The thermostat will keep the set temperature on the boiler. Thermostats DIN Rail Relays
1) maintaining a comfortable indoor climate;
2) saving money spent on energy and heat carriers.
The principle of operation and characteristics of temperature controllers
The thermostat (room temperature control and programming device) consists of the following main units:- the microcontroller performing control has a non-volatile memory, which allows storing user-specified parameters even when the power is off;
- digital sensor that measures the ambient temperature;
- electromagnetic thermal relaydisconnecting or connecting the load.
On the body of the device there is a display showing indicators and buttons with which you can configure temperature regulator:
- required t;
- range of deviations;
- operating mode (heating or cooling);
The number and variety of custom settings depends on the model temperature switch.
The device constantly scans the t-background of the environment and, being guided by the values \u200b\u200bset by the consumer, regulates it by controlling the operation of climatic installations. Influencing the on / off switching of air conditioners, fans and heating systems, the device allows you to save up to 30% of consumed energy resources and achieve a comfortable microclimate in the room.
Temperature relay is selected for specific conditions, taking into account its functionality.
- Single-channel. Since t is controlled by a single channel, this type of device can operate in either cooling or heating mode.
- Two-channel. A pair of measuring channels of the air temperature switch allows the device to simultaneously serve two sectors, using various combinations of modes (heating-cooling, heating-heating).
- Multichannel. The three-channel mechanism is used to optimize electrical heating systems and allows the remote climate control principle to be implemented by setting a weekly temperature schedule. Provides maximum savings.
Instrument models, in addition to the number of channels, may differ in the mass of parameters:
- types of user-configurable values;
- fastening - built into a socket or mounted on a DIN rail;
- temperature ranges;
- power;
- operating modes (heating, cooling).
Types of thermostats that can be bought in the DigiTOP online store
DigiTOP offers an impressive range of temperature controllers with any number of channels. On the site, you can choose a model of a climate regulating device with the most suitable characteristics.- Single-channel.
TC-3. Maintains the set room temperature.
TC-4. Designed to work with powerful air conditioning units (up to 11 kW).
TK-4TP. Used to control warm floors.
TK-4k. Able to operate at t up to 1000 °, the device can be used in muffle furnaces and combustion chambers.
- Two-channel.
TC-6. Temperature controller, containing two TK-3 devices at once and allowing to save up to 70% of energy resources due to precise temperature control of various zones.
Multichannel. TK-7 is a device that provides automatic operation using a weekly programmer. The user just needs to set up the temperature schedule, and the device will provide an optimal indoor climate using a modern controller and many sensors.
All devices provided by DigiTOP are powered by 220 V.
Benefits of buying from DigiTOP
Devices that can be purchased from the DigiTOP online store are under development the best specialists and have a number of advantages.- Manufactured from high quality components.
- They are distinguished by their compactness, ease of setup and installation.
- They have an affordable cost that does not depend on the markups of intermediaries.
- They make it possible to save resources due to low power consumption and optimal adjustment of the operating mode of heating and cooling systems.
- A wide range of models allows you to buy a device that exactly meets the necessary requirements.
- The devices are universal: compatible with modern and outdated air conditioning systems.
The sale of DigiTOP equipment is carried out throughout the country (Moscow and the regions) with the help of a Russian representative of the company (Rostok-Electro LLC). With a wholesale purchase, additional discounts may be provided, so the price of devices may become significantly less than those stated on the website
Production: "Relsib"
Additional input for connecting a level sensor (version with a semiconductor sensor)
... Possibility of connecting additional temperature protection devices: thermal relays, thermal switches, etc.
... Simplicity and ease of use
... DIN rail mount
Temperature regulator Ratar-02, -02M universal
Production: "Relsib"
Semi-universal login
... Bright LED display
... Intuitive programming
... High accuracy
... Ability to shift zero and tilt without disturbing the alignment (for vehicles and TPs)
... Five types of output device logic
Temperature regulator Ratar-02A-1 for unattended premises
Production: "Relsib"
Completely finished product, no cabinet installation required
... Built-in two-pole load switch
... Convenient wall-mounted enclosure with terminal compartment
... Large LED 2-digit indicator
... It is completed with an external temperature sensor for maintaining the temperature in industrial premises, warehouses, garages, etc.
