Learn how to create a platform with information from mechanized sets

It is possible to create your own data acquisition system using Arduino, a platform that allows you to obtain various information about mechanized sets.

Data acquisition and automation are essential activities in areas where there is a need to present, to the observer, the values ​​of variables and parameters that are being measured and to carry out decision making based on the values, controlling processes in real time, sending signals to a peripheral, controlling doors, actuators, motors, among other applications.

Since data collection is one of the most tedious steps in a research cycle, the acquisition system can be automated without compromising accuracy with the advantages of reducing errors generated by data transcription, eliminating operator-induced variations in data collection processes and increase the data reading rate.

In agriculture, for example, several researchers have worked in different areas, using some type of acquisition system in order to monitor events in their research. In addition to scientific application, data monitoring is also intensively applied to agricultural machines and systems, such as tractors, self-propelled harvesters, implements and product processing, drying and storage units. The versatility of an acquisition system is also important, allowing it to be adapted for different research without a large increase in costs.

Sensors are installed in the equipment that you want to monitor or control, which transform a physical phenomenon into electrical signals. The electrical signals produced vary depending on the physical parameters being monitored and must be conditioned to provide appropriate signals to the data acquisition board. Signal conditioning accessories amplify, isolate, filter and excite signals so that they are suitable for acquisition boards. Once conditioned and worked into the desired shape, the signals can be read on computers, with specific boards installed, and stored in different forms, such as text files. Position, speed, acceleration, force, flow, torque, pulse, GPS, temperature and humidity sensors are some examples of transducers used in a data acquisition system.

LOW COST ACQUISITION SYSTEM

The search for low-cost solutions is, nowadays, a requirement when it comes to purchasing equipment for companies and institutions - this search becomes even more imminent when commercially available solutions are expensive and do not fully reflect the objectives for which they are intended.

Arduino is an example of a low-cost system. Created in 2005 to facilitate the learning of electronics and programming for students on a design course by professor Massimo Banzi, the Arduino is an acquisition board based on a very versatile microcontroller that enhances its functions beyond a simple passive data acquisition interface. , being able to operate alone in the control of several devices and thus having applications in embedded instrumentation and robotics.

The entire electronic project, including the platform for developing control programs, is free and public access. An extensive international community has formed around the Arduino project, involving technicians and developers from different areas, students and teachers, hobbyists, visual artists, who interact through websites, blogs and events sponsored by different institutions around the world.

On the Web, it is possible to find abundant documentation about applications and the exchange of experiences between users. This international network of users, very cooperative, is a very auspicious fact for beginners who would otherwise encounter natural difficulties in using this technology. Another positive fact is that, currently, different versions of the Arduino board can be found on the national market, with very affordable prices, or even assembly instructions based on basic electronic components, which can meet the interest of professionals with greater qualifications. in electronics.

Arduino is an open source, easy-to-use hardware platform, ideal for creating devices that allow interaction with the environment, devices that use different types of sensors as input, and LEDs, motors, displays, speakers, etc. as output. , thus creating unlimited possibilities.

The platform uses a simple layer of software implemented on the board and a friendly interface on the computer that uses the Processing language, based on the C/C++ language, which is also open source. Through the software, there is no need to use programmers for the chip, making its use even easier, as it does not require compilers or additional hardware. In this development environment, libraries are available that allow interfacing with other hardware, allowing the complete development of simple or complex applications in any area. One of the simplest board models available on the market is the Arduino UNO.

SYSTEM DEVELOPMENT

Using an Arduino board, a specific acquisition system can be quickly assembled, according to operational demand, aiming for low cost and reliability. Under this assumption, this article proposes the assembly of a simple fuel flow measurement system. For its development, the Arduino UNO R3 model board and a computer for programming and data storage were used as hardware. The program used was the Arduino 1.0.5 development environment, in the installation version for the Windows operating system.

Using the Arduino development environment, an application was developed to collect and present fluid flow data on the USB serial port, while read by the flow sensor. To determine the fluid flow, the Oval M-III LSF45L0-M2 model flow sensor was used, with magnetic sensor, 10ml/pulse reading unit, maximum flow of 500L/h, 12V to 24V power supply. direct current (VCC), maximum consumption of 10mA and output pulse type 0/1 = maximum 0,5VDC/6,2 to 7,6VDC, with minimum resistance of 10kΩ.

The sensor was connected to a Protoboard 840 terminal board and, using jumpers and a USB AB cable, the sensor, Arduino board and computer were connected.

The data acquisition system, after being implemented, was tested with the purpose of verifying the accuracy of the data coming from the sensor and calibrating it.

The sensor was evaluated using the measurement of previously determined volumes of water, 250ml, 500ml, 1.000ml and 2.000ml, at a temperature of 20°C. To determine the volume, a graduated measuring cylinder with a capacity of 250ml, ± 2ml was used. The data from the sensor was collected through the computer's USB serial port, and was displayed on the Arduino program screen.

The developed application begins its execution with the variable declaration structure, defining the input port connected to the sensor and the initial values ​​of the variables that will be used in the system. Then, it carries out the Setup structure, defining the port's operating mode as input (Input) and starting serial transmission with definition of the data transmission rate of 9600bauds. Next, the Loop structure starts, counting the pulses, converting them to volume, where one pulse corresponds to 10ml, and printing the output from the Arduino board's serial port to the PC's input on the serial screen. The application used to determine the fluid flow used the source code.

To evaluate the system, the flow sensor was connected to the implemented data acquisition system and evaluated in the laboratory. The values ​​determined by the graduated cylinder and the values ​​determined by the flow sensor presented adjustment estimated by the linear equation y = 0,0043 + 0,9927x, with coefficient of determination r² = 0,9999, with the model being statistically significant at the 1% probability level. The scatter diagram showed a positive correlation of the variables.

CONSIDERATIONS

It was concluded that the developed application presented ease of operation of the system, allowing speed in the data acquisition operation, and the ability to combine the implemented system to meet the demands of different researches, and can be used in different types of agricultural machines and in different data acquisition needs, such as attributes of force, torque, speed, position, axis rotation frequency, among other examples.

In a more advanced application, it is suggested to install the flow sensor in the fuel supply line of an agricultural tractor to carry out field operations and determine the tractor's fuel consumption in agricultural work, in addition, the installation of a display digital on the Protoboard board, connected to the Arduino, to check, in real time, the volume consumed and the hourly consumption.

Other sensors can be connected to this same board, such as force, torque, radar and GPS, and an SD module with a memory card can be installed on the Arduino main board, with the purpose of storing data without the need for a Connected PC and power supply from the board with a 9V battery, or from the tractor itself, allows it to function properly in any working condition.

The price of an Arduino UNO R3 board is R$79,00, a GPS module for the Arduino costs R$299,00, a microSD card module costs R$69,00 and a basic 16-character display for two lines costs R$29,00. Adding all the equipment mentioned, the estimated cost to implement the project is below R$500,00.

Ricardo Ferreira Garcia, Rodrigo Cavalcante de Lima, Uenf; Alan Carvalho Galante, FSMA, INSG and FeMASS 

Article published in issue 147 of Cultivar Máquinas.