Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

e14sbhargav — Thu, 11 Dec 2025 14:57:33 GMT

Current Revision posted to Documents by e14sbhargav on 12/11/2025 2:57:33 PM

Join Milos as he tackles a familiar problem: it’s the holiday season, there’s lots of delicious food and candy everywhere, and it’s too cold to go out much. To help with that, Milos created a Smart Cookie Jar that keeps you true to your word. The jar locks itself with all those treats inside and won’t open until you reach your running goal!

In Milos' own words:

“It’s the holiday season… But if you want to get to that candy, we’ll make something that will make you run first.”

Watch the Project

https://youtu.be/jsQTD_6HNTA

What's the Idea

Milos first built this project more than six years ago, back before he owned a 3D printer. He’s rebuilt it now to make it smaller and more refined, taking advantage of 3D printing and modern microcontrollers.

The original mechanism was hand-cut from 4 mm plywood; the small push rods used sheet metal salvaged from a gutter, there was plenty of room for improvement.

This time he decided to use an established fitness app (Strava) to get activity data instead of a crude step counter app. The design brief was simple: the jar must look like an ordinary jar from the outside, no obvious electronics, just a jar full of candy.

Enacting the Mechanism

Milos began with the mechanism because it is the most critical part of the system. Instead of linear pistons in the original, the new lid uses small gears with swinging arms that extend to lock the lid in place. The whole mechanism is designed to be 3D printed and to use a very small servo (the common SG90).

The mechanism is compact and straightforward to assemble. All electronics are contained inside the lid: an ESP32-S3 microcontroller (for Wi-Fi), a battery, and a battery charger module. Optionally, you can add a power switch.

A quote from the video where Milos describes the mechanism:

“In the centre we have the servo horn… and around that we have the three pistons that move linearly. So they’re connected together using this small pushrod… For the new version, I want to go with gears.”

MR20 - Cookie Jar V2 - Video V1

The new lid packs everything tightly; from the outside (when unlocked) there’s no visual clue that anything special is inside — just candy.

Setting up the Software

The jar uses the Strava API to determine whether the running goal has been achieved. Milos chose Strava because he uses it personally and it offers a straightforward developer API.

As Milos says:

“To create a small web server on the ESP32, which will just grab the JSON packages from the Strava app so we can actually see my latest activity here.”

Strava flow (summary)

Create a Strava API application (Settings → My API Application) and note client_id and client_secret.
Build and open the authorise URL to obtain the temporary code.
Exchange the code for access_token and refresh_token (the example cURL is shown below).
Copy the tokens into the Arduino sketch and flash the ESP32-S3. The code refreshes tokens automatically as needed.
Open the device web page and choose Show last activity to verify the device returns your latest Strava activity with HTTP 200.

The video also explains the UI / user-flow: set a distance goal (for example, 6 km) and the jar unlocks when recent activity meets the goal.

“It will just give you the name of your last activity, the distance you ran… ”

Key code excerpts (from `CookieJarV2.ino`)

Below are short, focused excerpts from the project code to explain the important behaviours. These are included to show how the software actually operates.

Configuration constants (Wi-Fi, Strava tokens and servo settings) - set these before flashing:

// Wi-Fi credentials
const char *WIFI_SSID = "YOUR-SSID";
const char *WIFI_PASSWORD = "YOUR-PASSWORD";

// Strava tokens and keys (example placeholders)
const char *STRAVA_CLIENT_ID = "YOUR_STRAVA_CLIENT_ID";
const char *STRAVA_CLIENT_SECRET = "YOUR_STRAVA_CLIENT_SECRET";
const char *STRAVA_ACCESS_TOKEN = "YOUR_STRAVA_ACCESS_TOKEN";
const char *STRAVA_REFRESH_TOKEN = "YOUR_STRAVA_REFRESH_TOKEN";

// Servo configuration
const int PIN_SERVO = 3; // ESP32 GPIO (confirm for your board)
const int SERVO_LOCK_ANGLE = 0;
const int SERVO_UNLOCK_ANGLE = 110;
const int SERVO_PULSE_DELAY_MS = 800;

Servo motion helper - the code attaches the servo, moves to the angle, waits, and detaches. Detaching stops the constant PWM “holding” signal, saving battery and stopping buzzing:

void moveServoTo(int angle) {
  jarServo.attach(PIN_SERVO);
  delay(100);
  jarServo.write(angle);
  delay(SERVO_PULSE_DELAY_MS);
  jarServo.detach();
}

This corresponds with Milos’s on-camera note about saving power and avoiding servo buzzing:

“One important thing to point here is that I do attach and detach, because if you just move a servo to a position you will continue sending it the signal… You just do the detach which does stop sending the signal out, in order to save a bit of power, because this is a battery-powered project after all.”

Strava fetch (sketch of approach) - the code ensures Wi-Fi, calls the Strava API, parses activities and records the last activity details. The project polls Strava periodically (every five minutes by default):

bool fetchStravaLatestActivity() {
  ensureWiFi();
  if (WiFi.status() != WL_CONNECTED) {
    lastError = "WiFi disconnected";
    return false;
  }

  // HTTP call to Strava /athlete/activities or other endpoint
  // Parse JSON, extract last activity id, name, distance (m -> km), calories etc.
  // Update lastActivity struct and hasLastActivity flag
  ...
  return true; // or false on error
}

The sketch includes a regular poll loop:

const unsigned long STRAVA_POLL_INTERVAL_MS = 5UL * 60UL * 1000UL; // 5 minutes

// inside loop():
unsigned long now = millis();
if (now - lastPollMs >= STRAVA_POLL_INTERVAL_MS || now < lastPollMs) {
  lastPollMs = now;
  ActivityStats stats;
  if (fetchStravaToday(stats)) {
    lastStats = stats;
  } else if (fetchStravaLatestActivity()) {
    lastStats.distanceKm = lastActivity.distanceKm;
    lastStats.calories = lastActivity.calories;
    lastStats.fresh = true;
  }
  evaluateGoalAndMaybeUnlock();
}

evaluateGoalAndMaybeUnlock() is the function that takes the gathered activity stats and decides whether to call moveServoTo(SERVO_UNLOCK_ANGLE) (unlock) or moveServoTo(SERVO_LOCK_ANGLE) (lock).

Step-by-step: Strava auth/setup (short checklist)

Create a Strava API app in your Strava account and note the client_id and client_secret.
Build the authorisation URL (replace CLIENT_ID and REDIRECT_URI):
https://www.strava.com/oauth/authorize?client_id=CLIENT_ID&response_type=code&redirect_uri=http://localhost/exchange_token&approval_prompt=auto&scope=read,activity:read,activity:read_all
Open the URL in a browser, approve the app, capture the returned code (e.g. ...?code=YOUR_CODE).
Exchange the code for tokens (on your PC) — example cURL:

curl -X POST https://www.strava.com/api/v3/oauth/token \
  -d client_id=CLIENT_ID \
  -d client_secret=CLIENT_SECRET \
  -d code=YOUR_CODE \
  -d grant_type=authorization_code

Set STRAVA_CLIENT_ID, STRAVA_CLIENT_SECRET, STRAVA_ACCESS_TOKEN and STRAVA_REFRESH_TOKEN in the CookieJarV2 sketch.
Flash the ESP32-S3 and test by opening the device’s web page → “Show last activity”. You should see your latest Strava activity with HTTP 200.

Final assembly and test

Once assembled and flashed:

Lock the jar, set your target distance via the device web UI, go for your run, and wait for the device to poll Strava and evaluate your activity.
The sketch will automatically refresh tokens if required and will periodically check for new activities.

Milos demonstrates this flow in the video and finishes by going for a run to show the jar unlocking when the goal is met. He notes that the jar, when seen from the outside, looks like an ordinary jar of candy — the mechanism is hidden inside the lid.

“If you look at it from outside, it just looks like a jar full of candy bars… you won’t even know that there are some electronics inside.”

MR20 - Cookie Jar V2 - Video V1

Resources

Cookie Jar v1 Writeup: https://community.element14.com/challenges-projects/project14/theholidayspecial19/b/blog/posts/project-cookie-jar
Strava developer docs: https://developers.strava.com/docs/getting-started/
Code and files: Episode 694 Supporting Files

Bill of Materials

Product Name	Manufacturer	Quantity	Buy Kit
XIAO ESP32S3	SEEED STUDIO	1	Buy Now
SG90 Servo	DFROBOT	1	Buy Now
Battery Charger	DFROBOT	1	Buy Now

Additional Parts

Product Name	Manufacturer	Quantity
Glass Cookie Jar
1S LION Battery
3D Printing Filament like PLA

Tags: strava integration, 3d printed mechanism, wifi jar lock, diy smart jar, fitness reward system, esp32 project, esp32 servo control, fitness tracker diy, smart cookie jar, iot fitness project, strava API, friday_release, esp32 automation, locked biscuit barrel

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

cstanton — Thu, 11 Dec 2025 14:57:33 GMT

Revision 9 posted to Documents by cstanton on 12/11/2025 2:57:33 PM

In Milos' own words:

“It’s the holiday season… But if you want to get to that candy, we’ll make something that will make you run first.”

Watch the Project

https://youtu.be/jsQTD_6HNTA

What's the Idea

The original mechanism was hand-cut from 4 mm plywood; the small push rods used sheet metal salvaged from a gutter, there was plenty of room for improvement.

