• Product: First prototype of a stationary desktop game-playing robot with an animated face, camera, voice, buttons, moving head, and two expressive arms.
• Status: Draft for architecture review and staged prototype build.
• Implementation intent: Off-the-shelf Raspberry Pi and maker modules; jumper-wire/prototyping construction; no custom PCB in V1.
• Design priorities: Beginner-friendly assembly, robust power distribution, low integration risk, and local operation for games/basic reactions.

• Indoor, supervised desktop use in a home, studio, classroom, or demo environment.
• A person interacts using physical buttons, speech, and cards/dice/objects placed in a marked camera area in front of the robot.
• Local software runs simple games and basic expressive reactions without internet access.
• Wi-Fi is used for natural cloud-based conversation and optional software/content updates.
• V1 is a validation prototype, not a child-safe toy, unattended appliance, or production-ready product.

1. Boot into a friendly animated face and simple menu.
2. Run tic-tac-toe, quizzes, memory games, and reaction games locally.
3. Capture the tabletop area and recognize supported cards, dice faces, and trained objects.
4. Accept four primary physical inputs: select/confirm, back, left, and right.
5. Capture speech and play synthesized speech, effects, and prompts.
6. Use Wi-Fi for cloud conversation while degrading gracefully when offline.
7. Move a pan/tilt head and two small arms for gestures without moving the base.
8. Enter a safe neutral pose on startup, shutdown, software fault, or undervoltage detection.

• Raspberry Pi-class Linux compute with Wi-Fi and sufficient vision/UI performance.
• 4-inch touch display used as the animated face.
• Autofocus camera aimed at a defined play surface.
• Far-field USB microphone array with echo/noise processing and speaker output.
• Four independently controlled micro servos through an I2C PWM controller.
• Four panel buttons, optional illuminated rings, and an accessible power switch.
• Single external wall adapter feeding fused, separately regulated compute, auxiliary, and servo rails.
• Removable microSD storage and accessible USB/Ethernet for development.

Diagram

• Datasheet/product-confirmed: Raspberry Pi 5 accepts 5 V/5 A over USB-C; it has two MIPI camera/display transceivers. Camera Module 3 uses a 12 MP IMX708 sensor with autofocus. Waveshare's 4-inch DSI display is 480 x 800, capacitive-touch, and Pi 5 compatible. The Geekworm module is specified for 5 V/5 A output from a 9-24 V version. The Mean Well adapter is rated 12 V, 6.67 A, 80 W. The Pololu regulators are rated 5 V/6 A and 5 V/5 A respectively. Adafruit requires servo power to be separate from controller logic power.
• Engineering estimates pending measurement: Raspberry Pi workload current, display current, XVF3800 current/audio peaks, Camera Module 3 current, and MG90S moving/stall current. The power design intentionally uses conservative rounded estimates because module revisions, servo clones, mechanical load, volume, and software workload materially change consumption.

• Raspberry Pi 5, 4 GB, Raspberry Pi OS 64-bit, official Active Cooler, and 64 GB A2 microSD.
• Reserve one MIPI connector for DSI and one for CSI camera. Confirm the correct Pi 5 22-pin cables are included.
• Keep USB 3 and Ethernet physically accessible for setup and recovery.

• Display a full-screen animated face in portrait orientation at 480 x 800.
• Touch is optional for V1 game control; physical buttons remain the required accessible controls.
• Use four active-low GPIO buttons with internal pull-ups and software debounce. Add external 100 nF debounce capacitors only if testing shows cable-noise problems.

• Camera Module 3 Standard mounted above or within the head, looking downward toward a marked play zone.
• Provide adjustable tilt and rigid mounting; camera movement during recognition should be disabled or compensated.
• Start with controlled lighting, fixed background, fiducial markers, and known card/dice sets before attempting general object recognition.

• Mount the microphone array away from the speaker, servo gearboxes, fan exhaust, and loose panels.
• Use the XVF3800 processing features and keep speaker volume below acoustic-feedback onset.
• Cloud speech/conversation must have timeout, retry, mute, and offline fallback behavior.

• Four servos: head pan, head tilt, left arm, right arm.
• PCA9685 logic connects to the Pi I2C bus; servo V+ connects only to the dedicated 5 V servo rail.
• Software limits must be established before attaching limbs. Start near 90 degrees and expand travel slowly.
• Lightweight arms/head are required; do not design joints so a servo carries enclosure weight continuously.

