Thermal relay on/off. Thermostat in a socket for household heaters: types, device, tips for choosing. General concept of temperature controllers

Thermostat in the household - sometimes irreplaceable thing, which helps control the thermal conditions in a home incubator or vegetable drying. Built-in mechanisms for this purpose often quickly deteriorate or are not of decent quality, which forces you to invent a simple thermostat with your own hands.

If you are among those who urgently need a homemade device with a heat regulation function, stay here, because all suitable and tested schemes are combined with theory and useful tips are given below.

What is it applicable for?

A temperature controller or thermostat is a device that can start and stop the operation of heating or cooling units. For example, it allows you to support optimal mode in the incubator, and is also able to turn on heating in the basement, recording a low temperature.

How does this work?

Before you make a thermostat with your own hands, you need to understand the accompanying theory. Principle of this device is identical to the operation of simple measurement sensors capable of changing resistance depending on surrounding temperature conditions. A special element is responsible for changing the indicator, and the so-called reference resistance remains unchanged.

In the thermostat device, an integrated amplifier (comparator) reacts to changes in the resistance value, switching the microcircuits when a certain temperature is reached.

What should the scheme be?

It is easy to find thermostat diagrams on the Internet and in regulatory documentation. for various purposes, which you can assemble with your own hands. In most cases, the basis of a schematic drawing is the following elements:

Control zener diode, designated TL431;
Integrated amplifier (K140UD7);
Resistors (R4, R5, R6);
Quenching capacitor (C1);
Transistor (KT814);
Diode bridge (D1).

The circuit is powered by a transformerless power supply, and a car relay designed for a voltage of 12 Volts is ideal as an actuator, provided that the current supplied to the coil is at least 100 mA.

How to do it?

Instructions for making a thermostat with your own hands are based on strict adherence to the chosen scheme, according to which it is necessary to connect all the components into a single whole. For example, electronic circuit for the incubator is assembled according to the following algorithm:

Study the image (it’s better to print it out and put it in front of you).
Find the necessary parts, including the case and the board (old ones from the meter will do).
Start with the “heart” - the integrated amplifier K140UD7/8, connecting it with a positively charged reverse action, which will give it the functions of a comparator.
Connect the negative resistor MMT-4 in place of “R5”.
Connect the remote sensor using shielded wiring, and the cord length can be no more than a meter.
To control the load, include thyristor VS1 in the circuit, installing it on the radiator small sizes to ensure adequate heat transfer.
Set up the remaining elements of the circuit.
Connect to the power supply.
Check functionality.

By the way, by adding a temperature sensor, the assembled device can be safely used not only for incubators, dryers, but also for maintaining thermal regime in an aquarium or terrarium.

How to install correctly?

In addition to high-quality assembly, it is necessary to pay attention to the operating conditions, which should include:

Placement: lower part of the room;
Dry room;
The absence of nearby “knock-down” units: those emitting heat or cold (electrical equipment, air conditioning, open door with a draft).

Having figured out how to connect a thermostat with your own hands, you can start using it regularly. The main thing is that the power of the manufactured device is designed for the relay contacts. For example, when maximum load at 30 Amps, the power should not exceed 6.6 kW.

How to repair?

A factory or homemade thermostat can be repaired so as not to buy a new one and not waste time searching and assembling the necessary parts. First of all, you need to find the device (if you were not the one who installed it), because from the photo of the thermostat you can see that its dimensions are small, which makes the search somewhat difficult.

A tip will help: the thermostat is located next to the button temperature regime.

Signs of device failure may include the following:

The device has ceased to perform its main function: the temperature has dropped or increased significantly without the mechanism reacting;
The connected device works without going into standby or saving mode;
The unit turned off spontaneously.

Depending on the cause of the malfunction, you must take the following steps to repair the thermostat yourself:

Disconnect the device being repaired from the network.
Remove the protective housing from the device.
Check the quality of contacts and connections.
Disconnect and pull out the capillary tube.
Get the relay.
Change the bellows tube and secure it.
If necessary, replace other parts.
Reconnect the wiring.
Put the relay in place.

