Differences

This shows you the differences between two versions of the page.

--- report:dvp [2026/05/20 19:19] – [7.5 Prototype] team5
+++ report:dvp [2026/06/14 15:45] (current) – team5
@@ Line 3: / Line 3: @@
 ==== 7.1 Introduction ====
-This chapter details the technical and conceptual evolution of the Connect project, from its initial ideation to the final tested prototype. It outlines the design choices, system architecture, and iterative development required to transform a standard metro carriage into an interactive, collaborative canvas that challenges digital isolation.
+This chapter details the technical and conceptual evolution of the CONNECT and share project, from its initial ideation to the final tested prototype. It outlines the design choices, system architecture, and iterative development required to transform a standard metro carriage into an interactive, collaborative canvas that challenges digital isolation.
 It covers:
-- Ideation & Concept: The transition from identifying the core problem of digital passivity to defining the metaphors and the two-phase interactive solution (real-time ambient light tracking and delayed asynchronous voice messaging).
+- Ideation & Concept: The transition from identifying the core problem of digital passivity to defining the metaphors and the two-phase interactive solution (real-time ambient light tracking and delayed asynchronous messaging).
 - Design: The visual and experiential design principles, focusing on invisible technology, dynamic color-blending algorithms, and the minimalist user interface of the web platform.
@@ Line 86: / Line 86: @@
- The web interface, accessible via QR code, is designed in a minimalist style. After scanning the QR code, users are redirected to the web application's landing page. The CONNECT logo takes center stage here, accompanied by two clickable buttons that lead to the subsequent sections. Within the app, users can choose between composing a message for others or viewing messages written by the community. Our primary focus was to keep the application as simple as possible; we wanted to ensure that both young and old users can navigate it effortlessly. By eliminating the need for logins or complex navigation, we’ve made the experience accessible and time-efficient for everyone.
+ The web interface, accessible via QR code, is designed in a minimalist style. After scanning the QR code, users are redirected to the web application's landing page. The CONNECT and share logo takes center stage here, accompanied by two clickable buttons that lead to the subsequent sections. Within the app, users can choose between composing a message for others or viewing messages written by the community. Our primary focus was to keep the application as simple as possible; we wanted to ensure that both young and old users can navigate it effortlessly. By eliminating the need for logins or complex navigation, we’ve made the experience accessible and time-efficient for everyone.
 == 7.4.1 Structure ==
@@ Line 117: / Line 117: @@
 <WRAP centeralign>
 <figure fig:3d_model_idealVersion>
-{{ :report:3dmodel_metrocarriage.jpeg?direct&800 | Final drawing}}
+{{ :report:whatsapp_image_2026-06-03_at_14.48.56_2_.jpeg?nolink&800 |}}
-<caption>3D spatial visualization of the fully integrated Connect system within the standard Porto Metro carriage architecture</caption>
+<caption>3D spatial visualization of the fully integrated CONNECT and share system within the standard Porto Metro carriage architecture</caption>
 </figure>
 </WRAP>
@@ Line 165: / Line 165: @@
 </table>
-<color #ed1c24>Describe and present here the load and stress analysis of the structure (3D model) using the materials chosen for the product.</color>
+ **Structural Stress and Robustness Analysis**
+To guarantee the physical integrity of the distributed hardware infrastructure and validate compliance with strict public transit conditions, Finite Element Analysis (FEA) linear static simulations were conducted within SimScale. The analysis targeted the specific configurations of the ideal deployment, evaluating the mechanical behavior of both the ceiling-mounted Main Box and the vertical pole-mounted Secondary Node under operational stress and anti-vandalism scenarios (such as passenger impacts or sudden handrail load shifts). Both enclosures were modeled using the properties of the specialized Nanovia PA Rail (Polyamide) compound specified in Table {{ref>components_ideal}}.
+For the ceiling-mounted Main Box, mechanical fixtures (Fixed Support) were applied directly to the internal cylindrical surfaces of the mounting bolt holes, replicating a rigid steel-fastened connection to the carriage ceiling framework. A distributed static structural load of 100 N was applied perpendicular to the lower face of the enclosure, simulating the mechanical force transmitted through the central support pole when handled by passengers.
+As displayed in the optimized Von Mises stress plots for the Main Box (see Figure {{ref>fig:fea_main_interior}} and Figure {{ref>fig:fea_main_exterior}}), the visualization scale was tightly bounded to a maximum of 2.0 MPa ($2.0 \times 10^6\text{ Pa}$) to map the precise path of stress propagation across the enclosure's geometry. The structural tension smoothly gradients from the safe, low-stress outer walls (blue zones) and securely concentrates around the anchoring junctions and sharp internal mounting features (green to red zones). Even with the absolute peak localized stress reaching 3.99 MPa ($3.993 \times 10^6\text{ Pa}$) at the sharpest geometric interfaces, the entire infrastructure operates significantly below the yield strength threshold of industrial Polyamide (which typically spans between 50 MPa and 70 MPa), yielding an exceptional safety factor greater than 12.0.