• One 12 V desktop adapter enters the base through a locking or strain-relieved connector and master DC switch.
• Use star distribution and separate regulators for compute, auxiliary/audio/display, and servos.
• Do not power servos from the Raspberry Pi 5 V header, USB ports, or Pi power module output.
• All low-voltage grounds must join at the power-distribution star point so I2C/PWM signals have a common reference.

• Power source: Wall power only; no battery, charging, or runtime target in V1.
• Input: 12 V nominal from an 80 W desktop adapter.
• Expected typical input: approximately 1.5-2.0 A at 12 V during active games and ordinary motion, or roughly 18-24 W from the adapter before small conversion losses/variation.
• Calculated simultaneous peak estimate: approximately 4.2 A at 12 V before design margin, based on about 45 W of 5 V-rail load and 90% conversion efficiency.
• Sizing target with 25% transient margin: approximately 5.2 A at 12 V. The recommended 12 V/6.67 A adapter exceeds this target.
• Servo hard-stall must be treated as a brief fault/transient, not a continuous operating state. Motion software should detect repeated position commands/current symptoms and relax or disable affected servos.

Diagram

• Main input fuse: 7.5 A automotive blade fuse after the DC inlet and before the distribution split. This protects wiring; the certified adapter retains its own internal protection.
• Suggested 12 V branch fuses: 3 A compute, 3 A servo, and 1.5 A auxiliary. Validate against regulator inrush and revise only after measurement.
• Servo output fuse: approximately 5 A; use a holder and wiring rated above the fuse current.
• Servo bulk capacitance: begin with 2200-4700 uF, 10 V or higher, low-ESR electrolytic at the PCA9685 V+ terminal, plus the board's local ceramics. Adafruit's minimum rule of thumb is about 100 uF per servo; the larger value addresses four-servo transients and wiring inductance.
• Auxiliary rail: add 470-1000 uF near the audio/display split if measured dips or audio artifacts occur.
• Use 18 AWG for the main 12 V and servo-power trunk, 20-22 AWG for regulated power branches, and 24-26 AWG for short signals/buttons.
• Route servo power/ground as a pair and keep it separate from camera, MIPI, microphone, and speaker wiring. Join grounds at the distribution star, not through the Pi header.
• Check voltage at the load under motion. Target no lower than the connected module's documented minimum; investigate any Pi undervoltage warning immediately.

1. Build on an open baseplate before making the final enclosure.
2. Use crimped or screw-clamped power wiring; do not use solderless breadboard contacts for servo or main power.
3. Add strain relief to the DC input, USB-C lead, MIPI cables, and moving-head wiring.
4. Label both ends of every cable and use keyed connectors where possible.
5. Cover exposed distribution terminals and regulator undersides with insulating mounts/covers.
6. Keep the certified AC/DC adapter external; only SELV 12 V and lower enter the robot.
7. Use an accessible master power switch and retain access to the Pi power button, microSD, and recovery ports.

• Raspberry Pi OS 64-bit with Python 3.
• UI/animation: Pygame, Qt, Kivy, or browser kiosk; target stable 30 fps at 480 x 800.
• Vision: libcamera/Picamera2 and OpenCV; begin with fiducial/card templates and controlled dice recognition.
• GPIO: gpiozero or libgpiod for active-low buttons; software debounce of approximately 30-80 ms.
• Servo control: Adafruit CircuitPython PCA9685/ServoKit or equivalent; configurable center, direction, minimum, maximum, speed, and acceleration per joint.
• Audio: ALSA/PipeWire-compatible USB Audio Class device; echo-cancellation settings validated with the final speaker position.
• Networking: stored Wi-Fi credentials, NTP, TLS certificate validation, cloud API timeout, retry/backoff, and explicit offline state.
• Safety behavior: neutral pose at service start, motion inhibit during camera calibration, per-joint travel limits, rate limiting, watchdog, and clean shutdown.
• Data: local game assets and state must not require cloud access; cloud credentials stored outside source control.
• Diagnostics: log CPU temperature, undervoltage/throttling flags, camera/audio availability, servo-command faults, and cloud latency.

• Boots reliably 10 consecutive times without undervoltage or filesystem errors.
• Animated face runs at at least 30 fps for 30 minutes without thermal throttling.
• All four buttons register one event per press with no false events during idle.
• Tic-tac-toe and one quiz/memory game run fully offline.

