The correction factor generally lies between 2-4% change in resistance for each degree temperature change. Operation is via I2C protocol and readings are displayed on the Arduino serial monitor. You might find something else like this, but for us this was perfect. I'm trying to make a sensor to measure the salinity in a water tank.
Pass out the handouts and direct students to individually answer the four "preparing" questions on page 2. Construct a functional conductivity probe. Afterwards, you will build on your understanding of how the conductivity probe works to design and conduct an experiment of your own. within type by subtype, then by grade, etc. . Next, students complete the "analyzing" section of the lab activity, composed of an online reading about electrolytes and nonelectrolytes, including a six-minute video, followed by an online digital experiment to test their reading comprehension. Calibrating was done by taking multiple samples of demineralised water and adding different amounts of salt to them. then perhaps you should fine tune the resistor and/or the distance between the electrodes to improve your sensibility. This requires groups to design additional experiments that utilize their conductivity sensors.
Analyzing: Direct students to complete the "analyzing" section of the lab activity, composed of an online reading about electrolytes and nonelectrolytes, including a six-minute video, followed by an online digital experiment to test their reading comprehension. Once we have built the probes, we will look at two different ways to display the resultsusing light as well as an LCD numerical display. Then the two wires are taped onto opposite sides of the pen barrel. A system to maintain the pH level of a sample within a defined range. Real-time pH and salinity monitoring with LED indicators. The conductivity probe uses simple electrical circuits to communicate the measurement to the user. 
Students construct a simple electric circuit and a galvanic cell to help them understand voltage, current and resistance. Though both measurements are for the same solution, the means of communicating conductivity [light in Part 2 and a numerical measurement display in Part 3] are very different. The initial pH and EC of water are measured. We use a relatively simple code to measure the resistivity. See the schematic for the wiring. b) On your computer, open the Arduino IDE (You can download the IDE from HERE if you do not have it). Use of the TeachEngineering digital library and this website constitutes acceptance of our Terms of Use and Privacy Policy. Plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles. This lab activity requires students to make simple solutions by dissolving various solutes into measured volumes of water.
Both are simple to make; students stir in a spoonful of either salt or sugar into a cup filled halfway with distilled water. Then they answer three handout questions. I plan to use this sensor to trigger opening a water valve that would dispose the water till a certain low threshold of salt concentration is reached, and then the cycle repeats. They enter the code provided on the handout (or copy/paste the code if a digital version of the handout is made available). As students begin Part 3, each group uses a computer connected to an Arduino UNO to upload its codes to the Arduino.
(Answer: In addition to identifying solutions as electrolytic or nonelectrolytic, the sensor could differentiate between solutions of differing concentrations.). As students complete their breadboard circuits, require them to have the teacher check their circuits.
Compile and upload the pH_EC_led_indicator code to your, on your keyboard. Do you agree with this alignment? https://thecavepearlproject.org/2017/08/12/measuring-electrical-conductivity-with-an-arduino-part1-overview/. The problem I faced with this design is that regardless of the concentration of salt there is in the water, it always gives me the same reading/value which is similar to having a short between the voltage source and the analogue pin. HS-PS1-3. We are glad that this curriculum met your expectations. Advise students to take their time building the breadboard circuitry and frequently reference. a) Calibrate the sensors. Share it with us! Hence, if the solution has a high resistance, such as with a nonelectrolytic solute, the conductivity will be very low and if the solution has a low resistance, such as with an electrolytic solute like table salt, the conductivity will be very high. From the reading you already have now, try to calculate the resistance between the electrodes. Once the circuits are checked by the teacher, students test their probes by immersing them into cups of four different solutions: salt water, sugar water, distilled water and tap water. We need the following components: For this example the DS18B20 waterproof digital thermometer was used. The code for this project makes use of a customized library and header file for the EZO circuits in I2C mode. Did you make this project? Why did tap water have a measureable conductivity in Part 3, but not light the LED in Part 2? The serial monitor will open. Use appropriate symbols, numbers, and words to communicate key ideas about technological products and systems.
