Microcontroller control device for the incubator. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Microcontrollers

 Comments on the article

The device offered to the attention of readers is one of the options developed by the author of devices for controlling a small-sized incubator. It provides temperature stabilization and periodic activation of the actuator motor to turn the trays. It can also be used as a precise temperature controller with the possibility of periodically connecting an additional load, such as a fan.

The device differs from the previously described ones in that it performs fully digital temperature control and stabilization with an accuracy of 0,1 °C and a variable hysteresis, and also allows you to adjust the operating time of the actuator within 1 ... 999 s and the pause between turning on the engine within 1 ...999 min.

The device consists of control and switching units connected by a five-wire cable.

The schematic diagram of the control unit is shown in fig. 1. It contains a DDI microcontroller that performs all the necessary operations for comparing temperature and counting time intervals, a DD2 decoder, HG1-HG3 indicators and two supply voltage regulators: DA1 - the digital part of the device and DA2 - analog.

The switching unit (Fig. 2) consists of two electronic keys, one of which (R22, U1, VD5, R24, VS1) is designed to turn the heater on and off (illuminating lamp EL1), and the other (R23, U2, VD6, R25, VS2) - electric motor of the actuator.

To measure the temperature, an integral temperature sensor DA3 with a linear dependence of the output voltage on temperature was used [1]. On transistors VT3, VT4, a 1 mA current generator is assembled to power DA3. The voltage taken from its output 1 is supplied to the voltage-frequency converter, made on the DA5 chip (iA02PP1 [2]).

Since the voltage at pin 1 of the DA3 sensor relative to its pin 2 depends on the temperature with a coefficient of 10 mV / K (K - Kelvin), to shift the readings to the Celsius scale, a reference voltage of +8 V is applied to pin 5 of DA2,732, taken from pin 3 of the stabilizer DA4

The pulses from pin 9 of the DA5 converter are fed to the shaper, assembled on transistors VT1, VT2 (see Fig. 1), amplified oscillations from its output are fed to the counting input RA4 DD1. The microcontroller measures the frequency of the incoming signal and controls the indicators HG1-HG3. The first of them displays tens, the second and third - units and tenths of a degree Celsius, respectively.

Control the device with buttons SB1-SB3. When you first press SB1 ("Installation"), the indicators display the value of the temperature of the lower limit (if it falls below this value, the heater will turn on). After releasing the button, the device enters the setting mode, as evidenced by the blinking of the indicator, which represents the modifiable digit of the parameter. Initially, the least significant digit (HG3) is available for change. The desired bit is selected by pressing the SB2 ("Select") button, and the desired value is set using SB3 ("+").

The next press of the SB1 button puts the device into the upper temperature limit setting mode (if it is exceeded, the heater turns off). The desired value is set by manipulating the same buttons SB2 and SB3.

After the third pressing of the SB1 button, the indicators display the time (in seconds) for which the tray rotation mechanism is activated after the next pause. The next press on SB1 displays for modification the interval (in minutes) between switching on the electric motor. If at least one of these parameters (work or pause time) is equal to zero, the actuator does not turn on.

Finally, the fifth press of the SB1 button puts the device into operation mode, and the current temperature value appears on the indicators. All set parameters are stored in the non-volatile memory of the DDI microcontroller. It should be noted that in the setting mode, temperature measurement and comparison are not performed.

The program codes for the DD1 microcontroller are shown in the table.

(click to enlarge)

The control and switching units, as well as the measuring part of the device (circled in Fig. 2 by a dash-dotted line) are mounted on separate prototyping boards of suitable sizes (printed boards were not developed).

It is permissible to use any small-sized unit that provides an output voltage of at least 12 V at a current of 150 mA as a power source for the device.

Instead of PIC16F84, microcontrollers PIC16F84A, PIC16CR84 or PIC16C84 can be used in the control unit. Fixed resistors R16 - R18 - with a tolerance of ± 1 ... 2% from the nominal value, the rest - with a tolerance of ± 10%, tuning resistors R19 and R20 - SPZ-19a, SPZ-39a or wire SP5-2. AOU115G optocouplers are replaceable with AOU115D, AOU1 V devices, ALS324B indicators - with similar imported ones with a common anode (at the same time, the resistance of resistors R5-R12 can be increased two to three times).

In addition to KU208G, triacs TS112-10, TS112-16 can be used in the switching unit. If the load power of the triac does not exceed 200 W, you can do without a heat sink, otherwise a ribbed heat sink is needed (with a switched power of up to 1 kW, its dimensions are approximately 60x50x25 mm).

The temperature sensor K1019ChT1 differs from that described in [1] K19Ml (foreign analogue of LM335) by the absence of a calibration output. When using K1019EM1, its output 3 is connected instead of output 2 K1019ChT1, output 2 - instead of output 1, and the calibration output is left free.

The VFC chip UA02PP1 is a modified analogue of the foreign LM331, the switching circuit of which is shown in fig. 3. In extreme cases, instead of UA0PP1, you can use KR1108PP1 by turning it on in accordance with the diagram in fig. 1, given in [3], and reducing the value of any of the frequency-setting elements by half (preferably capacitor C1). However, such a replacement will require the use of a bipolar power supply with a voltage of +15 and -15 V.