Enacting the Mechanism

A quote from the video where Milos describes the mechanism:

“In the centre we have the servo horn… and around that we have the three pistons that move linearly. So they’re connected together using this small pushrod… For the new version, I want to go with gears.”

MR20 - Cookie Jar V2 - Video V1

The new lid packs everything tightly; from the outside (when unlocked) there’s no visual clue that anything special is inside — just candy.

Setting up the Software

The jar uses the Strava API to determine whether the running goal has been achieved. Milos chose Strava because he uses it personally and it offers a straightforward developer API.

As Milos says:

“To create a small web server on the ESP32, which will just grab the JSON packages from the Strava app so we can actually see my latest activity here.”

Strava flow (summary)

Create a Strava API application (Settings → My API Application) and note client_id and client_secret.
Build and open the authorise URL to obtain the temporary code.
Exchange the code for access_token and refresh_token (the example cURL is shown below).
Copy the tokens into the Arduino sketch and flash the ESP32-S3. The code refreshes tokens automatically as needed.
Open the device web page and choose Show last activity to verify the device returns your latest Strava activity with HTTP 200.

The video also explains the UI / user-flow: set a distance goal (for example, 6 km) and the jar unlocks when recent activity meets the goal.

“It will just give you the name of your last activity, the distance you ran… ”

Key code excerpts (from `CookieJarV2.ino`)

Below are short, focused excerpts from the project code to explain the important behaviours. These are included to show how the software actually operates.

Configuration constants (Wi-Fi, Strava tokens and servo settings) - set these before flashing:

// Wi-Fi credentials
const char *WIFI_SSID = "YOUR-SSID";
const char *WIFI_PASSWORD = "YOUR-PASSWORD";

// Strava tokens and keys (example placeholders)
const char *STRAVA_CLIENT_ID = "YOUR_STRAVA_CLIENT_ID";
const char *STRAVA_CLIENT_SECRET = "YOUR_STRAVA_CLIENT_SECRET";
const char *STRAVA_ACCESS_TOKEN = "YOUR_STRAVA_ACCESS_TOKEN";
const char *STRAVA_REFRESH_TOKEN = "YOUR_STRAVA_REFRESH_TOKEN";

// Servo configuration
const int PIN_SERVO = 3; // ESP32 GPIO (confirm for your board)
const int SERVO_LOCK_ANGLE = 0;
const int SERVO_UNLOCK_ANGLE = 110;
const int SERVO_PULSE_DELAY_MS = 800;

Servo motion helper - the code attaches the servo, moves to the angle, waits, and detaches. Detaching stops the constant PWM “holding” signal, saving battery and stopping buzzing:

void moveServoTo(int angle) {
  jarServo.attach(PIN_SERVO);
  delay(100);
  jarServo.write(angle);
  delay(SERVO_PULSE_DELAY_MS);
  jarServo.detach();
}

This corresponds with Milos’s on-camera note about saving power and avoiding servo buzzing:

“One important thing to point here is that I do attach and detach, because if you just move a servo to a position you will continue sending it the signal… You just do the detach which does stop sending the signal out, in order to save a bit of power, because this is a battery-powered project after all.”

bool fetchStravaLatestActivity() {
  ensureWiFi();
  if (WiFi.status() != WL_CONNECTED) {
    lastError = "WiFi disconnected";
    return false;
  }

  // HTTP call to Strava /athlete/activities or other endpoint
  // Parse JSON, extract last activity id, name, distance (m -> km), calories etc.
  // Update lastActivity struct and hasLastActivity flag
  ...
  return true; // or false on error
}

The sketch includes a regular poll loop:

const unsigned long STRAVA_POLL_INTERVAL_MS = 5UL * 60UL * 1000UL; // 5 minutes

// inside loop():
unsigned long now = millis();
if (now - lastPollMs >= STRAVA_POLL_INTERVAL_MS || now < lastPollMs) {
  lastPollMs = now;
  ActivityStats stats;
  if (fetchStravaToday(stats)) {
    lastStats = stats;
  } else if (fetchStravaLatestActivity()) {
    lastStats.distanceKm = lastActivity.distanceKm;
    lastStats.calories = lastActivity.calories;
    lastStats.fresh = true;
  }
  evaluateGoalAndMaybeUnlock();
}

evaluateGoalAndMaybeUnlock() is the function that takes the gathered activity stats and decides whether to call moveServoTo(SERVO_UNLOCK_ANGLE) (unlock) or moveServoTo(SERVO_LOCK_ANGLE) (lock).

Step-by-step: Strava auth/setup (short checklist)

Create a Strava API app in your Strava account and note the client_id and client_secret.
Build the authorisation URL (replace CLIENT_ID and REDIRECT_URI):
https://www.strava.com/oauth/authorize?client_id=CLIENT_ID&response_type=code&redirect_uri=http://localhost/exchange_token&approval_prompt=auto&scope=read,activity:read,activity:read_all
Open the URL in a browser, approve the app, capture the returned code (e.g. ...?code=YOUR_CODE).
Exchange the code for tokens (on your PC) — example cURL:

curl -X POST https://www.strava.com/api/v3/oauth/token \
  -d client_id=CLIENT_ID \
  -d client_secret=CLIENT_SECRET \
  -d code=YOUR_CODE \
  -d grant_type=authorization_code

Set STRAVA_CLIENT_ID, STRAVA_CLIENT_SECRET, STRAVA_ACCESS_TOKEN and STRAVA_REFRESH_TOKEN in the CookieJarV2 sketch.
Flash the ESP32-S3 and test by opening the device’s web page → “Show last activity”. You should see your latest Strava activity with HTTP 200.

Final assembly and test

Once assembled and flashed:

Lock the jar, set your target distance via the device web UI, go for your run, and wait for the device to poll Strava and evaluate your activity.
The sketch will automatically refresh tokens if required and will periodically check for new activities.

“If you look at it from outside, it just looks like a jar full of candy bars… you won’t even know that there are some electronics inside.”

MR20 - Cookie Jar V2 - Video V1

Resources

Cookie Jar v1 Writeup: https://community.element14.com/challenges-projects/project14/theholidayspecial19/b/blog/posts/project-cookie-jar
Strava developer docs: https://developers.strava.com/docs/getting-started/
Code and files: Episode 694 Supporting Files

Bill of Materials

Product Name	Manufacturer	Quantity	Buy Kit
XIAO ESP32S3	SEEED STUDIO	1	Buy Now
SG90 Servo	DFROBOT	1	Buy Now
Battery Charger	DFROBOT	1	Buy Now

Additional Parts

Product Name	Manufacturer	Quantity
Glass Cookie Jar
1S LION Battery
3D Printing Filament like PLA

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

cstanton — Thu, 11 Dec 2025 14:53:56 GMT

Revision 8 posted to Documents by cstanton on 12/11/2025 2:53:56 PM

In Milos' own words:

“It’s the holiday season… But if you want to get to that candy, we’ll make something that will make you run first.”

Watch the Project

https://youtu.be/jsQTD_6HNTA

What's the Idea

The original mechanism was hand-cut from 4 mm plywood; the small push rods used sheet metal salvaged from a gutter, there was plenty of room for improvement.

Enacting the Mechanism

A quote from the video where Milos describes the mechanism:

“In the centre we have the servo horn… and around that we have the three pistons that move linearly. So they’re connected together using this small pushrod… For the new version, I want to go with gears.”

MR20 - Cookie Jar V2 - Video V1

The new lid packs everything tightly; from the outside (when unlocked) there’s no visual clue that anything special is inside — just candy.

Setting up the Software

The jar uses the Strava API to determine whether the running goal has been achieved. Milos chose Strava because he uses it personally and it offers a straightforward developer API.

As Milos says:

“To create a small web server on the ESP32, which will just grab the JSON packages from the Strava app so we can actually see my latest activity here.”

Strava flow (summary)

Create a Strava API application (Settings → My API Application) and note client_id and client_secret.
Build and open the authorise URL to obtain the temporary code.
Exchange the code for access_token and refresh_token (the example cURL is shown below).
Copy the tokens into the Arduino sketch and flash the ESP32-S3. The code refreshes tokens automatically as needed.
Open the device web page and choose Show last activity to verify the device returns your latest Strava activity with HTTP 200.

The video also explains the UI / user-flow: set a distance goal (for example, 6 km) and the jar unlocks when recent activity meets the goal.

“It will just give you the name of your last activity, the distance you ran… ”

Key code excerpts (from `CookieJarV2.ino`)

Below are short, focused excerpts from the project code to explain the important behaviours. These are included to show how the software actually operates.