Many household and household appliances are equipped with thermostats, and knowing how to repair them, reassemble them with your own hands and install them will significantly save your money, time and effort.

DIY thermostat photo

People's mood, well-being and performance depend on the air temperature in the surrounding space. Its meaning, comfortable for each person, is very individual. While some people work well at +18°C, others need at least +23°C.

In such cases, it is convenient to install a thermostat in a socket for household heaters to set the desired temperature. The device independently reads the room temperature and controls the operation of the heater.

Agree, this is very convenient - you don’t have to constantly be distracted by turning the heater on and off. All that remains is to select the optimal thermostat and install it. We'll show you how to do it.

To understand the variety of offers, you need to find out the operating features of different thermostats, take into account the parameters that determine the practicality of the device itself and the comfortable operation of the heater. Installing the thermostat is quite simple; the main thing is to adhere to the installation rules outlined in the article.

When you are in the office, you want there to be no distractions, and all thoughts are focused only on the work process. Optimal temperature conditions in the room help achieve this goal.

It’s good if you don’t need to bring a warm jumper with you in the cold season to warm up a little, or run to the heater or air conditioner, setting and changing the settings. A thermostat will help regulate the temperature in the room.

Image gallery

In this article we will consider devices that support a certain thermal regime, or signal when the desired temperature has been reached. Such devices have very wide scope applications: they can maintain a given temperature in incubators and aquariums, warm floors and even be part smart home. For you, we have provided instructions on how to make a thermostat with your own hands and at a minimum cost.

A little theory

The simplest measuring sensors, including those that respond to temperature, consist of a measuring half-arm of two resistances, a reference and an element that changes its resistance depending on the temperature adjusted to it. This is shown more clearly in the picture below.

As can be seen from the diagram, resistor R2 is the measuring element of a homemade thermostat, and R1, R3 and R4 are the reference arm of the device. This is a thermistor. It is a conductor device that changes its resistance with temperature changes.

The thermostat element that responds to changes in the state of the measuring arm is an integrated amplifier in comparator mode. This mode abruptly switches the output of the microcircuit from the off state to working position. Thus, at the output of the comparator we have only two values “on” and “off”. The load of the chip is a PC fan. When the temperature reaches a certain value in the arm R1 and R2, a voltage shift occurs, the input of the microcircuit compares the value on pins 2 and 3 and the comparator switches. The fan cools the required object, its temperature drops, the resistance of the resistor changes and the comparator turns off the fan. In this way, the temperature is maintained at a given level and the operation of the fan is controlled.

Overview of circuits

The difference voltage from the measuring arm is supplied to a paired transistor with a high gain, and an electromagnetic relay acts as a comparator. When the coil reaches a voltage sufficient to retract the core, it is triggered and connected through its contacts of actuators. When the set temperature is reached, the signal on the transistors decreases, the voltage on the relay coil synchronously drops, and at some point the contacts are disconnected and the payload is turned off.

A feature of this type of relay is the presence - this is a difference of several degrees between turning on and off a homemade thermostat, due to the presence of an electromechanical relay in the circuit. Thus, the temperature will always fluctuate a few degrees around the desired value. The assembly option provided below is practically free of hysteresis.

Schematic electronic circuit of an analog thermostat for an incubator:

This scheme was very popular for repetition in 2000, but even now it has not lost its relevance and copes with the function assigned to it. If you have access to old parts, you can assemble a thermostat with your own hands almost free of charge.

The heart of the homemade product is the K140UD7 or K140UD8 integrated amplifier. In this case, it is connected with positive feedback and is a comparator. The temperature-sensitive element R5 is a resistor of the MMT-4 type with negative TKE, which means that when heated its resistance decreases.

The remote sensor is connected via a shielded wire. To reduce and false trigger the device, the length of the wire should not exceed 1 meter. The load is controlled through thyristor VS1 and the maximum permissible power of the connected heater depends on its rating. In this case, a 150 Watt electronic switch - a thyristor - must be installed on a small radiator to remove heat. The table below shows the ratings of radio elements for assembling a thermostat at home.

