Barograph. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Measuring technology

 Comments on the article

The device is designed to record changes in atmospheric pressure during the flight of a model aircraft. It is based on the MCS-51 family microcontroller and non-volatile memory chip. Analog-to-digital conversion is implemented in software. The recorded information can be transferred to a computer and used, for example, to plot the flight altitude.

Performing measurements is perhaps the most common "profession" of microcontrollers. In this case, the voltage proportional to the measured parameter is first converted into a digital equivalent - a multi-bit binary code. Upon completion of this operation, the microcontroller receives from the analog-to-digital converter (ADC) a signal of readiness to transfer the result to it in parallel or serial form.

Rice. 1 (click to enlarge)

However, such a solution is not always justified, since the need to use the ADC as a separate microcircuit or even built into the microcontroller inevitably increases the cost of the device, and sometimes its power consumption. Secondly, adding an ADC to the design of the microcircuit complicates the device and reduces its reliability, since it is required to organize many electrical connections between it and the microcontroller.

But often, especially with low requirements for the speed of analog-to-digital conversion, it can be implemented using a simple program for a cheap microcontroller that does not have a built-in ADC.

The barograph, whose circuit is shown in the figure, uses the still popular AT89C2051 (DD1) microcontroller without a built-in ADC, belonging to the MCS-51 family in terms of architecture and instruction set. Atmospheric pressure sensor - MPX4115A (B1). Proportional to the measured pressure, the output voltage of the sensor, amplified by the op-amp DA1.1, is fed to one of the inputs of the voltage comparator built into the microcontroller. At its other input, a linearly increasing voltage is supplied, which is formed on the capacitor C5 when it is charged with a stable source current on the zener diode VD1 and the transistor VT2. The deviation of the law of change of this voltage from the linear one does not exceed ±0,3%.

The result of the conversion is the number of pulses counted by the internal timer-counter of the microcontroller, received at its input from the moment the voltage on the capacitor begins to rise until the moment it is equal to the amplified sensor voltage recorded by the comparator. After that, the microcontroller generates a pulse at the output P1.4, which opens the transistor VT1. Capacitor C5 is discharged through resistor R10 and an open transistor, after which the measurement cycle is repeated.

The timer operates in Mode 0, it is eight-bit, its counting input receives pulses with the frequency of the microcontroller's crystal oscillator divided by 12, which have passed a preliminary five-bit divider. At the frequency of the quartz resonator ZQ1 Fkv = 11,059 MHz, the frequency of the counting pulses is equal to

Fsch \u12d Fkv / (2 * XNUMX⁵) = 11059/384 = 28,8 kHz.

Since the state of the prescaler at the end of the count is stored in the TNO register of the microcontroller, the total bit length of the conversion result reaches 13.

If the barograph is turned on with the SB1 button pressed, the conversion results are stored in the 24LC02B (DS1) non-volatile memory chip connected to the microcontroller via the I2C interface. If, at the time of power-on, the SB1 button was not pressed, all information previously recorded in non-volatile memory is sent byte-by-byte through the XS1 connector to the RXD input of the computer's COM port. Any terminal program running on the computer can accept it.

The shaper of the output signal corresponding to the RS-232 standard is the op-amp DA1.2, included as a comparator. Although the version of the microcontroller program offered to readers does not provide for receiving information from a computer, the level converter required for this is available in the barograph. It is assembled on a transistor VT3.

The XS1 connector must be connected to the computer's COM port connector directly or using a "modem" (without crossover) cable. In most cases, it is enough to have only two wires in the cable - the RXD and SG circuits. To organize the reception of information transmitted by the computer by the barograph, one more, TXD, will be required. The remaining five wires and jumpers between the contacts of the XS1 connector are only needed for the correct operation of computer programs that generate the DTR and RTS control signals and analyze the state of the DCD, DSR and CTS inputs. In the microcontroller program, the speed of its serial port is set to 9600 baud.

The barograph is powered by two galvanic batteries with a voltage of 9 V (for example, "Krona"). When developing the program, examples of the implementation of communication via the I2C interface of the AT89C2051 microcontroller with a memory chip were used on the Atmel website.