Configuration constants (Wi-Fi, Strava tokens and servo settings) - set these before flashing:

// Wi-Fi credentials
const char *WIFI_SSID = "YOUR-SSID";
const char *WIFI_PASSWORD = "YOUR-PASSWORD";

// Strava tokens and keys (example placeholders)
const char *STRAVA_CLIENT_ID = "YOUR_STRAVA_CLIENT_ID";
const char *STRAVA_CLIENT_SECRET = "YOUR_STRAVA_CLIENT_SECRET";
const char *STRAVA_ACCESS_TOKEN = "YOUR_STRAVA_ACCESS_TOKEN";
const char *STRAVA_REFRESH_TOKEN = "YOUR_STRAVA_REFRESH_TOKEN";

// Servo configuration
const int PIN_SERVO = 3; // ESP32 GPIO (confirm for your board)
const int SERVO_LOCK_ANGLE = 0;
const int SERVO_UNLOCK_ANGLE = 110;
const int SERVO_PULSE_DELAY_MS = 800;

Servo motion helper - the code attaches the servo, moves to the angle, waits, and detaches. Detaching stops the constant PWM “holding” signal, saving battery and stopping buzzing:

void moveServoTo(int angle) {
  jarServo.attach(PIN_SERVO);
  delay(100);
  jarServo.write(angle);
  delay(SERVO_PULSE_DELAY_MS);
  jarServo.detach();
}

This corresponds with Milos’s on-camera note about saving power and avoiding servo buzzing:

“One important thing to point here is that I do attach and detach, because if you just move a servo to a position you will continue sending it the signal… You just do the detach which does stop sending the signal out, in order to save a bit of power, because this is a battery-powered project after all.”

bool fetchStravaLatestActivity() {
  ensureWiFi();
  if (WiFi.status() != WL_CONNECTED) {
    lastError = "WiFi disconnected";
    return false;
  }

  // HTTP call to Strava /athlete/activities or other endpoint
  // Parse JSON, extract last activity id, name, distance (m -> km), calories etc.
  // Update lastActivity struct and hasLastActivity flag
  ...
  return true; // or false on error
}

The sketch includes a regular poll loop:

const unsigned long STRAVA_POLL_INTERVAL_MS = 5UL * 60UL * 1000UL; // 5 minutes

// inside loop():
unsigned long now = millis();
if (now - lastPollMs >= STRAVA_POLL_INTERVAL_MS || now < lastPollMs) {
  lastPollMs = now;
  ActivityStats stats;
  if (fetchStravaToday(stats)) {
    lastStats = stats;
  } else if (fetchStravaLatestActivity()) {
    lastStats.distanceKm = lastActivity.distanceKm;
    lastStats.calories = lastActivity.calories;
    lastStats.fresh = true;
  }
  evaluateGoalAndMaybeUnlock();
}

evaluateGoalAndMaybeUnlock() is the function that takes the gathered activity stats and decides whether to call moveServoTo(SERVO_UNLOCK_ANGLE) (unlock) or moveServoTo(SERVO_LOCK_ANGLE) (lock).

Step-by-step: Strava auth/setup (short checklist)

Create a Strava API app in your Strava account and note the client_id and client_secret.
Build the authorisation URL (replace CLIENT_ID and REDIRECT_URI):
https://www.strava.com/oauth/authorize?client_id=CLIENT_ID&response_type=code&redirect_uri=http://localhost/exchange_token&approval_prompt=auto&scope=read,activity:read,activity:read_all
Open the URL in a browser, approve the app, capture the returned code (e.g. ...?code=YOUR_CODE).
Exchange the code for tokens (on your PC) — example cURL:

curl -X POST https://www.strava.com/api/v3/oauth/token \
  -d client_id=CLIENT_ID \
  -d client_secret=CLIENT_SECRET \
  -d code=YOUR_CODE \
  -d grant_type=authorization_code

Set STRAVA_CLIENT_ID, STRAVA_CLIENT_SECRET, STRAVA_ACCESS_TOKEN and STRAVA_REFRESH_TOKEN in the CookieJarV2 sketch.
Flash the ESP32-S3 and test by opening the device’s web page → “Show last activity”. You should see your latest Strava activity with HTTP 200.

Final assembly and test

Once assembled and flashed:

Lock the jar, set your target distance via the device web UI, go for your run, and wait for the device to poll Strava and evaluate your activity.
The sketch will automatically refresh tokens if required and will periodically check for new activities.

“If you look at it from outside, it just looks like a jar full of candy bars… you won’t even know that there are some electronics inside.”

MR20 - Cookie Jar V2 - Video V1

Resources

Cookie Jar v1 Writeup: https://community.element14.com/challenges-projects/project14/theholidayspecial19/b/blog/posts/project-cookie-jar
Strava developer docs: https://developers.strava.com/docs/getting-started/
Code and files:

Bill of Materials

Product Name	Manufacturer	Quantity	Buy Kit
XIAO ESP32S3	SEEED STUDIO	1	Buy Now
SG90 Servo	DFROBOT	1	Buy Now
Battery Charger	DFROBOT	1	Buy Now

Additional Parts

Product Name	Manufacturer	Quantity
Glass Cookie Jar
1S LION Battery
3D Printing Filament like PLA

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

cstanton — Thu, 11 Dec 2025 14:46:21 GMT

Revision 7 posted to Documents by cstanton on 12/11/2025 2:46:21 PM

In this video, Milos tackles a familiar problem: it’s the holiday season, there’s lots of delicious food and candy everywhere, and it’s too cold to go out much. To help with that, he created a Smart Cookie Jar that keeps you true to your word. The jar locks itself with all those treats inside and won’t open until you reach your running goal.

In Milos' own words:

“It’s the holiday season… But if you want to get to that candy, we’ll make something that will make you run first.”

Watch the Project

https://youtu.be/jsQTD_6HNTA

What's the Idea

The original mechanism was hand-cut from 4 mm plywood; the small push rods used sheet metal salvaged from a gutter, there was plenty of room for improvement.

Enacting the Mechanism

A quote from the video where Milos describes the mechanism:

“In the centre we have the servo horn… and around that we have the three pistons that move linearly. So they’re connected together using this small pushrod… For the new version, I want to go with gears.”

MR20 - Cookie Jar V2 - Video V1

The new lid packs everything tightly; from the outside (when unlocked) there’s no visual clue that anything special is inside — just candy.

Setting up the Software

The jar uses the Strava API to determine whether the running goal has been achieved. Milos chose Strava because he uses it personally and it offers a straightforward developer API.

As Milos says:

“To create a small web server on the ESP32, which will just grab the JSON packages from the Strava app so we can actually see my latest activity here.”

Strava flow (summary)

Create a Strava API application (Settings → My API Application) and note client_id and client_secret.
Build and open the authorize URL to obtain the temporary code.
Exchange the code for access_token and refresh_token (the example cURL is shown below).
Copy the tokens into the Arduino sketch and flash the ESP32-S3. The code refreshes tokens automatically as needed.
Open the device web page and choose Show last activity to verify the device returns your latest Strava activity with HTTP 200.

The video also explains the UI / user-flow: set a distance goal (for example, 6 km) and the jar unlocks when recent activity meets the goal.

“It will just give you the name of your last activity, the distance you ran… ”

Key code excerpts (from `CookieJarV2.ino`)

Below are short, focused excerpts from the project code to explain the important behaviours. These are included to show how the software actually operates.

Configuration constants (Wi-Fi, Strava tokens and servo settings) - set these before flashing:

// Wi-Fi credentials
const char *WIFI_SSID = "YOUR-SSID";
const char *WIFI_PASSWORD = "YOUR-PASSWORD";

// Strava tokens and keys (example placeholders)
const char *STRAVA_CLIENT_ID = "YOUR_STRAVA_CLIENT_ID";
const char *STRAVA_CLIENT_SECRET = "YOUR_STRAVA_CLIENT_SECRET";
const char *STRAVA_ACCESS_TOKEN = "YOUR_STRAVA_ACCESS_TOKEN";
const char *STRAVA_REFRESH_TOKEN = "YOUR_STRAVA_REFRESH_TOKEN";

// Servo configuration
const int PIN_SERVO = 3; // ESP32 GPIO (confirm for your board)
const int SERVO_LOCK_ANGLE = 0;
const int SERVO_UNLOCK_ANGLE = 110;
const int SERVO_PULSE_DELAY_MS = 800;

Servo motion helper - the code attaches the servo, moves to the angle, waits, and detaches. Detaching stops the constant PWM “holding” signal, saving battery and stopping buzzing:

void moveServoTo(int angle) {
  jarServo.attach(PIN_SERVO);
  delay(100);
  jarServo.write(angle);
  delay(SERVO_PULSE_DELAY_MS);
  jarServo.detach();
}

This corresponds with Milos’s on-camera note about saving power and avoiding servo buzzing:

“One important thing to point here is that I do attach and detach, because if you just move a servo to a position you will continue sending it the signal… You just do the detach which does stop sending the signal out, in order to save a bit of power, because this is a battery-powered project after all.”

bool fetchStravaLatestActivity() {
  ensureWiFi();
  if (WiFi.status() != WL_CONNECTED) {
    lastError = "WiFi disconnected";
    return false;
  }

  // HTTP call to Strava /athlete/activities or other endpoint
  // Parse JSON, extract last activity id, name, distance (m -> km), calories etc.
  // Update lastActivity struct and hasLastActivity flag
  ...
  return true; // or false on error
}

The sketch includes a regular poll loop:

const unsigned long STRAVA_POLL_INTERVAL_MS = 5UL * 60UL * 1000UL; // 5 minutes

// inside loop():
unsigned long now = millis();
if (now - lastPollMs >= STRAVA_POLL_INTERVAL_MS || now < lastPollMs) {
  lastPollMs = now;
  ActivityStats stats;
  if (fetchStravaToday(stats)) {
    lastStats = stats;
  } else if (fetchStravaLatestActivity()) {
    lastStats.distanceKm = lastActivity.distanceKm;
    lastStats.calories = lastActivity.calories;
    lastStats.fresh = true;
  }
  evaluateGoalAndMaybeUnlock();
}

evaluateGoalAndMaybeUnlock() is the function that takes the gathered activity stats and decides whether to call moveServoTo(SERVO_UNLOCK_ANGLE) (unlock) or moveServoTo(SERVO_LOCK_ANGLE) (lock).

