Measuring CO2 with an Arduino: Creating a Low-Cost, Pocket-Sized

Technology Report Cite This: J. Chem. Educ. XXXX, XXX, XXX−XXX

pubs.acs.org/jchemeduc

Measuring CO2 with an Arduino: Creating a Low-Cost, Pocket-Sized Device with Flexible Applications That Yields Benefits for Students and Schools Hernan Pino,*,† Vanesa Pastor,† Carme Grimalt-Á lvaro,‡ and Víctor López‡ †

Learn It With Us (LIWU), Avinguda de la Concordia 9, 1-1, 08206 Sabadell, Barcelona, Spain Centre de Recerca per a l’Educació Científica i Matemàtica (CRECIM), Edifici GL-304, Campus de la Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain

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‡

S Supporting Information *

ABSTRACT: In this article, a low-cost and pocket-sized setup for measuring CO2 is presented. This setup is based on Arduinos, making it economic and open to modifications or improvements that satisfy other needs. It is composed of an Arduino board, a CO2 sensor, an SDcard module, and a control panel. The device has been tested in three different experimental contexts that are typically used in primary and secondary science education: chemical reactions, plant photosynthesis and respiration, and gas diffusion. Results show major potential for the device, both for promoting students’ model-based inquiry and for encouraging students to build their own devices and develop engineering practices. The other advantages of the proposal, compared with commercial data loggers, are also discussed. KEYWORDS: High School/Introductory Chemistry, General Public, Demonstrations, Interdisciplinary/Multidisciplinary, Computer-Based Learning, Laboratory Computing/Interfacing

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INTRODUCTION Carbon dioxide is one of the trace gases in the atmosphere, and because of its harmless properties and presence in many common phenomena, it can be a very useful compound for learning different topics and in different contexts in primary and secondary schools. Several educational experiences using CO2 can be identified in the literature. For example, the study of how CO2 is formed as a product of a chemical reaction or behaves under particular environmental conditions, such as pressure or temperature, can help students to develop and refine their ideas about the particle model of matter in chemistry.1 In other school subjects, such as biology, the study of CO2 can be related to animal and plant respiration and can be used to help students to construct models of life.1 In environmental sciences, CO2 can also be used to study the greenhouse effect while constructing a light−atmosphere interaction model.2 These examples and many others involving CO2 can help to connect the learning experience to a real-life contexts3 and offer an opportunity for students to overcome their most common misconceptions about gases and matter− energy interactions. To make the most of these educational opportunities, teachers need to know how to measure CO2 with an appropriate level of accuracy, which can often present a challenge because of the limited resources available at most schools.4 Traditionally, CO2 has been measured roughly by solubilization in a particular water solution with indirect © XXXX American Chemical Society and Division of Chemical Education, Inc.

measurements of its effects (e.g., studying the precipitation of CaCO3 from the reaction of CO2 in limewater5 or measuring the acidification of water with a pH indicator). However, these methods are not very accurate and do not make it easy to study the variation in CO2 concentration over time. Data loggers, which have gradually been introduced to schools since the 1990s,6 have opened up new possibilities for indirectly measuring CO2 with pH electrodes or infrared (IR)-absorption sensors in water. Instruments to directly measure the concentration of CO2 gas in the atmosphere or in a container have also been developed; these calculate how much IR light is absorbed as it passes through an air sample.7 The use of sensors has provided higher levels of accuracy and, in the case of gas sensors, the possibility to measure CO2-gas variations in a sample over time. Moreover, some of these devices can also display real-time graphics, providing immediate feedback to students about the results of their experiments and avoiding time-consuming manual data acquisition and data-recording tasks. This has been viewed as one of their major educational benefits in school science classes.8 However, commercial sensors are usually too expensive for schools,6 which is why most schools still use limewater and titrations with pH indicators as the main method for measuring CO2 in water.9 Received: June 21, 2018 Revised: November 29, 2018

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DOI: 10.1021/acs.jchemed.8b00473 J. Chem. Educ. XXXX, XXX, XXX−XXX

Journal of Chemical Education

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Figure 1. Photo of the proposed device (left) and diagram of the proposed CO2 device (right). (A−D) Four principal elements: (A) Arduino board, (B) CO2 sensor, (C) SD-card module, and (D) control panel.