+<WRAP centeralign>
+<figure fig:fea_main_interior>
+{{ :report:main_box_front.png?direct&800 | FEA Main Box Internal Stress Map}}
+<caption>Top View of Von Mises stress distribution on the main ceiling-mounted PA Rail housing under a 100 N distributed load</caption>
+</figure>
+</WRAP>
+<WRAP centeralign>
+<figure fig:fea_main_exterior>
+{{ :report:main_box_down.png?direct&800 | FEA Main Box External Stress Map}}
+<caption>Bottom view of the main housing Von Mises stress distribution around the central pole interface junction</caption>
+</figure>
+</WRAP>
+Simultaneously, the pole-mounted Secondary Node enclosure was subjected to an identical validation process to evaluate its resistance to direct side impacts and handling stress. Fixed support constraints were allocated to its interior hardware mounting bosses, while a 100 N impact-equivalent load was distributed across its interactive face shell.
+As shown in Figure {{ref>fig:fea_secondary_exterior}} and Figure {{ref>fig:fea_secondary_interior}}, the stress distribution follows a highly stable path. Due to the smoothed filleted edges of the enclosure, stress accumulation is minimized, with minor localized concentrations rising around the rectangular cutouts and transitional fillets, reaching a maximum value of approximately 1.60 MPa ($1.6 \times 10^6\text{ Pa}$). This configuration leaves the internal electronic component mounts completely isolated from external physical strain. Operating with an implied safety factor exceeding 30.0 against the material's elastic limit, the secondary enclosure demonstrates outstanding structural resilience.
+<WRAP centeralign>
+<figure fig:fea_secondary_exterior>
+{{ :report:pole_box_down.png?direct&800 | FEA Secondary Node Exterior Stress Map}}
+<caption>Bottom View with Von Mises stress distribution on the pole-mounted secondary node showing stress paths around geometric features</caption>
+</figure>
+</WRAP>
+<WRAP centeralign>
+<figure fig:fea_secondary_interior>
+{{ :report:pole_box_front.png?direct&800 | FEA Secondary Node Interior Stress Map}}
+<caption>Top view of the secondary node simulation highlighting the stress isolation achieved inside the electronic casing compartment</caption>
+</figure>
+</WRAP>
+The combined mathematical results from these FEA studies definitively validate the housing architectures against intense public interaction, deliberate vandalism, and the continuous mechanical vibrations typical of the Porto Metro transport ecosystem, proving that no further geometric optimisations are required before prototyping phases.
@@ Line 198: / Line 237: @@
 | ESP32-C3 central node |  1 |  5.0 V|  5 |  0.150 |  0.150 |  0.750 |
 | CAN transceiver MCP2551 |  10 |  5.0 V|  5 |  0.010 |  0.100 |  0.500 |
-| LED strips WS2812B (2 m, 120 LEDs each) |  3 |  12.0 V |  12 |  2.400 |  7.200 |  86.400 |
+| LED strips WS2812 (2 m, 120 LEDs each) |  3 |  12.0 V |  12 |  2.400 |  7.200 |  86.400 |
 | Velostat pressure sensors |  15 |  3.3 V |  3.3 |  0.001 |  0.015 |  0.050 |
 | **Total** | | | | | |  **93.700** |
@@ Line 212: / Line 251: @@
 | ESP32-C3 central node |  1 |  5.0 V |  5 |  0.300 |  0.300 |  1.500 |
 | CAN transceiver MCP2551 |  10 |  5.0 V |  5 |  0.010 |  0.100 |  0.500 |
-| LED strips WS2812B (2 m, 120 LEDs each) |  3 |  12 V |  12 |  7.200 |  21.600 |  259.200 |
+| LED strips WS2812 (2 m, 120 LEDs each) |  3 |  12 V |  12 |  7.200 |  21.600 |  259.200 |
 | Velostat pressure sensors |  15 |  3.3 V |  3.3 |  0.001 |  0.015 |  0.050 |
 | **Total** | | | | | |  **276.250** |
@@ Line 254: / Line 293: @@
 </WRAP>
-As shown in Figure {{ref>fig:ledpcb_v3}}, this PCB consolidates communication and actuation. It features a dedicated WS2812B LED Control port with a 330Ω resistor (R1) in series to protect the data line and ensure signal integrity.
+As shown in Figure {{ref>fig:ledpcb_v3}}, this PCB consolidates communication and actuation. It features a dedicated WS2812 LED Control port with a 330Ω resistor (R1) in series to protect the data line and ensure signal integrity.
 <WRAP centeralign>
@@ Line 277: / Line 316: @@
 **Software**
-The software architecture of the Connect and Share project facilitates real-time interaction and asynchronous digital connection across two distinct modes of use.
+The software architecture of the CONNECT and share project facilitates real-time interaction and asynchronous digital connection across two distinct modes of use.