Temperature regulator Ratar-02U with built-in level control relay
Production: "Relsib"
Two devices in one: thermostat and level control relay
... Simultaneous maintenance of temperature and a given liquid level
... Load current up to 16 A
... Possibility of setting the type of input: 50M, 100P, Pt100
... The ability to control the heater and refrigerator
... High accuracy of temperature measurement and maintenance
... DC and AC supply voltage in a wide range
... Heating blocking in the absence of liquid
... Customizable for any conductive fluid
... Wave protection function
Temperature controller Ratar-03.2UV.SH1 two-channel with universal inputs
Production: "Relsib"
Measurement and regulation of temperature or other physical quantity through two independent channels according to the two-position law
... Regulation on one channel according to a three-position law (two setpoints, two control devices)
... Display of measured values \u200b\u200bin required units (scaling)
... Ability to connect to two sensor inputs different types
... Measurement and regulation: on one channel - physical quantity, on the other channel - differences in physical quantities
... Displaying on the alphanumeric LCD display simultaneously the values \u200b\u200bof the measured values \u200b\u200band the set settings
... Millivoltmeter operation
Thermostat with timer and humidity control function for the PUSK-1 drying chamber
Production: "Relsib"
A ready-made solution for the automation of drying chambers for clothes, wood, herbal preparations, grain, etc.
... Automatic end of the drying process by time or relative humidity
... Clear user interface
. Easy installation and connection
... One dedicated device replaces three standard
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
- Control of both heaters and cooling devices, each device has its own rotary scale
Thermostat KTO-011
A device for maintaining the temperature in a residential or industrial room, office, etc. by controlling executive devices (air heaters, cooling devices, fans, heat exchangers), as well as to turn 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 the temperature in a residential or industrial room, office, etc. by controlling executive devices (air heaters, cooling devices, fans, heat exchangers), as well as to turn 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 management
Thermostat FTO 011
A device for maintaining the temperature in a residential or industrial room, office, etc. by controlling executive devices (air heaters, cooling devices, fans, heat exchangers), as well as to turn on signaling devices
- 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
Electric thermostat - a device that allows you to maintain a certain temperature level in any heating system. It will turn off the heating element at the moment the medium 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 you to autonomously maintain the optimum temperature at any facility.
The classification of regulators is practiced simultaneously on several grounds:
- by appointment (thermostat for the incubator, for controlling the temperature in the room, heating boiler);
- by operating temperature range;
- by the type of working substance (thermostat with a temperature sensor for air, liquids, solids);
- by functionality (availability of programming, remote control, etc. matters),
- according to the principle of operation and design (it can be an electronic, mechanical or electromechanical thermostat).
The price for a thermostat is made up of the factors described above, as well as depending on the purpose in which you want to use it.
The principle of operation 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 a built-in element). Thus, the device can obtain information about the temperature level in the area of \u200b\u200bthe sensor location and, based on them, control the operation of heating elements or heating devices.
The main types of thermostats and thermostats
- Mechanical devices - ethese are the simplest and most affordable devices in their device, which are especially often used when working in a small room. They are not susceptible to power surges or electronic failures, therefore they are reliable and easy to use. For their price, mechanical thermostats are the most democratic of all.
- Electric thermostat -such devices are often used in the assembly of 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, 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 gives a control signal to the heating devices.
Call, order, Terainsvest specialists are always ready to help in choosing, to advise on all issues.
You can buy thermostats, thermostats from Terainvest by affordable price in the cities of Russia.
In household electrical appliances, temperature control is very often required. For this, a special sensor is used. By itself, it is a bimetallic contact that opens when heated above a certain temperature.
In everyday life, this sensor is called a thermostat, thermal fuse, thermal switch, thermal relay, thermal sensor, thermal cutout. In general, whatever they call it, although the part itself is a rather simple device.
This miracle looks like this.
Thermal switch KSD 301 for a response temperature of 115 ° С without fixing the flange.
