Haptic Child Proximity Detector Wearable Device - Prototype

Problem statement

Public places today are more crowded than ever. Following the COVID-19 pandemic, there has been a reported rise in crowd disorder and unruly behaviour at crowded places and live events [1]. In these kind of busy environments, such as events, amusement parks or shopping centres, children can easily become separated from their parents, leading to distressing situations for both the child and the parent. Crowded areas can expose children to interactions with strangers, increasing the risk of abduction or getting lost. According to Missing Children Europe [2], a child is reported missing every two minutes in Europe, amounting to over 250 000 disappearances annually. Ensuring the well-being of a child is not only a moral obligation but a societal necessity. The problem of children getting lost in such scenarios poses significant challenges, including delayed awareness of the child’s absence, increased anxiety for both the child and the parents, and heightened safety risks.

Child safety is a fundamental concern, not only for parents and caregivers, but also for society as a whole. Various stakeholders are involved in ensuring the safety of children. Police and law enforcement agencies are often involved in search efforts when a child goes missing. But also event organisers bear a duty of care to attendees and must ensure proper safety measures and protocols to act swiftly when a child goes missing, which could possibly disrupt the event. Schools and educators also play a vital role in child safety by maintaining secure environments during school hours and educating children on safety protocols.

As technology evolves, it provides new tools and solutions to enhance child safety, addressing the complexities and dangers that children and their parents face today. The implementation of haptic technologies presents a promising solution to mitigate these challenges. By integrating haptic feedback mechanisms into wearable devices or accessories worn by children, such as wristbands or clothing, parents can receive immediate alerts through tactile sensations when their child strays beyond a predetermined distance. This proactive notification system enables parents to react swiftly, minimizing the duration of separation and improving the likelihood of a prompt reunion. Such technologies not only enhances physical safety but also contribute to the emotional well-being of both children and parents. Children could feel more protected and independent, knowing they can explore with a safety net in place. Parents experience a greater piece of mind, confident they can quickly know when their child is far. These advancements represent a significant step forward in creating a safer, more secure environment for children in our increasingly crowded world.

State of the art

Today, various solutions exist to track a child’s location, including smartphones, Bluetooth devices, smartwatches, GPS devices, etc [3].

Smartphones, in particular, can utilize GPS to track a child's location. By linking the parent's phone with the child's phone, parents can receive updates about their child's whereabouts [3]. Several apps support this system, such as Google Find My Device, Apple Find My Network, Life360 and Google Maps. Each app has its own pros and cons. For example, Google Find My Device is already installed on every Android phone and is easy to set-up. Apple Find my Network can be used even when the phone that you are searching is switched off, but it can only be used with Apple devices. However, both apps rise questions about personal safety, as the precise location tracking pose a risk of stalking [4]. Life360 offers features like crash detection and detailed location and device hardware reports, such as low battery, providing comprehensive safety measures. However, it requires a subscription for premium features and children, especially teenagers can start feeling micromanaged, given the amount of details shared by the app. Additionally, some have had concerns regarding device privacy [5]. Google Maps is known for consuming few battery power during location transmission but is not specifically designed for tracking kids, which may result in less accurate location updates and potential delays [6]. To conclude the discussion about smartphones as a tool to track children, it is important to address the significant drawbacks associated with their use. One of the major issues is that children do not always carry their phones with them. Additionally, smartphones often suffer from low battery life, rendering them for most apps ineffective in critical moments. Furthermore, younger children might not have smartphones at all, limiting the accessibility of this technology for a significant portion of the population.

In response to these limitations, Taha et al. developed a child tracking system using smartphones that leverages global positioning system (GPS) and global system for mobile communication (GSM) technology for real-time tracking [7]. The main component of this system include a GPS/GPRS/GSM worn by the child, which determines child’s precise location and transmits this information to a smartphone via a GSM modem. The hardware setup include an Arduino Uno microcontroller that processes and transmits the location data. Parents receive SMS alerts on their smartphones through the associated app, enabling them to monitor their child's location on Google Maps at any time and from anywhere [7].

