**Project: Photometer kit **

Design : 1.0 version

Zachary Marlow OPEN source

A photometer measures the intensity of a light and the can be used to determine the amount of light being blocked by the sample. The amount of light can help determine suspended solids and the quality of the water sample

In my design the photometer is mostly 3d printed and has a total of four 3d printed parts. There is also the light source (modified laser pointer), GA1A1S202WP sensor (adafruit), Arduino Nano . There is a small area where a custom filter can be added if wanted. The entire device can fit completely in one hand.

Size

Total size : 80 mm x 30 mm

Cuvette

The Cuvettes sold by Pubic Labs works perfect for this application and very affordable.

**Light Source **

In my design, I wanted to keep the overall price down, to allow for this to happen the light source needed to be creative. Dollar General sells a laser pointer for $3, by removing the lens you essentially convert the laser into a red diode.

Method of running the Photometer

Connect the Arduino Nano to your computer and launch the code provided using the Arduino Compiler, once successfully uploaded launch Arduino Serial Graph. Insert a control sample into the photometer to get a base level, copy and paste this data into excel or google docs. Now insert the test sample and repeat these steps for each sample you want to test.

To determine loss:

Sample = S, C= Control, R = Remainder

S/C=R-1

R-1= Loss

Proof of concept test:

Control: Distilled Water

Sample 1: 1/3 Coffee Grounds 2/3 Water

Sample 2: 2/3 Coffee Grounds 1/3 Water

In this test, I created two different samples each with different amounts of coffee in them. I went one by one starting with the control of course just to create a base line on the amount of light. Next went sample one and then sample 2, I copy and pasted each data into google docs and created this chart.

From this data, it can be determined that Sample 1 blocked a total of 14.51 %~ of the light and Sample 2 blocked 18.32%~ of the light.

Coding the Arduino:

Now in this project there is a little bit of coding necessary but for the most part all you must do is load the code. It has already been coded and prepared for upload. For those who have interest in coding I have posted the code below. Most of this is the generic code provided by Adafruit, I just took out a few things lines to make it a little easier to transfer the data to excel.

Code: Copy everything between the lines

int sensorPin = A0; // select the input pin for the potentiometer

float rawRange = 1024; // 3.3v

float logRange = 5.0; // 3.3v = 10⁵ lux

void setup()

{

analogReference(EXTERNAL); //

Serial.begin(9600);

Serial.println("Adafruit Analog Light Sensor Test");

}

void loop()

{

// read the raw value from the sensor:

float rawValue = analogRead(sensorPin);

Serial.println(rawValue);

delay(500);

}

float RawToLux(int raw)

{

float logLux = raw * logRange / rawRange;

return pow(10, logLux);

}

Photos of the Photometer:

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