Process of creation

If we talk about how to make a thermostat with your own hands, then it is worth saying that the sensor here is a thermistor that reduces its resistance during the heating process. It is connected to the voltage divider circuit. R2 is also included in the circuit, through which the response temperature is set. From the divider, the voltage is supplied to the 2I-NOT element, which is switched on in inverter mode, and then to the base of the transistor, which serves as a discharge gap for capacitor C1. It, in turn, is connected to the input (S) of the RS flip-flop, which is assembled on a pair of elements, as well as to the input of another 2I-NOT. From the divider, the voltage is supplied to the 2I-NOT input, which controls the second input (R) of the RS flip-flop.

How it works

So, we're looking at how to create a simple DIY thermostat, so it's important to understand how it works in different situations. At high temperatures, thermistors are characterized by low voltage, so there is a voltage on the divider that is perceived by logic circuits as zero. In this case, the transistor is open, a logical zero is perceived at the input of the S-trigger, and capacitor C1 is discharged. The output of the trigger is set to a logical one. The relay is in the on mode, and transistor VT2 is open. To understand exactly how to make a thermostat, it is worth noting that this particular relay implementation is focused on cooling the object, that is, it turns on the fan when the temperature is high.

Temperature drop

When the temperature decreases, the resistance of the thermistor increases, which leads to an increase in the voltage across the divider. At a certain moment, transistor VT1 closes, after which capacitor C1 begins charging through R5. Eventually the moment comes to reach the logical one level. It is this that is supplied to one of the inputs of D4, and the voltage from the divider is supplied to the second input of this element. When both inputs are set to logical ones, and a zero appears at the output of the element, the trigger switches to the opposite state. In this case, the relay will be turned off, which will allow you to turn off the fan, if necessary, or turn on the heating. This way you can make a thermostat so that it turns the fan on and off when necessary.

Temperature rise

So, the temperature began to increase again. A zero on the divider will first appear at one of the inputs of D4, and it will remove the zero at the trigger input, changing it to one. Further, as the temperature increases, zero will appear on the inverter. After changing it to one, the transistor will open, which will lead to the discharge of element C1 and the setting of zero at the input of the trigger, which turns off the heating of the coolant in the water heating system or turns on the fan. These handmade ones work quite effectively.

Blocks C1, R5 and VT1 are designed to eliminate self-generation, due to the fact that a turn-off delay time is set on them. It can range from a few seconds to several minutes. We are considering a fairly simple thermostat, created with our own hands, so the above unit also allows us to eliminate the bounce of the temperature sensor. Even with a very small very first pulse, the transistor opens and the capacitor instantly discharges. The chatter will then be ignored. When the transistor closes, the situation repeats. Charging of the capacitor begins only after the completion of the last bounce pulse. Thanks to the introduction of a trigger into the circuit, it is possible to ensure maximum clarity of relay operation. As you know, a trigger can only have two positions.

Assembly

To make a thermostat with your own hands, you can use a special circuit board on which the entire circuit will be assembled using a hinged method. You can also use a printed circuit board. You can use any power within the range of 3-15 volts. Relays should be selected according to this.

Using a similar scheme, you can make a thermostat for an aquarium with your own hands, but please note that it must be attached to the glass from the outside, then there will be no problems with its use.

The relay described above demonstrated very high reliability during operation. The temperature is maintained to within a fraction of a degree. However, it is directly dependent on the time delay determined by the R5C1 circuit, as well as the response to operation, that is, the power of the cooler or heater. The temperature range and the accuracy of its setting are determined by the selection of divider resistors. If you made such a thermostat with your own hands, then it does not need adjustment, but starts working immediately.