The device does not have galvanic isolation from the 220 Volt network; when setting up, be careful; there is mains voltage on the regulator elements, which is life-threatening. After assembly, be sure to insulate all contacts and place the device in a non-conductive housing. The video below shows how to assemble a thermostat using transistors:

Homemade thermostat using transistors

Now we’ll tell you how to make a temperature controller for a heated floor. Working diagram copied from a serial sample. It will be useful for those who want to familiarize themselves and repeat, or as a sample for troubleshooting a device.

The center of the circuit is a stabilizer chip connected in an unusual way, LM431 begins to pass current when the voltage is above 2.5 Volts. This is exactly the size of the internal reference voltage source for this microcircuit. At a lower current value, it does not pass anything. This feature began to be used in all kinds of thermostat circuits.

As we see, classic scheme The following remains with the measuring arm: R5, R4 are additional resistors, and R9 is a thermistor. When the temperature changes, the voltage shifts at input 1 of the microcircuit, and if it reaches the operating threshold, the voltage moves further along the circuit. In this design, the load for the TL431 microcircuit is the operation indication LED HL2 and optocoupler U1, for optical isolation of the power circuit from the control circuits.

As in the previous version, the device does not have a transformer, but receives power from the quenching capacitor circuit C1, R1 and R2, so it is also under life-threatening voltage, and you need to be extremely careful when working with the circuit. To stabilize the voltage and smooth out the ripples of network surges, a zener diode VD2 and a capacitor C3 are installed in the circuit. To visually indicate the presence of voltage, an HL1 LED is installed on the device. The power control element is a VT136 triac with a small harness for control via optocoupler U1.

At these ratings, the control range is within 30-50°C. Despite the apparent complexity at first glance, the design is simple to set up and easy to repeat. A visual diagram of a thermostat on a TL431 chip, with an external 12 volt power supply for use in home automation systems is presented below:

This thermostat is capable of controlling a computer fan, power relays, indicator lights, and sound alarms. To control the temperature of the soldering iron, there is an interesting circuit using the same TL431 integrated circuit.

To measure the temperature of the heating element, a bimetallic thermocouple is used, which can be borrowed from a remote meter in a multimeter or purchased at a specialized radio parts store. To increase the voltage from the thermocouple to the triggering level of TL431, an additional amplifier is installed on LM351. Control is carried out through an optocoupler MOC3021 and triac T1.

When connecting the thermostat to the network, it is necessary to observe the polarity, the minus of the regulator must be on the neutral wire, otherwise phase voltage will appear on the body of the soldering iron, through the thermocouple wires. This is what main drawback this circuit, because not everyone wants to constantly check that the plug is correctly connected to the socket, and if you neglect this, you can get an electric shock or damage electronic components during soldering. The range is adjusted by resistor R3. This scheme will ensure long-term operation of the soldering iron, prevent overheating and increase the quality of soldering due to the stability of the temperature regime.

Another build idea simple thermostat reviewed on video:

Temperature controller on TL431 chip

A simple regulator for a soldering iron

The analyzed examples of temperature controllers are quite sufficient to meet the needs home handyman. The schemes do not contain scarce and expensive spare parts, are easily repeated and practically do not require adjustment. These homemade products can easily be adapted to regulate the temperature of water in a water heater tank, monitor the heat in an incubator or greenhouse, and upgrade an iron or soldering iron. In addition, you can restore an old refrigerator by converting the regulator to work with negative values temperature by swapping resistances in the measuring arm. We hope our article was interesting, you found it useful and understood how to make a thermostat with your own hands at home! If you still have questions, feel free to ask them in the comments.

Production: "Relsib"

Additional input for connecting a level sensor (version with semi-automatic sensor)
. Possibility of connecting additional temperature protection devices: thermal relays, thermal switches, etc.
. Simplicity and ease of use
. DIN rail mount

Thermostat Ratar-02, -02M universal

Production: "Relsib"

Semi-universal input
. Bright LED display
. Intuitive programming
. High accuracy
. Possibility of shifting zero and tilt without disturbing the adjustment (for vehicles and transformers)
. Five types of output device logic

Thermoregulator Ratar-02A-1 for unattended premises

Production: "Relsib"

Complete product, no cabinet installation required
. Built-in two-pole automatic load switch
. Convenient wall-mounted housing with terminal compartment
. Large two-digit LED indicator
. It is equipped with a remote temperature sensor to maintain the temperature in production premises, storage facilities, garages, etc.

Temperature regulator Ratar-02U with built-in level control relay

Production: "Relsib"

Two devices in one: thermostat and level control relay
. Simultaneously maintaining temperature and a given liquid level
. Load current up to 16 A
. Ability to set input type: 50M, 100P, Pt100
. Ability to control heater and refrigerator
. High accuracy of temperature measurement and maintenance
. DC and AC supply voltage over a wide range
. Heating block when there is no liquid
. Can be adjusted to any conductive liquid
. Anti-wave function

Temperature regulator Ratar-03.2UV.Shch1 two-channel with universal inputs

Production: "Relsib"

Temperature measurement and control or other physical quantity through two independent channels according to the two-position law
. Regulation per one channel according to a three-position law (two settings, two control devices)
. Display of measured values in required units (scaling)
. Possibility of connecting to two sensor inputs different types
. Measurement and regulation: on one channel - physical quantities, on another channel - differences in physical quantities
. Display on the alphanumeric LCD display simultaneously the values of the measured quantities and the set settings
. Operation in millivoltmeter mode

Thermostat with timer and humidity control function for the drying chamber PUSK-1

Production: "Relsib"

A ready-made solution for automating drying chambers for clothes, wood, herbal infusions, grains, etc.
. Automatic end of the drying process based on time or relative air humidity
. Clear user interface
. Easy installation and connection
. One specialized device replaces three standard ones

Thermostat OGD-011

Temperature control ranges: 0...60°С, −10...50°С
2 relays: ~10 (2) A, 250 V
Mounting: DIN rail
2 bimetallic thermostats in one housing
Simultaneous control of heaters and cooling devices, each device has its own rotary scale

Thermostat KTO-011

A device for maintaining temperature in a residential or production premises, office, etc. by controlling actuators (heaters, cooling devices, fans, heat exchangers), as well as for turning on signaling devices

Temperature control ranges: −20...40°C, −10...50°C, 0...60°C
Relay: ~10 (2) A, 250 V
Protection: IP20
Mounting: DIN rail
Heater control

Thermostat KTS-011

A device for maintaining temperature in a residential or industrial premises, office, etc. by controlling actuators (heaters, cooling devices, fans, heat exchangers), as well as for turning on signaling devices

Temperature control ranges: −10...50°C, 0...60°C
Relay: ~10 (2) A, 250 V
Protection: IP20
Mounting: DIN rail
Cooling Device Control

Thermostat FTO 011

On/off temperature: 5°C/15°C, 15°C/25°C
Relay: ~5 (1.6) A, 240 V
Protection: IP20
Mounting: DIN rail
Control of air heaters, heaters

ThermoRegulators: types, purpose and principle of operation

An electric thermostat is a device that allows you to maintain a certain temperature level in any heating system. It will turn off the heating element when the ambient temperature reaches the set value and will automatically turn on again when it drops below the limit level. Such work does not require the involvement of personnel, therefore it allows autonomous support optimal temperature on any object.

It is practiced to classify regulators simultaneously according to several criteria:

for its intended purpose (temperature regulator for an incubator, for controlling the temperature in a room, heating boiler);
by operating temperature range;
by type of working substance (thermostat with temperature sensor for air, liquids, solids);
By functionality(programming availability matters, remote control etc.),
according to the principle of operation and design (it can be an electronic, mechanical or electromechanical thermostat).

The price of a thermostat depends on the factors described above, as well as depending on the purpose for which you want to use it.

Operating principle of thermostats

The device is installed in an area that is not exposed to the direct heating effect of devices (in this case, it can be a thermostat with a remote sensor or an element of a built-in structure). In this way, the device can obtain information about the temperature level in the area where the sensor is located and, based on this information, control the operation of heating elements or heating devices.

