General information

Thermostat for incubator do it yourself


The diagram below is a development of the topic of the triac power control. In this case, thermosensitive and heating elements are added due to which the required temperature is maintained. Including-disconnecting the load, which serves as an electric heater, the thermostat regulates the temperature of the microenvironment of the incubator, aquarium or other confined space.

The principle of operation of the thermostat

So, let us consider how the thermostat circuit for the incubator works with its own hands: the basis of this device is the DA1 operational amplifier operating in the voltage comparator mode. A variable voltage is supplied to one input from a thermistor R2, and to the second, given by a variable resistor R5 and a trimmer R4. For fine and coarse adjustment. Depending on the application, the trimmer can be eliminated.
When the input voltages are equal, the VT1 transistor, an output controlled comparator is closed, the VS1 control electrode is zero, which means the triac is also closed. When the temperature changes, the resistance R2 changes, and the comparator responds to the voltage difference at the inputs by applying an opening signal to VT1. Appears on the R8 voltage will open the thyristor, letting the current through the load. When the voltages at the inputs of the operational amplifier equalize, it will disconnect the load.
The power supply of the control stage is carried out through a rectifying diode VD2 and damping resistance R10. With its ultra-low current consumption, this is perfectly acceptable, as is the use of just one Zener diode VD1 for stabilizing the supply voltage. In addition, the control circuits are powered through the load on which the voltage drop also occurs, especially in the heated state.

Replacement parts

Pay attention to the power of the resistor R10 - 2W, as this resistor must withstand an instantaneous voltage of 400V, if such a resistor can not be found, it can be replaced with several series-connected resistors for lower power and voltage.
As a Zener diode VD1, you can set the BZX30C12 or any other Zener diode to 12V close in parameters.
Instead of VD2, you can put a diode with a reverse voltage of at least 400V and a current of at least 0.3A: for example, from the 1N4004 - 1N4007 series
In place of DA1 you can install almost any operational amplifier, the main thing is that it works in the range of supply voltages 10..15V.

But the single junction transistor KT117 (VT1) is not such a common component of electronic circuits (foreign single junction transistors: 2N6027, 2N6028), but it can be replaced by a circuit of two bipolar transistors of different structure and one 47 kΩ resistor. The circuit uses common KT315 and KT361, but other low-power complimentary bipolar transistors can be used.

How to mount an incubator heater

  • the lamps should be evenly located above the surface of the eggs, at a distance of 25-30 cm from their surface,
  • the thermistor should be as close as possible to the surface of the eggs, but not touch them,
  • other heaters can be used instead of light bulbs, but with a low heat capacity, for example, tungsten wire stretched over a ceramic frame in the shape of a tetrahedron.

Aquarium Heater

More rarely, such a thermostat was used to maintain the desired temperature in aquariums with tropical fish. Such a need arose due to the fact that most of the thermal heaters produced for this purpose have a mechanical thermostat combined with the heating element in the same housing. And consequently, they maintain their own, and not the ambient temperature, in the given limits. It works well only in rooms with a stable, within one or two degrees, its air temperature.

Installation Features

  • due to the inertness of the water, the sensor and the heater must be separated, but within the direct line of sight (without overlapping by plants and decorative elements) from each other,
  • due to the electrical conductivity of water, the sensor must be isolated, either by means of good thermal conductivity, or by a thin layer of conventional sealant,
  • It is allowed to use both usual aquarium heaters and adjustable ones with temperature set at maximum.

You can find other applications of this, simple to manufacture the device. For example, for rassadny parnichkov, drying cabinets, various thermovanochochek. What is your imagination enough. Only if the load allows for the possibility of a short circuit, it is necessary to add a fuse of 1 A.

As mentioned above, this simple thermostat was used in incubators earlier, now it has been replaced by thermostats with microcontroller control, capable of automatically lowering the temperature during the incubation cycle. And the incubators themselves have acquired the function of controlling humidity and turning eggs.