Figure 2. Experimental setup used to measure the CO2 produced in a 1 mg of NaHCO3 and the concentration of the acid reaction (left). Graph obtained (right). Marker 1 represents the time when 1 mg of NaHCO3 was placed in the container, and marker 2 represents the time when the saturation level was reached.

education.19 However, these proposals entail a high level of technical knowledge in their setups, which is an especially large challenge and barrier for primary-school teachers,20 or are mostly focused on the technical description of its complex configuration, disconnecting the setup from its educational applications. In order to help teachers make the most of Arduinos’ components in their science lessons, in this proposal we present a step-by-step configuration of a simple device that measures CO2 concentrations in air and automatically saves the data obtained, as well as three school science activities where it can be used.

For all these reasons, educators have recently turned to Arduino microcontroller boards, which can be connected to a wide variety of low-cost sensors to produce highly accurate and reliable measurements. Some proposals for the use of Arduinos for chemical measurements can be found in the literature. For example, Kubinova and Š legr have recently defined the term ChemDuino as the general practice of applying Arduinos to improving chemistry teaching and learning.10 Other authors have used this term and certain sensors to measure temperature, pressure, and pH levels, combining them with Excel or Power Point in other studies for real-time measurements.11 pH determination with Arduinos is one of the most widespread uses of the measuring device, whether using an open-source potentiometric instrument with Bluetooth wireless connectivity for pH-determination experiments12 or other more straightforward setups.13 Other examples of projects using Arduinos for chemistry education have focused on the construction of photometers,14 as well as automated titrators, nanoliter-volume-dispensing systems, and generic control devices for automated essays,15,16 or on general dataacquisition devices that can be implemented with a variety of instruments to conduct a variety of experiments.17 All these proposals show the versatility of applications that Arduinos offer18 for chemistry education, and they are in line with recent trends and the influence of the maker movement in

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TECHNICAL DESCRIPTION Our proposal is a CO2 device that logs the data from the CO2 sensor onto an SD card for further analysis. The aim is to keep this design as simple as possible, making it easy to implement and affordable for all educational centers. This device is composed of four principal elements (Figure 1): (A) The first component is an Arduino board, a microcontroller board based on the ATmega328 microprocessor. This part controls the other components that are going to be used. (B) Next is the CO 2 sensor for measuring the CO 2 concentration in the air. B



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Figure 3. Left: Experimental setup used to measure CO2 concentration during plant photosynthesis and respiration (left). Graph obtained (right). Marker 1 represents the time when the measurement is stabilized and the leaves are directly in the sun, marker 2 represents the time when the students cover the container with a translucent cloth, and marker 3 represents the time when the students cover the container with a black cloth.

Figure 4. Experimental setup used to measure the CO2 concentration in a room with a window (left). Graph obtained (right). Marker 1 represents the time when the students open the window to ventilate the room, and marker 2 represents the time when the students close the window, leaving it slightly open.

In the first activity, students measure how different factors, such as the concentration, temperature, and agitation of the reagents, influence the rate of CO2 production in a typical acid−base reaction (Figure 2). The sensor is placed inside a closed container with a HCl solution in a beaker. When 1 mg of NaHCO3 is placed in the container (see Figure 2, marker 1), the concentration of CO2 quickly rises, before reaching a saturation level (see Figure 2, marker 2). This measurement allows students to identify the sudden increase in CO2 concentration inside the container and interpret the different slopes of the obtained graphs in light of the kinetic theory. The sensor shows some limitations with inertia (the velocity of the reaction is faster than the velocity of measurement). For this reason, in this experiment, care should be taken with the initial quantities to ensure that the reaction occurs within a considerable amount of time (>15 s) and with colder reagents when studying the effect of temperature of the rate of CO2 production. The second activity proposes that students should measure the variation of CO2 in plant photosynthesis and respiration (Figure 3). The sensor is placed inside a closed container with tree leaves, which initially has a high CO2 concentration. At the beginning of the measurement, the container is illuminated by the sun, which produces a decrease in the CO2 concentration (see Figure 3, marker 1 to marker 2). After a brief period of time (see Figure 3, marker 2), the students cover the container with a translucent cloth to decrease the intensity of the sunlight the leaves are receiving. At this point, the rate of the decrease of CO2 concentration diminishes, but the concen-

(C) Third is the SD-card module with the corresponding memory card for logging the data from the sensor in a CSV file. (D) The final component is the control panel, consisting of a breadboard with an RGB LED and a switch. This component is used to switch the CO2 sensor on or off, and the LED light indicates when the sensor is off, initializing, or taking and saving measurements. These four elements are connected via jumper wires to the Arduino board, which in turn is connected to a standard USB port on any laptop or desktop computer to supply power and enable data acquisition. Others power sources for the Arduino, such as mains or battery, are also possible. Moreover, connecting it to a battery will make it mobile. Though not shown here, a box enclosure can be used to protect the device. Before starting CO2 measurements, the code must be loaded onto the Arduino board. The details of how to connect to the device, load the code, and obtain and plot the data are explained in the Supporting Information. Although this article proposes one construction of the device and sketch code, optimizations of the setup are always possible.