Step-by-step: Strava auth/setup (short checklist)

Create a Strava API app in your Strava account and note the client_id and client_secret.
Build the authorisation URL (replace CLIENT_ID and REDIRECT_URI):
https://www.strava.com/oauth/authorize?client_id=CLIENT_ID&response_type=code&redirect_uri=http://localhost/exchange_token&approval_prompt=auto&scope=read,activity:read,activity:read_all
Open the URL in a browser, approve the app, capture the returned code (e.g. ...?code=YOUR_CODE).
Exchange the code for tokens (on your PC) — example cURL:

curl -X POST https://www.strava.com/api/v3/oauth/token \
  -d client_id=CLIENT_ID \
  -d client_secret=CLIENT_SECRET \
  -d code=YOUR_CODE \
  -d grant_type=authorization_code

Set STRAVA_CLIENT_ID, STRAVA_CLIENT_SECRET, STRAVA_ACCESS_TOKEN and STRAVA_REFRESH_TOKEN in the CookieJarV2 sketch.
Flash the ESP32-S3 and test by opening the device’s web page → “Show last activity”. You should see your latest Strava activity with HTTP 200.

Final assembly and test

Once assembled and flashed:

Lock the jar, set your target distance via the device web UI, go for your run, and wait for the device to poll Strava and evaluate your activity.
The sketch will automatically refresh tokens if required and will periodically check for new activities.

“If you look at it from outside, it just looks like a jar full of candy bars… you won’t even know that there are some electronics inside.”

MR20 - Cookie Jar V2 - Video V1

Resources

Cookie Jar v1 Writeup: https://community.element14.com/challenges-projects/project14/theholidayspecial19/b/blog/posts/project-cookie-jar
Strava developer docs: https://developers.strava.com/docs/getting-started/
Code and files:

Bill of Materials

Product Name	Manufacturer	Quantity	Buy Kit
XIAO ESP32S3	SEEED STUDIO	1	Buy Now
SG90 Servo	DFROBOT	1	Buy Now
Battery Charger	DFROBOT	1	Buy Now

Additional Parts

Product Name	Manufacturer	Quantity
Glass Cookie Jar
1S LION Battery
3D Printing Filament like PLA

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

cstanton — Thu, 11 Dec 2025 12:59:40 GMT

Revision 6 posted to Documents by cstanton on 12/11/2025 12:59:40 PM

In Milos' own words:

“It’s the holiday season… But if you want to get to that candy, we’ll make something that will make you run first.”

Watch the Project

https://youtu.be/jsQTD_6HNTA

What's the Idea

The original mechanism was hand-cut from 4 mm plywood; the small push rods used sheet metal salvaged from a gutter, there was plenty of room for improvement.

Enacting the Mechanism

A quote from the video where Milos describes the mechanism:

“In the centre we have the servo horn… and around that we have the three pistons that move linearly. So they’re connected together using this small pushrod… For the new version, I want to go with gears.”

MR20 - Cookie Jar V2 - Video V1

The new lid packs everything tightly; from the outside (when unlocked) there’s no visual clue that anything special is inside — just candy.

Setting up the Software

The jar uses the Strava API to determine whether the running goal has been achieved. Milos chose Strava because he uses it personally and it offers a straightforward developer API.

As Milos says:

“To create a small web server on the ESP32, which will just grab the JSON packages from the Strava app so we can actually see my latest activity here.”

Strava flow (summary)

Create a Strava API application (Settings → My API Application) and note client_id and client_secret.
Build and open the authorize URL to obtain the temporary code.
Exchange the code for access_token and refresh_token (the example cURL is shown below).
Copy the tokens into the Arduino sketch and flash the ESP32-S3. The code refreshes tokens automatically as needed.
Open the device web page and choose Show last activity to verify the device returns your latest Strava activity with HTTP 200.

The video also explains the UI / user-flow: set a distance goal (for example, 6 km) and the jar unlocks when recent activity meets the goal.

“It will just give you the name of your last activity, the distance you ran… ”

Key code excerpts (from `CookieJarV2.ino`)

Below are short, focused excerpts from the project code to explain the important behaviours. These are included to show how the software actually operates.

Configuration constants (Wi-Fi, Strava tokens and servo settings) - set these before flashing:

// Wi-Fi credentials
const char *WIFI_SSID = "YOUR-SSID";
const char *WIFI_PASSWORD = "YOUR-PASSWORD";

// Strava tokens and keys (example placeholders)
const char *STRAVA_CLIENT_ID = "YOUR_STRAVA_CLIENT_ID";
const char *STRAVA_CLIENT_SECRET = "YOUR_STRAVA_CLIENT_SECRET";
const char *STRAVA_ACCESS_TOKEN = "YOUR_STRAVA_ACCESS_TOKEN";
const char *STRAVA_REFRESH_TOKEN = "YOUR_STRAVA_REFRESH_TOKEN";

// Servo configuration
const int PIN_SERVO = 3; // ESP32 GPIO (confirm for your board)
const int SERVO_LOCK_ANGLE = 0;
const int SERVO_UNLOCK_ANGLE = 110;
const int SERVO_PULSE_DELAY_MS = 800;

Servo motion helper - the code attaches the servo, moves to the angle, waits, and detaches. Detaching stops the constant PWM “holding” signal, saving battery and stopping buzzing:

void moveServoTo(int angle) {
  jarServo.attach(PIN_SERVO);
  delay(100);
  jarServo.write(angle);
  delay(SERVO_PULSE_DELAY_MS);
  jarServo.detach();
}

This corresponds with Milos’s on-camera note about saving power and avoiding servo buzzing:

“One important thing to point here is that I do attach and detach, because if you just move a servo to a position you will continue sending it the signal… You just do the detach which does stop sending the signal out, in order to save a bit of power, because this is a battery-powered project after all.”

bool fetchStravaLatestActivity() {
  ensureWiFi();
  if (WiFi.status() != WL_CONNECTED) {
    lastError = "WiFi disconnected";
    return false;
  }

  // HTTP call to Strava /athlete/activities or other endpoint
  // Parse JSON, extract last activity id, name, distance (m -> km), calories etc.
  // Update lastActivity struct and hasLastActivity flag
  ...
  return true; // or false on error
}

The sketch includes a regular poll loop:

const unsigned long STRAVA_POLL_INTERVAL_MS = 5UL * 60UL * 1000UL; // 5 minutes

// inside loop():
unsigned long now = millis();
if (now - lastPollMs >= STRAVA_POLL_INTERVAL_MS || now < lastPollMs) {
  lastPollMs = now;
  ActivityStats stats;
  if (fetchStravaToday(stats)) {
    lastStats = stats;
  } else if (fetchStravaLatestActivity()) {
    lastStats.distanceKm = lastActivity.distanceKm;
    lastStats.calories = lastActivity.calories;
    lastStats.fresh = true;
  }
  evaluateGoalAndMaybeUnlock();
}

evaluateGoalAndMaybeUnlock() is the function that takes the gathered activity stats and decides whether to call moveServoTo(SERVO_UNLOCK_ANGLE) (unlock) or moveServoTo(SERVO_LOCK_ANGLE) (lock).

Step-by-step: Strava auth/setup (short checklist)

Create a Strava API app in your Strava account and note the client_id and client_secret.
Build the authorisation URL (replace CLIENT_ID and REDIRECT_URI):
https://www.strava.com/oauth/authorize?client_id=CLIENT_ID&response_type=code&redirect_uri=http://localhost/exchange_token&approval_prompt=auto&scope=read,activity:read,activity:read_all
Open the URL in a browser, approve the app, capture the returned code (e.g. ...?code=YOUR_CODE).
Exchange the code for tokens (on your PC) — example cURL:

curl -X POST https://www.strava.com/api/v3/oauth/token \
  -d client_id=CLIENT_ID \
  -d client_secret=CLIENT_SECRET \
  -d code=YOUR_CODE \
  -d grant_type=authorization_code

Set STRAVA_CLIENT_ID, STRAVA_CLIENT_SECRET, STRAVA_ACCESS_TOKEN and STRAVA_REFRESH_TOKEN in the CookieJarV2 sketch.
Flash the ESP32-S3 and test by opening the device’s web page → “Show last activity”. You should see your latest Strava activity with HTTP 200.

Final assembly and test

Once assembled and flashed:

Lock the jar, set your target distance via the device web UI, go for your run, and wait for the device to poll Strava and evaluate your activity.
The sketch will automatically refresh tokens if required and will periodically check for new activities.

“If you look at it from outside, it just looks like a jar full of candy bars… you won’t even know that there are some electronics inside.”

MR20 - Cookie Jar V2 - Video V1

Resources

Original project write-up (older version): https://community.element14.com/challenges-projects/project14/theholidayspecial19/b/blog/posts/project-cookie-jar
Strava developer docs: https://developers.strava.com/docs/getting-started/
Code and files:

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

cstanton — Thu, 11 Dec 2025 12:55:12 GMT

Revision 5 posted to Documents by cstanton on 12/11/2025 12:55:12 PM

In Milos' own words:

“It’s the holiday season… But if you want to get to that candy, we’ll make something that will make you run first.”

Watch the Project

https://youtu.be/jsQTD_6HNTA

What's the Idea

The original mechanism was hand-cut from 4 mm plywood; the small pushrods used sheet metal salvaged from a gutter, there was plenty of room for improvement.

Enacting the Mechanism

A quote from the video where Milos describes the mechanism:

“In the centre we have the servo horn… and around that we have the three pistons that move linearly. So they’re connected together using this small pushrod… For the new version, I want to go with gears.”

MR20 - Cookie Jar V2 - Video V1

The new lid packs everything tightly; from the outside (when unlocked) there’s no visual clue that anything special is inside — just candy.

Setting up the Software

The jar uses the Strava API to determine whether the running goal has been achieved. Milos chose Strava because he uses it personally and it offers a straightforward developer API.

As Milos says:

“To create a small web server on the ESP32, which will just grab the JSON packages from the Strava app so we can actually see my latest activity here.”

Strava flow (summary)

Create a Strava API application (Settings → My API Application) and note client_id and client_secret.
Build and open the authorize URL to obtain the temporary code.
Exchange the code for access_token and refresh_token (the example cURL is shown below).
Copy the tokens into the Arduino sketch and flash the ESP32-S3. The code refreshes tokens automatically as needed.
Open the device web page and choose Show last activity to verify the device returns your latest Strava activity with HTTP 200.

The video also explains the UI / user-flow: set a distance goal (for example, 6 km) and the jar unlocks when recent activity meets the goal.

“It will just give you the name of your last activity, the distance you ran… ”

Key code excerpts (from `CookieJarV2.ino`)

Below are short, focused excerpts from the project code to explain the important behaviours. These are included to show how the software actually operates.

Configuration constants (Wi-Fi, Strava tokens and servo settings) - set these before flashing:

// Wi-Fi credentials
const char *WIFI_SSID = "YOUR-SSID";
const char *WIFI_PASSWORD = "YOUR-PASSWORD";

// Strava tokens and keys (example placeholders)
const char *STRAVA_CLIENT_ID = "YOUR_STRAVA_CLIENT_ID";
const char *STRAVA_CLIENT_SECRET = "YOUR_STRAVA_CLIENT_SECRET";
const char *STRAVA_ACCESS_TOKEN = "YOUR_STRAVA_ACCESS_TOKEN";
const char *STRAVA_REFRESH_TOKEN = "YOUR_STRAVA_REFRESH_TOKEN";

// Servo configuration
const int PIN_SERVO = 3; // ESP32 GPIO (confirm for your board)
const int SERVO_LOCK_ANGLE = 0;
const int SERVO_UNLOCK_ANGLE = 110;
const int SERVO_PULSE_DELAY_MS = 800;

Servo motion helper - the code attaches the servo, moves to the angle, waits, and detaches. Detaching stops the constant PWM “holding” signal, saving battery and stopping buzzing:

void moveServoTo(int angle) {
  jarServo.attach(PIN_SERVO);
  delay(100);
  jarServo.write(angle);
  delay(SERVO_PULSE_DELAY_MS);
  jarServo.detach();
}

This corresponds with Milos’s on-camera note about saving power and avoiding servo buzzing:

“One important thing to point here is that I do attach and detach, because if you just move a servo to a position you will continue sending it the signal… You just do the detach which does stop sending the signal out, in order to save a bit of power, because this is a battery-powered project after all.”

bool fetchStravaLatestActivity() {
  ensureWiFi();
  if (WiFi.status() != WL_CONNECTED) {
    lastError = "WiFi disconnected";
    return false;
  }

  // HTTP call to Strava /athlete/activities or other endpoint
  // Parse JSON, extract last activity id, name, distance (m -> km), calories etc.
  // Update lastActivity struct and hasLastActivity flag
  ...
  return true; // or false on error
}

The sketch includes a regular poll loop:

const unsigned long STRAVA_POLL_INTERVAL_MS = 5UL * 60UL * 1000UL; // 5 minutes

// inside loop():
unsigned long now = millis();
if (now - lastPollMs >= STRAVA_POLL_INTERVAL_MS || now < lastPollMs) {
  lastPollMs = now;
  ActivityStats stats;
  if (fetchStravaToday(stats)) {
    lastStats = stats;
  } else if (fetchStravaLatestActivity()) {
    lastStats.distanceKm = lastActivity.distanceKm;
    lastStats.calories = lastActivity.calories;
    lastStats.fresh = true;
  }
  evaluateGoalAndMaybeUnlock();
}

evaluateGoalAndMaybeUnlock() is the function that takes the gathered activity stats and decides whether to call moveServoTo(SERVO_UNLOCK_ANGLE) (unlock) or moveServoTo(SERVO_LOCK_ANGLE) (lock).

Step-by-step: Strava auth/setup (short checklist)

Create a Strava API app in your Strava account and note the client_id and client_secret.
Build the authorisation URL (replace CLIENT_ID and REDIRECT_URI):
https://www.strava.com/oauth/authorize?client_id=CLIENT_ID&response_type=code&redirect_uri=http://localhost/exchange_token&approval_prompt=auto&scope=read,activity:read,activity:read_all
Open the URL in a browser, approve the app, capture the returned code (e.g. ...?code=YOUR_CODE).
Exchange the code for tokens (on your PC) — example cURL:

curl -X POST https://www.strava.com/api/v3/oauth/token \
  -d client_id=CLIENT_ID \
  -d client_secret=CLIENT_SECRET \
  -d code=YOUR_CODE \
  -d grant_type=authorization_code

Set STRAVA_CLIENT_ID, STRAVA_CLIENT_SECRET, STRAVA_ACCESS_TOKEN and STRAVA_REFRESH_TOKEN in the CookieJarV2 sketch.
Flash the ESP32-S3 and test by opening the device’s web page → “Show last activity”. You should see your latest Strava activity with HTTP 200.

Final assembly and test

Once assembled and flashed:

Lock the jar, set your target distance via the device web UI, go for your run, and wait for the device to poll Strava and evaluate your activity.
The sketch will automatically refresh tokens if required and will periodically check for new activities.

“If you look at it from outside, it just looks like a jar full of candy bars… you won’t even know that there are some electronics inside.”

MR20 - Cookie Jar V2 - Video V1

Resources

Original project write-up (older version): https://community.element14.com/challenges-projects/project14/theholidayspecial19/b/blog/posts/project-cookie-jar
Strava developer docs: https://developers.strava.com/docs/getting-started/
Code and files:

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

cstanton — Thu, 11 Dec 2025 11:39:15 GMT

Revision 4 posted to Documents by cstanton on 12/11/2025 11:39:15 AM

A line from the video sums the idea up:

“It’s the holiday season… But if you want to get to that candy, we’ll make something that will make you run first.”

https://youtu.be/jsQTD_6HNTA

Idea

The original mechanism was hand-cut from 4 mm plywood; the small pushrods used sheet metal salvaged from a gutter, there was plenty of room for improvement.

This time he decided to use an established fitness app (Strava) to get activity data instead of a crude step counter app. The design brief was simple: the jar must look like an ordinary jar from the outside — no obvious electronics, just a jar full of candy.

Mechanism

A quote from the video where Milos describes the mechanism:

“In the centre we have the servo horn… and around that we have the three pistons that move linearly. So they’re connected together using this small pushrod… For the new version, I want to go with gears.”

MR20 - Cookie Jar V2 - Video V1

The new lid packs everything tightly; from the outside (when unlocked) there’s no visual clue that anything special is inside — just candy.

Software

The jar uses the Strava API to determine whether the running goal has been achieved. Milos chose Strava because he uses it personally and it offers a straightforward developer API.

From the video:

“To create a small web server on the ESP32, which will just grab the JSON packages from the Strava app so we can actually see my latest activity here.”

MR20 - Cookie Jar V2 - Video V1

Strava flow (summary)

Create a Strava API application (Settings → My API Application) and note client_id and client_secret.
Build and open the authorize URL to obtain the temporary code.
Exchange the code for access_token and refresh_token (the example cURL is shown below).
Copy the tokens into the Arduino sketch and flash the ESP32-S3. The code refreshes tokens automatically as needed.
Open the device web page and choose Show last activity to verify the device returns your latest Strava activity with HTTP 200.

The video also explains the UI / user-flow: set a distance goal (for example, 6 km) and the jar unlocks when recent activity meets the goal.

“It will just give you the name of your last activity, the distance you ran… ”

MR20 - Cookie Jar V2 - Video V1

Key code excerpts (from `CookieJarV2.ino`)

Below are short, focused excerpts from the project code to explain the important behaviours. These are included to show how the software actually operates.