Record Navigation

Scheme thermostat for incubator do it yourself: 12 comments

For the future of microcontrollers, I don’t argue, thanks to Harvard architecture in general and Microchip Technology in particular. But is their application everywhere profitable, with their capabilities? They themselves are not expensive, but the peripherals they need may be different. And without knowledge of programming on a low, machine level - you should not take on them. In a word - a chip for professionals and professional use.
But to master digital technologies is also necessary for amateurs, of course, where now without them.

I saw an incubator with a circuit that is much simpler, where a low-power closed heater and a thermal relay regulator are used. Of course, this scheme is good, but for the amateur is complicated, because it must also be configured.

This scheme is not necessary to set up, should earn immediately. Here you will need to adjust the temperature.
If you take a ready-made regulator, then you don’t need to solder anything: just screw the wires to the terminals and it’s ready. By the way, the thermostat with a digital indicator, a microprocessor and a temperature sensor on the aliexpress can buy something for about $ 2. Dollars for 10-15, you can take the thermostat for underfloor heating with a schedule of temperature changes during the day and by day of the week.

If for an unpretentious incubator, then it is possible for $ 2, or better for 3-4, with the task of temperature play, so that the light bulbs do not “rattle” because of the sensitivity of the sensor. For good, it is good to take with a full schedule (and memory for a few) for $ 15-20 to set a full cycle for the entire incubation period (for different birds), and connect a slow-moving (or reduced) turn-over engine to the shadows.
But, really well - to study pic-processors and create on their base their devices, of any functionality. And on aliexpress you can buy a programmer.

Microcontrollers are a good thing, but when it comes to living souls, it is better easier but more reliable in my opinion. In order not to freeze the eggs or not to cook aquarium fish.
Because it happens that you lick the firmware to shine, mplab and proteus are already smoking from the simulation, and the layout would seem to work. But suddenly one day there are certain conditions in which the program comes to a standstill and the device on the MK falls into insanity. And that is typical, right on the level ground, where it would seem nothing should happen. However, I did not see any of the possible options, and please - a glitch. The thermostat with a comparator certainly does not stop with good parts.

Is it possible to use a similar (close to this) principle to create a current load relay, but with 12 volt power supply of the device

Yes, it is even easier to get a Zener diode and a powerful resistor, a single junction transistor, and a MOSFET instead of a simistor (if the load is small, then you can do with a bipolar transistor).

A comparator without hysteresis and a sufficiently powerful heater will not give unexpected effects for devices working in the neighborhood? I did a similar for heating the casing of an outdoor analog camera. But the heater was made of MLT resistors and, as a key, a powerful bipolar resistor (powered by a 15 volt heater). During the switching of the comparator, the “bounce” was such that for a few seconds it was impossible to make out anything on the video from the camera. And in frosty weather, these smithereens appeared every few minutes. Interference from multiple switches on the threshold of the comparator. I had to remove the camera, solder the resistor between the output and the non-inverting input to cover the board to ensure hysteresis. The incubator and the aquarium, of course, is not a camera, but you never know what will be connected with them to one outlet ...

Naturally, bounce switching - the main disadvantage of this device. And the higher the sensitivity and inertia of the thermal sensor - the more noticeable it is. This should be remembered and, if it creates an inconvenience, then eliminate it, although it would be the above Root method.
In closed, thermally insulated systems with “tight” thermal sensors, this problem is not particularly inconvenient.
Do not forget that in those ancient times there was practically no highly sensitive electronics.

Hello to all! Who can make an order for an incubator?

It is not clear - why is there a triac in the circuit? After all, management is only during one half-wave?

Reasonably, in this circuit, you can do with a thyristor, for example, KU202N.

Why do we need a thermostat for an incubator

Farmers use a digital thermostat for an incubator. The device is able to create in the device the temperature necessary for the development of embryos. Modern incubators are necessarily equipped with such devices. However, if there is no such device, you need to buy this part or design it yourself. The advantages of technology:

  1. thermostat will help maintain the desired temperature all the time
  2. you can set a specific mode for each type of bird,
  3. as soon as the device overheats the space, it turns off,
  4. function contributes to energy savings.