Main types of thermostats and thermostats

Mechanical devices - uh they are the simplest in their design and available devices, which are especially often used when working in a small area. They are not susceptible to power surges or electronic failures, therefore they are reliable and easy to use. At their price, mechanical thermostats are the most affordable of all.
Electric thermostat - such devices are often used in configurations household electric stoves, electric kettles. Depending on the principle of operation, you can buy devices whose operation is based on the use of a working membrane (bimetallic plate) or a capillary tube.
Electronic thermostat with temperature sensor - Such devices are used most often today: they are accurate, reliable, and convenient. Their work is based on the fact that a temperature sensor, which is installed in an area without intense heating or draft, constantly transmits information about the temperature of the environment to the controller. The latter processes the data and supplies a control signal to the heating devices.

Call, order, Terainvest specialists are always ready to help you choose and advise on all issues.

You can buy thermostats and thermostats from Terainvest at an affordable price in Russian cities.

Maintaining temperature conditions is a very important technological condition not only in production, but also in everyday life. Having so great value, this parameter must be regulated and controlled somehow. Produce huge amount such devices having many features and parameters. But making a thermostat with your own hands is sometimes much more profitable than buying a ready-made factory analogue.

Make your own thermostat

General concept of temperature controllers

Devices that record and simultaneously regulate a given temperature value are more common in production. But they also found their place in everyday life. To maintain the necessary microclimate in the house, water thermostats are often used. They make such devices with their own hands for drying vegetables or heating an incubator. Such a system can find its place anywhere.

In this video we will find out what a temperature regulator is:

In reality, most thermostats are only part general scheme, which consists of the following components:

A temperature sensor that measures and records, as well as transmits the received information to the controller. This happens due to the conversion of thermal energy into electrical signals recognized by the device. The sensor can be a resistance thermometer or a thermocouple, which have metal in their design that reacts to changes in temperature and changes its resistance under its influence.
The analytical unit is the regulator itself. It receives electronic signals and reacts depending on its functions, after which it transmits the signal to the actuator.
An actuator is some kind of mechanical or electronic device, which behaves in a certain way when receiving a signal from the block. For example, when the set temperature is reached, the valve will shut off the coolant supply. Conversely, as soon as the readings drop below the specified values, the analytical unit will give a command to open the valve.

These are the three main parts of the system for maintaining specified temperature parameters. Although, in addition to them, other parts, such as an intermediate relay, may also participate in the circuit. But they perform only an additional function.

Operating principle

The principle on which all regulators work is the removal of a physical quantity (temperature), transmission of data to the control unit circuit, which decides what needs to be done in a particular case.

If you are making a thermal relay, the simplest option will be to have a mechanical control circuit. Here, using a resistor, a certain threshold is set, upon reaching which a signal will be given to the actuator.

To get additional functionality and the ability to work with a wider temperature range, you will have to integrate a controller. This will also help increase the service life of the device.

In this video you can see how to make your own thermostat for electric heating:

Homemade temperature controller

There are actually a lot of schemes for making a thermostat yourself. It all depends on the area in which such a product will be used. Of course, it is extremely difficult to create something too complex and multifunctional. But a thermostat that can be used to heat an aquarium or dry vegetables for the winter can be created with a minimum of knowledge.

The simplest scheme

The most simple circuit The do-it-yourself thermal relay has a transformerless power supply, which consists of a diode bridge with a parallel-connected zener diode that stabilizes the voltage within 14 volts, and a quenching capacitor. If desired, you can also add a 12-volt stabilizer here.

Creating a thermostat does not require much effort or financial investment.

The entire circuit will be based on a zener diode TL431, which is controlled by a divider consisting of a 47 kOhm resistor, a 10 kOhm resistance and a 10 kOhm thermistor that acts as a temperature sensor. Its resistance decreases with increasing temperature. It is better to select the resistor and resistance to achieve the best operating accuracy.

The process itself is as follows: when a voltage of more than 2.5 volts is generated at the control contact of the microcircuit, it will make an opening, which will turn on the relay, applying a load to the actuator.

You can see how to make a thermostat for an incubator with your own hands in the video presented:

Conversely, when the voltage drops lower, the microcircuit will close and the relay will turn off.