Configuration constants (Wi-Fi, Strava tokens and servo settings) — set these before flashing:

// Wi-Fi credentials
const char *WIFI_SSID = "YOUR-SSID";
const char *WIFI_PASSWORD = "YOUR-PASSWORD";

// Strava tokens and keys (example placeholders)
const char *STRAVA_CLIENT_ID = "YOUR_STRAVA_CLIENT_ID";
const char *STRAVA_CLIENT_SECRET = "YOUR_STRAVA_CLIENT_SECRET";
const char *STRAVA_ACCESS_TOKEN = "YOUR_STRAVA_ACCESS_TOKEN";
const char *STRAVA_REFRESH_TOKEN = "YOUR_STRAVA_REFRESH_TOKEN";

// Servo configuration
const int PIN_SERVO = 3; // ESP32 GPIO (confirm for your board)
const int SERVO_LOCK_ANGLE = 0;
const int SERVO_UNLOCK_ANGLE = 110;
const int SERVO_PULSE_DELAY_MS = 800;

Servo motion helper — the code attaches the servo, moves to the angle, waits, and detaches. Detaching stops the constant PWM “holding” signal, saving battery and stopping buzzing:

void moveServoTo(int angle) {
  jarServo.attach(PIN_SERVO);
  delay(100);
  jarServo.write(angle);
  delay(SERVO_PULSE_DELAY_MS);
  jarServo.detach();
}

This corresponds with Milos’s on-camera note about saving power and avoiding servo buzzing:

“One important thing to point here is that I do attach and detach, because if you just move a servo to a position you will continue sending it the signal… You just do the detach which does stop sending the signal out, in order to save a bit of power, because this is a battery-powered project after all.”

MR20 - Cookie Jar V2 - Video V1

Strava fetch (sketch of approach) — the code ensures Wi-Fi, calls the Strava API, parses activities and records the last activity details. The project polls Strava periodically (every five minutes by default):

bool fetchStravaLatestActivity() {
  ensureWiFi();
  if (WiFi.status() != WL_CONNECTED) {
    lastError = "WiFi disconnected";
    return false;
  }

  // HTTP call to Strava /athlete/activities or other endpoint
  // Parse JSON, extract last activity id, name, distance (m -> km), calories etc.
  // Update lastActivity struct and hasLastActivity flag
  ...
  return true; // or false on error
}

The sketch includes a regular poll loop:

const unsigned long STRAVA_POLL_INTERVAL_MS = 5UL * 60UL * 1000UL; // 5 minutes

// inside loop():
unsigned long now = millis();
if (now - lastPollMs >= STRAVA_POLL_INTERVAL_MS || now < lastPollMs) {
  lastPollMs = now;
  ActivityStats stats;
  if (fetchStravaToday(stats)) {
    lastStats = stats;
  } else if (fetchStravaLatestActivity()) {
    lastStats.distanceKm = lastActivity.distanceKm;
    lastStats.calories = lastActivity.calories;
    lastStats.fresh = true;
  }
  evaluateGoalAndMaybeUnlock();
}

evaluateGoalAndMaybeUnlock() is the function that takes the gathered activity stats and decides whether to call moveServoTo(SERVO_UNLOCK_ANGLE) (unlock) or moveServoTo(SERVO_LOCK_ANGLE) (lock).

Step-by-step: Strava auth/setup (short checklist)

Create a Strava API app in your Strava account and note the client_id and client_secret.
Build the authorisation URL (replace CLIENT_ID and REDIRECT_URI):
https://www.strava.com/oauth/authorize?client_id=CLIENT_ID&response_type=code&redirect_uri=http://localhost/exchange_token&approval_prompt=auto&scope=read,activity:read,activity:read_all
Open the URL in a browser, approve the app, capture the returned code (e.g. ...?code=YOUR_CODE).
Exchange the code for tokens (on your PC) — example cURL:

curl -X POST https://www.strava.com/api/v3/oauth/token \
  -d client_id=CLIENT_ID \
  -d client_secret=CLIENT_SECRET \
  -d code=YOUR_CODE \
  -d grant_type=authorization_code

Set STRAVA_CLIENT_ID, STRAVA_CLIENT_SECRET, STRAVA_ACCESS_TOKEN and STRAVA_REFRESH_TOKEN in the CookieJarV2 sketch.
Flash the ESP32-S3 and test by opening the device’s web page → “Show last activity”. You should see your latest Strava activity with HTTP 200.

Final assembly and test

Once assembled and flashed:

Lock the jar, set your target distance via the device web UI, go for your run, and wait for the device to poll Strava and evaluate your activity.
The sketch will automatically refresh tokens if required and will periodically check for new activities.

“If you look at it from outside, it just looks like a jar full of candy bars… you won’t even know that there are some electronics inside.”

MR20 - Cookie Jar V2 - Video V1

Resources

Original project write-up (older version): https://community.element14.com/challenges-projects/project14/theholidayspecial19/b/blog/posts/project-cookie-jar
Strava developer docs: https://developers.strava.com/docs/getting-started/
Code and files:

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

cstanton — Thu, 11 Dec 2025 10:43:24 GMT

Revision 3 posted to Documents by cstanton on 12/11/2025 10:43:24 AM

A line from the video sums the idea up:

“It’s the holiday season… But if you want to get to that candy, we’ll make something that will make you run first.”

MAIN VIDEO LINK

Idea

The original mechanism was hand-cut from 4 mm plywood; the small pushrods used sheet metal salvaged from a gutter, there was plenty of room for improvement.

This time he decided to use an established fitness app (Strava) to get activity data instead of a crude step counter app. The design brief was simple: the jar must look like an ordinary jar from the outside — no obvious electronics, just a jar full of candy.

Mechanism

A quote from the video where Milos describes the mechanism:

“In the centre we have the servo horn… and around that we have the three pistons that move linearly. So they’re connected together using this small pushrod… For the new version, I want to go with gears.”

MR20 - Cookie Jar V2 - Video V1

The new lid packs everything tightly; from the outside (when unlocked) there’s no visual clue that anything special is inside — just candy.

Software

The jar uses the Strava API to determine whether the running goal has been achieved. Milos chose Strava because he uses it personally and it offers a straightforward developer API.

From the video:

“To create a small web server on the ESP32, which will just grab the JSON packages from the Strava app so we can actually see my latest activity here.”

MR20 - Cookie Jar V2 - Video V1

Strava flow (summary)

Create a Strava API application (Settings → My API Application) and note client_id and client_secret.
Build and open the authorize URL to obtain the temporary code.
Exchange the code for access_token and refresh_token (the example cURL is shown below).
Copy the tokens into the Arduino sketch and flash the ESP32-S3. The code refreshes tokens automatically as needed.
Open the device web page and choose Show last activity to verify the device returns your latest Strava activity with HTTP 200.

The video also explains the UI / user-flow: set a distance goal (for example, 6 km) and the jar unlocks when recent activity meets the goal.

“It will just give you the name of your last activity, the distance you ran… ”

MR20 - Cookie Jar V2 - Video V1

Key code excerpts (from `CookieJarV2.ino`)

Below are short, focused excerpts from the project code to explain the important behaviours. These are included to show how the software actually operates.

Configuration constants (Wi-Fi, Strava tokens and servo settings) — set these before flashing:

// Wi-Fi credentials
const char *WIFI_SSID = "YOUR-SSID";
const char *WIFI_PASSWORD = "YOUR-PASSWORD";

// Strava tokens and keys (example placeholders)
const char *STRAVA_CLIENT_ID = "YOUR_STRAVA_CLIENT_ID";
const char *STRAVA_CLIENT_SECRET = "YOUR_STRAVA_CLIENT_SECRET";
const char *STRAVA_ACCESS_TOKEN = "YOUR_STRAVA_ACCESS_TOKEN";
const char *STRAVA_REFRESH_TOKEN = "YOUR_STRAVA_REFRESH_TOKEN";

// Servo configuration
const int PIN_SERVO = 3; // ESP32 GPIO (confirm for your board)
const int SERVO_LOCK_ANGLE = 0;
const int SERVO_UNLOCK_ANGLE = 110;
const int SERVO_PULSE_DELAY_MS = 800;

Servo motion helper — the code attaches the servo, moves to the angle, waits, and detaches. Detaching stops the constant PWM “holding” signal, saving battery and stopping buzzing:

void moveServoTo(int angle) {
  jarServo.attach(PIN_SERVO);
  delay(100);
  jarServo.write(angle);
  delay(SERVO_PULSE_DELAY_MS);
  jarServo.detach();
}

This corresponds with Milos’s on-camera note about saving power and avoiding servo buzzing:

“One important thing to point here is that I do attach and detach, because if you just move a servo to a position you will continue sending it the signal… You just do the detach which does stop sending the signal out, in order to save a bit of power, because this is a battery-powered project after all.”

MR20 - Cookie Jar V2 - Video V1

bool fetchStravaLatestActivity() {
  ensureWiFi();
  if (WiFi.status() != WL_CONNECTED) {
    lastError = "WiFi disconnected";
    return false;
  }

  // HTTP call to Strava /athlete/activities or other endpoint
  // Parse JSON, extract last activity id, name, distance (m -> km), calories etc.
  // Update lastActivity struct and hasLastActivity flag
  ...
  return true; // or false on error
}

The sketch includes a regular poll loop:

const unsigned long STRAVA_POLL_INTERVAL_MS = 5UL * 60UL * 1000UL; // 5 minutes

// inside loop():
unsigned long now = millis();
if (now - lastPollMs >= STRAVA_POLL_INTERVAL_MS || now < lastPollMs) {
  lastPollMs = now;
  ActivityStats stats;
  if (fetchStravaToday(stats)) {
    lastStats = stats;
  } else if (fetchStravaLatestActivity()) {
    lastStats.distanceKm = lastActivity.distanceKm;
    lastStats.calories = lastActivity.calories;
    lastStats.fresh = true;
  }
  evaluateGoalAndMaybeUnlock();
}

evaluateGoalAndMaybeUnlock() is the function that takes the gathered activity stats and decides whether to call moveServoTo(SERVO_UNLOCK_ANGLE) (unlock) or moveServoTo(SERVO_LOCK_ANGLE) (lock).