Thermal switches of the KSD 201, KSD 301, KSD 302 series are included in almost all household electrical appliances that are used for heating. They can be found in the electrical circuits of thermos kettles (thermopots), storage water heaters (boilers), electric stoves, ovens, microwave ovens.
These temperature switches have a movable or fixed flange for surface mounting for temperature control. Some models may not have a flange. To reduce the temperature resistance between the thermal switch and the controlled object (tank, reservoir, chamber, etc.), heat-conducting paste can be used. The terminals of the KSD series thermoswitches are stamped and designed for connection of conductors without soldering.
Application of temperature switches.
Thermal switches are very simple and easy to use. Used in electrical engineering for the following purposes:
Emergency power off of the appliance at temperature overload. So, for example, if the main circuit of the water heater thermostat fails, then the temperature of the water tank will soon reach a critical one (more than 100 - 105 ° C). In this case, the thermal switch opens its contacts and removes the voltage from the electrical device. This is how the fire safety of the electrical appliance is ensured.
It is worth noting that the reason for the inoperability of the electrical appliance can be just a thermal switch. The fact is that there are self-resetting thermal switches, such as, for example, the KSD 201 type, and a forced closing thermal relay. Thermostat (thermostat) type KSD 302S is just one of the devices with forced switching.
When this sensor is triggered, its thermal contacts open. To close the thermal contacts of the sensor again, you need to press the small button on the side of the thermal relay contacts. The photo shows that there is a button on the side of the thermal relay contacts. It also serves to restore the working state of contacts.
Thermal relay KSD 302S
Appearance and pinout of the KSD 302S thermostat is shown in the figure.
Dimensions and appearance thermal relay KSD 302S
Appearance and typical dimensions of thermal switches with one pair of thermal contacts and a fixed flange
Temperature control ... Thermal switches are very actively used in thermos kettles (thermopots). There they are used both as a protective thermal fuse and to turn off the heating element when the boiling point of water is reached.
You can learn more about the device of thermos kettles and their repair.
Basic parameters of KSD series thermal switches.
Response temperature. Temperature at which the thermal contacts open. Indicated on the body of the device. Rarely exceeds the value of 150 ° C, since such sensors are mainly used in devices for heating water.
Rated voltage and current. Operating voltage and permissible current for the thermal switch. Usually the rated voltage is 250V, and the allowable current is at least 10 amperes.
Type nominal. For instance, KSD 201.
Reset temperature. Temperature at which cooled thermal contacts close again. This parameter is not indicated on the body of the thermal switch, but usually it is on 13 - 30 ° C below the response temperature. More precisely, this parameter can be found from the description of the specific type of the thermal switch.
Thermal relay check.
Since the thermal switches of the KSD series are a conventional thermocontrolled contact, they are checked by a simple "continuity" method using a tester. In the normal “cold” state, the contacts of the thermal switch are closed.
To check the operation of the thermal switch, you can heat it above the shutdown temperature with a conventional lighter and measure the resistance of the contacts. Since the operating temperature range of the KSD series thermal switches mainly lies in the range from 50 to 160 ° C, they can be heated with a conventional soldering iron.
In some cases, to restore the inoperative thermostat of the KSD series, you can vigorously shake it several times. Oddly enough, but strong shock vibration helps to restore the normal operation of thermal contacts. Of course, it is advisable to replace the faulty thermal switch with a new one. This recommendation only applies if there is no suitable replacement for the defective part at hand.
As already mentioned, thermal switches (thermostats, thermal relays) of the KSD series are actively used in household electrical appliances. When repairing them, sometimes it is necessary to replace just a thermostat such as KSD 301, KSD 302, KSD 201 and similar ones. Where can I buy them if I could not find them in the nearest radio stores? Can be bought online at AliExpress. The prices are very affordable, however, if you choose free shipping, then its terms can reach 1 - 1.5 months. If you don't know how to purchase parts on AliExpress, then
Efficient heating management is a vital part of the efficient operation of a boiler and home heating system. Proper use of controls will reduce the energy consumption of the unit, while creating a comfortable temperature in every room of the house, avoiding overheating of the premises. A thermostat (or a programmer) controls the operation of the boiler depending on the temperature in the room.
