DIY thermostat: simple instructions and connection diagram. Operating principle and setup at home. How to make thermostats with your own hands? DIY temperature sensor
Autonomous heating of a private house allows you to choose individual temperature conditions, which is very comfortable and economical for residents. To avoid setting a different mode indoors every time the weather changes outside, you can use a thermostat or thermostat for heating, which can be installed on both radiators and the boiler.
Automatic room heat regulation
What is it for
- The most common on the territory of the Russian Federation is , on gas boilers. But such, so to speak, luxury is not available in all areas and localities. The reasons for this are the most banal - the lack of thermal power plants or central boiler houses, as well as gas mains nearby.
- Have you ever visited a residential building, pumping station or weather station remote from densely populated areas in winter, when the only means of communication is a sleigh with a diesel engine? In such situations, very often they arrange heating with their own hands using electricity.
- For small rooms, for example, one room for the person on duty at a pumping station, it is enough - it will be enough for the harshest winter, but for a larger area a heating boiler and a radiator system will be required. To maintain the desired temperature in the boiler, we bring to your attention a homemade control device.
Temperature sensor
- This design does not require thermistors or various TCM type sensors, here an ordinary bipolar transistor is used instead. Like all semiconductor devices, its operation largely depends on the environment, more precisely, on its temperature. As the temperature rises, the collector current increases, and this negatively affects the operation of the amplifier stage - the operating point shifts until the signal is distorted and the transistor simply does not respond to the input signal, that is, it stops working.
- Diodes are also semiconductors, and rising temperatures negatively affect them too. At t25⁰C, the “continuity” of a free silicon diode will show 700 mV, and for a permanent one - about 300 mV, but if the temperature rises, then the forward voltage of the device will decrease accordingly. So, when the temperature increases by 1⁰C, the voltage will decrease by 2mV, that is, -2mV/1⁰C.
- This dependence of semiconductor devices allows them to be used as temperature sensors. The entire operation circuit of the thermostat is based on this negative cascade property with a fixed base current (diagram in the photo above).
- The temperature sensor is mounted on a transistor VT1 type KT835B, the cascade load is resistor R1, and the direct current operating mode of the transistor is set by resistors R2 and R3. To ensure that the voltage at the transistor emitter at room temperature is 6.8V, a fixed bias is set by resistor R3.
Advice. For this reason, in the diagram R 3 is marked with * and special accuracy should not be achieved here, as long as there are no large differences. These measurements can be made relative to a transistor collector connected by a power source to a common drive.
- Transistor pnp KT835B specially selected, its collector is connected to a metal body plate that has a hole for attaching the semiconductor to the radiator. It is through this hole that the device is attached to the plate, to which the underwater wire is also attached.
- The assembled sensor is attached to the heating pipe using metal clamps, and the structure does not need to be insulated with any gasket from the heating pipe. The fact is that the collector is connected by one wire to the power source - this greatly simplifies the entire sensor and makes contact better.
Comparator
- Comparator, mounted on an operational amplifier OR1 type K140UD608, sets the temperature. The invertible input R5 is supplied with voltage from the emitter VT1, and through R6 the non-invertible input is supplied with voltage from the engine R7.
- This voltage determines the temperature for switching off the load. The upper and lower ranges for setting the threshold for triggering the comparator are set using R8 and R9. The required posteresis of the comparator is provided by R4.
Load management
- On VT2 and Rel1 a load control device has been made and the thermostat operating mode indicator is located here - red when heating, and green when the required temperature has been reached. A diode VD1 is connected in parallel to the Rel1 winding to protect VT2 from voltage caused by self-induction on the Rel1 coil when turned off.
Advice. The figure above shows that the permissible switching current of the relay is 16A, which means it allows control of a load of up to 3 kW. Use a device with a power of 2-2.5 kW to lighten the load.
power unit
- An arbitrary instruction allows for a real thermostat, due to its low power, to use a cheap Chinese adapter as a power supply. You can also assemble a 12V rectifier yourself, with a circuit current consumption of no more than 200mA. For this purpose, a transformer with a power of up to 5 W and an output of 15 to 17 V is suitable.
- The diode bridge is made using 1N4007 diodes, and the voltage stabilizer is based on an integrated type 7812. Due to the low power, it is not necessary to install a stabilizer on the battery.
Adjusting the thermostat
- To check the sensor, you can use a very ordinary table lamp with a metal shade. As noted above, room temperature allows the voltage at the emitter of VT1 to withstand about 6.8V, but if you increase it to 90⁰C, the voltage drops to 5.99V. For measurements, you can use a regular Chinese multimeter with a thermocouple type DT838.
