Published January 4, 2020 © GPL3+

Positive Habit Enforcement Device

Stick with your New Year's resolution this time by setting goals and getting a reward upon completing them.

IntermediateFull instructions provided5 hours2,108

Things used in this project

Hardware components

Particle Photon

Driver DRV8825 for Stepper Motors for Theremino System

Stepper Motor, Mini Step

2828 OLED

Seeed Studio Grove - Micro Switch

Pushbutton Switch, Momentary

Software apps and online services

Autodesk Fusion

Particle Build Web IDE

Microsoft VS Code

Hand tools and fabrication machines

3D Printer (generic)

Story

The Premise

It’s almost a new year, which means many people are going to come up with something they would like to do or change, such as going to the gym more or keeping the house clean. These resolutions are great things, but most likely, they will be broken a mere two to four weeks into the year.

Behavior modification is a way to cause new habits to form by either giving a reward for exhibiting the correct behavior (positive reinforcement) or a punishment for incorrect behavior (negative reinforcement). People use these techniques all the time, such as giving a treat to a dog for doing a trick or paying your kid a dollar for cleaning the bathroom. Since people usually don’t want to willingly subject themselves to pain and/or discomfort, I decided to build a machine that can give a reward of the user’s choosing whenever a goal is reached.

Initially, the user will place an object that they like to receive, such as money or food. Then, they can enter in a goal on a webpage, which sends it to the machine and displays it on a screen. The door will also close at this time and lock, preventing the user from getting what’s inside without first completing the task.

Sliding Door Mechanism

Doors come in many varieties: hinged vertically, hinged horizontally, or sliding. One of my goals in the project was to keep the box small and simple, so a sliding door would have best accomplished this.

A 3D printed door gets placed onto two aluminum guides, and a stepper motor uses a timing belt and pulley to drag the door side-to-side. A limit switch is used to “home” the machine, so the microcontroller can know exactly where the door is.

Electronics

In order to make a door move, you must first have a motor. I went with a stepper motor in this case because it is able to move a precise amount, and therefore, the distance it has traveled can be tracked. It is driven by a DRV8825 bipolar stepper motor driver, which only requires two pins to operate. Goals are displayed on an ILI9341 OLED screen, which is controlled via the SPI interface.

Every time a new goal is received, its text is sent to the display. Finally, the brain of the device is a Particle Photon, which lets the machine communicate with the webserver via WiFi and get new data.

Particle Photon Program

At a high level, the program flows as follows: Enter new goal -> Display goal on screen -> Close and “lock” door -> Wait for button press -> Open door and allow person to retrieve prize. There is a delay between entering the goal and having the door close to allow for a treat to be placed in case it was forgotten previously. The program utilizes the mDNS library to allow users to navigate to a hostname rather than an IP address. The HTML file is hosted externally to save space on the device, and it is fetched and placed into an iframe by the client whenever the index page is loaded. When a new goal is set, a POST request is sent to the photon, where the goal string is extracted and saved to a variable. Whenever the webpage is loaded, a function is called that retrieves the current goal from the device, thus maintaining consistency between client devices.

Making Good Habits

Psychologists tend to claim that it takes around 10 times of doing something consistently for it to become a habit, so by using a metaphorical carrot on a stick, you can cause yourself to eventually perform tasks without even having to think about them.

Code

<!DOCTYPE html>
<html>
<head>
<title>Positive Reinforcement Device</title>

<meta name="viewport" content="width=device-width,initial-scale=1">
<meta charset="UTF-8">

<style type="text/css">
html,
body {
	font-family: sans-serif;
}

fieldset {
	margin-left: auto;
	margin-right: auto;
	max-width: 480px;
	border-radius: 8px;
}

p {
	clear: both;
	width: 100%;
	line-height: 1.5em;
}

label {
	width: 49%;
	text-align: right;
	display: inline-block;
	line-height: 1.5em;
	float: left;
	margin-left: -1em;
}
</style>

<!-- Download microajax.minified.js from https://code.google.com/archive/p/microajax/ -->
<script type="text/javascript" src="microajax.minified.js"></script>

<script type="text/javascript">
var $goal
var mA = microAjax;

window.onload = function() {
	$goal = document.querySelector('#goal');

	// Load our data
	get_settings();
}

// Get the settings from mydevice.local
function get_settings() {
	mA('http://mydevice.local/settings.json', function(res) {
		var d = JSON.parse(res);

		console.log('goal', d);

		document.querySelector('#loading').style.display = 'none';