However, the system has several drawbacks. The initial cost of purchasing the necessary components, such as the Arduino and GPS/GSM modules, might be a barrier for some families. The response time of the system can vary, taking from 30 seconds to up to 5 minutes to provide location updates, which might not be quick enough in emergency situations. The accuracy of the location data depends heavily on the GPS signal quality, which can be affected by environmental factors such as weather and physical obstructions. Additionally, security concerns also arise from the use of SMS for communication, as messages can potentially be intercepted. Finally, the need for parents to manually send an SMS to receive location updates may not be convenient in urgent situations [7].

Smartwatches present an alternative to smartphones for child tracking by ultilising GPS signals to determine and transmit the child’s location. While they function similarly to smartphones in terms of location tracking, they may exhibit slower performance and require manual updates to the location information [6]. For example, the AngelSense Watch, which employs GPS tracking, offers an unlimited tracking distance and a battery life up to 16 hours. Specifically designed for children with special needs, this smartwatch provides proactive alerts to parents through an accompanying mobile application. Additionally, it features an alarm that can be activated to help locate the child more easily [8].

However, despite these benefits, there are notable drawbacks to using smartwatches for child tracking. The limited battery life necessitates frequent recharging, which may render the device ineffective if it runs out of power during critical moments. Furthermore, the need for manual updates can be inconvenient and may result in delayed location information. Lastly, the cost of smartwatches can be prohibitively high for some families, and their bulkiness can make them uncomfortable for young children to wear consistently.

AngelSense offers not only a smartwatch but also a wearable GPS device designed for tracking children [5]. Similar to this device, Jiobit Smart Tag is also a wearable device that can be used for child tracking [3]. The Jiobit Smart Tag allows for tracking the child anywhere and includes an emergency alert button that the child can press in case of an emergency. Additionally, parents can receive real-time updates on the child's location and access a history of the places the child has visited [9]. A significant limitation of the Jiobit Smart Tag is its restricted usability to the United States due to 5G network constraints, rendering it ineffective in other regions globally.

Another wearable device is Smart Target’s Kiddo Kidkeeper, a wireless proximity alarm system designed to enhance child safety by helping parents track and contain wandering children within a preset boundary [10]. Developed in Portugal, the system consists of a transmitter for the child and a receiver for the adult, emitting audible alerts if the child strays beyond the set distance. It is user-friendly, offering two monitoring distances and the ability to track up to four children simultaneously [10]. However, the audible alerts may not always be heard in crowded places due to the background noise. 

Lastly, Bluetooth devices such as Apple AirTags can be used to track children [3]. The AirTag’s Bluetooth signal is detected by nearby Apple devices, which send the location to the parent’s IPhone [8]. The device can be placed anywhere, for example in the child’s backpack or clothing [8]. However, this method has several drawbacks. It poses a risk of stalking, as the linked phone's security can be compromised, potentially exposing the child’s location to unauthorized users [11]. Furthermore, the Bluetooth-based tracking can be inaccurate if the receiving Apple device is distant from the child [11]. Additionally, the AirTag must be near an Apple device to function, limiting its reliability in areas where Apple devices might not be available.

Samsung offers a similar device to Apple's AirTag: the Samsung SmartTag [12]. This device functions in the same manner, using Bluetooth signals to track items. However, it is designed to work exclusively with Samsung smartphones, meaning parents must own a Samsung device to use it effectively. Additionally, the Bluetooth signal from the SmartTag will only be detected by other Samsung devices, limiting its utility compared to more universally compatible options [12].

The solution

The proposed solution involves wearable bracelets for both the parent and the child, each equipped with a Bluetooth module and a vibration component. As long as the child remains within the Bluetooth range, both bracelets stay connected and no alerts are triggered. If the child moves out of range and the connection to the parent’s bracelet is lost, both bracelets will start vibrating. This immediate alert system notifies the parent that the child has strayed too far and informs the child to return.