- The comparator works as follows: if the voltage of the temperature sensor at the inverting input is higher than the voltage at the non-inverting input, then at the output it will be equal to the voltage of the power source - this will be a logical one. Therefore, VT2 opens and the relay turns on, moving the relay contacts to heating mode.
- Temperature sensor VT1 heats up as the heating circuit heats up and as the temperature rises, the voltage at the emitter decreases. At the moment when it drops slightly below the voltage that is set on the R7 engine, a logical zero is obtained, which leads to the transistor turning off and the relay turning off.
- At this time, no voltage is supplied to the boiler and the system begins to cool, which also entails the cooling of the VT1 sensor. This means that the voltage at the emitter increases and as soon as it crosses the limit set by R7, the relay starts again. This process will be repeated constantly.
- As you understand, the price of such a device is low, but it allows you to maintain the desired temperature in any weather conditions. This is very convenient in cases where there are no permanent residents in the room monitoring the temperature, or when people constantly replace each other and are also busy with work.
The operation of a gas or electric boiler can be optimized by using external control of the unit. Commercially available remote thermostats are designed for this purpose. This article will help you understand what these devices are and understand their varieties. It will also discuss the question of how to assemble a thermal relay with your own hands.
Purpose of thermostats
Any electric or gas boiler is equipped with an automation kit that monitors the heating of the coolant at the outlet of the unit and turns off the main burner when the set temperature is reached. Solid fuel boilers are also equipped with similar means. They allow you to maintain the water temperature within certain limits, but nothing more.
In this case, the climatic conditions indoors or outdoors are not taken into account. This is not very convenient; the homeowner has to constantly select the appropriate operating mode for the boiler on his own. The weather can change during the day, then the rooms become hot or cool. It would be much more convenient if the boiler automation was oriented towards the air temperature in the premises.
To control the operation of boilers depending on the actual temperature, various heating thermostats are used. Being connected to the boiler electronics, such a relay turns off and starts heating, maintaining the required temperature of the air, not the coolant.
Types of thermal relays
A conventional thermostat is a small electronic unit installed on the wall in a suitable location and connected to a heat source by wires. There is only a temperature regulator on the front panel; this is the cheapest type of device.
In addition to it, there are other types of thermal relays:
- programmable: they have a liquid crystal display, are connected using wires or use wireless communication with the boiler. The program allows you to set temperature changes at certain times of the day and by day during the week;
- the same device, only equipped with a GSM module;
- autonomous regulator powered by its own battery;
- wireless thermal relay with a remote sensor to control the heating process depending on the ambient temperature.
Note. A model where the sensor is located outside the building provides weather-dependent control of the operation of the boiler installation. The method is considered the most effective, since the heat source responds to changing weather conditions even before they affect the temperature inside the building.
Multifunctional thermal relays that can be programmed significantly save energy. During those hours of the day when no one is home, there is no point in maintaining a high temperature in the rooms. Knowing his family's work schedule, the homeowner can always program the temperature switch so that at certain times the air temperature drops and the heating turns on an hour before people arrive.
Household thermostats equipped with a GSM module are capable of providing remote control of the boiler installation via cellular communications. A budget option is sending notifications and commands in the form of SMS messages from a mobile phone. Advanced versions of devices have their own applications installed on a smartphone.
How to assemble a thermal relay yourself?
Heating control devices available for sale are quite reliable and do not cause any complaints. But at the same time, they cost money, and this does not suit those homeowners who have at least a little knowledge of electrical engineering or electronics. After all, understanding how such a thermal relay should function, you can assemble and connect it to the heat generator with your own hands.
Of course, not everyone can make a complex programmable device. In addition, to assemble such a model, it is necessary to purchase components, the same microcontroller, digital display and other parts. If you are new to this matter and have a superficial understanding of the issue, then you should start with some simple circuit, assemble it and put it into operation. Having achieved a positive result, you can move on to something more serious.
First, you need to have an idea of what elements a thermostat with temperature control should consist of. The answer to the question is given by the circuit diagram presented above, which reflects the operating algorithm of the device. According to the diagram, any thermostat must have an element that measures temperature and sends an electrical impulse to the processing unit. The latter’s task is to amplify or convert this signal in such a way that it serves as a command to the actuator - the relay. Next we will present 2 simple circuits and explain their operation in accordance with this algorithm, without resorting to specific terms.