To avoid rattling of the relay contacts, it is necessary to select it with a minimum holding current. And parallel to the inputs you need to solder a 470×25 V capacitor.

When using an NTC thermistor and a microcircuit that have already been used, you should first check their performance and accuracy.

Thus, it turns out to be a simple device regulating temperature. But with the right components, it works excellently in wide range applications.

Indoor device

Such do-it-yourself thermostats with an air temperature sensor are optimally suited for maintaining the specified microclimate parameters in rooms and containers. It is fully capable of automating the process and controlling any heat emitter starting from hot water and ending with tens. At the same time, the thermal switch has excellent performance data. And the sensor can be either built-in or remote.

Here the thermistor, designated R1 in the diagram, acts as a temperature sensor. The voltage divider includes R1, R2, R3 and R6, the signal from which is sent to the fourth pin of the microcircuit operational amplifier. The fifth pin of DA1 receives a signal from the divider R3, R4, R7 and R8.

The resistance of the resistors must be selected in such a way that at the minimum low temperature of the measured medium, when the resistance of the thermistor is maximum, the comparator is positively saturated.

The voltage at the output of the comparator is 11.5 volts. At this time, transistor VT1 is in open position, and relay K1 turns on the actuator or intermediate mechanism, as a result of which heating begins. Temperature environment as a result, it increases, which decreases the resistance of the sensor. At input 4 of the microcircuit, the voltage begins to increase and, as a result, exceeds the voltage at pin 5. As a result, the comparator enters the negative saturation phase. At the tenth output of the microcircuit, the voltage becomes approximately 0.7 Volts, which is a logical zero. As a result, transistor VT1 closes, and the relay turns off and turns off the actuator.

On the LM 311 chip

This do-it-yourself temperature controller is designed to work with heating elements and is capable of maintaining the specified temperature parameters within the range of 20-100 degrees. This is the safest and reliable option, since its operation uses galvanic isolation of the temperature sensor and regulatory circuits, and this completely eliminates the possibility of electric shock.

Like most similar schemes, it is based on a bridge DC, in one arm of which a comparator is connected, and in the other – a temperature sensor. The comparator monitors the mismatch of the circuit and reacts to the state of the bridge when it passes the balance point. At the same time, he tries to balance the bridge using a thermistor, changing its temperature. And thermal stabilization can occur only at a certain value.

Resistor R6 sets the point at which balance should be formed. And depending on the temperature of the environment, the thermistor R8 can be included in this balance, which allows you to regulate the temperature.

In the video you can see an analysis of a simple thermostat circuit:

If the temperature set by R6 is lower than required, then the resistance on R8 is too high, which reduces the current on the comparator. This will cause current to flow and open the seven-stor VS1, which will turn on the heating element. The LED will indicate this.

As the temperature rises, the resistance of R8 will begin to decrease. The bridge will tend to a balance point. On the comparator, the potential of the inverse input gradually decreases, and on the direct input it increases. At some point the situation changes, and the process occurs in reverse side. Thus, the temperature controller with its own hands will turn the actuator on or off depending on the resistance R8.

If LM311 is not available, then it can be replaced with the domestic KR554CA301 microcircuit. It turns out to be a simple do-it-yourself thermostat with minimal costs, high accuracy and reliability.

Required materials and tools

The assembly of any electric temperature controller circuit itself does not take much time and effort. But to make a thermostat, you need minimal knowledge in electronics, set of parts according to the diagram and tools:

Pulse soldering iron. You can use a regular one, but with a thin tip.
Solder and flux.
PCB.
Acid to etch the tracks.

Advantages and disadvantages

Even a simple do-it-yourself thermostat has a lot of advantages and positive aspects. There is no need to talk about factory multifunctional devices at all.

Temperature regulators allow:

Maintain a comfortable temperature.
Save energy resources.
Do not involve a person in the process.
Observe process, improving quality.

The disadvantages include the high cost of factory models. Of course, this does not apply to homemade devices. But the production ones, which are required when working with liquid, gaseous, alkaline and other similar media, have a high cost. Especially if the device must have many functions and capabilities.