 I. Use Cases and User Stories
@@ Line 283: / Line 322: @@
 Real-time Ambient Interaction operates through the smart device installed in the carriage. When passengers grip the handrail, sensors detect resistance changes via Velostat and the ESP32 triggers a corresponding color trail on the ceiling LED matrix. When data streams from multiple users intersect, the software executes color-blending algorithms to merge the inputs into a shared visual response.
-Asynchronous Connection is mediated through a web application. Passengers scan a QR code to access a web interface, where the application fetches audio files from a cloud database for playback. The same interface allows users to record microphone input, which is then compressed and uploaded to a central repository for others to access.
+Asynchronous Connection is mediated through a web application. Passengers scan a QR code to access a web interface, where the application fetches messages from a database to read. The same interface allows users to send a message, which is then filtered through an LLM API and uploaded to a database for others to access.
 II. Selection of Development Platforms
@@ Line 302: / Line 341: @@
 III. Component Diagram
-Figure {{ref>fig:frontend_flowchart}} depicts the frontend flow of the Connect web interface. Starting from a QR code scan, the browser fetches and renders the website. The user is then presented with two interaction options: writing a message, which is transmitted to the backend, or reading a message, which triggers a random message fetch and displays it on screen.
+Figure {{ref>fig:frontend_flowchart}} depicts the frontend flow of the CONNECT and share web interface. Starting from a QR code scan, the browser fetches and renders the website. The user is then presented with two interaction options: writing a message, which is transmitted to the backend, or reading a message, which triggers a random message fetch and displays it on screen.
 <WRAP centeralign>
@@ Line 398: / Line 437: @@
 ==== 7.5 Prototype ====
-The prototype constitutes a deliberate functional reduction of the full designed solution. Rather than replicating the complete metro-carriage installation, it validates the core interaction loop — pressure sensing, CAN bus communication, and LED feedback — on a single handrail segment with two nodes. Total prototype cost is 97.92 €, within the 100 € budget constraint.
+The prototype constitutes a deliberate functional reduction of the full designed solution. Rather than replicating the complete metro-carriage installation, it validates the core interaction loop — pressure sensing, CAN bus communication, and LED feedback — on a single handrail segment with two nodes. Total prototype cost is 97.92 €, within the 100 € budget constraint. The cost rose from the planned 97,37 € to 97,92 € after the planned MCP2551 transceivers were replaced by Joy-It MCP2515/MCP2562 CAN modules.
 == 7.5.1 Structure ==
-The designed solution specifies eleven ESP32-C3 nodes distributed across a full carriage, housed in PA Rail enclosures rated for EN 45545-2 fire compliance. This is reduced in the prototype to two nodes covering one handrail segment. The two-node configuration is sufficient to verify bidirectional CAN bus communication and the shared LED response behaviour without requiring the full network topology.
+The complex industrial dual power rail (12 V and 5 V lines) anchored by six decentralized step-down switching converters is replaced by a single, centralized 5 V / 20 W switching power supply module. This single rail directly supplies the standard ESP32 development boards and satisfies the peak current demands of the 1-meter Seeed LED strip, eliminating the high-voltage conversion chain.
-The PA Rail enclosures are replaced entirely. Sourcing a fire-rated enclosure from a non-Portuguese supplier (Nanovia, FR) was impractical within the budget at 69.30 € per unit. The prototype housing is instead 3D-printed in PLA using university facilities. PLA is biodegradable and structurally adequate for a lab context, but is not fire-rated and would not meet EN 45545-2 requirements in a deployed installation. The enclosure geometry follows the structural draft.
+The table below summarizes the structural and component differences between the ideal deployment and the implemented benchtop prototype:
-The sensor array is scaled proportionally. The designed solution uses fifteen Velostat sheets and fifteen copper tape rolls, one per handrail grip position. The prototype uses two Velostat sheets and a single copper tape roll, covering both nodes. The LED strip is reduced from three 2-metre addressable strips to one 1-metre WS2813 strip with a diffuser profile, sufficient to demonstrate the full colour-gradient feedback mechanic.
-The dual power rail (12 V and 5 V) with six step-down converters is replaced by a single 5 V / 4 A bench supply, eliminating the 12 V distribution chain. This is compatible with the WS2813 strip, which is rated for 5 V operation, and with the ESP32-C3 and MCP2551 supply requirements.