Circuit with zener diode
A zener diode is the same semiconductor diode that passes current only in one direction. The difference from a diode is that the zener diode has a control contact. As long as the set voltage is supplied to it, the element is open and current flows through the circuit. When its value falls below the limit, the chain breaks. The first option is a thermal relay circuit, where the zener diode plays the role of a logical control unit:
As you can see, the diagram is divided into two parts. On the left side is the part preceding the relay control contacts (designation K1). Here the measuring unit is a thermal resistor (R4), its resistance decreases with increasing ambient temperature. The manual temperature controller is a variable resistor R1, the power supply to the circuit is 12 V. In normal mode, a voltage of more than 2.5 V is present at the control contact of the zener diode, the circuit is closed, the relay is turned on.
Advice. Any inexpensive commercially available device can serve as a 12 V power supply. Relay – reed switch brand RES55A or RES47, thermal resistor – KMT, MMT or similar.
As soon as the temperature rises above the set limit, the resistance of R4 will drop, the voltage will become less than 2.5 V, and the zener diode will break the circuit. Then the relay will do the same, turning off the power part, whose diagram is shown on the right. Here, a simple thermal relay for the boiler is equipped with a triac D2, which, together with the closing contacts of the relay, serves as an executive unit. The boiler supply voltage of 220 V passes through it.
Circuit with logic chip
This circuit differs from the previous one in that instead of a zener diode, it uses a K561LA7 logic chip. The temperature sensor is still a thermistor (designation VDR1), only now the decision to close the circuit is made by the logical block of the microcircuit. By the way, the K561LA7 brand has been produced since Soviet times and costs mere pennies.
For intermediate amplification of pulses, the KT315 transistor is used; for the same purpose, a second transistor, KT815, is installed in the final stage. This diagram corresponds to the left side of the previous one; the power unit is not shown here. As you might guess, it may be similar - with the KU208G triac. The operation of such a homemade thermal relay has been tested on boilers ARISTON, BAXI, Don.
Conclusion
Connecting a thermostat to the boiler yourself is not a difficult task; there is a lot of material on this topic on the Internet. But making it yourself from scratch is not so easy; in addition, you need a voltage and current meter to make the settings. Whether you buy a finished product or start making it yourself is a decision you make.
I present an electronic development - a homemade thermostat for electric heating. The temperature for the heating system is set automatically based on changes in outside temperature. The thermostat does not need to manually enter or change readings to maintain the temperature in the heating system.
There are similar devices in the heating network. For them, the relationship between average daily temperatures and the diameter of the heating riser is clearly stated. Based on these data, the temperature for the heating system is set. I took this heating network table as a basis. Of course, some factors are unknown to me; the building may, for example, not be insulated. The heat loss of such a building will be large; the heating may be insufficient for normal heating of the premises. The thermostat has the ability to make adjustments for tabular data. (you can read more about the material at this link).
I planned to show a video of the thermostat in operation, with an eclectic boiler (25KW) connected to the heating system. But as it turned out, the building for which all this was done had not been inhabited for a long time; upon inspection, the heating system had almost completely fallen into disrepair. It is not known when everything will be restored; perhaps it will not be this year. Since in real conditions I cannot adjust the thermostat and observe the dynamics of changing temperature processes, both in heating and outside, I took a different route. For these purposes, I built a model of the heating system.
The role of an electric boiler is performed by a glass floor liter jar, the role of a heating element for water is a five hundred watt boiler. But with such a volume of water, this power was in excess. Therefore, the boiler was connected via a diode, reducing the heater power.
Connected in series, two aluminum flow radiators remove heat from the heating system, forming a kind of battery. Using a cooler, I create dynamics of cooling of the heating system, since the program in the thermostat monitors the rate of increase and decrease in temperature in the heating system. On the return, there is a digital temperature sensor T1, based on the readings of which the set temperature in the heating system is maintained.
In order for the heating system to start working, it is necessary for the T2 (outdoor) sensor to record a temperature drop below +10C. To simulate changes in outside temperature, I designed a mini refrigerator using a Peltier element.
There is no point in describing the operation of the entire homemade installation; I filmed everything on video.