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THREE EXAMPLES OF EDUCATIONAL ACTIVITIES

We now present three examples of educational activities implemented in different educational scenarios in order to show how suitable this measurement system is for different school inquiry activities. C



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Information Section 1). At the school level, these effects are not relevant, but at a professional level, they can lead to excessive error.

tration still decreases. Around 100 s (see Figure 3, marker 3), the students cover the container with a black cloth so that leaves are no longer in the sun. At this point, the CO2 concentration begins to increase. In contrast with the previous activity, in this case, no limitations in terms of measurement can be found. Instead, the graphical representation offers very valuable information for calculating and comparing the CO2 absorption and emission of the leaves. However, as the sensor shows some limitations with inertia in the measurement, some seconds of stabilization are required at the beginning of the experiment (see Figure 3, before marker 1). The third activity consists of measuring the CO 2 concentration in a room with a window (see Figure 4). The measurement begins when some people have already been in the room for a period of time. After a few minutes, the students open the window to ventilate the room (see Figure 4, marker 1), and the CO2 level rapidly decreases. After 3 min, the students close the window again, but this time they leave it slightly open (see Figure 4, marker 2). A dynamic equilibrium between the CO2 emissions of the people in the room and the slight ventilation can now be observed. In our experience, these kinds of activities offer ample opportunities to discuss with students how, why, and when they should open the windows in their schools.

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CONCLUSIONS We have presented a device composed of an Arduino board, a CO2 sensor, an SD-card module, and a control panel that allows easy measurement of CO2 in a variety of phenomena. The device has strong potential value for primary- and secondary-school science education because of its low cost and small size combined with its good level of accuracy and reliability in the measurements. The device can be also used from different educational approaches, such as the modelbased-inquiry approach (challenging students to use the experimental results to revise and improve their explanatory models) or the maker approach (challenging students to build their own device).

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available on the ACS Publications website at DOI: 10.1021/acs.jchemed.8b00473. Details of the setup; sketch code; and guide to retrieving the data gathered on the SD card, the Serial Monitor, or the Serial Plotter. (PDF)

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DISCUSSION OF ADVANTAGES AND LIMITATIONS OF THE DEVICE On the basis of the experiences presented above, we can highlight some advantages and limitations of the device.

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AUTHOR INFORMATION

Corresponding Author

Advantages

*E-mail: [email protected].

Economic. The entire cost of the setup is around $50, which is six times cheaper than some commercial sensors. The costs of the materials are available in Supporting Information Section 2. Experimental Versatility. The device can be used in multiple situations (inside a closed container, in a classroom, outdoors, etc.). Pedagogical Versatility. The Arduino setup can be used from multiple approaches. Obviously, it enables inquiry-based instruction, in which students design their own experiments and carry out their own measurements using the device. In addition, because the sensor records the data, and the data can be shown in real-time, it enables modeling-based instruction, in which students express their predictions (mental models) before making the measurements, and then they refine their models after obtaining the results. Other educational approaches that are closer to technology and computer science can also be used, for instance by asking the students to build the physical setup or the associated computer code.

ORCID

Hernan Pino: 0000-0002-2875-8724 Carme Grimalt-Á lvaro: 0000-0002-5314-7706 Víctor López: 0000-0002-2161-9211 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This paper was produced within the ACELEC research group, acknowledged by the Catalan Government (grant number 2017SGR1399).