Is it possible to make a thermostat with your own hands

Most incubators on the market have this item in the package. You can compensate for the lack of such a controller yourself. Make the device is not easy, you will need certain skills. There are 2 options for how to create a digital temperature controller:

  • Electrical - a complex method that involves the use of electrical circuits and other devices. Only a person with knowledge in the field of electromechanics will be able to construct a regulator in this variant.
  • Thermostat method will require the use of parts, previously in household electrical appliances. Parts can be found in Chinese, Russian and European appliances, whose work is based on temperature control (iron, kettle, curling iron).

Electrotechnical thermal sensors for on-off

To make the thermostat for the incubator with your own hands, you need to find or buy the necessary radio components and solder them to the electrical circuit. To work you will need a spare part that is responsible for providing constant voltage. In your case, take a zener diode. Any type will do. In addition, purchase the following parts:

  • transistors (CT 315 and MP 42),
  • thyristor KU 201-202 (note that the designation was the letter H),
  • diodes CD 202 with power from 600 W - 4 pcs. (they should have the letters H or NA)
  • variable resistor (30-50 kΩ), it is designed to regulate the mode,
  • thermal switch

One transistor must be placed in a tube made of glass, put the design on the eggs. Get a kind of thermometer for an incubator. He will control the increase or decrease in temperature. The principle of operation of the device is based on the fact that when the controller is turned on, the contacts open. Incubator heats up from the lamps. If the device is disconnected from the network, the battery starts working.

Device assignment

The principle of operation of the thermostat - feedback, in which one controlled quantity indirectly affects the other. For artificial breeding of birds, it is very important to maintain the desired temperature, because even a slight glitch and deviations can affect the number of hatched birds - the thermostat for incubation is precisely for this purpose.

The device heats the elements so that the temperature remains unchanged even with changes in ambient air. In the already finished device there is a sensor for an incubator thermostat that controls the temperature process. Each poultry farmer must know the basics of the device’s workflow, especially as the connection scheme is very simple: a heat source is connected to the output wires, electricity is supplied through others, and a temperature sensor is connected to the third wire, through which the temperature value is read.

Is independent production possible?

If you decide to create a digital thermostat for an incubator yourself, it is worthwhile to approach the issue of creation responsibly. Those who know the basics of radio electronics and know how to handle measuring devices and a soldering iron can do this kind of work. In addition, useful knowledge of printed circuit boards, configuration and assembly of electronic devices. If you focus on factory products, you may encounter problems during assembly, especially during the instrument setup phase. For easier work you need to choose a scheme that is available for the manufacture of the house.

The main criterion for any type of device is to ensure high sensitivity to internal temperature extremes, as well as a quick response to such changes.

To create a thermostat for the incubator with his own hands, mainly used scheme in two versions:

  • the creation of a device with an electrical circuit and radio components is a complicated method, but accessible to specialists,
  • the creation of the device, based on the thermostat of household appliances.

Self-manufacture scheme

Many are wondering how to make a thermostat for an incubator with your own hands.

As an independent manufacturer consider a simple scheme - thermostat as a regulator. This option is simple to make, but no less reliable to use. The creation requires any thermostat, for example, from an iron or other household appliances. First you need to prepare it for work, and for this the thermostat case is filled with ether, and then well sealed.

The ether tends to react sensitively to the smallest changes in air temperature, which affects changes in the state of the thermostat.

The screw, soldered to the body, is connected to the contacts. At the right time, the heating element is turned on and off. The temperature is set during screw rotation. Before laying eggs it is necessary to warm up the incubator. It is obvious that it is easy to manufacture the thermostat, and even a schoolboy who is passionate about electronics can do it. The circuit has no rare parts that cannot be obtained. If you yourself are making an "electric hen," it would be useful to provide a device for the automatic rotation of eggs in the incubator itself.

