is always more accurateThe thermostat for the incubator should provide accuracy of ± 0.1˚С, with the possibility of its change in the range from 35 to 39˚С.This requirement is met by the majority of commercially available digital and analog devices. Sufficiently accurate thermostat can be made at home, subject to elementary knowledge of electronics and the ability to hold a soldering iron. In ancient times. ..
In the first household and industrial incubators of the last century, the temperature was regulated using bimetallic relays. To remove the load and eliminate the effect of overheating of the contacts, 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 precisely with an adjusting screw on a 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.
The first electronic
. An analog temperature controller for an incubator is somewhat more complex. Usually, this term implies a 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 in the range of 0.3-0.5 ˚С, and when using operational amplifiers, the accuracy rises to 0.1-0.05С.
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For a rough installation of the required mode on the body of the device there is a jackal. The stability of the readings depends little on the indoor 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 parameters:
- Load power at standard mains voltage from 5 to 500 watts.
- Adjustment range - 36-41˚С with accuracy not worse than ± 0.1˚С.
- Ambient temperature from 15 to 35˚С, permissible humidity up to 80%.
- Contactless triac inclusion of the load.
- The overall dimensions of the case are 120x80x50 mm.
In figures it is always more accurate.
. Digital adjustment devices provide greater accuracy of adjustment. 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.
This structure significantly improves the measurement accuracy, minimally dependent on ambient temperature and noise. 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 a LED or liquid crystal 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 Ringder THC-220 budget digital thermostat features are enough for a homemade home 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 offseason - for example, to control the climate of the room.
For acquaintance we give brief characteristics of the device:
- The current temperature and humidity around the sensor are displayed on the LCD display.
- Display temperature range from -40 отС to 100˚С, humidity 0-99%.
- The selected modes are displayed on the screen as symbols.
- Temperature setting step 0.1˚С.
- Ability to adjust humidity up to 99%.
- 24 hour clock format with division by day / night.
- Load capacity of one channel 1200 watts.
- Accuracy of maintaining temperature in large rooms ± 1˚С.
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A more complex and expensive design is a universal controller 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:
- . Operating temperature range 0-40.5˚С with accuracy ± 0.1˚С.
- Adjustment of humidity 0-99% with an accuracy of ± 5%.
- Maximum load on the heater channel 1760 watts.
- The maximum load on the humidity channels, motors and alarms is not more than 220 watts.
- Interval between egg turning 0-999 min.
- Cooling fan runtime 0-999 sec.with an interval between the periods of 0-999 min.
- Permissible room temperature -10 to + 60˚С, relative humidity not more than 85%.
When choosing temperature controllers 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 advanced options of expensive equipment will remain unclaimed.
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Thermostat - with your own hands
Despite the large selection of finished products, many people prefer to assemble a thermostat for their own hands. The simplest option presented below was one of the most popular amateur radio designs in the 1980s. The simple assembly and the available element base were dragging the flaws - dependence on the room temperature and instability to network interference. 
Amateur radio circuits on operational amplifiers often outperformed industrial analogues. 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 elements, 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 chips, whose functions are changed by flashing. The thermostats performed 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 appropriate 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!
Thermostat Review for Incubator - Video
