Hackathon Fall 2026

Sentry Car

A Raspberry Pi 5 robot, driven from a laptop, that moves, turns, explores, speaks, and senses.

arpitran/hackathon-fall-2026

The idea

Built milestone by milestone toward an AI agent

Plan

Eight milestones, 24 hours

#MilestoneStatus
M0Prep: order parts, bring up the Pi 5done
M1Eyes on the Pi: person detection on the boardtodo
M2Hardware bring-up: L298N on the Pi's GPIO, all four motors turndone
M3Wheels: Car class + drive CLIin progress
M4Laptop control: FastAPI + WebSocket + watchdogtodo
M5Sentry vision: live stream with person boxestodo
M6Stretch: voice or obstacle sensingtodo
M7Demo video + docstodo

Hardware

Parts

Brain

Raspberry Pi 5 with active cooler

Motor control

Pi 5 GPIO pins drive the L298N directly, no co-processor

Drive

L298N driver, four BO motors and wheels (skid steering), separate 4×AA battery pack (6V)

Eyes

Logitech USB webcam

Voice

USB speaker (the Pi 5 has no 3.5mm jack)

Body

Doubled cardboard chassis, breadboard for prototyping

Architecture

Laptop to Pi to motors

Architecture diagram: the laptop talks WebSocket to a FastAPI server on the Pi 5; the Pi's Car class drives the L298N directly from four GPIO pins and the L298N drives four motors from a separate AA pack; the Pi reads a USB webcam and runs on a USB power bank

Wiring

Pi GPIO to driver to motors, one shared ground

Wiring diagram: Pi 5 GPIO17, 27, 22 and 23 go to the L298N inputs IN1 to IN4, its outputs drive four motors, two per side, a 4 x AA pack feeds 12V and GND, and a shared ground bus ties in Pi pin 14

Header pins

The five header pins the driver needs

Pi 5 header map: pins 11, 13, 15 and 16 (GPIO17, 27, 22 and 23) go to IN1 to IN4, pin 14 is ground, and pins 2 and 4 are 5V and stay unconnected

Working today

Four motors, driven from the Pi

Pi pinGPIOL298NSide
11GPIO17IN1left
13GPIO27IN2left
15GPIO22IN3right
16GPIO23IN4right
14GNDGNDshared ground

Verified on the real car on 2026-09-21: all four motors turn, both sides, both directions. The drive code is tested and runs as drive-car.

Electronics

Why an LED needs a resistor

A Pi pin puts out 3.3 V and should supply about 16 mA at most. The resistor decides how much current flows.

Pi GPIO pin3.3 V
→
Resistor220 Ω
→
LED, drops about 2 Vlit
→
PiGND
none471002204701k10k
0 mA16 mA pin limit30 mA
5.9 mA

Red and yellow LEDs drop about 2 V. Blue, white and green drop about 3 V, so use a smaller resistor (100 Ω) if one looks dim. Drag the slider; press Esc to get the arrow keys back.

Vision

Person detection, already working

A YOLO11n detector runs on webcam frames with tracking and a live FPS counter. It is the base for the sentry view in M5.

uv run --extra vision detect-people

Demo

Live demo

Drive the car from the laptop, watch the person boxes.

Fallback: recorded demo video

Next

After the hackathon

← → / space / click