Connecting the thermostat to the incubator

When connecting the thermostat to the incubator, you need to know exactly location and function of the device:

  • the thermostat must be outside the incubator,
  • The temperature sensor is lowered inward through the hole and should be at the level of the upper part of the egg, without touching them. A thermometer is located in the same area. If necessary, the wires are extended, and the regulator itself remains outside,
  • heating elements should be located approximately 5 centimeters above the sensor,
  • the air flow starts from the heater, goes further in the area of ​​the eggs, then enters the temperature sensor. The fan, in turn, is located in front of or after the heater,
  • The sensor must be protected from direct radiation from the heater, fan or lighting the lamp. Such infrared waves transmit energy through the air, glass, and other transparent objects, but do not penetrate through a thick sheet of paper.

Purpose and principle of operation of the thermostat

The thermostat, sometimes called a thermostat (which is not entirely true, a thermostat can be called the entire incubator), serves to maintain the set temperature by turning the heater on and off depending on the set temperature. The temperature is determined using a sensor.

With the help of the thermostat, farmers maintain the desired temperature in the incubator.

The sensor can be:

  • bimetallic thermostat,
  • thermocouple,
  • resistance thermometer
  • thermistor
  • semiconductor sensor.

As an example, we can cite the sensor of the American company Dallas Semiconductor, which has a single-wire digital interface. It can be used in the circuit on the microcontroller. The scheme is simple, the details are inexpensive, but it requires a lot of programming skills and knowledge, almost professional, to make it all work reliably and reliably. After all, a party of hundreds of eggs may depend on it.

When the temperature of the sensor exceeds the set value, the power supply circuit of the heater, for example, incandescent lamps, is turned off and the incubator starts to cool down gradually. Когда температура становится ниже другого заданного значения, лампочки снова включаются.

Получается выключатель-автомат с обратной связью по температуре. Даже с двумя: отрицательная обратная связь автомат отключает, а положительная – включает. Промежуток между порогами включения и отключения называется гистерезисом. If this hysteresis is zero (which in practice does not happen), or is very close to it, then the regulator will turn on and off too often and something, rather soon, will fail.

The thermostat for the incubator can be made independently.

There are simple regulators in which the hysteresis is not standardized and has a value sufficient for practice. But there are those where the switching threshold and hysteresis are set separately and very accurately. They are used in industry and research.

What is better: buy or make yourself

Temperature controllers on sale, suitable for work in incubators, are on the market, their price ranges from several hundred to several thousand rubles. If you search well, you can find a very suitable option. How well they work, you can read on the forums of poultry farmers and farmers.

Independent production is also quite affordable, and this is the most budget option. All necessary parts can be purchased at online stores with postal delivery. For those who love to do everything on their own, and such people are worthy of all respect if they are serious about the matter, the rest of the article is intended.

How to make the thermostat yourself

A hand-made hand-made device can in no way yield to an industrial one in its accuracy and stability, well, except that its ergonomics will be a little worse. But for those who breed birds, this is not primarily of concern.

Temperature controllers, manufactured independently, are not inferior to those that are on sale.

Self-made device is made of the same industrial parts, and it is not clear why it should be worse? Unfortunately, in Russia such an opinion is not uncommon: if self-made, it means bad, but if it’s factory-made, then for the sake of it you can even get into credit “by the ears”. You will see that this is not the case.

Homemade electronic thermostat

His diagram is shown below. There are few details in it, they are inexpensive, and it is not difficult to get them.

Details can be bought in the store. This is not an advertisement, ChipDip has not needed any advertising for a long time. It is a little about the prices: zener diodes 1N4742A, 1N4736A stand there 2 rubles apiece. A similar Russian Zener diode, especially in a metal case, can cost under a hundred. Operational amplifier LM328N costs about 30 rubles, 1N4004 rectifier diodes cost three rubles apiece.

The field-effect transistor IRF730PBF costs about 30 rubles. Two diodes 1N5406 cost 10 rubles together. If instead of them to use the Soviet diode in a metal case at 10A, then it can cost hundreds of rubles because of the precious metals inside. In general, it is necessary to understand the element base in order not to overpay many times.

The photo shows a diagram of a homemade thermostat for an incubator.