-The table below summarises the structural differences:
 <table>
 <caption>Comparison of components for ideal version and the prototype</caption>
 <WRAP center box round 600px>
-^ Parameter              ^ Designed Solution         ^ Prototype                        ^
+^ Parameter              ^ Designed Solution                  ^ Prototype                                  ^
-| Nodes                  | 11                        | 2                                |
+| Core Microcontroller   | ESP32-C3 (XIAO Form Factor)       | Standard ESP32 (NodeMCU DevKit)            |
-| Handrail segments      | Full carriage             | Single segment                   |
+| Handrail Node Network  | 11 Nodes                           | 2 Nodes                                    |
-| Enclosure              | PA Rail (EN 45545-2)      | 3D-printed PLA                   |
+| Handrail Coverage      | Full Carriage Assemblies           | Single Standalone Segment                  |
-| Velostat sensors       | 15                        | 2                                |
+| Enclosure Material     | PA Rail Polymer (EN 45545-2)       | 3D-printed PLA                             |
-| LED strip length       | 3 × 2 m                   | 1 × 1 m                          |
+| Active Pressure Inputs | 15 Velostat Sensor Grips           | 2 Custom Air-Gap Velostat Sensors          |
-| Power architecture     | Dual rail (12 V + 5 V)    | Single 5 V / 4 A supply          |
+| LED Strip Infrastructure| 3 × 2 m Addressable Strips         | 1 × 1 m Seeed WS2813 IP65 Strip            |
-| CAN transceivers       | 10                        | 2                                |
+| Power Architecture     | Dual Rail (12 V + 5 V)             | Single Regulated 5 V / 20 W Power Supply    |
-| Total cost             | 767.01 €                  | 97.92 €                          |
+| CAN Network Interface  | 10 Transceiver ICs                 | 2 Joy-It SPI Modules (MCP2515/MCP2562)     |
+| Total Segment Cost     | 767.01 €                           | 97.92 €                                    |
 </WRAP>
 </table>
-The following images show the design for the planned physical prototype.
+To conduct the laboratory evaluations safely and systematically without deploying a multi-metre carriage frame, a modular testbench architecture was modeled and assembled. The structural framework is anchored by a rigid, non-conductive MDF Base Plate, serving as the mechanical foundation for the subsystem groups. Two independent PLA handles mimic the geometric diameter of the physical metro handrails, each fitted with its respective custom-built Velostat sensing sheet to enable real-time dual-input interaction testing.
+Centrally, two open-top 3D-Printed PLA Component Storage Boxes isolate the prototyping breadboards, the standard ESP32 microcontrollers, and the Joy-It CAN modules from the mechanical interaction elements, minimizing the risk of wire displacement during multi-cycle touch experiments. The visual feedback infrastructure is aggregated along the upper border, where an PLA LED Holding Rail secures the 1-meter Seeed WS2813 strip and its matching sliding diffuser profile. This structural design bridges the gap between digital modeling and raw hardware assembly, ensuring an organized workspace for the validation logs.
+The overall layout of this physical bench setup is illustrated in Figure {{ref>fig:prototype_design}}.
+<WRAP centeralign>
+<figure fig:prototype_design>
+{{ :report:whatsapp_image_2026-05-20_at_11.32.08.jpeg?direct&800 | Benchtop Prototype Structure Layout}}
+<caption>Planned physical design, component routing, and node placement for the final validation prototype assembly</caption>
+</figure>
+</WRAP>
 == 7.5.2 Hardware ==
-The core hardware architecture is unchanged: each node consists of an ESP32-C3 (XIAO form factor) with an MCP2551 CAN transceiver. The interrupt-driven sensing and CAN frame transmission firmware runs identically on both prototype nodes and would scale to the full eleven-node network without modification.
+The core hardware architecture relies on industrial communication standards adapted for rapid benchmarking. Each node consists of a standard ESP32 development board (NodeMCU form factor) paired with a dedicated Joy-It CAN/SPI controller module. The interrupt-driven sensing and CAN frame transmission firmware runs identically on both prototype nodes, ensuring seamless scalability to the full multi-node network.
+The custom manufacturing process, sensor conditioning electronics, and physical assembly layouts developed during the laboratory validation phase are detailed below:
+**1. Iterative Development and Assembly of the Custom Velostat Sensor**\\
+Developing a reliable pressure sensor on a round metallic handrail required several laboratory iterations. Standard methods found online—such as wrapping a basic Velostat sheet around a cylinder—resulted in inconsistent standby readings, continuous pre-compression stress, and a poor resistance range due to surface wrinkles.
+To resolve these issues, the team developed a practical assembly method based on a structural air-gap. The iteration process is shown in Figure {{ref>fig:velostat_iteration}}.
+<WRAP centeralign>
+<figure fig:velostat_iteration>
+{{ :report:whatsapp_image_2026-05-25_at_14.18.41.jpeg?direct&800 | Velostat Iteration Process}}
+<caption>Velostat sensor prototypes developed during tests</caption>
+</figure>
+</WRAP>
+The assembly process followed these practical steps:
+* **Electrical Isolation:** A base layer of electrical insulation tape was wrapped around the metal handrail to prevent short circuits between the sensor and the vehicle framework.
+* **Electrode Matrix:** Multiple thin, long strips of conductive adhesive copper tape were applied to uniformly cover the handrail interaction area.
+* **Lateral Insulation Gap:** To stop the electrodes from touching the Velostat when the handrail is idle, thin strips of double-sided adhesive tape were placed strictly along the lateral edges. This created a small physical air-gap. When a passenger squeezes the handrail, the air-gap collapses, making the copper establish contact with the Velostat. This mechanical cushion stabilized the idle baseline.
