Thermostat for mini-incubator. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

Thermostat for mini-incubator

Free technical library

Encyclopedia of radio electronics and electrical engineering / Power regulators, thermometers, heat stabilizers

Comments on the article

Several types of mini-incubators are produced in the CIS. The temperature in them is maintained by a mechanical thermostat, there is no indication of exceeding the limit temperature inside the incubator. To replace the mechanical thermostat, the proposed electronic one (Fig. 1) with additional service functions is intended. The accuracy of maintaining the temperature inside the mini-incubator is 0,2°C. The temperature can be adjusted within 37...39°С. The performance of the thermostat is maintained when the mains voltage fluctuates within ± 20% of the nominal value.

Fig.1. Schematic diagram of the thermostat (click to enlarge)

The thermostat consists of:

thermoresistive bridge R1...R6;
two comparators on operational amplifiers DA1, DA2;
display unit "heating" on LED HL3;
node indication "norm" on the LED HL2;
node indication "overheating" on the LED HL1;
current control unit through the heating element on the HL4 LED;
node for sound indication of exceeding the limit temperature on VT6...VT9, VT11 and piezoelectric BQ1;
a power switch on a VT10 transistor that provides current through the heating element.

The circuit is powered by a transformerless circuit with quenching capacitors C8, C9. The voltage is rectified by the diode bridge VD2, filtered by capacitors C6, C7, stabilized by the zener diode VD1. The diode bridge VD3...VD6 is used to supply voltage of the required polarity to the transistor VT10. A threshold element is assembled on the DA2 comparator, which includes the heating of the EK1 element. When the air temperature inside the incubator is below the threshold set by resistor R2, pin 6 of DA2 is high. Amplified by the emitter follower on VT3, VT4, the signal through R11, HL3 enters the base of the transistor VT10, the transistor opens, and the current flows through the heating element EK1. The voltage drop across the resistor R17 is enough to light the HL4 LED, which controls the flow of current through the heating element.

At the same time, the HL3 LED indicates the inclusion of the "Heating" mode. When the set temperature is reached, the voltage at terminal 6 DA2 decreases, VT10 closes, the heating element EK1 is de-energized, the HL3, HL4 LEDs go out, and the HL2 LED lights up (indication of the "Norm" mode). When the temperature inside the incubator drops, the "Heating" mode is switched on again. For a clearer switching between modes, a positive feedback is introduced in the comparator using a resistor R8.

So, changing each other, the "Heating" and "Normal" modes allow you to bring out the chicks. But, as a result of a short circuit of the VT10 transistor or for some other reason, the temperature inside the incubator may exceed 39,4 ° C. Overheating above this temperature is dangerous for the development of embryos. In the last days of incubation, it causes mass death of embryos [1]. To prevent this situation, another comparator was introduced into the circuit on the operational amplifier DA1. It switches when the temperature reaches 39°C. In this case, the HL1 LED lights up, and the key on the VT5 transistor opens. A modified multivibrator with a high load capacity is assembled on transistors VT6 ... VT9. This low-frequency relaxation oscillator serves as a modulating high-tone self-oscillator based on a VT11 transistor and a BQ1 piezo call. In this mode, the emitter emits an intermittent alarm signal. To provide better visual control over the operating modes of the thermostat, the current through the LEDs HL1...HL3 is chosen relatively large. Since the output current of the op-amp DA1, DA2 is not enough for their bright glow, amplifiers based on transistors VT1 ... VT4 are introduced into the circuit.

Details

Resistors R3 ... R6 must be used highly stable, for example, type C2-29, thermistor R1 - type MMT-1, trimmer resistor R2 - SP5-16VA-0,25 W. The remaining resistors can be MLT, C2-23, C2-33. Capacitors C1, C2, C7 - small-sized, ceramic; capacitors C8, C9 - type K73-17. Capacitors C4 ... C6 - K50-35. Operational amplifiers can be replaced by K140UD6 or KR140UD708. Transistors VT1 ... VT9, VT11 can be replaced with other low-power silicon of the corresponding structure. The VT10 transistor can be replaced with a powerful composite high-voltage one. The zener diode must be 9 ... 10 V. The diode bridge VD2 can be replaced with a bridge of individual diodes of the KD209A type, VD3 ... VD6 can be replaced with the same diodes.

Establishment the thermostat is as follows. The tone generator is pre-assembled on VT11 and BQ1 on the breadboard and the resistance of the resistors R21, R22 is specified for reliable generation, then these elements are installed on the working board. The thermistor is mounted inside the incubator. Connect the heater EK1 with a power of 30 ... 35 W to the board. As a heater, you can use 4 series-connected 60-watt incandescent lamps or heating elements. Plug in the incubator. By controlling the air temperature inside the incubator with a thermometer with a division value of 0,1 ° C, for example, TL-4 (GOST 215-73), the threshold for turning on the heating element with resistor R2 is set at a temperature of 37,7 ... 38 ° C. After half an hour of operation of the incubator, the switching threshold is specified. Then close the conclusions of the collector-emitter of the transistor VT10. At a temperature of 39 ° C, the light and sound alarms should turn on. The switching threshold is set by selecting R5. By selecting R17, the desired brightness of the HL4 LED is set. On this, the adjustment of the thermostat can be considered complete.

Literature

What you need to know about poultry farming. Recommendations to owners of household incubator "Kvochka".

Author: O. Belousov, Cherkasy; Publication: radioradar.net

See other articles Section Power regulators, thermometers, heat stabilizers.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive

Leisure time has a detrimental effect on a person 23.01.2023

The best option is to do nothing - no more than two hours a day.

American researchers from the University of California and Pennsylvania found that excess free time has a negative effect on a person. In particular, the feeling of his well-being.

Scientists analyzed data from two surveys of more than 35 Americans. In which the participants talked in detail about what they did during the previous day and how it affected them.

It turned out that the state of health improved with the increase in free time, but it was no more than two hours. But after five hours of free time, the state of health, on the contrary, worsened.

Two online experiments were also conducted, in which more than six thousand people took part.

For six months, each participant received from 15 minutes to seven hours of free time.

The experiment showed that people with the minimum and maximum time felt worse.

Other interesting news:

▪ Bill Gates will create a supercow

▪ Digital TV Tuner for Xbox One

▪ Ecological packaging from tomato leaves

▪ ASRock Rack TRX40D8-2N2T motherboard

▪ The concentration of carbon in the air has reached a record high

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Metal detectors. Article selection

▪ article Cadmeian victory. Popular expression

▪ article What is a mold and casting mold? Detailed answer

▪ article Tractor driver (tractor driver). Standard instruction on labor protection

▪ article Low-noise amplifier at 144 MHz. Encyclopedia of radio electronics and electrical engineering

▪ article A simple lithium-ion battery tester. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews