Perfect Temp Park Table (PT square)

Simps Bhebhe | Hannah Bonestroo | Itay Porat | Xuezhu (Gillian) Zhao

PT square is a thermal comfort enhancement structure designed for public space such as parks and neighborhood gardens. It is equipped with abilities to cool down the environment through fine misting. Different from conventional misters, the PT square mister will only start misting when people are using the space in hot temperatures. This low-cost, highly versatile product aims to invite people to enjoy the outdoors and also protects populations that are vulnerable to heat. This blog post will describe the motivation behind the project, explain the design process, showcase a working demonstration, and recommend further considerations.

Motivation

Situated across from City Hall, Love Park is centrally located in the heart of Philadelphia. In 2016, in order to improve accessibility and fix the leaking roof of the parking lot underneath it, the park underwent a complete overhaul. However, the redesign was not well-received and the park reopened in 2018 to much criticism. The most frequent complaint was that the new plan left the park feeling like a barren “granite sahara.” The lack of shade incorporated into the new open hardscape comes at a time when the city is struggling with the effects of urban heat island effect. In the last 50 years, the average summertime temperature in Philadelphia has increased by 3°F. Additionally, as the effects of the COVID-19 pandemic subside, activity is increasingly picking back up as workers and shoppers return to Center City.

These challenges inspired the development of our project, the Perfect Temp Park Table (PT square), as an additional thermal-control fixture to the park. The following points highlight our main motivations behind the project which were inspired by the unique design challenges of Love Park:

Parks should act as a refuge from the city. They should be a destination in their own right and not just a place people pass through. Love Park’s new barren design prevents it from serving this role in the city.
Landscape projects take time to grow into their fully realized form. While many new trees were planted with the Love Park redesign, it will take many years before they start providing meaningful shade.

We envision that, if implemented, the Perfect Temp Park Table could help make Love Park a more comfortable, sought-after destination on hot summer days. We hope that the design would welcome visitors to stay awhile and not just pass through.

Design and Site Selection

When considering an intervention that would answer the unique challenges of Love Park we turned to examples from other cities that were working to improve their thermal environment. We found many case studies of cities using a combination of shade and water misters to improve the ambient temperature of the city and provide relief to residents from rising temperatures.

This includes a study in Osaka Japan which demonstrated that misters can be effective cooling mechanisms even in humid climates. Paris has also worked to include misters into its heat mitigation plan as part of what it calls green-blue infrastructure. Drawing from these examples, our proposal is a highly customizable mister that can be activated for people in the park during hot summer days.

Sensor Design

The diagram below outlines the operation of the PT square sensor. When motion is detected and the calculated heat index is above the set threshold (at 85 Fahrenheit) the mister is activated.

The infrared motion sensor scans for motion every second. If motion is detected, it will give a “yes” signal to the Arduino UNO board.
The temperature and humidity sensor measures temperature and humidity every second. It will tell Arduino UNO the sensed numbers, and the Arduino UNO will use them to calculate a heat index.
If human presence is detected and the heat index is above the threshold at 85 Fahrenheit, the mister will be triggered.
In the absence of human activity after the initial trigger, we have set up a “lag time” for the mister to continue misting for a short time before stopping. Although the motion detection sensor is highly sensitive, this helps in the situation if the people are still there but their motion was missed. The “lag time” countdown will restart after any movement is sensed.

Structure Design

The concept diagram below shows the evolution of the design for a tree pergola. The shape took inspiration from the shape of a tree canopy and is integrated with the four-legged structure of the pergola. The motivation for the tree-like design is to create an additional element that helps people feel the connection to nature while waiting for the newly planted tree in the park to become fully grown. However, the sensor is highly versatile and we envision that PT square can take on many forms depending on the atmospheres and needs of future placement sites.

Site Selection

The PT square sensor will need electricity and water supply. However, the sensors can be powered through batteries or solar panel so that allows for more flexibility. The sensor needs to be in close proximity to a waterline lead to provide water for the mist. As shown in the site plan below, there is a waterline lead in Love Park.

Besides consideration of the waterline lead, our site selection decision also took account of foot traffic flow and availability of space. One possibility of the project area is depicted by the green box, while the others are highlighted in light blue, along the ellipse-shaped central area or at the current table and chairs sitting area.

Here is a set of before and after rendering to help visualize the PT sqaure structure. We designed the project such that, on a hot summer day, it can serve as a cool oasis for people to sit, talk, have lunch, or breathe in some fresh air. The mist will also help keep the plants hydrated which provide another layer of attractiveness to the park pergola.

Technical Specifications

The following section describes in detail how to create your own functioning PT square prototype.

This tutorial draws from Lessons 10, 11, and 17 in the Elegoo Super Starter Kit Manual.

*note: In order for a mister to work, we will need access to a pressurized water line. In our prototype we used a pump in lieu of a valve for the mister and fans. While the mister and fans will work successfully in theory, the pump does a good job of representing the movement of water.

Parts

1 Infrared IR Body Motion Module – Stemedu HC-SR501 PIR Sensor
1 Arduino Uno
1 Breadboard
1 DC 3V 5V Micro Submersible Mini Water Pump (or equivalent) (x1)
1 Mosfet transistor IRF520 (or equivalent) (x1)
1 Rectifier diode 1N4007 (or equivalent) (x1)
1 Photoresistor – ambient light detector HW5P-1 (or equivalent) (x1)
1 10 kΩ (kiloohm) resistor (x1)
1 9V battery + snap connector (x1)
1 A container with water to submerge the pump
male to male jumper wires
male to female jumper wires

(The following are optional for with solar panel instead of batteries. For more information on how to power an Arduino Uno with a solar cell, check out the following post.)

Wiring

The wiring diagram shows how each part of the sensor can be connected. The temperature sensor can be connected at pin 4 and the PIR motion sensor at pin 3. The output response can be connected using pin 9. All components must be grounded. The apparatus is powered through a battery connect at pin 5v.

Code

//  Code for Perfect Temp Park Table (PT square) Prototype
// This code takes inputs of motion and temperature. If motion is detected
// and temperature is above the designated threshold, a water pump is activated.
// This code draws from Lessons 10, 11, and 17 from the Elegoo Super Starter Kit.

//  include any relevant libraries
#include "DHT.h"

//  initialize variables
const int pumpPin =  9; // the number of the pump pin

//  setup
void setup() {
  Serial.begin(9600);
}

//  main loop
void loop() {
  int presence = sensing_motion();
  Serial.println(presence);
  int heat = temp();
  Serial.println(heat);

  if(presence == 1 && heat == 1){  //setting the parameters for activation
    Serial.println("Mist ON");
    digitalWrite(pumpPin, HIGH);
    delay(1000);
    digitalWrite(pumpPin, LOW);
    delay(5000);
  }

  else{
    Serial.println("Mist OFF");
    digitalWrite(pumpPin, LOW);
  }
  
    Serial.println();
    delay(1000);
}


int sensing_motion() {
    int delayTime = 3000;
    int lagValue = 15;
    int pirPin = 2; 
    int pirPin2 = 3;
    int pirStat = 0; 
    int pirStat2 = 0;
    long dist; 
    int pValue = 0; 

//  pinMode(pumpPin, OUTPUT);   // initializes digital pin named ledPin as output 
    pinMode(pirPin, INPUT); // initializes pirPin as input 
    pinMode(pirPin2, INPUT); // initializes pirPin as input 

    Serial.begin(9600);

    pirStat = digitalRead(pirPin); // store the status of infrared sensor in pirStat
    pirStat2 = digitalRead(pirPin2); // store the status of infrared sensor in pirStat

    if (pirStat == HIGH && pirStat2 == HIGH) {   
      Serial.println("Motion detected");
      pValue = lagValue;
      }

    else { 
      Serial.println("No motion detected");
      //Serial.println(pirStat);
      //Serial.println(pirStat2);
      pValue = pValue-1; // start the count down
      }

    if (pValue > 0) { 
      return 1;
      delay(delayTime);
      }

    else { 
      return 0;
      delay(delayTime);  
      }
    }   // end sengins_motion function


int temp() {
#define DHTPIN 4     // what pin we're connected to
#define DHTTYPE DHT11   // DHT 11 
// Initialize DHT sensor for normal 16mhz Arduino
DHT dht(DHTPIN, DHTTYPE);
dht.begin();

  // Wait a few seconds between measurements.
  //delay(1000);
  // Reading temperature or humidity takes about 250 milliseconds!
  // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
  float h = dht.readHumidity();
  // Read temperature as Celsius
  float t = dht.readTemperature();
  // Read temperature as Fahrenheit
  float f = dht.readTemperature(true);
  
  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
}

  // Compute heat index
  // Must send in temp in Fahrenheit!
  float hi = dht.computeHeatIndex(f, h);

  /*Serial.print("Humidity: "); 
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Temperature: "); 
  Serial.print(t);
  Serial.print(" *C ");
  Serial.print(f);
  Serial.print(" *F\t");
    */
  Serial.print("Heat index: ");
  Serial.print(hi);
  Serial.println(" *F");

  if (hi > 85) {
  Serial.println("Activate Mist System");
  return 1;
  } 
  else {
  Serial.println("No need for mist system");
  return 0;
  }
}

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// Code for Perfect Temp Park Table (PT square) Prototype

// This code takes inputs of motion and temperature. If motion is detected

// and temperature is above the designated threshold, a water pump is activated.