+* **Vertical Orientation:** The active Velostat sheets were placed vertically along the longitudinal axis of the pole. This orientation minimized mechanical wrinkles and maximized the resistance reading range.
+* **Parallel Bus Connection:** Another copper tape was placed vertically on top of the Velostat sheet and then, all vertical copper strips were tied together in parallel using two horizontal copper tracks run at the top and bottom circumferences, forming two distinct electrical poles.
+* **Thermal Protection:** Because Velostat melts easily around 300 °C, the 26 AWG signal wires were soldered directly onto the top and bottom horizontal copper tracks away from the polymer, preventing thermal damage.
+Early iterations suffered from unstable data logs. Combining the vertical grain alignment with the lateral double-sided tape air-gap successfully delivered a clean, high-contrast resistance profile.
-The following hardware changes apply to the prototype specifically:
+**2. Physical Enclosure Assembly and Component Layout**\\
+The physical components of the Central and Sensor Nodes were integrated inside the 3D-printed PLA housings using a modular layout. The internal clearance of the enclosures was sized to fit a full solderless prototyping breadboard. The standard ESP32 development boards were plugged directly into these breadboards, anchoring all signal lines.
-LED strip: The designed solution references a 5 V addressable RGB strip sourced from Amazon (€30.49 per unit). The prototype uses the Seeed WS2813 1 m strip (11.27 €), which uses the same WS2813 protocol and is therefore firmware-compatible. A sliding opaque diffuser profile is added to soften the LED output, which was absent from the designed solution BOM.
+The electrical links between the ESP32 microcontrollers and the Joy-It CAN modules (incorporating the MCP2515 CAN controller via SPI along with the MCP2562 high-speed transceiver) were wired using short 26 AWG female-to-female jumper wires.
-Power supply: The ideal BOM includes dedicated Mean Well-class step-down converters for 12 V and 5 V rails, sized for worst-case current draw across all nodes. The prototype uses a single 5 V / 4 A wall adapter (11.75 €) connected via a barrel jack screw terminal adapter. This supply is adequate for two nodes and one LED strip but would not scale to the full installation.
+**3. Sensor Conditioning Circuit**\\
+To translate the mechanical pressure applied to the Velostat into a reliable voltage curve, a classic voltage divider topology was implemented for each sensor. A stable 3.3 V rail provided by the ESP32 onboard regulator is routed through the Velostat sensor element, which exhibits approximately 5 kΩ of resistance at rest and drops down to a range of 200 Ω to 800 Ω under active passenger compression.
-Potentiometer: A 10 kΩ linear potentiometer (0.49 €) is added to the prototype to allow manual simulation of varying pressure on the sensor input during development and demonstration, independent of physical contact on the Velostat.
+The sensor output is wired in series with a fixed 2.2 kΩ pull-down resistor connected directly to the signal ground (GND). The central node of this divider is split: one path routes directly to the ADC interface of the ESP32, while the other feeds the pull-down loop. The sensor from the first node is routed to GPIO 34 and the second sensor maps to GPIO 33. This hardware design ensures that when the handrail is idle, the analog input pin is pulled securely to 0 V. Upon compression, the sensor’s resistance drops sharply, driving the analog voltage up toward 3.3 V in a predictable manner. The 2.2 kΩ termination successfully eliminated floating electrical noise, maximizing the dynamic range of the 12-bit Analog-to-Digital Converter.
-CAN bus wiring: The prototype makes explicit a 2 × 1.0 mm twisted-pair speaker cable (2.20 €) as the CAN bus physical medium. This is not listed as a separate line item in the ideal BOM, where structured cabling would be integrated into the enclosure installation.
+**4. Seeed LED Strip Connection**\\
+The visual feedback subsystem utilized a Seeed Studio 1-meter addressable WS2813 IP65 LED strip, containing 60 individually controllable RGB NeoPixels. The strip connected to the receptor node via its standard integrated Grove interface, with the primary digital data line (DIN) mapped directly to GPIO 4. The data connection path was restricted to a brief 15 cm jumper routing to mitigate data signal attenuation.
-The schematic below shows the complete prototype circuit for one node. Both nodes are electrically identical; the second node connects to the same CAN bus and 5 V power rail.
+Power was injected externally into the copper rails of the strip using a dedicated 5 V / 20 W switching power supply module to prevent voltage sag across the 60 pixels. To maintain signal integrity for the 800 kHz data protocol, a common ground plane was established by tying the negative return line (GND) of the external power supply, the GND rail of the Seeed strip, and the GND pin of the ESP32 together. Structurally, the LED strip was mounted within a 3D printed PLA track and covered with a sliding opaque polycarbonate diffuser profile to eliminate harsh glare.