Some points about assembling an electronic device:
The thermostat electronics are located on two printed circuit boards; to view and print you will need the SprintLaut program, version 6.0 or higher. The thermostat for heating is mounted on a DIN rail, thanks to the Z101 series housing, but nothing prevents you from placing all the electronics in another housing of suitable size, the main thing is that it suits you. The Z101 case does not have a window for the indicator, so you will have to mark and cut it yourself. The ratings of the radio components are indicated on the diagram, except for the terminal blocks. To connect the wires, I used terminal blocks of the WJ950-9.5-02P series (9 pcs.), but they can be replaced with others; when choosing, make sure that the pitch between the legs coincides, and the height of the terminal block does not interfere with the housing being closed. The thermostat uses a microcontroller that needs to be programmed; of course, I also provide the firmware for free access (it may have to be modified during operation). When flashing the microcontroller, set the internal clock generator of the microcontroller to 8 MHz.
In everyday life and farmsteads, it is often necessary to maintain the temperature regime of a room. Previously, this required a fairly huge circuit made on analog elements; we will consider one of these for general development. Today everything is much simpler; if it is necessary to maintain the temperature in the range from -55 to +125°C, then the programmable thermometer and thermostat DS1821 can perfectly cope with this goal.
Thermostat circuit on a specialized temperature sensor. This DS1821 temperature sensor can be bought cheaply from ALI Express (to order, click on the picture just above)
The temperature threshold for turning on and off the thermostat is set by the TH and TL values in the sensor memory, which must be programmed into the DS1821. If the temperature exceeds the value recorded in the TH cell, a logical one level will appear at the sensor output. To protect against possible interference, the load control circuit is implemented in such a way that the first transistor is locked into that half-wave of the mains voltage when it is equal to zero, thereby applying a bias voltage to the gate of the second field-effect transistor, which turns on the optosimistor, which already opens the VS1 smistor that controls the load . The load can be any device, such as an electric motor or a heater. The locking reliability of the first transistor must be adjusted by selecting the desired value of resistor R5.
The DS1820 temperature sensor is capable of recording temperatures from -55 to 125 degrees and operating in thermostat mode.
Thermostat circuit on the DS1820 sensor
If the temperature exceeds the upper threshold TH, then the output of the DS1820 will be a logical one, the load will be disconnected from the network. If the temperature drops below the lower programmed level TL, a logical zero will appear at the output of the temperature sensor and the load will be turned on. If there are any unclear points, the homemade design was borrowed from No. 2 for 2006.
The signal from the sensor passes to the direct output of the comparator on the CA3130 operational amplifier. The inverting input of the same op-amp receives the reference voltage from the divider. Variable resistance R4 sets the required temperature regime.
Thermostat circuit on sensor LM35
If the potential at the direct input is lower than that set at pin 2, then at the comparator output we will have a level of about 0.65 volts, and if vice versa, then at the comparator output we will have a high level of about 2.2 volts. The signal from the output of the op-amp through transistors controls the operation of the electromagnetic relay. At a high level it turns on, and at a low level it turns off, switching the load with its contacts.
TL431 is a programmable zener diode. Used as a voltage reference and power supply for low power circuits. The required voltage level at the control pin of the TL431 microassembly is set using a divider on resistors Rl, R2 and a thermistor with negative TKS R3.
If the voltage at the TL431 control pin is higher than 2.5V, the microcircuit passes current and turns on the electromagnetic relay. The relay switches the control output of the triac and connects the load. As the temperature increases, the resistance of the thermistor and the potential at the control contact TL431 decreases below 2.5V, the relay releases its front contacts and turns off the heater.
Using resistance R1, we adjust the level of the desired temperature to turn on the heater. This circuit is capable of controlling a heating element up to 1500 W. The relay is suitable for RES55A with an operating voltage of 10...12 V or its equivalent.
The design of an analog thermostat is used to maintain a set temperature inside an incubator, or in a box on the balcony for storing vegetables in winter. Power is supplied from a 12 volt car battery.
The design consists of a relay in the event of a temperature drop and turns off when the preset threshold rises.
The temperature at which the thermostat relay operates is set by the voltage level on pins 5 and 6 of the K561LE5 microcircuit, and the relay off temperature is set by the potential on pins 1 and 21. The temperature difference is controlled by the voltage drop across resistor R3. A thermistor with negative TCR is used as temperature sensor R4, i.e.
The design is small and consists of only two units - a measuring unit based on a comparator based on the 554CA3 op amp and a load switch up to 1000 W built on the KR1182PM1 power regulator.
The third direct input of the op-amp receives a constant voltage from a voltage divider consisting of resistances R3 and R4. The fourth inverse input is supplied with voltage from another divider across resistance R1 and the MMT-4 thermistor R2.
The temperature sensor is a thermistor located in a glass flask with sand, which is placed in the aquarium. The main unit of the design is the m/s K554SAZ - voltage comparator.