// This code draws from Lessons 10, 11, and 17 from the Elegoo Super Starter Kit.

// include any relevant libraries

#include "DHT.h"

// initialize variables

const int pumpPin = 9; // the number of the pump pin

// setup

void setup() {

Serial.begin(9600);

}

// main loop

void loop() {

int presence = sensing_motion();

Serial.println(presence);

int heat = temp();

Serial.println(heat);

if(presence == 1 && heat == 1){ //setting the parameters for activation

Serial.println("Mist ON");

digitalWrite(pumpPin, HIGH);

delay(1000);

digitalWrite(pumpPin, LOW);

delay(5000);

}

else{

Serial.println("Mist OFF");

digitalWrite(pumpPin, LOW);

}

Serial.println();

delay(1000);

}

int sensing_motion() {

int delayTime = 3000;

int lagValue = 15;

int pirPin = 2;

int pirPin2 = 3;

int pirStat = 0;

int pirStat2 = 0;

long dist;

int pValue = 0;

// pinMode(pumpPin, OUTPUT); // initializes digital pin named ledPin as output

pinMode(pirPin, INPUT); // initializes pirPin as input

pinMode(pirPin2, INPUT); // initializes pirPin as input

Serial.begin(9600);

pirStat = digitalRead(pirPin); // store the status of infrared sensor in pirStat

pirStat2 = digitalRead(pirPin2); // store the status of infrared sensor in pirStat

if (pirStat == HIGH && pirStat2 == HIGH) {

Serial.println("Motion detected");

pValue = lagValue;

}

else {

Serial.println("No motion detected");

//Serial.println(pirStat);

//Serial.println(pirStat2);

pValue = pValue-1; // start the count down

}

if (pValue > 0) {

return 1;

delay(delayTime);

}

else {

return 0;

delay(delayTime);

}

} // end sengins_motion function

int temp() {

#define DHTPIN 4 // what pin we're connected to

#define DHTTYPE DHT11 // DHT 11

// Initialize DHT sensor for normal 16mhz Arduino

DHT dht(DHTPIN, DHTTYPE);

dht.begin();

// Wait a few seconds between measurements.

//delay(1000);

// Reading temperature or humidity takes about 250 milliseconds!

// Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)

float h = dht.readHumidity();

// Read temperature as Celsius

float t = dht.readTemperature();

// Read temperature as Fahrenheit

float f = dht.readTemperature(true);

// Check if any reads failed and exit early (to try again).

if (isnan(h) || isnan(t) || isnan(f)) {

Serial.println("Failed to read from DHT sensor!");

return;

}

// Compute heat index

// Must send in temp in Fahrenheit!

float hi = dht.computeHeatIndex(f, h);

/*Serial.print("Humidity: ");

Serial.print(h);

Serial.print(" %\t");

Serial.print("Temperature: ");

Serial.print(t);

Serial.print(" *C ");

Serial.print(f);

Serial.print(" *F\t");

Serial.print("Heat index: ");

Serial.print(hi);

Serial.println(" *F");

if (hi > 85) {

Serial.println("Activate Mist System");

return 1;

}

else {

Serial.println("No need for mist system");

return 0;

}

Demonstration

The following video demonstrates how the sensor would work. We used a blow-dryer to increase the temperature to above 85 Fahrenheit. The pump (representing the water going through a valve and then the mister) starts working after a person walks by and sits down in front of the motion sensor.

Implementation / Future Considerations

Love Park is not the only park in Philadelphia which suffers from a lack of shade and accessible cooling. This map highlights the parks with the highest land surface temperature in the city. This includes Lower Mayfair Playground and McVeigh Recreation Center. If the pilot project in Love Park were to prove successful, PT square could be dispersed throughout the city to parks in need. The PT square sensor could become part of the city’s heat mitigation strategy to combat the urban heat island effect.

We envision that the highly customizable PT square sensor can be redesigned to meet the specific needs and atmosphere of different locations. As long as the area has a pressurized waterline lead, it can take on many different forms including being attached to tents or playground. The diagram below shows another possible iteration of design of the structure where the sensors could be integrated, with solar panel and a more robust tree-like appearance.

Motivation

Design and Site Selection

Sensor Design

Structure Design

Site Selection

Technical Specifications

Parts

Wiring

Code

Demonstration

Implementation / Future Considerations

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