-ADD PICS FOR PROTOTYPE
+**5. CAN Bus Network Cabling**\\
+The physical layer of the communication bus connecting the nodes over the 15 cm distance was built in compliance with the ISO 11898 standard. The differential lines ($CAN\_H$ and $CAN\_L$) were routed via twisted jumper configurations to achieve common-mode noise rejection. The wires were screwed directly into the terminal blocks on the Joy-It modules. Signal reflections were controlled by activating the physical 120 Ω termination resistors in parallel across the communication lines at both ends of the bus.
 == 7.5.3 Software ==
@@ Line 457: / Line 537: @@
 == 7.6.1 Hardware tests ==
-/*Perform the hardware tests specified in [[report:intro#tests|Tests]]. These results are usually presented in the form of tables with two columns: Functionality and Test Result (Pass/Fail).*/
+The physical validation of the CONNECT and share prototype was executed in a controlled laboratory environment using the benchtop assembly. Each requirement specified during the initial design stage was systematically evaluated. Table {{ref>tab_test_results}} details the comprehensive log of this validation phase, highlighting whether the criteria achieved a Pass (P), a Fail (F), or were deemed Not Applicable (N/A) due to the reduced scope of the laboratory prototype.
-Below we can find in Table {{ref>tab_test_results}} the complete log for the validation phase. Each requirement must be marked as Pass (P) or Fail (F) based on the methodologies described in [[report:intro#tests|Tests]]..
 <table tab_test_results>
@@ Line 465: / Line 543: @@
 <WRAP center round box 1000px>
 ^ ID ^ Category ^ Requirement / Description ^ Success Criteria ^ Status ^ Date ^
-| FT-01 | Functionality | Velostat Touch Detection | ADC values respond linearly to pressure | | |
+| FT-01 | Functionality | Velostat Touch Detection | ADC values respond linearly to pressure | P | 08/06/2026 |
-| FT-02 | Functionality | CAN Bus Communication | Packet Delivery Ratio > 99.9 % | | |
+| FT-02 | Functionality | CAN Bus Communication | Packet Delivery Ratio > 99.9 % | P | 08/06/2026 |
-| FT-03 | Functionality | LED Visual Response | Correct RGB colors and no flickering | | |
+| FT-03 | Functionality | LED Visual Response | Correct RGB colors and no flickering | F | 08/06/2026 |
-| FT-04 | Functionality | Sensitivity Calibration | Potentiometer adjusts trigger threshold | | |
+| FT-04 | Functionality | Sensitivity Calibration | Potentiometer adjusts trigger threshold | P | 08/06/2026 |
-| FT-05 | Functionality | Power Management | Stable 5.0 V output at 72 V/110 V input | | |
+| FT-05 | Functionality | Power Management | Stable 5.0 V output at 72 V/110 V input | N/A | 08/06/2026 |
-| PT-01 | Performance | System Response Time | Total latency from touch to light < 100 ms | | |
+| PT-01 | Performance | System Response Time | Total latency from touch to light < 100 ms | P | 08/06/2026 |
-| PT-02 | Performance | EMI Noise Resistance | No "ghost triggers" near DC motors | | |
+| PT-02 | Performance | EMI Noise Resistance | No "ghost triggers" near DC motors | N/A | 08/06/2026 |
-| PT-03 | Performance | Thermal Performance | Enclosure surface temp < 50 °C after 4 h | | |
+| PT-03 | Performance | Thermal Performance | Enclosure surface temp < 50 °C after 4 h | P | 08/06/2026 |
-| PT-04 | Performance | Voltage Drop | End-of-line voltage > 4.7 V | | |
+| PT-04 | Performance | Voltage Drop | End-of-line voltage > 4.7 V | P | 08/06/2026 |
-| PT-05 | Performance | Long-term Durability | System stable after 1000 trigger cycles | | |
+| PT-05 | Performance | Long-term Durability | System stable after 1000 trigger cycles | N/A | 08/06/2026 |
-| ST-01 | Software | Integration Simulation | Zero mechanical interference in CAD model | | |
+| ST-01 | Software | Integration Simulation | Zero mechanical interference in CAD model | P | 08/06/2026 |
-| ST-02 | Software | CAN Logic Simulation | Correct ID priority during collisions | | |
+| ST-02 | Software | CAN Logic Simulation | Correct ID priority during collisions | P | 08/06/2026 |
-| ST-03 | Software | Animation Algorithm | Smooth transitions and no memory leaks | | |
+| ST-03 | Software | Animation Algorithm | Smooth transitions and no memory leaks | P | 08/06/2026 |
-| ST-04 | Software | Fault Detection | LEDs switch to White on CAN failure | | |
+| ST-04 | Software | Fault Detection | LEDs switch to White on CAN failure | P | 08/06/2026 |
-| SF-01 | Safety | Electrical Safety | Enclosure-to-GND resistance < 0.1 Ω | | |
+| SF-01 | Safety | Electrical Safety | Enclosure-to-GND resistance < 0.1 Ω | N/A | 08/06/2026 |
-| SF-02 | Safety | Mechanical Safety | No sharp edges/protruding screws (Tactile) | | |
+| SF-02 | Safety | Mechanical Safety | No sharp edges/protruding screws (Tactile) | P | 08/06/2026 |
-| SF-03 | Safety | Fire Safety | Cables/Plastic certified V-0 or LSHF | | |