From the voltage divider, which also includes a thermistor, the control voltage goes to the direct input of the comparator. The other input of the comparator is used to adjust the required temperature. A voltage divider is made from resistances R3, R4, R5, which form a bridge sensitive to temperature changes. When the temperature of the water in the aquarium changes, the resistance of the thermistor also changes. This creates a voltage imbalance at the comparator inputs.
Depending on the voltage difference at the inputs, the output state of the comparator will change. The heater is made in such a way that when the water temperature decreases, the aquarium thermostat automatically starts up, and when it increases, on the contrary, it turns off. The comparator has two outputs, collector and emitter. To control the field-effect transistor, a positive voltage is required, therefore, it is the collector output of the comparator that is connected to the positive line of the circuit. The control signal is obtained from the emitter terminal. Resistors R6 and R7 are the output load of the comparator.
To turn the heating element on and off in the thermostat, an IRF840 field-effect transistor is used. To discharge the transistor gate, there is a diode VD1.
The thermostat circuit uses a transformerless power supply. Excess alternating voltage is reduced due to the reactance of capacitance C4.
The basis of the first thermostat design is a PIC16F84A microcontroller with a DS1621 temperature sensor having an l2C interface. When the power is turned on, the microcontroller first initializes the internal registers of the temperature sensor and then configures it. The thermostat on the microcontroller in the second case is already made on PIC16F628 with a DS1820 sensor and controls the connected load using relay contacts.
DIY temperature sensor |
The dependence of the voltage drop at the p-n junction of semiconductors on temperature is perfectly suitable for creating our homemade sensor.
The operation of a gas or electric boiler can be optimized by using external control of the unit. Commercially available remote thermostats are designed for this purpose. This article will help you understand what these devices are and understand their varieties. It will also discuss the question of how to assemble a thermal relay with your own hands.
Purpose of thermostats
Any electric or gas boiler is equipped with an automation kit that monitors the heating of the coolant at the outlet of the unit and turns off the main burner when the set temperature is reached. Solid fuel boilers are also equipped with similar means. They allow you to maintain the water temperature within certain limits, but nothing more.
In this case, the climatic conditions indoors or outdoors are not taken into account. This is not very convenient; the homeowner has to constantly select the appropriate operating mode for the boiler on his own. The weather can change during the day, then the rooms become hot or cool. It would be much more convenient if the boiler automation was oriented towards the air temperature in the premises.
To control the operation of boilers depending on the actual temperature, various heating thermostats are used. Being connected to the boiler electronics, such a relay turns off and starts heating, maintaining the required temperature of the air, not the coolant.
Types of thermal relays
A conventional thermostat is a small electronic unit installed on the wall in a suitable location and connected to a heat source by wires. There is only a temperature regulator on the front panel; this is the cheapest type of device.
In addition to it, there are other types of thermal relays:
- programmable: they have a liquid crystal display, are connected using wires or use wireless communication with the boiler. The program allows you to set temperature changes at certain times of the day and by day during the week;
- the same device, only equipped with a GSM module;
- autonomous regulator powered by its own battery;
- wireless thermal relay with a remote sensor to control the heating process depending on the ambient temperature.
Note. A model where the sensor is located outside the building provides weather-dependent control of the operation of the boiler installation. The method is considered the most effective, since the heat source responds to changing weather conditions even before they affect the temperature inside the building.
Multifunctional thermal relays that can be programmed significantly save energy. During those hours of the day when no one is home, there is no point in maintaining a high temperature in the rooms. Knowing his family's work schedule, the homeowner can always program the temperature switch so that at certain times the air temperature drops and the heating turns on an hour before people arrive.
Household thermostats equipped with a GSM module are capable of providing remote control of the boiler installation via cellular communications. A budget option is sending notifications and commands in the form of SMS messages from a mobile phone. Advanced versions of devices have their own applications installed on a smartphone.
How to assemble a thermal relay yourself?
Heating control devices available for sale are quite reliable and do not cause any complaints. But at the same time, they cost money, and this does not suit those homeowners who have at least a little knowledge of electrical engineering or electronics. After all, understanding how such a thermal relay should function, you can assemble and connect it to the heat generator with your own hands.
Of course, not everyone can make a complex programmable device. In addition, to assemble such a model, it is necessary to purchase components, the same microcontroller, digital display and other parts. If you are new to this matter and have a superficial understanding of the issue, then you should start with some simple circuit, assemble it and put it into operation. Having achieved a positive result, you can move on to something more serious.