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REFERENCES

(1) Stout, R. P. CO2 Investigations: An Open Inquiry Experiment for General Chemistry. J. Chem. Educ. 2016, 93, 713−717. (2) Andersson, B.; Wallin, A. Students’ understanding of the greenhouse effect, the societal consequences of reducing CO2 emissions and the problem of ozone layer depletion. J. Res. Sci. Teach. 2000, 37, 1096−1111. (3) Maenpaa, H.; Varjonen, S.; Hellas, A.; Tarkoma, S.; Mannisto, T. Assessing IOT projects in university education - A framework for problem-based learning. Proc. - 2017 IEEE/ACM 39th Int. Conf. Softw. Eng. Softw. Eng. Educ. Track, ICSE-SEET 2017 2017, 37−46. (4) Ertmer, P. A.; Ottenbreit-Leftwich, A. T.; Sadik, O.; Sendurur, E.; Sendurur, P. Teacher beliefs and technology integration practices: A critical relationship. Comput. Educ. 2012, 59, 423−435. (5) National Oceanic and Atmospheric Administration. Lab activity: Getting to know CO2, 2005. NOAA Education and Outreach. https:// www.esrl.noaa.gov/gmd/outreach/info_activities/pdfs/Teacher_LA_ getting_to_know_co2.pdf (accessed Nov 2018). (6) Newton, L. R. Data-logging in practical science: Research and reality. Int. J. Sci. Educ. 2000, 22, 1247−1259.

Limitations

Inertia. The sensor (like commercial ones) undergoes some delay in measuring the concentration of CO2. The setup is not recommended for fast phenomena occurring in less than 15 s. Saturation. As is detailed in Supporting Information Section 1, the measurement range is 0−5000 ppm. Concentrations not included in this range will not be measured (for >5000 ppm concentrations, the sensor will indicate 5000 ppm). The usual range of a commercial sensor is 0−10,000 ppm. Dependence of the Measurement on Other Factors. Extreme relative humidity, temperature, and voltage can affect the measurements (see the detailed information in Supporting D



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(7) CO2 Gas Sensor User Manual. Vernier. https://www.vernier. com/manuals/co2-bta/ (accessed November 2018). (8) Hennessy, S.; Wishart, J.; Whitelock, D.; Deaney, R.; Brawn, R.; la Velle, L.; McFarlane, A.; Ruthven, K.; Winterbottom, M. Pedagogical approaches for technology-integrated science teaching. Comput. Educ. 2007, 48, 137−152. (9) Lajium, D. Science Teachers’ Acceptance towards Microcomputer-Based Laboratories. Int. J. E-Learning Pract. 2016, 3, 83−90. (10) Kubínová, Š .; Š légr, J. ChemDuino: Adapting Arduino for LowCost Chemical Measurements in Lecture and Laboratory. J. Chem. Educ. 2015, 92, 1751−1753. (11) Walkowiak, M.; Nehring, A. Using ChemDuino, Excel, and PowerPoint as Tools for Real-Time Measurement Representation in Class. J. Chem. Educ. 2016, 93, 778−780. (12) Jin, H.; Qin, Y.; Pan, S.; Alam, A.; Dong, S.; Ghosh, R.; Deen, M. J. Open-Source Low-Cost Wireless Potentiometric Instrument for pH Determination Experiments. J. Chem. Educ. 2018, 95, 326−330. (13) Milanovic, J. Z.; Milanovic, P.; Kragic, R.; Kostic, M. ‘Do-ItYourself’ reliable pH-stat device by using open-source software, inexpensive hardware and available laboratory equipment. PLoS One 2018, 13, e0193744. (14) McClain, R. L. Construction of a Photometer as an Instructional Tool for Electronics and Instrumentation. J. Chem. Educ. 2014, 91, 747−750. (15) Cao, T.; Zhang, Q.; Thompson, J. E. Designing, constructing, and using an inexpensive electronic buret. J. Chem. Educ. 2015, 92, 106−109. (16) Urban, P. L. Open-source electronics as a technological aid in chemical education. J. Chem. Educ. 2014, 91, 751−752. (17) Grinias, J. P.; Whitfield, J. T.; Guetschow, E. D.; Kennedy, R. T. An inexpensive, open-source USB Arduino data acquisition device for chemical instrumentation. J. Chem. Educ. 2016, 93, 1316−1319. (18) Arduino Project Hub. Arduino. https://create.arduino.cc/ projecthub/ (accessed Nov 2018). (19) Agency by Design Project Zero. Maker-Centered Learning and the Development of Self: Preliminary Findings of the Agency by Design Project, 2015. Harvard Graduate School of Education. http:// www.pz.harvard.edu/resources/maker-centered-learning-and-thedevelopment-of-self-preliminary-findings-of-abd (accessed Nov 2018). (20) Jang, S.-J.; Tsai, M.-F. Exploring the TPACK of Taiwanese elementary mathematics and science teachers with respect to use of interactive whiteboards. Comput. Educ. 2012, 59, 327−338.

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Measuring CO2 with an Arduino: Creating a Low-Cost, Pocket-Sized

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