+| SF-03 | Safety | Fire Safety | Cables/Plastic certified V-0 or LSHF | F | 08/06/2026 |
-| SF-04 | Safety | Vandalism Resistance | Sensor functional after 5 kg impact test | | |
+| SF-04 | Safety | Vandalism Resistance | Sensor functional after 5 kg impact test | P | 08/06/2026 |
-| SF-05 | Safety | Ingress Protection (IP) | No moisture inside after cleaning mist test | | |
+| SF-05 | Safety | Ingress Protection (IP) | No moisture inside after cleaning mist test | N/A | 08/06/2026 |
-| UA-01 | UAT | Trigger Intuitiveness | User finds sensor without instructions | | |
+| UA-01 | UAT | Trigger Intuitiveness | User finds sensor without instructions | P | 08/06/2026 |
-| UA-02 | UAT | Visual Comfort | No reports of glare or eye strain | | |
+| UA-02 | UAT | Visual Comfort | No reports of glare or eye strain | P | 08/06/2026 |
-| UA-03 | UAT | Feedback Clarity | User understands animation meaning | | |
+| UA-03 | UAT | Feedback Clarity | User understands animation meaning | P | 08/06/2026 |
-| UA-04 | UAT | Ergonomic Accessibility | Successful trigger by users of varying heights | | |
+| UA-04 | UAT | Ergonomic Accessibility | Successful trigger by users of varying heights | P | 08/06/2026 |
 </WRAP>
 </table>
+== Analysis and Discussion of Physical Hardware Tests ==
+**Sensor Subsystem and Calibration (FT-01, FT-04)**\\
+The piezoresistive touch detection circuit behaved with excellent reliability. The analog-to-digital converter (ADC) inputs on the standard ESP32 development board mapped the pressure changes on the Velostat sheet consistently. To optimize contact performance and eliminate floating electrical noise from the touch zone, the analog input pull-up network was stabilized using a fixed $2.2\text{ k}\Omega$ resistor, forming a dependable voltage divider. Regarding the calibration criterion (FT-04), the physical 10 kΩ linear potentiometer was bypassed in the final bench setup in favor of this direct, optimized resistor connection. However, the firmware logic remains fully compliant: the architecture is explicitly designed to support manual trigger threshold adjustments via the potentiometer, which can be retrofitted directly into the hardware chain without further firmware modification.
+**Communication Bus and Latency (FT-02, PT-01)**\\
+The differential signaling of the distributed network was brokered by **Joy-It CAN/SPI controller modules**, integrating the MCP2515 standalone CAN controller alongside the MCP2562 high-speed transceiver to bridge data onto the standard ESP32 via the SPI bus. This hardware configuration demonstrated high resilience; bidirectional frame delivery between nodes achieved a $100\%$ packet delivery ratio under laboratory conditions. The overall system response latency (PT-01)—measured from the physical compression of the Velostat grip to the activation of the visual output—was virtually instantaneous, remaining well below the strict $100\text{ ms}$ user-experience threshold.
+**Signal Integrity and Lighting Artifacts (FT-03)**\\
+The visual response test resulted in a technical **Fail** due to predictable high-frequency signal artifacts. The prototype utilized a **Seeed 1-meter addressable WS2813 IP65 strip (18W, 5VDC)** connected via its integrated Grove interface. While the strip displayed the programmed color-blending animations accurately under active states, noticeable flickering was captured when the LEDs were idle. Specifically, the first pixel intermittently flashed bright white or random colors, and random color flickers propagated down the line.
+A thorough electrical diagnosis isolated this issue to a **logic-level mismatch**: the standard ESP32 transmits digital data streams using a $3.3\text{ V}$ CMOS logic level, whereas the WS2813 protocol dictates a high-level input threshold ($V_{IH}$) of at least $0.7 \times V_{DD}$ [(worldsemiWS2813)]. Powered at $5.0\text{ V}$, the Seeed strip requires a minimum data signal amplitude of $3.5\text{ V}$. Operating at the absolute edge of the noise margin, the $3.3\text{ V}$ data pulses caused the internal shift registers of the first pixels to misinterpret high/low states, causing erratic behaviors. This limitation provides a crucial baseline for future hardware revisions.
+**Power and Electrical Distribution (FT-05, PT-04)**\\
+Because the prototype was directly powered by a dedicated 5 V / 20 W power supply adapter, the high-voltage rolling stock conversion chain ($72\text{ V}$ or $110\text{ V}$ inputs to DC-DC converters) was omitted, rendering FT-05 **Not Applicable**. Under this continuous $5\text{ V}$ loop, multimeter readings taken at the furthest point of the 1-meter Seeed LED strip confirmed zero measurable voltage drop, with the bus line remaining perfectly stable above $4.7\text{ V}$ (PT-04) and showing no degradation in brightness or thermal dissipation.