How this scheme works. Resistor R8 and capacitor C2 limit the current supplying the rectifier diodes VD2 and VD3. The voltage is stabilized by the Zener diode VD1 and filtered by the capacitor C1. This is 12 volts to power the comparator circuit assembled on the DA1 operational amplifier. The LM358 chip contains two op amps of which one is used.

The power part of the circuit is formed by the fuse F1, the lamps L1 ... Ln connected in parallel, the diode VD4 and the channel of the field-effect transistor VT1. Since this circuit only transmits current in one direction, the lamps will work fully. However, this will only increase the reliability and service life. We will return to the issue of lamps, but for now about the operation of the regulator.

At the input of the OU there is a bridge on the resistors R1-R5. The signal is formed on the resistors R1 and R2 (R2 is a thermistor). It is compared with the voltage on the engine variable resistor R4. The hysteresis is provided to the comparator by resistor R6 (along with resistor R2). The op amp boosts the signal difference between the input “minus” (inverting input) and “plus” (direct input).

Thermistor R2 with increasing temperature reduces its resistance. First, the output of the op-amp voltage is close to 12V. Field effect transistor VT1 is open and the lamps are turned on.

The photo shows the thermistors MMT-1 and MMT-4.

As soon as the difference between the reference voltage and the input signal becomes negative, at the output of the amplifier, the voltage abruptly drops to almost 0V. The transistor closes and the lights go out. Resistor R6 limits the output current of the op-amp through the Zener diode, and the Zener diode limits the voltage at the gate of the transistor to a safe value (6.8 V).

Now for the details without nominal values. Let's do a little development of electronic circuits. What will be the nominal values, depending on what we choose a thermistor.

Let's look at the generalized current-voltage characteristic of the MMT-1 thermistor (MMT-4 has a similar one).

You can get a thermistor with any rating, so it is important to be able to calculate the input part of the circuit. For example, the MMT-1 thermistor 1.5k 20% costs 14 rubles (there are thermistors and for five thousand rubles). 20% is the nominal error. This does not affect the accuracy of the calibrated instrument, the thermistors are very stable.

Note! It is undesirable to take thermistors with resistance less than 1 com. Otherwise, the operation mode of the circuit will be violated and the thermostat will work unstable.

Suppose we want to regulate the temperature in the range of 34-39 degrees. The graph shows what relative resistance the thermistor should have for these temperatures. We calculate the working resistance of the thermistor: R2 = 1500 * 0.7 = 1050 Ohm. Approximately the same should be the resistance R1, so that at the point of their connection was half the power supply 6V or so. OU is better to work in this area.

The photo shows a graph of the relative resistance of the thermistor for different temperatures.

At the same time, we calculate the voltage of the signal, assuming that R1 = 1k. At 30 ° C, the resistance of the thermistor will be 1500 * 0.8 = 1200 Ohm, and at 40 ° C - 1500 * 0.65 = 975 Ohm. In the first case, the current in half of the bridge with R1 and R2 will be 12 / (1000 + 1200) = 5.4545 mA, in the second case: 12 / (1000 + 975) = 6.0759 mA. We only need these currents to estimate the voltage of the signal.

In the first case, U = I * R = 5.4545 * 1200 = 6.5455 V, in the second case a similar calculation shows 5.9241 V. The difference will be 0.6214 V. To install the thermostat in this range, you will need to have the same reference voltage at the other OU input .

And the hysteresis will depend on the gain. If we want the regulator to maintain the temperature with an accuracy of 0.1 ° C, then we must first find out what voltage will correspond to such a change in temperature. It is not difficult to know: approximately 0.0062 V. We divide the temperature range by a step of one tenth of a degree and multiply by the voltage swing of the signal.

On the other hand, the output signal changes from 0 to 10-11 V. So, we need to get a gain: 11 / 0.0062 = 1774. Then the resistor R6 installed in the feedback circuit must be less than the resistance of the thermistor by the appropriate number of times: R6 = 1780/1090 = 1.63 ohms. That is, we divide the amplification value by the average value of the thermistor resistance in the operating range.

Making a thermostat with your own hands requires some knowledge.