Step-by-step: Strava auth/setup (short checklist)

Create a Strava API app in your Strava account and note the client_id and client_secret.
Build the authorisation URL (replace CLIENT_ID and REDIRECT_URI):
https://www.strava.com/oauth/authorize?client_id=CLIENT_ID&response_type=code&redirect_uri=http://localhost/exchange_token&approval_prompt=auto&scope=read,activity:read,activity:read_all
Open the URL in a browser, approve the app, capture the returned code (e.g. ...?code=YOUR_CODE).
Exchange the code for tokens (on your PC) — example cURL:

curl -X POST https://www.strava.com/api/v3/oauth/token \
  -d client_id=CLIENT_ID \
  -d client_secret=CLIENT_SECRET \
  -d code=YOUR_CODE \
  -d grant_type=authorization_code

Set STRAVA_CLIENT_ID, STRAVA_CLIENT_SECRET, STRAVA_ACCESS_TOKEN and STRAVA_REFRESH_TOKEN in the CookieJarV2 sketch.
Flash the ESP32-S3 and test by opening the device’s web page → “Show last activity”. You should see your latest Strava activity with HTTP 200.

Final assembly and test

Once assembled and flashed:

Lock the jar, set your target distance via the device web UI, go for your run, and wait for the device to poll Strava and evaluate your activity.
The sketch will automatically refresh tokens if required and will periodically check for new activities.

“If you look at it from outside, it just looks like a jar full of candy bars… you won’t even know that there are some electronics inside.”

MR20 - Cookie Jar V2 - Video V1

Resources

Original project write-up (older version): https://community.element14.com/challenges-projects/project14/theholidayspecial19/b/blog/posts/project-cookie-jar
Strava developer docs: https://developers.strava.com/docs/getting-started/
Code and files:

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

cstanton — Thu, 11 Dec 2025 10:25:25 GMT

Revision 2 posted to Documents by cstanton on 12/11/2025 10:25:25 AM

A line from the video sums the idea up:

“It’s the holiday season… But if you want to get to that candy, we’ll make something that will make you run first.”

MAIN VIDEO LINK

Idea

The original mechanism was hand-cut from 4 mm plywood; the small pushrods used sheet metal salvaged from a gutter — there was plenty of room for improvement. You can read his original, detailed write-up here:
https://community.element14.com/challenges-projects/project14/theholidayspecial19/b/blog/posts/project-cookie-jar

This time he decided to use an established fitness app (Strava) to get activity data instead of a crude step counter app. The design brief was simple: the jar must look like an ordinary jar from the outside — no obvious electronics, just a jar full of candy.

Mechanism

A quote from the video where Milos describes the mechanism:

“In the centre we have the servo horn… and around that we have the three pistons that move linearly. So they’re connected together using this small pushrod… For the new version, I want to go with gears.”

MR20 - Cookie Jar V2 - Video V1

The new lid packs everything tightly; from the outside (when unlocked) there’s no visual clue that anything special is inside — just candy.

Software

The jar uses the Strava API to determine whether the running goal has been achieved. Milos chose Strava because he uses it personally and it offers a straightforward developer API.

From the video:

“To create a small web server on the ESP32, which will just grab the JSON packages from the Strava app so we can actually see my latest activity here.”

MR20 - Cookie Jar V2 - Video V1

Strava flow (summary)

Create a Strava API application (Settings → My API Application) and note client_id and client_secret.
Build and open the authorize URL to obtain the temporary code.
Exchange the code for access_token and refresh_token (the example cURL is shown below).
Copy the tokens into the Arduino sketch and flash the ESP32-S3. The code refreshes tokens automatically as needed.
Open the device web page and choose Show last activity to verify the device returns your latest Strava activity with HTTP 200.

The video also explains the UI / user-flow: set a distance goal (for example, 6 km) and the jar unlocks when recent activity meets the goal.

“It will just give you the name of your last activity, the distance you ran… ”

MR20 - Cookie Jar V2 - Video V1

Key code excerpts (from `CookieJarV2.ino`)

Below are short, focused excerpts from the project code to explain the important behaviours. These are included to show how the software actually operates.

Configuration constants (Wi-Fi, Strava tokens and servo settings) — set these before flashing:

// Wi-Fi credentials
const char *WIFI_SSID = "YOUR-SSID";
const char *WIFI_PASSWORD = "YOUR-PASSWORD";

// Strava tokens and keys (example placeholders)
const char *STRAVA_CLIENT_ID = "YOUR_STRAVA_CLIENT_ID";
const char *STRAVA_CLIENT_SECRET = "YOUR_STRAVA_CLIENT_SECRET";
const char *STRAVA_ACCESS_TOKEN = "YOUR_STRAVA_ACCESS_TOKEN";
const char *STRAVA_REFRESH_TOKEN = "YOUR_STRAVA_REFRESH_TOKEN";

// Servo configuration
const int PIN_SERVO = 3; // ESP32 GPIO (confirm for your board)
const int SERVO_LOCK_ANGLE = 0;
const int SERVO_UNLOCK_ANGLE = 110;
const int SERVO_PULSE_DELAY_MS = 800;

Servo motion helper — the code attaches the servo, moves to the angle, waits, and detaches. Detaching stops the constant PWM “holding” signal, saving battery and stopping buzzing:

void moveServoTo(int angle) {
  jarServo.attach(PIN_SERVO);
  delay(100);
  jarServo.write(angle);
  delay(SERVO_PULSE_DELAY_MS);
  jarServo.detach();
}

This corresponds with Milos’s on-camera note about saving power and avoiding servo buzzing:

“One important thing to point here is that I do attach and detach, because if you just move a servo to a position you will continue sending it the signal… You just do the detach which does stop sending the signal out, in order to save a bit of power, because this is a battery-powered project after all.”

MR20 - Cookie Jar V2 - Video V1

bool fetchStravaLatestActivity() {
  ensureWiFi();
  if (WiFi.status() != WL_CONNECTED) {
    lastError = "WiFi disconnected";
    return false;
  }

  // HTTP call to Strava /athlete/activities or other endpoint
  // Parse JSON, extract last activity id, name, distance (m -> km), calories etc.
  // Update lastActivity struct and hasLastActivity flag
  ...
  return true; // or false on error
}

The sketch includes a regular poll loop:

const unsigned long STRAVA_POLL_INTERVAL_MS = 5UL * 60UL * 1000UL; // 5 minutes

// inside loop():
unsigned long now = millis();
if (now - lastPollMs >= STRAVA_POLL_INTERVAL_MS || now < lastPollMs) {
  lastPollMs = now;
  ActivityStats stats;
  if (fetchStravaToday(stats)) {
    lastStats = stats;
  } else if (fetchStravaLatestActivity()) {
    lastStats.distanceKm = lastActivity.distanceKm;
    lastStats.calories = lastActivity.calories;
    lastStats.fresh = true;
  }
  evaluateGoalAndMaybeUnlock();
}

evaluateGoalAndMaybeUnlock() is the function that takes the gathered activity stats and decides whether to call moveServoTo(SERVO_UNLOCK_ANGLE) (unlock) or moveServoTo(SERVO_LOCK_ANGLE) (lock).

Step-by-step: Strava auth/setup (short checklist)

Create a Strava API app in your Strava account and note the client_id and client_secret.
Build the authorisation URL (replace CLIENT_ID and REDIRECT_URI):
https://www.strava.com/oauth/authorize?client_id=CLIENT_ID&response_type=code&redirect_uri=http://localhost/exchange_token&approval_prompt=auto&scope=read,activity:read,activity:read_all
Open the URL in a browser, approve the app, capture the returned code (e.g. ...?code=YOUR_CODE).
Exchange the code for tokens (on your PC) — example cURL:

curl -X POST https://www.strava.com/api/v3/oauth/token \
  -d client_id=CLIENT_ID \
  -d client_secret=CLIENT_SECRET \
  -d code=YOUR_CODE \
  -d grant_type=authorization_code

Set STRAVA_CLIENT_ID, STRAVA_CLIENT_SECRET, STRAVA_ACCESS_TOKEN and STRAVA_REFRESH_TOKEN in the CookieJarV2 sketch.
Flash the ESP32-S3 and test by opening the device’s web page → “Show last activity”. You should see your latest Strava activity with HTTP 200.

Final assembly and test

Once assembled and flashed:

Lock the jar, set your target distance via the device web UI, go for your run, and wait for the device to poll Strava and evaluate your activity.
The sketch will automatically refresh tokens if required and will periodically check for new activities.

“If you look at it from outside, it just looks like a jar full of candy bars… you won’t even know that there are some electronics inside.”

MR20 - Cookie Jar V2 - Video V1

Resources

Original project write-up (older version): https://community.element14.com/challenges-projects/project14/theholidayspecial19/b/blog/posts/project-cookie-jar
Strava developer docs: https://developers.strava.com/docs/getting-started/
Code and files:

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

cstanton — Thu, 11 Dec 2025 10:24:37 GMT

Revision 1 posted to Documents by cstanton on 12/11/2025 10:24:37 AM

A line from the video sums the idea up:

“It’s the holiday season… But if you want to get to that candy, we’ll make something that will make you run first.”