		$goal.value = d.b;

		document.querySelector('#goal_form').style.display = 'block';
	});
}
</script>
</head>
<body>
<p id="loading">Please wait.  Loading settings . . .</p>
<form id="goal_form" method="POST" action="http://mydevice.local/save.html" style="display:none">
	<fieldset>
		<legend>Enter a Goal</legend>
		<p>
			<label for="b">Goal: </label>
			<input type="text" id="goal" name="goal">
		</p>
		<p>
			<label for="s"> </label>
			<input type="submit" id="s" value="Save">
		</p>
	</fieldset>
</form>
</body>
</html>

// This #include statement was automatically added by the Particle IDE.
#include <Adafruit_mfGFX.h>

// This #include statement was automatically added by the Particle IDE.
#include <WebServer.h>

// This #include statement was automatically added by the Particle IDE.
#include <MDNS.h>

// This #include statement was automatically added by the Particle IDE.
#include <Adafruit_SSD1351_Photon.h>

// This #include statement was automatically added by the Particle IDE.
#include <AccelStepper.h>

#define STEPSTOTAKE 200 //Go this many steps to the end to open

#define cs   A2
#define sclk A3
#define mosi A5
#define rst  D5
#define dc   D6

#define	BLACK           0x0000
#define WHITE           0xFFFF

#define homing_pin D4
#define goalCompleteBtn D7

AccelStepper stepper(1,3,2);
Adafruit_SSD1351 tft = Adafruit_SSD1351(cs, dc, rst);

MDNS mdns;
#define REMOTE_URL "http://localwebserver/device_page.html"

#define POST_NAME_LENGTH 32
#define POST_VALUE_LENGTH 120

WebServer webserver("", 80);

String goalString = "Enter a new goal";
bool goalActive = false;

void web_index(WebServer &server, WebServer::ConnectionType type, char *, bool) {
    server.httpSuccess();

    server.print("<!DOCTYPE html><html><head><title>Positive Reinforcement Machine</title><style type=\"text/css\">html,body,iframe{position:absolute;top:0;right:0;bottom:0;left:0;border:0;width:99%;height:99%;}</style></head><body><iframe src=\""+String(REMOTE_URL)+"/index.html\"></iframe></body></html>");
}

void web_settings(WebServer &server, WebServer::ConnectionType type, char *, bool) {
    server.httpSuccess("application/json");

    server.print("{\"goal\":"+goalString+"}");

}

void web_save(WebServer &server, WebServer::ConnectionType type, char *, bool) {
    URLPARAM_RESULT rc;
    char name[POST_NAME_LENGTH];
    char value[POST_VALUE_LENGTH];

    server.httpSeeOther(String(SETTINGS_URL)+"/index.html");

    // Loop through POSTed data
    while(server.readPOSTparam(name, POST_NAME_LENGTH, value, POST_VALUE_LENGTH)) {
        // Because strings are easier to test/manipulate
        String _name = String(name);
        String _value = String(value);

        if(_name.equals("goal") && !goalActive){
            goalString = _value;
            setNewGoal(goalString);
            goalActive = true;
        }
    }
}

void setup()
{
    stepper.setMaxSpeed(500);
    stepper.setSpeed(200);
    stepper.setAcceleration(150);
    tft.begin();
    pinMode(homing_pin, INPUT_PULLUP);
    pinMode(goalCompleteBtn, INPUT_PULLUP);
    //Home door position
    while(!digitalRead(homing_pin)) stepper.move(-1);
    bool mdns_success = mdns.setHostname("habitFormer");

    if(mdns_success) {
        mdns.addService("tcp", "http", 80, "Positive Reinforcement");
        mdns.begin();
    }
    webserver.setDefaultCommand(&web_index);
    webserver.addCommand("save.html", &web_save);
    webserver.addCommand("settings.json", &web_settings);
    webserver.begin();
}

void loop()
{
    mdns.processQueries();

    char web_buff[64];
    int web_len = 64;
    webserver.processConnection(web_buff, &web_len);
    if(!digitalRead(goalCompleteBtn))
    {
        goalActive = false;
        openDoor();
        goalString = "Enter a new goal";
    }
}

void displayGoal(String goal)
{
    tft.fillScreen(BLACK);
    tft.setCursor(0, 5);
    tft.setTextColor(WHITE);
    tft.setTextSize(2);
    tft.print(goal);
}

void setNewGoal(String newGoal)
{
    displayGoal(newGoal);
    stepper.move(STEPSTOTAKE);
}

void openDoor()
{
    if(goalActive) return;
    tft.fillScreen(BLACK);
    stepper.move(-STEPSTOTAKE);
}