First, you need to have an idea of what elements a thermostat with temperature control should consist of. The answer to the question is given by the circuit diagram presented above, which reflects the operating algorithm of the device. According to the diagram, any thermostat must have an element that measures temperature and sends an electrical impulse to the processing unit. The latter’s task is to amplify or convert this signal in such a way that it serves as a command to the actuator - the relay. Next we will present 2 simple circuits and explain their operation in accordance with this algorithm, without resorting to specific terms.
Circuit with zener diode
A zener diode is the same semiconductor diode that passes current only in one direction. The difference from a diode is that the zener diode has a control contact. As long as the set voltage is supplied to it, the element is open and current flows through the circuit. When its value falls below the limit, the chain breaks. The first option is a thermal relay circuit, where the zener diode plays the role of a logical control unit:
As you can see, the diagram is divided into two parts. On the left side is the part preceding the relay control contacts (designation K1). Here the measuring unit is a thermal resistor (R4), its resistance decreases with increasing ambient temperature. The manual temperature controller is a variable resistor R1, the power supply to the circuit is 12 V. In normal mode, a voltage of more than 2.5 V is present at the control contact of the zener diode, the circuit is closed, the relay is turned on.
Advice. Any inexpensive commercially available device can serve as a 12 V power supply. Relay – reed switch brand RES55A or RES47, thermal resistor – KMT, MMT or similar.
As soon as the temperature rises above the set limit, the resistance of R4 will drop, the voltage will become less than 2.5 V, and the zener diode will break the circuit. Then the relay will do the same, turning off the power part, whose diagram is shown on the right. Here, a simple thermal relay for the boiler is equipped with a triac D2, which, together with the closing contacts of the relay, serves as an executive unit. The boiler supply voltage of 220 V passes through it.
Circuit with logic chip
This circuit differs from the previous one in that instead of a zener diode, it uses a K561LA7 logic chip. The temperature sensor is still a thermistor (designation VDR1), only now the decision to close the circuit is made by the logical block of the microcircuit. By the way, the K561LA7 brand has been produced since Soviet times and costs mere pennies.
For intermediate amplification of pulses, the KT315 transistor is used; for the same purpose, a second transistor, KT815, is installed in the final stage. This diagram corresponds to the left side of the previous one; the power unit is not shown here. As you might guess, it may be similar - with the KU208G triac. The operation of such a homemade thermal relay has been tested on boilers ARISTON, BAXI, Don.
Conclusion
Connecting a thermostat to the boiler yourself is not a difficult task; there is a lot of material on this topic on the Internet. But making it yourself from scratch is not so easy; in addition, you need a voltage and current meter to make the settings. Whether you buy a finished product or start making it yourself is a decision you make.
For some reason, many car enthusiasts are simply not satisfied with the usual dial indicator of engine temperature on the car dashboard. This is mainly due to the fact that such sensors, in most cases, show inaccurate and sometimes incorrect data. In today's article we will talk about a possible solution to this problem, and the solution will be to install a new sensor with a digital temperature indicator.
The reason why dial indicators show incorrect data is usually that their operating range, which is approximately 300-400 ohms, has some error of up to 50 ohms. Because of this, inaccurate data is displayed. The digital indicator, in turn, does not have any errors in the data output and is able to more accurately determine the engine temperature and transmit its value to the dial. In addition, such indicators are equipped with an additional number of useful functions, such as:
Turning on the fan on the radiator when the engine temperature reaches 910C and turning it off at 880C;
Application of a sound signal, something in the form of an alarm, when the temperature reaches 990C and turns it off at 980C;
Turning on an additional signal at critical 1100C;
In a sense, we can say that this indicator not only measures the exact temperature of the engine, but also has (albeit reduced) functionality of on-board computers.
This device is configured in such a way that the switching temperature of the fan sensor 2103-07, the range of which is narrowed on both sides by 10C. This is needed to more accurately measure the temperature in the engine block, and not on the radiator.
The temperature sensor itself is placed in the housing of a standard, old temperature sensor TM106. Before placement, everything is treated with thermal paste and a connector is made so that if the temperature sensor is defective or goes out of service, it can be replaced without deforming the case itself.
If you do not have the sensor firmware, the diagram will not give you any useful information. The firmware for the above circuit can be found at this link. Well, this option will help you connect several thermometers at once, as well as use one of the PIC devices to choose from.
In our case, there was a VAZ 2110 car, which did not have an additional hole for the sensor dial, so we cut it out ourselves. Once the dial is installed, it may be that the brightness of the dial exceeds the brightness of the other instruments on the panel, so we applied a darkening surface to the dial, which reduced its brightness a little.