Now it only remains to calculate R3, R4, and R5. Potentiometer R4 should be selected from wire variable resistors. They have a linear characteristic and there will be fewer surprises with graduations. In the selected area, the characteristic of the thermistor is also more or less close to a straight line.

Unfortunately, wire variable resistors are quite expensive. But they are the most stable and accurate. On eBay or aliexpress, you can find one for 150 rubles with delivery. In Russian stores, they are much more expensive. Sometimes you can find such a potentiometer completely free in old devices left over from the times of the USSR. Best fit is a small potentiometer for power 0.25-0.5 W with a nominal value of 220-470 Ohms. In extreme cases, you can take 2.2 kOhm.

Suppose we found a 1-ohm wire potentiometer (quite common). What should be the resistors R3 and R5? At 1k accounted for approximately 0.63 V voltage, and the total on the resistor chain drops 12V. The current passing through the chain can be calculated according to Ohm’s law: I = U / R = 0.63 / 1000 = 0.63 mA. In order for the comparator to work in the signal range and the potentiometer scale is neither too stretched nor too compressed, the reference voltage must change in the same range as the signal itself.

For the calculated current, we find the sum of all resistances R3, R4, R5: R = U / I = 12 / 0.00063 = 19.048 kΩ. Now let us recall the lower limit of the signal range from sensor R2. It is 5.9241 V. At the current found, we calculate the resistance of the lower resistor R5 = U / I = 5.9241 / 0.00063 = 9400 Ohm.

Now it is easy to find the upper resistor: R3 = 19.048 - 1 - 9.4 = 8.65. Such must be the resistances of R3 and R5 so that the scale of R4 falls into the required “window”. This is not a dogma, but it is better to choose resistors closer to these values. If the scale when adjusting is a little wider, then there is nothing wrong with that, the main thing is that it should not be already. You can use composite resistors, connecting them in series or in parallel, and checking the total resistance with a multimeter.

For the manufacture of thermostat for the incubator requires different components.

Similarly, the calculation is done for other thermistors. We don’t need to take special care of the input currents of the OS, they are very small and do not affect the operation of the bridge.

The design of the thermostat

Here is how to make a device. Typing suitable parts you need to prepare in advance and configure those elements that were calculated (R3 and R5), so that they are neatly soldered and they can be mounted further.

Resistor R6 can be taken either 1.6 Ohm, but these rarely come across, or be made up of several parallel ones (due to its small rating), or take a piece of 16.3 Ohm nichrome wire (measured by a multimeter) and cut off exactly one-tenth from it part. Then it is wound on a large resistor, say, 10 or 100 kΩ, so that it does not affect the total resistance and is soldered on its terminals.

Parts are mounted, as usual, on a suitable size printed circuit board. The scheme is simple, you can draw tracks either manually or in a suitable program for the development of printed circuit boards, for example, Sprint Layout. This is a simple free program for radio amateurs. Unfortunately, the size of the article does not allow to describe the details of the manufacture of printed circuit boards, but to find information on the Internet is not difficult.

The photo shows the process of manufacturing the thermostat.

Attention. The field-effect transistor must be mounted on an aluminum heat sink with an area of ​​at least 100 cm2. Capacitor C2 should be used only new, better type K50-17, before use, you must ensure that it is not broken and does not leak.

A round scale with glued paper should be put on the potentiometer axis and fixed firmly. It will be applied graduation. The scale can be made mobile or not, the main thing is its sufficient size for future marking and “non-tolerance”. Finally, everything assembled is placed in a suitable enclosure. There is a lot of room for home design.

Now, as promised, about the lamps. The selected transistor has a maximum current of 5.5 A, but it is better to limit yourself to a smaller one. If you take incandescent bulbs of 100 W, then when powered through a diode, their power will be halved.

Take a current, for example, 4 A and determine the number of 100-watt lamps for this. The average current through the lamp will be about 0.23 A, taking into account the fact that the lamp operates for one half period. 4 / 0.23 = 17 lamps of 100 watts each. In practice, there will be fewer bulbs, since incubators are usually insulated. In addition, too much heat will lead to emissions of elevated temperature.

