RoboHub · Build spec sheet

This build delivers an expressive 3-DOF talking desktop companion running on a…

robohub.app/build/saved/d23cfd24-5253-4ab9-9541-b5c39e0cd7b1
11/10/2026

This build delivers an expressive 3-DOF talking desktop companion running on a Raspberry Pi 5 with hardware privacy controls, far-field audio, and physical servo limits. It trades off onboard local LLM speed by supporting lightweight quantized models (e.g. TinyLlama/Phi-2 via llama.cpp) or low-latency cloud fallback while ensuring zero local audio persistence.

Live total

$391 USD

Parts

Effort

—

Architecture

A weighted desktop base encloses an active-cooled Raspberry Pi 5 powered by a continuous 12V-to-5V regulated power brick with an emergency battery buffer. Compute orchestrates voice via a ReSpeaker USB 4-mic array and MAX98357A I2S amplifier with speaker, while an optional physical-shutter wide-angle camera handles face orientation. Actuation uses three enclosed metal-gear servos for yaw, pitch, and roll behind physical silicone stops to ensure pinch-safe interaction, coupled with a physical microphone mute switch and illuminated LED status ring.

Bill of Materials (14)

actuation

Part	Purpose	Qty	Unit	Line
KST DS113MG Digital Metal Gear Micro Servos	Precision, quiet 3-DOF head movement (yaw, pitch, roll)	3	$24	$72
PCA9685 16-Channel 12-bit I2C PWM Driver	Offloads jitter-free servo pulse generation from SBC	1	$4	$4

chassis

Part	Purpose	Qty	Unit	Line
Weighted Aluminum Desktop Stand Base with Anti-Vibration Feet	Provides ballast to prevent tip-over during rapid head gestures	1	$22	$22
PETG Filament 1kg & M3 Brass Heatset Insert Assortment	Rigid 3D printed skeleton, brackets, and silicone bump-stops	1	$28	$28

compute

Part	Purpose	Qty	Unit	Line
Raspberry Pi 5 8GB RAM	Primary onboard compute for STT, LLM inference, TTS, and servo orchestration	1	$88	$88
Raspberry Pi Official Active Cooler	Sustained CPU/GPU cooling under high continuous inference workloads	1	$7	$7

connectivity

Part	Purpose	Qty	Unit	Line
SanDisk Extreme 128GB A2 MicroSD Card	Fast OS, fast swap, and storage for quantized speech models	1	$19.5	$19.5

misc

Part	Purpose	Qty	Unit	Line
MAX98357A I2S Class D Mono Amplifier + 3W 4-Ohm Enclosed Speaker	Clean, distinct vocal playback for Piper TTS	1	$9	$9
Physical DPST Latching Toggle Switch with LED Indicator	Hardware microphone line cut and prominent physical mute light	2	$4.5	$9

power

Part	Purpose	Qty	Unit	Line
12V 5A 60W AC/DC Desktop Power Supply	Continuous wall power delivery for compute, servos, and sound	1	$14	$14
High-Efficiency Dual 5V 5A Buck Converter Module	Clean isolated 5.1V for Pi 5 and separate 5.0V for high-draw servos	1	$11	$11
UPS HAT for Raspberry Pi with 2x 18650 Cells	Brownout protection and graceful shutdown buffer	1	$29	$29

sensing

Part	Purpose	Qty	Unit	Line
ReSpeaker USB 4-Mic Array v2.0	Far-field spatial voice capture, noise cancellation, and DoA estimation	1	$59	$59
Raspberry Pi Camera Module 3 Wide with Mechanical Shutter Cover	Face tracking with a verifiable physical slide cover for visual privacy	1	$35	$35

Safety review

consumer prototype

✓ Human use allowed within stated constraints

Required controls

Physical silicone/ABS mechanical end-stops restricting head pan and tilt movement angles.
Hardware-level electrical mute switch breaking microphone line power.
Prominently visible LED illumination directly tied to microphone active state.
In-memory processing flags guaranteeing audio buffers are purged post-inference.

Red lines

Do not store unencrypted raw microphone PCM audio to local non-volatile flash storage.
Do not operate servos without physical end-stops fitted to the neck joint gimbal.
Do not power digital micro-servos directly from the SBC GPIO 5V rails.