Build and Test a Conductivity Probe with Arduino. Conductive solutions always result from the presence of a solute that is ionic, meaning it dissociates in water into charged particles called ions.
In this case, the limits are as follows: If the conductivity reading goes over 500 S/cm, the yellow LED will turn on; if the pH reading goes over 10, the red LED will turn on. Do you agree with this alignment? Check for Understanding: As students progress through Parts 1, 2 and 3, expect them to be able to describe how they know that a solution is conductive. The supplies for Part 1 are shown in Figure 1. Refer to Figures 2 and 3. Identify whether a solution is conductive. Does it have to be copper or can it be any conductive material? Once groups have constructed their circuitry and had it verified by the teacher, they open the Arduino software on their computers and use a USB cord to connect the Arduino to the computer. Conclude by facilitating a class discussion to share, compare and distill experiences, results and conclusions. The use of LEDs offers a demonstration of how sensor readings can be used to trigger other hardware. The STEMTera board was used in this project for its compact design where the Arduino is combined with the breadboard. The movement of these positive and negative ions enables the flow of charge through the solution. One part switches around the polarity and the other takes a measurement when the 8-pin is HIGH and the 7-pin is LOW. The LEDs are turned on if the sensor readings go out of the predefined limits. For this sensor we built three seperate housings; for the electrodes, for the Arduino and wiring and for the LCD display with the button.
Finally we add the LCD display.
You can also access it from the Ezo_I2c_lib zip folder downloaded above. Review their answers to gauge their depth of comprehension. Refer to Figure 9 for the completed circuit and Figure 10 for the circuit schematic. 5), Apply the technology and engineering design process. How to temperature compensate the Atlas conductivity sensor automatically. On your computer, open the Arduino IDE (You can download the IDE from, if you do not have it). Copyright 2015 Phillip Cook, Polytechnic Institute of NYU, Copyright 2015 Phillip Cook, Polytechnic Institute of NYU; image made with fritzing.org. Following the handout instructions, groups each create a simple circuit using a breadboard, LED, 470 resistor, 9V battery with wires and some jumper wires. The calibration and the switch to I2C MUST be done before implementing the sensors into this project. The measurement of conductivity is typically a measure of how easily electrical current is able to move through a solution. From one side the power cable could be let in and from the other side the electrodes and thermometer cables could be let out. That's because the circuit is a actually voltage divider right? Measure the conductivity of various common household chemicals. 12), laptop or desktop computer with USB cable and Internet access, 2 x 20 cm lengths of 22 gauge single-strand insulated copper wire; available at hardware stores, 2 x 10 cm lengths of 32 gauge nichrome wire; such as from, plastic barrel from a disposable pen, such as a BIC pen, four plastic cups, for the four test solutions, half-size or larger breadboard, such as the reasonably priced boards at, assorted jumper wires, such as a pack of 30 7-inch wires (PRT-11026) at, 470 resistor, such as the resistor multipacks at, red LED, such as the basic red 5 mm LED (COM-09590) at, 2 x 9V battery connector, such as the heavy-duty 9V snap connectors at, 16 x 2 LCD display, such as the basic 16-character by 2-line display with black text on green background (LCD-00255 ROHS) at, 10K trimpot (aka trimming potentiometer, a small variable resistor), such as the trimpot 10K with knob (COM-09806) at, 10K resistor, such as the resistor multipacks at, 220 resistor, such as the resistor multipacks at, soldering iron(s), such as the reasonably priced solder at, lead-free solder, a few tubes to share among one class, such as solder available at, wax pencil or tape and marker, to label the cups, distilled water, expect 1 gallon to be enough for an entire class, paper towels, for drying the rinsed probes, additional supplies may be needed to enable students to use their conductivity probes to conduct end-of-activity experiments of their own designs, for example, solutions of common household chemicals, lemon juice, sodium hydroxide, ammonia, at varying concentrations and temperatures, How to use a breadboard to construct simple circuits, Be able to identify the LED, resistor, jumper wire and related electrical components used in the activity, Aqueous solutions, including how to make a simple solution, Basic lab safety for conducting experiments in a chemistry laboratory. With the StudentsIntroduction/Team Formation, With the StudentsPart 1: Constructing the Probe, With the StudentsPart 2: Testing the Probe, With the StudentsPart 3: Connecting the Probe to the Arduino, With the StudentsPart 4: Critical Thinking and Analysis. Examples of what students might test: Monitor conductivity while an acid is added to a base, such as lemon juice added to a dilute solution of sodium hydroxide or ammonia. The process was fairly easy, but is necessary to have a working sensor which can also say something about the salinity. Any of these housings could of course also be self-designed and manufactured(3D printed). technology, engineering or math (STEM) educational standards. The Inline Voltage Isolator isolates the pH circuit from the salinity circuit, thus protecting it from any electrical interference (noise) that may originate from the salinity sensor or other electronics in the system. electrolyte: A substance that ionizes when dissolved in suitable ionizing solvents such as water. The thing is that the water could start with having small amounts of salt and with time the concentration would increase. Our sensor was already calibrated, so will not discuss calibrating the thermometer in this guide. During the activity, students require access to the following Internet resources: In addition, the CK-12 Foundation has an excellent little web app that serves as an appropriate follow up for students after completing the activity. 3 months ago. Plan and conduct an investigation individually and collaboratively to produce data to serve as the basis for evidence, and in the design: decide on types, how much, and accuracy of data needed to produce reliable measurements and consider limitations on the precision of the data (e.g., number of trials, cost, risk, time), and refine the design accordingly. solvent: The liquid in which a solute is dissolved to form a solution. (Grades e) In your IDE, go to Tools -> Serial Monitor or press Ctrl+Shift+M on your keyboard. Thanks for your feedback!
Make sure the longer leg of the LED is connected to the positive voltage source. Its what has been used for ever to measure salinity. Encourage students to feel free to design experiments that use the Part 2 or Part 3 lab activity setup. The less oxidation, the better. (Grades 9 - 12). Then students follow the handout instructions to repeat the testing of the four solutions they created in Part 2, this time recording in Data Table 2 of the handout the numerical relative conductivity values displayed on the LCD screen.
Engineers often design sensors to fit their exact needs. The 220 resistors limit the current to the LEDs, preventing them from blowing out. I think the sensor would last long enough before having to change its probes as I'm gonna have its voltage source enabled only when a reading is needed. isolates the pH circuit from the salinity circuit, thus protecting it from any electrical interference (noise) that may originate from the salinity sensor or other electronics in the system.
Free K-12 standards-aligned STEM curriculum for educators everywhere. Once students have finished testing the solutions, direct them to dispose of all solutions in a sink drain and clean up their lab work spaces. Through this lab, students are exposed to multiple ways that a conductivity probe can be used and challenged to consider its possible real-world applications. a) Download Ezo_I2c_lib, a zip folder from GitHub onto your computer. The very first important step in this process is to have the electrodes at a fixed distance from eachother. We already showed a bit of code after the wiring of the resistance sensor to find out if everything was working. In the second experiment, the feedback comes in the form of a digital numerical readout (constituting a quantitative measurement) in which, as the numerical value displayed increases, the conductivity of the solution increases. Depending upon the solute, the resulting solution will either conduct electricity or be non-conductive. solution is poured into the beaker, the pH increases and upon crossing 10 and the red LED turns on. Conductivity probes are also used to quickly identify the source of contaminants within wastewater streams and water supply systems. are used. solute: The minor component in a solution, dissolved in the solvent. See a few example discussion questions in the Assessment section. Measure the conductivity of solutions of varying concentrations. This was an exact fit and waterproof at once. PS: We do not share personal information or emails with anyone. Now we will add the full code to work with the entire sensor. Another common application involves the use of conductivity probes to monitor the ionic content of water used within cooling towers since too highly concentrated ionic solutions can prematurely corrode components and cause safety hazards. Using wire strippers, remove about 1 cm of insulating material from the ends of each of the two lengths of insulated copper wire. However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government. It's in ohm, but you can change the code with some calculations so if gives anything else. Point out that this value is related directly to how easily electrical current can pass through the solution.