Author: K. Dunaev

See other articles Section Measuring technology.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

The world's tallest astronomical observatory opened 04.05.2024

Exploring space and its mysteries is a task that attracts the attention of astronomers from all over the world. In the fresh air of the high mountains, far from city light pollution, the stars and planets reveal their secrets with greater clarity. A new page is opening in the history of astronomy with the opening of the world's highest astronomical observatory - the Atacama Observatory of the University of Tokyo. The Atacama Observatory, located at an altitude of 5640 meters above sea level, opens up new opportunities for astronomers in the study of space. This site has become the highest location for a ground-based telescope, providing researchers with a unique tool for studying infrared waves in the Universe. Although the high altitude location provides clearer skies and less interference from the atmosphere, building an observatory on a high mountain poses enormous difficulties and challenges. However, despite the difficulties, the new observatory opens up broad research prospects for astronomers. ... >>

Controlling objects using air currents 04.05.2024

The development of robotics continues to open up new prospects for us in the field of automation and control of various objects. Recently, Finnish scientists presented an innovative approach to controlling humanoid robots using air currents. This method promises to revolutionize the way objects are manipulated and open new horizons in the field of robotics. The idea of ​​controlling objects using air currents is not new, but until recently, implementing such concepts remained a challenge. Finnish researchers have developed an innovative method that allows robots to manipulate objects using special air jets as "air fingers". The air flow control algorithm, developed by a team of specialists, is based on a thorough study of the movement of objects in the air flow. The air jet control system, carried out using special motors, allows you to direct objects without resorting to physical ... >>

Purebred dogs get sick no more often than purebred dogs 03.05.2024

Caring for the health of our pets is an important aspect of the life of every dog ​​owner. However, there is a common assumption that purebred dogs are more susceptible to diseases compared to mixed dogs. New research led by researchers at the Texas School of Veterinary Medicine and Biomedical Sciences brings new perspective to this question. A study conducted by the Dog Aging Project (DAP) of more than 27 companion dogs found that purebred and mixed dogs were generally equally likely to experience various diseases. Although some breeds may be more susceptible to certain diseases, the overall diagnosis rate is virtually the same between both groups. The Dog Aging Project's chief veterinarian, Dr. Keith Creevy, notes that there are several well-known diseases that are more common in certain breeds of dogs, which supports the notion that purebred dogs are more susceptible to disease. ... >>

Random news from the Archive Hydrogen biobattery 17.06.2006 British scientists have replaced platinum in the fuel cell with enzymes. Typically, a fuel cell has a membrane, on both sides of which there are electrodes coated with a platinum catalyst. Thanks to him, a hydrogen molecule disintegrates on one electrode, and a water molecule gathers on the other. For those microorganisms that live by the oxidation of hydrogen, the same process, thanks to enzymes, goes much easier. Scientists have long tried to apply this biological method in a fuel cell. Another success in this matter was achieved by the group of Professor Fraser Armstrong from Oxford University. In the design proposed by him, enzymes isolated from a hydrogen-oxidizing microorganism are deposited on two electrodes. Since enzymes are selective, that is, each of them accelerates a single reaction, there is no need to separate the reacting gases with a special membrane. Namely, its extremely high price makes the fuel cell an expensive pleasure that no one can afford without the help of the state budget. In the Armstrong element, the electrodes are immersed directly in a vessel filled with air with the addition of a few percent hydrogen. And, as evidenced by the working electronic clock attached to the bioelement, they successfully generate electricity. Microbial enzymes are easy to obtain and much cheaper than platinum. In addition, carbon monoxide poisoning the platinum catalyst is harmless to them.

Other interesting news:

▪ CO2 emissions will save the Earth from the ice age

▪ The world's largest Cherenkov telescope launched

▪ The harm of music before bed

▪ New Year's Eve comes a second later

▪ Sleep doubles memory efficiency

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Preamplifiers. Article selection

▪ article It's a son of a bitch, but it's our son of a bitch. Popular expression

▪ article How correctly did Jules Verne predict the circumstances of the first flight to the moon? Detailed answer

▪ Alant article. Legends, cultivation, methods of application

▪ article Intercom on the network 220 V. Encyclopedia of radio electronics and electrical engineering

▪ article Controller for minimum and maximum voltage. 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