"Stupid Pet Trick"

Over the past couple of weeks, I have been working on creating a "stupid pet trick" using the Arduino, sensors, and a relay. My pet trick consists of a tiny inflatable character that stands up and moves when an ultrasonic detector identifies someone nearby. I am using a hairdryer on the cold setting to inflate the character. I was inspired by the inflatable sculptures that are used to promote car dealerships.  

Here is a video of the design in action:

As I was designing the character, I experimented with different forms. The form of the character directly impacts the types of movements it will make. 

The video below shows a form that I did not like because it created movements that where too constant and predictable. Since the arms and head space had similar lengths and widths, the air distributed too evenly and did not generate random movements.

Roll of bags

Throughout my process, I also tested materials such as cotton fabric sheets and different types of plastic bags.  The material is important because it affects the airflow within the character. If a material is too porous and heavy, like cotton, then there won't be enough air pressure to keep the character upright.

Ideally I would use "high strength polyamide nylon silk," which is the material that commercial manufacturers use for the inflatable dudes. I think this material, along with a specific type of air blowing system, is what allows the characters to move in their characteristic way. The closest materials I could find at home were plastic bags.

My character is made from a translucent plastic dog waste bags that I melted with a soldering iron at home. The dog bag plastic was the best material I found for this project because it is lightweight, strong, impermeable, and could easily be melted to join layers. In the above image, the soldering iron  is cutting the top and bottom layers of plastic while binding the edges. No sewing, taping, or gluing was required additional to this. All I had to do was trace the shape of my character's body with the iron. 

At first, I accidentally made the figure too small and thin. It could barely wrap around the opening of the hairdryer. I realized that I have to draw the form about 2.5x the width it appears to be when it's filled with air. This is kind of similar to the idea that pants look wider when they're laying flat but narrower when they're being worn.

The structure of the base is the top section of a 4L translucent blue water bottle. All the materials in this work are recycled. 

This work can be used to surprise people who walk by it. Right now, it is set up on the kitchen counter of my family's house. My dad and I decided to leave it there overnight to scare my mom or grandma if they try to get a snack in the middle of the night.  

The sensor is currently set up to detect someone standing a meter away. This was an appropriate distance for the kitchen area where it is set up. In the video demonstration, I placed my hand super close to the sensor so that viewers could see the effect better, but I could have placed my hand further away.

Here is the code I used to create this interactive object:

const int TRIG_PIN = 7; // Arduino pin connected to Ultrasonic Sensor's TRIG pin const int ECHO_PIN = 6; // Arduino pin connected to Ultrasonic Sensor's ECHO pin const int RELAY_PIN = 2; // Arduino pin connected to Relay's pin const int DISTANCE_THRESHOLD = 100; // centimeters // variables will change: float duration_us, distance_cm; void setup() { Serial.begin (9600); // initialize serial port pinMode(TRIG_PIN, OUTPUT); // set arduino pin to output mode pinMode(ECHO_PIN, INPUT); // set arduino pin to input mode pinMode(RELAY_PIN, OUTPUT); // set arduino pin to output mode } void loop() { // generate 10-microsecond pulse to TRIG pin digitalWrite(TRIG_PIN, HIGH); delayMicroseconds(10); digitalWrite(TRIG_PIN, LOW); // measure duration of pulse from ECHO pin duration_us = pulseIn(ECHO_PIN, HIGH); // calculate the distance distance_cm = 0.017 * duration_us; if(distance_cm < DISTANCE_THRESHOLD) digitalWrite(RELAY_PIN, HIGH); // turn on Relay else digitalWrite(RELAY_PIN, LOW); // turn off Relay // print the value to Serial Monitor Serial.print("distance: "); Serial.print(distance_cm); Serial.println(" cm"); delay(500); }