Up to 20% of the volume of consumed energy carriers can be saved using this kind of automation. And energy prices are quite high and everyone's desire normal person reduce your costs.
We consider a situation when the boiler is designed correctly, the necessary insulation of the premises has been completed, and the heating system is functioning normally.
Main types of boilers and temperature control
There are several types of boilers: solid fuel, gas, electric and liquid fuel.
Boilers are widely used all over the world. There are domestic samples, there are boilers and imported ones. The material of manufacture is steel or cast iron. Easy to operate, economical, with the function of adjusting the temperature of the coolant. In cheaper models, this function is implemented using a special device - a thermoelement.
Structurally, a thermoelement is a metal product, the geometric dimensions of which decrease or increase under the influence of temperatures (depending on the degree of heating). And from this, in turn, the position of the special lever changes, which closes and opens the traction flap. The photo shows a sample of such a regulator:
Photo: sample thermostatThe more the damper is open, the stronger the combustion process, and vice versa. Thus, the volume of air that enters the closed-type combustion chamber is completely controlled by the thermostat, and, if necessary, its supply is stopped and the combustion process dies out. In more modern models controllers are installed that, depending on the set thermal modes, control the air flow, turning on (or off) a special fan (see photo below):
Gas boilers - the most common and cheapest units to operate. Boilers are single-circuit and double-circuit. Single-circuit boilers have one heat exchanger and are intended for heating only. The connection diagram is shown in the figure below:
Single-circuit boiler switching circuit Double-circuit boilers have two heat exchangers and are designed for heating and receiving hot water. The boiler connection diagram is presented below:
Some boilers have separate regulators for heating and hot water temperatures.
Electric boilers
A fairly common alternative to gas and solid fuel boilers... A lot of advantages, high efficiency, but a long payback period. The connection is simple, like with gas boilers, but without a supply cold water... Provided for temperature regulation and overheating protection.
Boiler mechanical timer Using a simple mechanical timer for an electric boiler there are three options for starting the central heating system:
- The boiler is off;
- The boiler supplies warm water;
- The boiler switches on and off at the set time.
Mechanical timers usually have a large, round dial with a 24-hour scale in the center. You can turn the dial to set the desired time and then leave it that way. The boiler will turn on at the right time. The outer part consists of a set of 15-minute period tabs, which are inserted for easy adjustment of operation and setting modes. An emergency reconfiguration is possible, which is performed when the boiler is connected to the network.
Mechanical timers are easy to set up, but at the same time the boiler always turns on and off at the same time every day, and this may not satisfy the owners if the family is large and bath procedures are carried out several times a day at different times.
Types of thermostats
By the type of functions, they can be divided into several groups:
- with one function (temperature maintenance);
- with a large number of functions (programmable).
By design, thermostats are divided into types: wireless and with wires for communication with the boiler. Install thermostats in comfortable spot, connect the temperature sensor, connect to the boiler control system and use.
Room thermostats need a constant supply of air for proper and proper operation, so they should not be covered with curtains or blocked by furniture. Devices adjacent to an electric thermostat can interfere with the correct operation of the device: lamps, televisions, heating devices located nearby.
The programmable electronic room thermostat allows you to select the desired and comfortable temperature at any time, it is easy to reconfigure and change the operating mode. The time timer allows you to set a different pattern for heating on weekdays and weekends. Some timers allow you to set different parameters for each day of the week, this can be useful for people working part-time or in shifts. Many Terneo and KChM models are equipped with such thermostats.
The programmable room thermostat allows you to set individual heating standards for each day in accordance with your lifestyle and maintain the temperature of the house at all times, regardless of the presence or departure of the owners.
Video: Connecting a room thermostat to a gas boiler
If a boiler with a radiator is responsible for the heating system, as a rule, only one programmable room thermostat is needed to control the entire house. Some patterns need to be adjusted in the spring and fall when the clock has moved back and forth, or a certain change has occurred climatic conditions... We also recommend changing the temperature settings when changing day and night.
Such a climate controller has several options that expand its capabilities:
- "Party", which stops heating for several hours, then resumes;
- “Override” allows you to temporarily change the programmed temperatures during one of the configured periods;
- "Holiday", increases the heating intensity or decreases it for a certain number of days.