MR20 - Cookie Jar V2 - Video V1

MAIN VIDEO LINK

2. Idea

This time he decided to use an established fitness app (Strava) to get activity data instead of a crude step counter app. The design brief was simple: the jar must look like an ordinary jar from the outside — no obvious electronics, just a jar full of candy.

3. Mechanism

A quote from the video where Milos describes the mechanism:

“In the centre we have the servo horn… and around that we have the three pistons that move linearly. So they’re connected together using this small pushrod… For the new version, I want to go with gears.”

MR20 - Cookie Jar V2 - Video V1

The new lid packs everything tightly; from the outside (when unlocked) there’s no visual clue that anything special is inside — just candy.

4. Software

The jar uses the Strava API to determine whether the running goal has been achieved. Milos chose Strava because he uses it personally and it offers a straightforward developer API.

From the video:

“To create a small web server on the ESP32, which will just grab the JSON packages from the Strava app so we can actually see my latest activity here.”

MR20 - Cookie Jar V2 - Video V1

Strava flow (summary)

Create a Strava API application (Settings → My API Application) and note client_id and client_secret.
Build and open the authorize URL to obtain the temporary code.
Exchange the code for access_token and refresh_token (the example cURL is shown below).
Copy the tokens into the Arduino sketch and flash the ESP32-S3. The code refreshes tokens automatically as needed.
Open the device web page and choose Show last activity to verify the device returns your latest Strava activity with HTTP 200.

The video also explains the UI / user-flow: set a distance goal (for example, 6 km) and the jar unlocks when recent activity meets the goal.

“It will just give you the name of your last activity, the distance you ran… ”

MR20 - Cookie Jar V2 - Video V1

5. Key code excerpts (from `CookieJarV2.ino`)

Below are short, focused excerpts from the project code to explain the important behaviours. These are included to show how the software actually operates.

Configuration constants (Wi-Fi, Strava tokens and servo settings) — set these before flashing:

// Wi-Fi credentials
const char *WIFI_SSID = "YOUR-SSID";
const char *WIFI_PASSWORD = "YOUR-PASSWORD";

// Strava tokens and keys (example placeholders)
const char *STRAVA_CLIENT_ID = "YOUR_STRAVA_CLIENT_ID";
const char *STRAVA_CLIENT_SECRET = "YOUR_STRAVA_CLIENT_SECRET";
const char *STRAVA_ACCESS_TOKEN = "YOUR_STRAVA_ACCESS_TOKEN";
const char *STRAVA_REFRESH_TOKEN = "YOUR_STRAVA_REFRESH_TOKEN";

// Servo configuration
const int PIN_SERVO = 3; // ESP32 GPIO (confirm for your board)
const int SERVO_LOCK_ANGLE = 0;
const int SERVO_UNLOCK_ANGLE = 110;
const int SERVO_PULSE_DELAY_MS = 800;

Servo motion helper — the code attaches the servo, moves to the angle, waits, and detaches. Detaching stops the constant PWM “holding” signal, saving battery and stopping buzzing:

void moveServoTo(int angle) {
  jarServo.attach(PIN_SERVO);
  delay(100);
  jarServo.write(angle);
  delay(SERVO_PULSE_DELAY_MS);
  jarServo.detach();
}

This corresponds with Milos’s on-camera note about saving power and avoiding servo buzzing:

“One important thing to point here is that I do attach and detach, because if you just move a servo to a position you will continue sending it the signal… You just do the detach which does stop sending the signal out, in order to save a bit of power, because this is a battery-powered project after all.”

MR20 - Cookie Jar V2 - Video V1

bool fetchStravaLatestActivity() {
  ensureWiFi();
  if (WiFi.status() != WL_CONNECTED) {
    lastError = "WiFi disconnected";
    return false;
  }

  // HTTP call to Strava /athlete/activities or other endpoint
  // Parse JSON, extract last activity id, name, distance (m -> km), calories etc.
  // Update lastActivity struct and hasLastActivity flag
  ...
  return true; // or false on error
}

The sketch includes a regular poll loop:

const unsigned long STRAVA_POLL_INTERVAL_MS = 5UL * 60UL * 1000UL; // 5 minutes

// inside loop():
unsigned long now = millis();
if (now - lastPollMs >= STRAVA_POLL_INTERVAL_MS || now < lastPollMs) {
  lastPollMs = now;
  ActivityStats stats;
  if (fetchStravaToday(stats)) {
    lastStats = stats;
  } else if (fetchStravaLatestActivity()) {
    lastStats.distanceKm = lastActivity.distanceKm;
    lastStats.calories = lastActivity.calories;
    lastStats.fresh = true;
  }
  evaluateGoalAndMaybeUnlock();
}

evaluateGoalAndMaybeUnlock() is the function that takes the gathered activity stats and decides whether to call moveServoTo(SERVO_UNLOCK_ANGLE) (unlock) or moveServoTo(SERVO_LOCK_ANGLE) (lock).

6. Step-by-step: Strava auth/setup (short checklist)

Create a Strava API app in your Strava account and note the client_id and client_secret.
Build the authorisation URL (replace CLIENT_ID and REDIRECT_URI):
https://www.strava.com/oauth/authorize?client_id=CLIENT_ID&response_type=code&redirect_uri=http://localhost/exchange_token&approval_prompt=auto&scope=read,activity:read,activity:read_all
Open the URL in a browser, approve the app, capture the returned code (e.g. ...?code=YOUR_CODE).
Exchange the code for tokens (on your PC) — example cURL:

curl -X POST https://www.strava.com/api/v3/oauth/token \
  -d client_id=CLIENT_ID \
  -d client_secret=CLIENT_SECRET \
  -d code=YOUR_CODE \
  -d grant_type=authorization_code

Set STRAVA_CLIENT_ID, STRAVA_CLIENT_SECRET, STRAVA_ACCESS_TOKEN and STRAVA_REFRESH_TOKEN in the CookieJarV2 sketch.
Flash the ESP32-S3 and test by opening the device’s web page → “Show last activity”. You should see your latest Strava activity with HTTP 200.

7. Final assembly and test

Once assembled and flashed:

Lock the jar, set your target distance via the device web UI, go for your run, and wait for the device to poll Strava and evaluate your activity.
The sketch will automatically refresh tokens if required and will periodically check for new activities.

“If you look at it from outside, it just looks like a jar full of candy bars… you won’t even know that there are some electronics inside.”

MR20 - Cookie Jar V2 - Video V1

8. Resources

Original project write-up (older version): https://community.element14.com/challenges-projects/project14/theholidayspecial19/b/blog/posts/project-cookie-jar
Strava developer docs: https://developers.strava.com/docs/getting-started/
Code and files:

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

Watch the Project

What's the Idea

Enacting the Mechanism

Setting up the Software

Strava flow (summary)

Key code excerpts (from CookieJarV2.ino)

Step-by-step: Strava auth/setup (short checklist)

Final assembly and test

Resources

Bill of Materials

Additional Parts

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

Watch the Project

What's the Idea

Enacting the Mechanism

Setting up the Software

Strava flow (summary)

Key code excerpts (from CookieJarV2.ino)

Step-by-step: Strava auth/setup (short checklist)

Final assembly and test

Resources

Bill of Materials

Additional Parts

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

Watch the Project

What's the Idea

Enacting the Mechanism

Setting up the Software

Strava flow (summary)

Key code excerpts (from CookieJarV2.ino)

Step-by-step: Strava auth/setup (short checklist)

Final assembly and test

Resources

Bill of Materials

Additional Parts

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

Watch the Project

What's the Idea

Enacting the Mechanism

Setting up the Software

Strava flow (summary)

Key code excerpts (from CookieJarV2.ino)

Step-by-step: Strava auth/setup (short checklist)

Final assembly and test

Resources

Bill of Materials

Additional Parts

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

Watch the Project

What's the Idea

Enacting the Mechanism

Setting up the Software

Strava flow (summary)

Key code excerpts (from CookieJarV2.ino)

Step-by-step: Strava auth/setup (short checklist)

Final assembly and test

Resources

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

Watch the Project

What's the Idea

Enacting the Mechanism

Setting up the Software

Strava flow (summary)

Key code excerpts (from CookieJarV2.ino)

Step-by-step: Strava auth/setup (short checklist)

Final assembly and test

Resources

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

Idea

Mechanism

Software

Strava flow (summary)

Key code excerpts (from CookieJarV2.ino)

Step-by-step: Strava auth/setup (short checklist)

Final assembly and test

Resources

Earn Your Fitness Reward with a Smart Cookie Jar Using Strava and ESP32 -- Episode 694

Idea

Key code excerpts (from `CookieJarV2.ino`)

Key code excerpts (from `CookieJarV2.ino`)

Key code excerpts (from `CookieJarV2.ino`)

Key code excerpts (from `CookieJarV2.ino`)

Key code excerpts (from `CookieJarV2.ino`)

Key code excerpts (from `CookieJarV2.ino`)

Key code excerpts (from `CookieJarV2.ino`)

Key code excerpts (from `CookieJarV2.ino`)

Key code excerpts (from `CookieJarV2.ino`)

5. Key code excerpts (from `CookieJarV2.ino`)