How to Make: Water Turbidity Sensor

In this tutorial, we will explain how to make a water turbidity sensor that can measure three different levels of turbidity.

This is our final product in action!

- Particle Photon + breadboard

- Laser

- LDR

- On/off button

- Small resistor (220 Ohm)

- Electrical wires (different sizes)

- PVC tube

- Smaller see through tube

- 4 plastic cards (cut in circles with diameter that of the PVC tube)

- Solder tin

- Glue

- Sealant

For more details on how to connect to your Photon, see this link: https://docs.particle.io/guide/getting-started/start/photon/

Connect all the components you have according to the pictures! Make sure every pin is tightly connected. For the LDR and laser to fit in the tube, it is advised to connect and solder them to longer wires (2nd picture). Lead all the wires through a plastic card (cut in circle) because this is going to cover up the tube.

This is the program we initiall used while developing our sensor. It has not been calibrated yet. It is advised to run this program on your Photon to see if it works.

Make a hole in the tube, the exact location does not really matter. As long as the LDR and laser still fit without hindering the hole.

Place the LDR and the laser in a plastic circle as seen on the picture.

Put the LDR and the laser in the tube.

The LDR should be on the opposite side from the hole compared to the laser.

Glue both plastic circles (with the LDR and laser) To the side of the tube just next to the hole.

Place the plastic invisible tube through the hole and cut it so it looks nice to you.

Finally glue the other 2 plastic cards to the top and bottom of the tube to close it off.

TIP: Colour code all the wires so that you still know which wire belongs where once you closed the tube.

Seal all the connections and open edges with sealant to prevent water from reaching the inside of the tube.

Our sensor is made to measure 3 types of turbidity levels. To calibrate your sensor, take some fresh water and something to make the turbidity higher (we used coffee with creamer).

Start by measuring the clear water. Write down this value.

Then add some of the coffee until the measured value is well above the clear water value. (we had a difference of 300). Measure and write down the value.

The add the rest and measure again. Write down the value.

The more often you do this the more accurate you can calibrate your sensor.

Now in your program adjust the limits to match your measured values! In the picture you can see what our values are after calibration.