# Turbidity Sensor

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## Introduction: Turbidity Sensor

For our project we had to build a sensor which could measure a water related phenomena. The phenomena that we choose was turbidity. We came up with 10 different ways to measure the turbidity. After comparing the different methods, we choose the method that involves a laser and LDR. In this tutorial we show you how to build our turbidity sensor.

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## Step 1: Tools and Components

This is what you will need to build our turbidity sensor:

• Particle Photon
• 10k resistor
• LDR
• Laser pointer
• Electrical wires
• Wooden plank
• Transparent plastic box
• Glue
• Duct tape

The setup is very simple, in the figure is a schematic view of photon. We chose to use a 10k resistor instead of a 220 resistor.

## Step 3: Making It Waterproof

The circuit showed in step 2, won't work underwater yet so in this step we will make sure that we can measure turbidity underwater without short circuit.To realize this we solder the LDR to waterproof electrical wires. Next we put the LDR in a transparent plastic box, with the LDR close to the plastic. After that we closed the box and glued it so it is waterproof. We connected the box to a wooden plank, at the other end of the plank we connected the laser pointer which we fixed so the laser would always point on the LDR. The last thing left to do is to add ducttape/ a mark between the laser and sensor so you ll have a fixed depth to measure from.

## Step 4: Particle Build

We wrote a program for three different levels of turbidity: high, medium and low. To determine what values would define these levels we did the following.

First we used Tinker, which is part of the Particle app, with Tinker you can read values of each pin of your Photon. After you opened Tinker you can start reading the value of pin A4.

To determine the different levels you will have to do a couple of measurements. To do this you will have to put the plastic box in clear water till you reach the duct tape, read of the value a couple of times and write down the average value. Now make the water a bit more turbid, we did this by adding coffee creamer to the water. Write down the average value again, do this a couple of times to get values for different turbidities. With the results you can define the different levels of turbidity.

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