Integrating haptic feedback mitigates drawbacks associated with current tracking technologies, such as inaudible alerts in noisy environments, short battery life of smartphones and smartwatches, and the discomfort of bulky devices. The bracelets are designed to be user-friendly, small, and easy to wear, enhancing both comfort and functionality.

This system significantly reduces the likelihood of children getting lost in crowded spaces, thereby lowering the incidence of missing children. Consequently, the need for police intervention is minimized, allowing law enforcement to focus on other urgent matters. Additionally, this proactive alert system decreases parental anxiety, enabling parents to enjoy activities without the constant stress of losing sight of their child. This innovative approach promises to contribute to a safer and more secure society.

This solution is elaborated step-by-step at the bottom of this page. A video of the solution, which contains a demonstration of the device is also provided.

References

[1]       Suzanne, ‘Why Has Crowd Disorder Risen Post-Pandemic?’, Mind Over Matter. Accessed: May 27, 2024. [Online]. Available: https://www.momconsultancy.com/blog/2023/03/29/why-has-crowd-disorder-risen-post-pandemic/

[2]       ‘Our campaign for Missing Children Europe’, MOJO Agency. Accessed: May 27, 2024. [Online]. Available: https://mojo-agency.org/case/missing-children-europe/

[3]       ‘The Best Ways to Track Your Kid (And Why You Might Not Want To)’, Wirecutter: Reviews for the Real World. Accessed: May 27, 2024. [Online]. Available: https://www.nytimes.com/wirecutter/blog/best-ways-to-track-your-kid/

[4]       S. Ovide, ‘Google’s new “Find My” device network is useful but a stalking risk’, Washington Post, May 10, 2024. Accessed: May 27, 2024. [Online]. Available: https://www.washingtonpost.com/technology/2024/05/10/android-find-my-network-google-is-it-safe/

[5]       ‘Pros and Cons of Life360: Is the Family Locator App Right for You?’, Life360. Accessed: May 27, 2024. [Online]. Available: https://www.life360.com/learn/pros-and-cons/

[6]       K. Shukla, ‘10 Best Mobile Tracker Apps in 2024 (Tested)’, MySmartPrice. Accessed: May 27, 2024. [Online]. Available: https://www.mysmartprice.com/gear/internet/internet-features/best-mobile-tracker-apps/

[7]       T. A. Taha, ‘Child tracking system using smartphone’, Bull. Electr. Eng. Inform., vol. 12, no. 5, pp. 2745–2752, 2023.

[8]       ‘Parents are using AirTags to track kids and give them freedom’, Washington Post. Accessed: May 27, 2024. [Online]. Available: https://www.washingtonpost.com/technology/2023/07/26/tracking-kids-airtags/

[9]       ‘#1 Kid Tracker: The Best GPS Tracker For Kids, Pets & Loved Ones | Jiobit’. Accessed: May 27, 2024. [Online]. Available: https://www.jiobit.com/

[10]     ‘Kiddo proximity alarm system offers parents peace of mind’. Accessed: May 27, 2024. [Online]. Available: https://newatlas.com/kiddo-proximity-alarm-system/8834/

[11]     ‘Why Apple AirTags Are Not Ideal for Kids’ Tracking: Exploring Safer Alternatives’. Accessed: May 27, 2024. [Online]. Available: https://blog.findmykids.org/blog/en/air-tags-for-kids

[12]     ‘Samsung Galaxy SmartTag2 review - Android Authority’. Accessed: May 27, 2024. [Online]. Available: https://www.androidauthority.com/samsung-galaxy-smarttag-2-review-3378184/

[13]     ‘HC-05 Bluetooth module met adapter - clone’, Opencircuit. Accessed: May 24, 2024. [Online]. Available: https://opencircuit.be/product/hc-05-bluetooth-module-met-adapter

This system involves following hardware and software components:

·       2x breadboards

·       2x Arduino Micro

·       2x HC-05 Bluetooth module

·       2x DRV 2605L drive

·       2x Linear Magnetic Rams (LRMs)

·       2x 1 kOhm resistor

·       2x 2 kOhm resistor

·       Jumper wires

·       2x computers provided with Arduino IDE

An image of the bill of materials (BOM) is provided. Some of these prices are only an estimate, since we had some of the materials already provided.

