Photoresitor Level Detection

Overview

This tutorial will cover how to use a photoresistor to detect the liquid level of a bottle. This was used in making the Cocktail Maker. This detection alerts when the ingredients in the bottles need to be refilled.

Materials and Requisites

- An LED of any color (Blue seems to have the most accuracy)

- a photo resistor

- an Arduino Uno

- 11 wires

-Breadboard

-a clear bottle containing liquid

-two resistors

-Multimeter

Process

Sizing the resistor for the Voltage Divider

1. Connect the photoresistor to a Multimeter.

2. Set up an LED on a bread Board with Arduino as seen below.

3. Fill clear bottle with liquid

4. Turn off lights.

5. Hold LED against one side of the bottle and then hold the photoresistor parallel to the LED light across the bottle underneath the surface of the water.

6. Read the output of the Photoresistor and record.

7. Repeat step 5 and six but make sure the LED and the Photoresistor are above the liquid line.

8. With these numbers plug them into the following equation. V_out= (first reading)/(first reading +R) - (second reading)/(second reading +R)

9. Take the derivative with respect to r.

10. Set derivative equal to 0 and solve for R. This will give you the resistance for the resistor that accompanies the photoresistor. The number does not have to be exact. The desired Resistance can be around that value/

Physical Setup

11. Set up the breadboard to connect the LED to the arduino and the Photoresistor to the Arduino as seen below. the LED and the Photoresistor will be seperate loops.

12. Set up the LED and The Photoresitor to the bottle as previously done in step 5.

Code

12. Enter the following code into arduino and load. This code will take an initial reading of the bottle with a full liquid level. Then this will continuously read the level. once the level reaches a predetermined number then it will notify that the bottle is empty.

int lightPen1 = A0; //define a pin for Photo resistor of bottle
int full1=analogRead(lightPen1);//sets initial condition for bottle 1
  
void setup()
{
    Serial.begin(9600);  //Begin serial communcation
analogReference(INTERNAL);
}

void loop()
{
  if (analogRead(lightPen1)<.8*full1){ //Tests to see if bottle 1 is empty
  Serial.println("Bottle 1 Empty");
  delay(10);
  }

}

We chose to do the .8 full because that is a drastic enough change from the initial read. This makes sure that it isn't a random toss of the bottle that has one off reading. This would be a significant change.

Authors

Cj Wilson

Weronika Pach

Tom Fare

Group Link

Cocktail Maker

Cocktail Maker Log