This small tuning of your car will provide you with more accurate monitoring of the car’s engine temperature parameters, and will also notify you in time about overheating.
Before installing the device, it is better to become more familiar with the principle of its operation. The Russian market offers an impressive number of models from different companies, almost all of them operate according to the same scheme, regardless of their purpose.
According to this plan, devices are made to maintain the atmosphere in an aquarium, incubator, floor, etc. It allows you to maintain thermal conditions with an accuracy of ±0.5 0 C.
The device includes a bellows for the liquid composition, a spool, a rod and an adjustable valve.
simple thermostat circuit diagramthermostat diagram for incubator
Assembly instructions
Required materials, parts and tools:
- magnifying glass;
- pliers;
- insulating tape;
- several screwdrivers;
- copper wires;
- semiconductors;
- standard red LEDs;
- pay;
- forged textolite;
- lamps;
- Zener diode;
- thermistor;
- thyristor.
- display and internal generator with a capacity of 4 MGU (for creating digital devices on a microcontroller);
Step-by-step instruction:
- First of all, you need a corresponding microcircuit, for example, K561LA7, CD4011
- Fee must be prepared for laying tracks.
- To similar schemes Thermistors with a power of 1 kOm to 15 kOm are quite suitable, and it must be located inside the object itself.
- Heating device must be included in the resistor circuit, due to the fact that the change in power, which directly depends on the decrease in degrees, affects the transistors.
- Subsequently, such a mechanism will warm the system until the power inside the temperature sensor returns to its original value.
- Regulator sensors of a similar type need adjustment. During significant changes in the surrounding atmosphere, it is necessary to control the heating inside the object.
Assembling a digital device:
- Microcontroller should be connected together with the temperature sensor. It must have the output ports that are required to install standard LEDs that work in conjunction with the generator.
- After connecting the device to the network with a voltage of 220V, the LEDs will automatically turn on. This will indicate that the device is in working condition.
- The microcontroller design contains memory. If the device settings are lost, the memory automatically returns them to the originally specified parameters.
When assembling the structure, we must not forget about safety precautions. When using a temperature sensor in a watery or humid atmosphere, its terminals must be hermetically sealed. The value of thermistor R5 can be indicated from 10 to 51 kOhm. In this case, the resistance of resistor R5 must have a similar value.
Instead of the designated K140UD6 microcircuits, you can use K140UD7, K140UD8, K140UD12, K153UD2. Any instrument with a stabilization power of 11…13 V can be used as a zener diode VD1.
In the case when the heater exceeds the voltage of 100 W, then VD3-VD6 must be superior in power (for example, KD246 or their analogs, with a reverse power of at least 400V), and the thyristor must be mounted on small radiators.
The value of FU1 should also be made larger. Controlling the device comes down to selecting resistors R2, R6 in order to safely close and open the SCR.
Device
mechanical thermostat circuit diagram
The temperature always remains at the same level by turning the heating device (heating element) on and off. A similar control principle is used on all simple structures.
It may seem that the thermostat circuit is very simple, but as soon as it comes to assembling the device, a lot of questions arise related to the technical part.
The thermostat device includes:
- Temperature sensor– created on the basis of the DD1 comparator.
- Key circuit of the thermostat is the comparator DA1, made on an operational amplifier.
- Required temperature indicator is set by resistor R2, which is connected to inverting input 2 of the DA1 board.
- As a temperature sensor Thermistor R5 (type MMT-4) appears, connected to the input of the 3rd device.
- Design diagram has no galvanic isolation from the network, and takes energy from the parametric stabilizer on parts R10, VD1.
- As a power supply for the device You can take a cheap network adapter. When connecting it, you must be guided by the rules and requirements for new wiring, since the room conditions can be electrically hazardous.
A small supply of capacitor C1 contributes to a gradual increase in power, which leads to a smooth (no more than 2 seconds) switching on of electric lamps.
Self-assembly costs
Today, any such gadget can be purchased in a store. The price range is quite wide, and the cost of many models is over 1000 rubles. In terms of financial investments, this is quite unprofitable, so it is much cheaper to do it yourself.