The first diagram shows how to wire the HC-05 module and the DRV 2605L module. The table details which Arduino connection port should be connected to the ports on the HC-05 module and the DRV 2605L module. This wiring scheme should be applied on both breadboards. Both Arduino's should additionally be connected to two different computers.

Parts of the wiring scheme were obtained from Fritzing and opencircuit.be.

The AT commands are used to change the default behaviour and settings of the Bluetooth HC-05 module. To get into AT commands of this Bluetooth module, the HC-05 module must be powered on while pressing down the button on the module itself. The red LED will start blinking very slowly (every 2 seconds). When this happens, follow these steps:

1.    Open Arduino IDE

2.    Upload the program shown in the first figure for both the Arduino’s. This program will check if Bluetooth is available and if so, a message will be sent and read by both the master and the slave.

3.    Open the Serial Monitor by clicking on the icon on the top right corner of the app. Make sure to indicate “Both NL & CR” and to set your transmission rate to “38400 bauds”. These settings are indicated in the second figure.

4.    To check if the module is in AT mode, type “AT” in the message prompt bar of the serial monitor. The app will give an “OK” message back. Next, the settings of the module will be set up. One Arduino will be setup as master, the other as slave.

For the slave configuration, following commands should be entered in the message prompt:

AT+NAME=”name”                 // Fill in a name of choice

AT+ROLE=0                           // Set as slave

AT+UART=38400,0,0             // Ensure baud rate is set to 38400

AT+ADDRESS?                      // Returns the IP address of the slave, copy this address

For the master configuration, following commands should be entered in the message prompt:

AT+NAME=”name”                // Fill in a name of choice

AT+ROLE=1                          // Set as master

AT+CMODE=0                      // Connect to specific address

AT+BIND=ADDRESS            // Bind to the slave's address (replace "ADDRESS" with the actual slave's address and replace the ":" by ",")

AT+UART=38400,0,0            // Ensure baud rate is set to 38400

Now unplug the modules of both breadboards, and immediately plug them back in. If the LEDs of both modules start blinking twice every two seconds, the modules are successfully connected. This could take a few seconds. To double check the connection, both Serial Monitors should see a connection message (of your own choice) being printed.

Note: When the LED begins to blink rapidly, it indicates that the device is in Normal mode. To revert to AT mode, disconnect the Arduino from the computer and reconnect it while holding the button on the HC-05 module down. This process will reset the device to the appropriate mode for further configuration.

Following link, obtained from Aced Inventor explains these steps in a video: https://www.youtube.com/watch?v=I2qFXSe0W3w&t=5s&ab_channel=AcedInventor

For the desired application, two LRMs (motors), each on a separate board, should start vibrating when the distance between the Bluetooth modules become too large and the connection is lost. In our application, the two modules constantly send a message to each other. When this message is lost, the connection is deemed lost and the motors vibrate. The code for both the master and slave is identical, except for the message that is sent, which you can choose yourself. The sent message of the master should be identical to the sent message of the slave, and vice versa. It cannot contain spaces.

Explanation of the code snippets:

1) Initialization:

• The SoftwareSerial library is used to create a software-based serial port for Bluetooth communication.
• The setup function initializes the serial communication and sets the pin mode for the motor.

2) Main Loop:

• The loop function constantly checks for incoming Bluetooth messages.
• If a message is received, it checks if it is the connection message ("ConnectedToSlave"). If so, it updates the connection status and records the time.
• If no message is received within the timeout period (3 seconds), it considers the connection lost and activates the motor.
• It also reads from the serial monitor and sends any data to the Bluetooth module.
• Finally, it sends a "connected" message every second to maintain the connection, and such that exactly the same can be seen in the slave.

3) Motor Control:

• The pulseMotor function is used to activate the motor for a specified duration.

The last step is to test the program and adapt it if necessary.