• Camera recognizes the selected card set and all six dice faces in controlled lighting with at least 90% accuracy over a documented 50-sample test per class/set condition.
• Voice capture works from approximately 1 m in a quiet room.
• Robot plays prompts and speech without clipping at the intended volume.
• Cloud conversation completes a 10-turn test with graceful timeout/error feedback; games continue when Wi-Fi is disabled.

• Each rail is within its module's allowed voltage before loads are connected.
• No Pi undervoltage/throttling event occurs during 100 repeated gesture cycles with display, camera, microphone, and audio active.
• Head and arms remain inside calibrated software/mechanical limits and return to neutral after restart or controlled fault.
• A deliberately obstructed joint does not reset the Pi; firmware stops or relaxes motion promptly.
• Main and branch wiring, connectors, regulators, and fuses remain below an agreed touch-safe temperature after 30 minutes of worst normal use.

• Camera play zone, face visibility, button access, speaker clarity, microphone pickup, and full servo travel are unobstructed.
• Cables do not rub, pinch, or enter servo linkages through the complete motion range.
• The robot completes a 2-hour mixed game/voice/motion soak test without crash, reset, thermal throttling, or loose connections.

• Stationary weighted base with rubber feet; no drive motors in V1.
• Approximate target envelope: 180-250 mm wide, 150-220 mm deep, and 250-400 mm tall, to be refined after module mock-up.
• Face display: 3-4 inch visible area, near vertical, readable from seated desktop distance.
• Camera: centered above/below the face or in the forehead, with an unobstructed view of a marked play zone roughly 200-400 mm in front of the base.
• Arms and head must be lightweight, rounded, and mechanically limited so linkages cannot over-rotate.
• Provide ventilation around the Pi cooler, regulators, and audio amplifier; do not vent directly into the microphone.
• Keep the adapter external and prevent user access to live electrical terminals.

• Use Raspberry Pi 5, 4 GB as the primary compute platform; performance margin is favored over the lower power of Pi 4.
• Use one MIPI port for DSI display and the second for Camera Module 3, avoiding HDMI/USB video clutter.
• Use a processed USB microphone array with speaker support to minimize acoustic/driver integration risk.
• Use PCA9685 rather than software-generated servo PWM.
• Use a 12 V external adapter and three separately fused 5 V branches; the Pi remains powered through USB-C and the servos never use Pi 5 V.
• Keep local games, core UI, and basic reactions independent of cloud availability.
• Defer custom PCB, battery, locomotion, large local language models, and production enclosure engineering.

• Four MG90S-class servos are sufficient if the head and arms are lightweight. Actual stall current and torque vary significantly among genuine units and clones; buy from a reputable source and measure one sample before finalizing fuses/mechanics.
• Display and XVF3800 peak currents are not stated in the reviewed public product pages; estimates must be replaced by bench measurements.
• The XVF3800 speaker interface and exact speaker impedance/power wiring must be confirmed against the purchased board revision before connection.
• The auxiliary-power method must not backfeed the Pi through DSI or USB. Use only documented power paths; otherwise keep the display/microphone on the Pi rail and remeasure compute-rail margin.
• Servo noise may reduce microphone and vision performance. Mechanical isolation, motion scheduling, and acoustic tuning may be required.
• Cloud provider, speech/LLM API, privacy policy, ongoing cost, and latency targets remain undecided.
• Vision acceptance depends on defined cards, dice style, object classes, play-zone geometry, and lighting; unconstrained general recognition is outside V1.
• The final enclosure must be checked for tip stability and pinch points before use around children or the public.

• Raspberry Pi 5 product page
• Raspberry Pi 27 W USB-C Power Supply
• Raspberry Pi Camera Module 3
• Waveshare 4inch DSI LCD wiki
• Seeed Studio ReSpeaker XVF3800 introduction
• Adafruit PCA9685 servo-driver wiring guidance
• Geekworm Pi5-5V5APD
• Pololu D42V55F5 5 V/6 A regulator
• Pololu D24V50F5 5 V/5 A regulator
• Mean Well GST90A series datasheet

• 2026-08-15 - Initial draft: Captured confirmed product behavior, selected a current Raspberry Pi 5 module architecture, added alternatives, defined a separately fused three-rail power system, calculated typical/peak input needs, documented staged implementation, and added measurable acceptance criteria.