After assembly, you need to check how the self-assembled thermostat works.

Adjusting the thermostat

The adjustment consists in testing the performance after installation and applying divisions to the scale in the following order:

  1. Graduation divisions.
  2. Divisions in increments of half a degree.
  3. The divisions in increments of 0.1 degrees.

One light bulb is included in the load, simply as a work indicator. The sensor is placed in a dry sand bath next to an exemplary thermometer. The bath, carefully and slowly, in order not to overheat, is heated on the hotplate switched on through LATR or another suitable power regulator.

Consider a single point calibration, for example 35 ° C. First, it is necessary to balance the temperature of the sensor and the reference thermometer in the bath. Then, rotating the potentiometer, mark with a pencil the points on the circle of the scale, where the lamp lights up and where it goes out. The middle can be marked by dividing 35 degrees.

Similarly, divisions are made for other values. It does not hurt to make a graduation for tenths of a degree, given that, after all, the scale will not be linear. After performing the calibration, it will be possible to estimate the hysteresis. It should be in the range of 0.1 ... 0.15 g. Celsius

The device will only be reliable if all connections are soldered carefully and the terminal clamp connections are clean and well tightened.

In the video, an expert talks about how to make a thermostat with your own hands.

The thermostat is an integral part of almost any incubator, and its design depends on how complex and bulky it is. Depending on the type of incubator, such a device of the required modification can be purchased ready-made or assembled by hand.

In ancient times…

In the first domestic and industrial incubators of the last century, the temperature was controlled using bimetallic relays. To remove the load and eliminate the effect of contact overheating, the heaters were turned on not directly, but through powerful power relays. Such a combination can be found in cheap models to this day. The simplicity of the scheme was the key to reliable operation, and any high school student could make such a thermostat for an incubator with his own hands.

All the positive aspects were negated by the low resolution and complexity of the adjustment. The temperature in the process of incubation must be reduced according to the schedule in increments of 0.5 ° C, and it is very difficult to do this with an exactly adjusting screw on the relay located inside the incubator. As a rule, the temperature remained constant throughout the "incubation" period, which led to a decrease in hatchability. Designs with an adjustment knob and a graduated scale were more convenient, but the accuracy of retention was reduced by ± 1-2˚С.

First electronic

The analog temperature controller for an incubator is somewhat more complicated. Usually, this term implies the type of control in which the level of voltage taken from the sensor is directly compared with the reference level. The load is switched on / off in a pulsed mode, depending on the difference in voltage levels. The accuracy of adjusting even simple circuits is within 0.3-0.5 -0С, and when using operational amplifiers, the accuracy increases to 0.1-0.05˚С.

For a rough installation of the required mode on the instrument case there is a jackal. The stability of the readings depends little on the room temperature and the mains voltage drops. To eliminate the influence of interference, the sensor is connected with a shielded wire of the minimum required length. This category includes rarely encountered models with analog load control. The heating element in them is turned on constantly, and the temperature is regulated by a smooth change in power.

A good example is the TRi-02 model - an analog thermostat for an incubator, the price of which does not exceed 1,500 rubles. Since the 90s of the last century, they were equipped with serial incubators. The device is simple to operate and is equipped with a remote sensor with a 1 m cable, power cord and meter load wire. Technical specifications:

  1. Load power at standard mains voltage from 5 to 500 watts.
  2. The adjusting range is 36-41˚С with accuracy not worse than ± 0.1˚С.
  3. Ambient temperature from 15 to 35 доС, permissible humidity up to 80%.
  4. Contactless triac inclusion of the load.
  5. The overall dimensions of the case are 120x80x50 mm.

In numbers it is always more accurate.

Greater precision adjustments provide digital measuring devices. The classic digital thermostat for an incubator differs from the analog method of signal processing. The voltage removed from the sensor passes an analog-to-digital converter (ADC) and only then enters the comparison unit. Initially set in digital form, the value of the required temperature is compared with that obtained from the sensor, and the corresponding command is sent to the control device.