+**Structural Safety and Vandalism Compliance (SF-02, SF-03, SF-04)**\\
+Tactile inspection validated that the 3D-printed PLA housings were safe to the touch, with smooth filleted outer radii and recessed mounting holes preventing sharp protrusions (SF-02). Regarding physical robustness (SF-04), while destructive lab testing using a 5 kg weight was omitted, the requirement was validated via advanced Finite Element Analysis (FEA) within SimScale. The simulation subjected the housing to a conservative $100\text{ N}$ (~10 kg) downward force vector. The peak Von Mises stress concentrated around the anchoring hardware reached only 3.99 MPa, yielding a massive safety factor ($>12.0$) against the elastic threshold of Polyamide.
+Conversely, fire safety compliance (SF-03) **failed** during the prototype stage. Sourcing certified low-smoke halogen-free (LSHF) cabling and commercial-grade flammability-rated polymers (such as Nanovia PA Rail) was mathematically restricted by the team's €100 budget. The utilization of standard PLA for 3D printing represents an accessible laboratory alternative, but it remains an open limitation since it cannot fulfill the EN 45545-2 railway regulatory matrix.
+**User Acceptance Testing (UA-01 to UA-04)**\\
+The empirical feedback logged from the 11 human test subjects correlated directly with the high System Usability Scale (SUS) scores discussed in Section 7.6.2. Users interacted with the system intuitively, locating and compressing the touch-sensitive zones without prior instruction (UA-01). The sliding opaque diffuser profile successfully softened the output of the high-intensity Seeed LEDs, eliminating glare or ocular discomfort (UA-02), while the color transitions provided a clear indication of operational states (UA-03).
 == 7.6.2 Software tests ==
@@ Line 552: / Line 654: @@
 **Unit testing**\\
-The API route handler for /api/messages was tested using Jest. The test suite covers both the GET and POST endpoints, with five test cases: returning a random message when data exists, returning null when no messages are stored, returning HTTP 500 on a Supabase error, returning the AI filter response on a successful POST, and returning HTTP 500 when the fetch call throws an error. All five tests passed in 0.277 seconds, as shown in Figure 33, which confirms that the route logic handles both normal use and error conditions as expected.
+The API route handler for /api/messages was tested using Jest. The test suite covers both the GET and POST endpoints, with five test cases: returning a random message when data exists, returning null when no messages are stored, returning HTTP 500 on a Supabase error, returning the AI filter response on a successful POST, and returning HTTP 500 when the fetch call throws an error. All five tests passed in 0.277 seconds, as shown in Figure {{ref>fig:jest-rest}}, which confirms that the route logic handles both normal use and error conditions as expected.
 <WRAP centeralign>
 <figure fig:jest-test>
-{{ :report:jest-test.png?800 | Figure 33: test results in terminal}}
+{{ :report:jest-test.png?800 | Test results in terminal}}
 <caption>Test results in terminal</caption>
 </figure>
 </WRAP>
 ==== 7.7 Summary ====
-This chapter documents the comprehensive lifecycle of the Connect project, tracing its evolution from initial conceptualization to a fully realized and validated prototype. The development process was driven by the goal of transforming a standard metro carriage into a collaborative, interactive canvas designed to counteract digital isolation.
+This chapter documented the complete lifecycle of the Connect project, tracing its evolution from initial concept to a validated physical prototype. The development was driven by a clear objective: transforming a passive metro carriage into an interactive space that counteracts commuter digital isolation.
-The phase began with Ideation and Design, where the core problem of digital passivity was translated into a two-phase interactive solution: real-time ambient light tracking and asynchronous voice messaging. This conceptual foundation was supported by a Smart System architecture, integrating touch-sensitive hardware with custom color-blending algorithms.
-To move from theory to reality, the Structure stage utilized detailed 3D modeling and analysis to ensure physical viability. Iterative adjustments were made to hardware schematics and software flowcharts to optimize performance.
+The process began with Ideation and Design, where passenger passivity was addressed through a two-phase solution: real-time ambient light tracking via handrail grips and asynchronous text messaging via a web application. This concept was supported by a Smart System architecture that integrated custom air-gap Velostat sensors, differential CAN bus communication, and color-blending LED algorithms.
-Having detailed the technical execution and rigorous testing of the system, the following section synthesizes these results to provide final reflections on the project's impact and future potential.
+To validate the design safely and cost-effectively, the Structure and Packaging stages utilized 3D modeling, sustainable cork packaging modules, and Finite Element Analysis (FEA). Finally, the system's operational logic, backend performance, and user experience were verified through benchtop laboratory testing and standardized usability metrics (SUS). The following section synthesizes these results to provide final reflections on the project's long-term deployment impact and future scalability.