Costs for self-assembly are several times lower, namely:
- K561LA7 board will cost no more than 50 rubles;
- thermistor with a power of 1 kOm to 15 kOm - about 5 rubles;
- LED (2 pcs) – 10 rub.;
- Zener diode - 50 rubles;
- thyristor - 20 rubles;
- display – 200 rubles (for creating digital devices on a microcontroller);
The purchase of lamps, foil and other materials will cost no more than 100 rubles. It turns out that the cost of self-assembly will have to be spent no more than 430 rubles and a little personal time. The owner can completely adapt the device to his needs, using a simple circuit for this.
Operating principle
The thermostat circuit is multifunctional. Starting from its foundation, you can create any adapted device that will be as convenient and simple as possible. The supply power is selected in accordance with the available relay coil voltage.
The principle of operation of the adjusting device is the ability of gases and liquids to compress or expand during cooling or heating. Therefore, the operation of water and gas configurations is based on the same essence.
They differ from each other only in the speed of reaction to changes in temperature in the house.
The principle of operation of the device is based on the following stages:
- As a result of changes in the temperature of the heated object, there is a change in the operation of the coolant in the heating mechanism.
- Together with that, this causes the siphon to increase or decrease its dimensions.
- After that, there is a displacement of the spool, which balances the coolant inlet.
- Siphon interior filled with gas, facilitating uniform temperature regulation. The built-in temperature sensor monitors the external temperature.
- Each heat level value the specific value of the pressure force of the working atmosphere inside the siphon is equated. The missing pressure is compensated by a spring that controls the operation of the rod.
- As a result of increasing degrees the valve cone begins to move towards closing until the operating pressure level in the siphon becomes balanced due to the forces of the spring.
- If the degrees drop, The work of the spring is reversed.
The result of the work depends on the type and functionality of the control valve, which is directly subordinate to the heating circuit and the diameter of the supply pipe.
Kinds
Manufacturing companies offer customers 3 types of thermostats, each of which has different internal signals. They control the heating process of the coolant and equalize the temperature order.
Signal expansion methods:
- Directly from the coolant. It is considered insufficiently effective, so it is used infrequently. Its operation is based on an immersion sensor or similar mechanisms. Compared to other types, it is one of the most expensive.
- Internal air waves. It is the most reliable and economical option. It balances the air during its changes, and not the level of water heating. Easy to install in an apartment. It communicates with heating communications using a cable through which the signal is transmitted. Thermostats of this type are constantly being updated with new functions and are quite convenient to use.
- External air waves. High efficiency is achieved by providing an immediate response to any weather changes. Signs in the form of a signal sent by the diaphragm give the system a command to open or close the pipe with the heating device.
In addition, the devices can be electrical and electronic.
According to the scheme and option for receiving a signal, devices are divided into semi-automatic and automatic, which, in turn, can:
- Control heating level of the radiator and line branch.
- Track according to the boiler power.
Review of thermostats on the market
Thermostat IWarm 710
The most popular models today include the E 51.716 and IWarm 710. Their non-flammable, plastic-polymer body is small in size, but has a large number of useful tasks and a built-in battery. It has a fairly large built-in display that displays the corresponding temperature characteristics.
The cost of these models is presented in the range of 2,700 thousand rubles.
The features of E 51.716 include the fact that it has a 3 m long cable, is able to balance the temperature simultaneously from the floor itself, and that the device can be built into the wall in any position.
The only thing you should think about before installing it is how exactly it will be located so that the switch buttons are not covered by foreign objects and are easily accessible.
The disadvantages of the thermostat include an insignificant set of functions, however, similar devices perform them quite easily. This may cause discomfort during operation. Also, the memory of the E 51.716 and IWarm 710 does not have an automatic heating function, so you will have to do this yourself.
Electronic regulators with a mechanical operating principle:
- Regulation of work based on automation, and carried out using buttons located on the panel.
- Includes display, which indicates the previous and specified degrees.
- It is possible to configure the device yourself: number, operating time, heating cycle with maintaining a specific mode, you can also specify the degree of heating.
- Compared to mechanical analogues, the temperature of electric models is easily adjusted by approximately 0.5 values.
The purchase of such a model will cost no more than 4 thousand.
Electronic components:
- Independently control the temperature.
- Just one device can control the atmosphere several days in advance and separately for each room.
- Allows you to set the “absence” mode, and don’t spend extra money on it if no one is at home.
- The system automatically analyzes the quality of work devices in every room. The owner will not have to guess about possible malfunctions in the operation, since the system will identify all the defects on its own.
- Manufacturers of expensive models provided the ability to control modes while away from home. Adjustment is carried out using the built-in Wi-Fi router.
The cost of such devices depends on the set of built-in functions, so it varies from 6,000 to 10,000 thousand rubles and more.