Such a structure significantly improves the measurement accuracy, minimally dependent on ambient temperature and interference. Stability and sensitivity are usually limited by the capabilities of the sensor itself and the system capacity. The digital signal allows you to display the value of the current temperature on the LED or LCD display without complicating the circuitry. A significant part of industrial models has advanced functionality, which we consider on the example of several modern devices.

The possibilities of the budget digital thermostat Ringder THC-220 is enough for a homemade incubator. Adjusting the temperature within 16-42˚С and an external power outlet for connecting the load allows you to use the device in the off-season - for example, to control the climate of the room.

For review, we give a brief description of the device:

  1. Текущая температура и влажность в районе датчика индицируются на ЖК-дисплее.
  2. Диапазон индицируемой температуры от -40˚С до 100˚С, влажности 0-99%.
  3. Выбранные режимы отображаются на экране в виде символов.
  4. Шаг установки температуры 0,1˚С.
  5. Возможность регулировки влажности до 99%.
  6. 24 часовой формат таймера с делением на день/ночь.
  7. Нагрузочная способность одного канала 1200 Вт.
  8. Точность поддержания температуры в больших помещениях ±1˚С.

Более сложную и дорогостоящую конструкцию представляет собой универсальный контроллер XM-18. The device is produced on the territory of the People's Republic of China, and comes to the Russian market in two versions - with English and Chinese interfaces. The export option for Western Europe is naturally preferable when choosing.

Mastering the device does not take much time. Depending on what temperature should be in the incubator, you can adjust the factory program with the help of 4 keys. On 4 screens of the front panel displays the current values ​​of temperature, humidity and additional operating parameters. Indication of active modes is carried out by 7 LEDs. Audible and visual alarms for dangerous deviations greatly facilitate monitoring. Device features:

  1. The working temperature range is 0-40.5 ° C with an accuracy of ± 0.1 ° C.
  2. Humidity adjustment 0-99% with an accuracy of ± 5%.
  3. The maximum load on the channel heater 1760 watts.
  4. The maximum load on the channels of humidity, motors and alarm no more than 220 watts.
  5. The interval between turning eggs 0-999 minutes.
  6. Cooling fan running time 0-999 sec. with an interval between the periods of 0-999 minutes.
  7. Allowable room temperature -10 to + 60˚С, relative humidity not more than 85%.

When choosing thermostats with an air temperature sensor for an incubator, consider the possibilities of your design. A small incubator with its head will be enough control of temperature and humidity, and most of the additional options of expensive equipment will remain unclaimed.

Thermostat - do it yourself

Despite the large selection of finished products, many people prefer to assemble a thermostat scheme for an incubator with their own hands. The simplest option presented below was one of the most popular amateur radio designs in the 1980s. A simple assembly and accessible element base were dragging the flaws - dependence on the room temperature and instability to network interference.

Radio amateur circuits on operational amplifiers often outperformed their industrial counterparts. One of such schemes, assembled at OU KR140UD6, can even be repeated for beginners. All the details are found in household radio equipment of the end of the last century. With good components, the circuit starts working immediately and needs only calibration. If desired, you can find similar solutions on other OU.

Now more and more circuits are being made on PIC controllers - programmable microcircuits, the functions of which are changed by flashing. The thermostats made on them are distinguished by simple circuitry, in functionality not inferior to the best industrial designs. The diagram below is for illustrative purposes only, as it requires corresponding firmware. If you have a programmer, on amateur forums it’s easy to download ready-made solutions along with the firmware code.

The response speed of the regulator directly depends on the mass of the thermal sensor, because an excessively massive body has a high inertia. You can “chop up” the sensitivity of a miniature thermistor or diode by putting a plastic cambric on the part. Sometimes for tightness it is filled with epoxy resin. For single-row designs with top heating, it is better to place the sensor directly above the surface of the eggs at an equal distance from the heating elements.

Incubation is not only profitable, but also fascinating. Combined with technical creativity, for many it becomes a hobby for life. Do not be afraid to experiment and wish you a successful implementation of projects!