Setting up the device comes down to calibrating the measuring part.

To do this, the DA3 sensor is placed in melting snow or ice and the trimming resistor R19 sets zero readings of the indicators. Then the sensor, together with an accurate thermometer, is lowered into a thermos with water heated to a temperature of +30...40 °C. After some time, the trimming resistor R20 achieves the corresponding readings of the indicators. In some cases, it may be necessary to select the resistor R16 within 90 ... 110 kOhm.

Various device designs are possible. For example, the control unit is located outside the incubator and is connected by a five-wire cable to a switching device located inside the incubator chamber. In any case, it is recommended to make the measuring part in the form of a remote sensor installed above the trays and connected to the device with a three-wire cable. In the author's version, this unit is mounted on a small board and placed in a sealed plastic case.

Recommendations for the design of the actuator are given in [4]. It should be noted that due to the possibility of accurately setting the operating time of the engine, there is no need for a cam mechanism and contact switches on the shaft of the engine gearbox. During the adjustment of the device, it is only necessary to accurately select such an engine operation time so that the gearbox shaft rotates to the desired angle.

Literature

1. Biryukov. Thermal sensors K1019EM1, K1019EM1A. - Radio, 1996, No. 7, p. 59.
2. Technical description UA02PP1. -
3. Integrated voltage-frequency-voltage converter KR1108PP1 and its application. - Radio, 2001, No. 8, S. 51.
4. Grigoriev A. Incubator kinematics control unit. - Radio, 1999, No. 10, p. 32.

Author: A.Borisevich, Sevastopol, Ukraine

See other articles Section Microcontrollers.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

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 ... >>

The threat of space debris to the Earth's magnetic field 01.05.2024

More and more often we hear about an increase in the amount of space debris surrounding our planet. However, it is not only active satellites and spacecraft that contribute to this problem, but also debris from old missions. The growing number of satellites launched by companies like SpaceX creates not only opportunities for the development of the Internet, but also serious threats to space security. Experts are now turning their attention to the potential implications for the Earth's magnetic field. Dr. Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics emphasizes that companies are rapidly deploying satellite constellations, and the number of satellites could grow to 100 in the next decade. The rapid development of these cosmic armadas of satellites can lead to contamination of the Earth's plasma environment with dangerous debris and a threat to the stability of the magnetosphere. Metal debris from used rockets can disrupt the ionosphere and magnetosphere. Both of these systems play a key role in protecting the atmosphere and maintaining ... >>

Solidification of bulk substances 30.04.2024

There are quite a few mysteries in the world of science, and one of them is the strange behavior of bulk materials. They may behave like a solid but suddenly turn into a flowing liquid. This phenomenon has attracted the attention of many researchers, and we may finally be getting closer to solving this mystery. Imagine sand in an hourglass. It usually flows freely, but in some cases its particles begin to get stuck, turning from a liquid to a solid. This transition has important implications for many areas, from drug production to construction. Researchers from the USA have attempted to describe this phenomenon and come closer to understanding it. In the study, the scientists conducted simulations in the laboratory using data from bags of polystyrene beads. They found that the vibrations within these sets had specific frequencies, meaning that only certain types of vibrations could travel through the material. Received ... >>

Random news from the Archive China banned cryptocurrency 09.09.2017 The People's Bank of China has announced the completion of its investigation into the initial offering of cryptocurrency tokens (Initial coin offering, ICO), Bloomberg news agency reported, citing an official statement from the Central Bank of China. According to the regulator, more than 90% of ICOs are potential violators of laws on illegal financing and combating fraud in the financial sector. The share of projects that raise funds for investment does not exceed 1%, representatives of the Central Bank of China said. According to the official position of the Central Bank of China, all ICOs in the country are now considered illegal. The regulator intends to severely punish such violations in the future and at the same time threatened with legal consequences for already completed ICOs. The Central Bank of China also insists that organizations and individuals who have already raised money on the placement of cryptocurrency tokens should immediately return the funds to investors, although they did not specify the mechanism for such a return. According to the order of the Central Bank of China, digital tokens are not payment instruments issued by monetary institutions and do not have the legal and legal status of money, therefore it is strictly forbidden to use them as funds for market and bank settlements. Online platforms that offered initial placement and exchange services involving cryptocurrencies will be closed, the regulator promised to leave violators of the order without licenses. The same measures threaten banks, which are now also prohibited from providing ICO services. In addition, the People's Bank of China also intends to enforce the removal of all mobile applications from the relevant trading platforms.

Other interesting news:

▪ Flying racing electric car Alauda Airspeeder Mk3

▪ Plankton of the Black Sea rids the Earth of carbon

▪ Solar power plant on a roll

▪ Microsoft Multitouch Touch Mouse

▪ Cyborg transistor

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Factory technology at home. Article selection

▪ article by Gene Lollobrigida. Famous aphorisms

▪ article What is Impressionism? Detailed answer

▪ article Assembler of wood products. Standard instruction on labor protection

▪ article Antenna current indicator. Encyclopedia of radio electronics and electrical engineering

▪ article Simple converter, 12/220 volts. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

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

www.diagram.com.ua
2000-2024