Central thermostat
Such a thermostat is located far from your boiler and usually allows you to turn on or off heating throughout the house. Older versions are wired to the boiler, newer systems usually send signals to the command post of the device. It is with devices of a new type that rather expensive but effective devices are equipped: double-circuit boilers Ferroli, Beretta and domestic AOGV.
The best known are room thermostats for a double-circuit boiler of the Gsm and Protherm brands. They have a built-in dilatometric thermostat for the boiler, which, depending on the model, can work remotely; this technology is often used for an electric boiler or solid fuel units.
The room thermostat turns off the heating of the system as needed. It works by measuring the air temperature, and turning on the heating when the air temperature drops below the thermostat setting, and turning it off when the set temperature is reached.
Advice:
- It is recommended to set the thermostat at 20 ° C;
- At night, the set temperature should be between 19-21 ° C.
- It is desirable that the children's room is about 22 ° C.
- The temperature should not fall below 22 ° C in the premises for the elderly and people with disabilities.
As a rule, the temperature of the whole house or individual rooms is based on only one climate microcontroller in the heating system. The best way its location in the living room or bedroom, which should probably be the most visited place in the house.
Room thermostats need free air flow to measure temperature, so they should not be covered with curtains or blocked by furniture. Devices adjacent to the electric thermostat can interfere with the correct operation of the device. These include lamps, televisions, neighborhood boilers through the wall, touch switches.
Thermostatic control valves
The thermostatic valve is a simple solution to the problem of obtaining a heat carrier of a given temperature by mixing colder water with warmer water. The three-way valve is shown below:
The thermostatic radiator valve allows you to control the room temperature by changing the flow of hot water through the radiator. They regulate the flow of hot water through the radiator, but do not control the boiler. Such devices must be installed to adjust the temperature that is needed in each individual room.
This idea should be considered as a complement to the thermoregulation installation. Also, such devices need periodic readjustment and regular performance checks (every six months during a change in operating modes).
Homemade external thermostat for the boiler: instruction
Below is a diagram of a homemade boiler thermostat device, which is assembled on Atmega-8 and 566 series microcircuits, an LCD display, a photocell and several temperature sensors. Atmega-8 programmable microcircuit and is responsible for compliance with the specified parameters of the thermostat settings.
Strictly speaking, this circuit turns on or off the heating boiler when the outside temperature drops (increases) (U2 sensor), and also performs these actions when the room temperature changes (U1 sensor). Adjustment of the operation of two timers is provided, which allow you to adjust the time of these processes. A piece of a circuit with a photoresistor affects the process of turning on the boiler by the time of day.
The U1 sensor is located directly in the room, and the U2 sensor is outside. It is connected to the boiler and installed next to it. If necessary, you can add electrical part schemes that allow you to turn on and off high-power units:
Another thermostat circuit with one control parameter based on the K561LA7 microcircuit:
The assembled thermostat based on the K651LA7 microcircuit is distinguished by its simplicity and ease of adjustment. Our thermostat is a special thermistor that significantly reduces resistance when heated. This resistor is included in the electricity voltage divider network. Resistor R2 is also located in this circuit, with which we can set the required temperature. Based on this scheme, you can make a thermostat for any boiler: Baksi, Ariston, Evp, Don.
Another circuit for a microcontroller-based thermostat:
The device is assembled on the basis of the PIC16F84A microcontroller. The role of the sensor is performed by a digital thermometer DS18B20. The small relay controls the load. Microswitches set the temperature that is displayed on the indicators. Before assembly, you will need to program the microcontroller. First, erase everything from the chip and then reprogram, and then reassemble and use it for health. The device is not moody and works fine.
The cost of parts is 300-400 rubles. A similar regulator model costs five times more.
A few final tips:
- although they fit most models different variants thermostats, it is still desirable that the thermostat for the boiler and the boiler itself be produced by the same manufacturer, this will greatly simplify the installation and the operation itself;
- before buying such equipment, you need to calculate the area of \u200b\u200bthe room and the required temperature in order to avoid "downtime" equipment, and change the wiring in connection with the connection of devices of higher power;
- before installing the equipment, you need to take care of the thermal insulation of the room, otherwise high heat losses will be inevitable, and this is an additional cost item;
- if you are not sure that you need to purchase expensive equipment, then you can conduct a consumer experiment. Buy a cheaper mechanical thermostat, adjust it and see the result.
In everyday life and subsidiary farming, it is often required to maintain temperature regime any premises. Previously, this required a rather huge circuit made on analog elements, we will consider one such 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 thermal sensor can be bought cheaply in ALI Express (to order, click on the picture just above)
The thermostat on and off temperature threshold is set by the TH and TL values \u200b\u200bin the sensor memory, which must be programmed into the DS1821. If the temperature rises above the value recorded in the TH cell, a logical unit level will appear at the sensor output. To protect against possible interference, the load control circuit is implemented so that the first transistor is locked in that half-wave of the mains voltage when it is equal to zero, thereby supplying a bias voltage to the gate of the second field-effect transistor, which turns on the optosimistor, and that already opens the VS1 smistor that controls the load ... The load can be any device, such as an electric motor or heater. The reliability of blocking the first transistor must be adjusted by selecting the required value of the resistor R5.
The DS1820 temperature sensor is capable of recording temperatures from -55 to 125 degrees and operates 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 unit, the load will be disconnected from the mains. If the temperature drops below the lower programmed TL level, then a logical zero will appear at the temperature sensor output and the load will be turned on. If there are any incomprehensible moments, homemade construction was borrowed from # 2 for 2006.
The signal from the sensor goes 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. The variable resistance R4 sets the required temperature regime.
Thermostat circuit on the LM35 sensor
If the potential at the direct input is lower than that set at pin 2, then at the output of the comparator we will have a level of about 0.65 volts, and if on the contrary, then at the output of the comparator we will get a high level of about 2.2 volts. The signal from the op-amp output through the 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.
The 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 across the resistors Rl, R2 and a thermistor with a negative TCS 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. With an increase in temperature, the resistance of the thermistor and the potential on the control contact of TL431 decreases below 2.5V, the relay releases its front contacts and turns off the heater.
With the help of resistance R1, we adjust the level of the desired temperature to turn on the heater. This circuit is capable of driving 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 analogue thermostat design is used to maintain the set temperature inside the incubator, or in a box on the balcony for storing vegetables in winter. Meals are organized from car battery 12 volts.
The design consists of a relay in the event of a temperature drop and disconnects when the set threshold rises.
The temperature of the thermostat relay actuation is set by the voltage level on pins 5 and 6 of the K561LE5 microcircuit, and the relay switch-off temperature is set by the potential on pins 1 and 21. The temperature difference is controlled by the voltage drop across the resistor R3. In the role of temperature sensor R4, a NTC thermistor is used, i.e.
The design is small and consists of only two blocks - a measuring unit based on a comparator on an op-amp 554SA3 and a load switch up to 1000 W built on a power regulator KR1182PM1.
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 the resistance R1 and the MMT-4 R2 thermistor.
The temperature sensor is a thermistor located in a glass flask with sand, which is located in the aquarium. The main unit of the structure is 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 of resistances R3, R4, R5, which form a bridge that is 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 drops, the aquarium thermostat automatically starts up, and when it rises, 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 received from the emitter pin. Resistors R6 and R7 are the output load of the comparator.
The IRF840 field-effect transistor is used to turn on and off the heating element in the thermostat. For the discharge of the gate of the transistor, a diode VD1 is present.
The thermostat circuit uses a transformerless power supply. The excess alternating voltage is reduced due to the reactance of the capacitor C4.
The basis of the first design of the thermostat is a PIC16F84A microcontroller with a DS1621 temperature sensor with an l2C interface. At the moment of power-up, the microcontroller first initializes the internal registers of the temperature sensor, and then adjusts it. The thermostat on the microcontroller in the second case is already made on the PIC16F628 with the DS1820 sensor and controls the connected load using the relay contacts.
DIY temperature sensor |
Dependence of voltage drop across p-n junction semiconductors from temperature, is the best fit for creating our homemade sensor.
