This project will allow you to create your own conductivity sensor and use an Arduino to gather data about the pollution levels of your community water sources! Understanding this data will help you understand how different events in and around your community effect the pollution level of your local water sources.
My hope is that this will be a fun and fairly inexpensive project middle or high school students can complete to become more involved in understanding and impacting community water sources such as creeks and rivers. These waterways can flood in heavy rains, leading to trash and other harmful pollutants finding their way into the water. Additionally, companies often dump waste into these rivers, which can negatively effect their quality and the ecosystems that rely on them.
While this project is meant to help students understand the levels of water pollution, and get them involved in the community surrounding that water, it also brings in several math, science, and computer science themes.
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Step 1: Gather Your Materials
Here's what you'll need for this project:
- Computer with internet access
- USB cable
- Arduino Uno
- 9 volt battery
- 9 volt battery connector
- disposable pen
- electrical tape
- 2x 22 gauge single strand insulated copper wire
- 2x 10cm lengths of 32 gauge nichrome wire
- wire strippers (not pictured)
- soldering iron (not pictured)
- lead-free solder (not pictured)
Step 2: Make Sure You Have Arduino Installed
Step 3: Break Down Your Pen
You'll need to prepare your disposable pen for use. To do this, remove the top, then pull out the spring and ink cartridge. All that should remain is the plastic tube.
Step 4: Prepare Your Wires
In order to make your conductivity sensor, you'll have to solder(pronounced "saw-der") two wires together. In order to do this, you'll need to strip a small section of your wire. "Stripping" your wire is when you take some of the insulation material(the black and white stuff in the picture above) off of the copper wire that is inside of it. We're doing this today so that the copper wires can touch the other metal wires we will be soldering to them. Be careful to only do this to one end of each wire. We will need the plug the other end into something later.
Step 5: Twist Your Wires Together and Solder!
For this step, you'll need the two wires you just stripped, and the two pieces of nichrome wire.
Twist the top 3cm of the nichrome wire around the exposed copper wire. Repeat this for your other color wire(my photos only show the white one, but I repeated the same step for my black wire too).
Next, you'll need to solder these wires together. PLEASE BE VERY VERY CAREFUL!!!
This must be done with adult supervision. Soldering irons are extremely HOT...like 600 degrees! You can badly burn yourself if you aren't careful, so please have an adult know knows how to solder watching you at all times. If you have never soldered before, it is best to have an adult do this part and teach you while they do.
Step 6: Attach Your Wires to Your Pen
Here is where we finish our conductivity sensor!
You will need to attach the wires you just soldered to your pen. You'll do this using the electrical tape from Step 1.
The important thing here is that you do not let the wires toucheach other on the pen. Make sure you tape them on opposite sides of the pen, as shown in the picture.
Then, take your wire strippers and cut the wire so that it does not stick out past the bottom of the pen.
Leave that electrical tape out! You'll need it for the next step!
Step 7: Finish Taping Your Wires Down
Wrap a small piece of electrical tape around the bottom of the pen, securing the bottom of the wires to the pen.
Then, wrap tape down your pen making sure the wires are not touching, until you are approximately 1 millimeter away from the top of the piece of tape you put on the bottom of the pen.
Allowing this small amount of nichrome wire to be exposed is what allows us to measure the conductivity of the water. The electrical tape is to protect us from the electricity and heat that comes from the wires, so make sure to only touch the tape once they're plugged in to a battery!
Step 8: Plug Your Sensor Into Your Arduino Board
Now we will wire our sensor into the Arduino board. Its safe to touch everything at this point, because there is no power running through the wires.
One wire will be plugged into the 5v port on the Arduino board. The other needs to be plugged into the A0 port on the Arduino board.
The wires I used in the example are short, yours will be longer if you go by the materials list.
Step 9: Plug in Your Battery Connection
It is still safe to touch wires, as we don't have a battery in this step.
Get your 9 volt battery connector, and plug the red wire into "vin" and the black wire into one of the two "GND" ports next to it.
Step 10: Time to Write Some Code!
In this step, you'll need to open your Arduino programming environment and write a program!
First you will need to open Arduino on your computer. You should see a window come up that looks something like the photo above. You'll need to type in the code exactly as you see it in the photo.
Once you have finished typing your program, you can plug the Arduino board into your computer's USB port using the USB cable. To do this, plug in the board and click the arrow in the top left hand corner to upload your program onto the board. If this process was successful, you should see "Done Uploading" written in the bottom left of the programming environment.
You're almost ready to test your creation!
Step 11: Test Your Water!
Now, with your Arduino still plugged into your computer, plug the 9 volt battery into the battery connector on the Arduino. Be careful not to touch the exposed nichrome wire on the conductivity sensor.
Open the Serial monitor on your computer by clicking the magnifying glass in the top right hand corner of your Arduino programming environment. This is where you can see the data your sensor is reading!
Now you can dip your sensor in water to get an idea of how polluted it might be!
This project was specifically designed to test the pollution of creek water, but can be used in many different types of water.
Step 12: What Do These Numbers Mean?!
Well, according to this definition of water quality parameters:
Most streams have conductivity ranging from .05 to 1.5 volts. (I did some math here to convert microsiemens per centimeter to volts)
Freshwater streams should have a conductivity between .15 and .5 volts. (again, math)
Now, when you test your local creek or river, you have some idea of what numbers your conductivity sensor should be reading! If you find your readings are higher than those ranges, it might be worth it to investigate where some of those pollutants may be coming from! Was there a big storm that sent lots of trash down river? Did somebody dump something in the river that caused the spike? Understanding these readings can begin to help you understand the impact people have on the the quality of community water systems!
I hope you had fun doing this project, I know I did! This is my first instructable and was for a class project, so please feel free to leave feedback...I'm always looking to improve!
Note: This project can absolutely be extended to include a much more complex representation of the data. You could include an LCD screen on your Arduino so that you don't need to be tethered to your computer to see the sensor readings. You could create a visualization program that maps the pollution data over time, and connect spikes or drops to events in and around your community. Have fun and make it your own!