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Eagle PCB Design for an Autonomous Crane Car Competition Robot

04 May 2026

Crane Car Competition Robot

Overview

This project was built for a robotics competition requiring an autonomous vehicle to navigate to objects and retrieve them using a motorised crane. The car had to operate fully autonomously — driving, positioning, extending the crane arm, and picking up targets without human input.

The custom control electronics were designed from scratch in Autodesk EAGLE, etched in-house, assembled, and integrated onto the RC car chassis.

The Challenge

The competition task demanded simultaneous control of multiple independent systems:

  • Autonomous navigation — driving to a target position without manual control
  • Crane actuation — extending and retracting a boom arm precisely enough to pick up an object
  • Object interaction — triggering a gripper or hook mechanism at the right moment

All of this had to run from a single embedded controller, coordinating motor drive outputs, sensor reads, and servo commands in real time.

System Architecture

Subsystem Implementation
Main controller ESP32 (dual-core, 240 MHz, Wi-Fi + Bluetooth)
Drive motors Two DC motors via dual H-bridge motor driver ICs
Crane actuation Servo motor(s) controlling arm extension and gripper
Power supply LiPo battery pack with regulated 3.3 V / 5 V rails
Comms Wi-Fi for telemetry and remote monitoring during testing

PCB Design in Eagle

Custom Control PCB with ESP32

The control board was laid out in Autodesk EAGLE and fabricated in-house on single-sided copper-clad FR4. EAGLE’s schematic-to-layout workflow was used throughout: the schematic was fully captured with net connections before switching to the PCB editor, ensuring the layout was electrically validated against the design before committing to fabrication.

ESP32 Microcontroller

The ESP32 sits at the centre of the design, providing:

  • PWM outputs — independent channels driving each motor driver enable pin, controlling speed of both drive wheels and the crane lift motor
  • Direction GPIO — logic-level signals into the motor driver direction inputs
  • Servo PWM — 50 Hz PWM signal to the crane servo(s) for position control
  • Sensor inputs — ADC and digital GPIO for distance sensors or limit switches on the crane
  • Wi-Fi — used during development for live telemetry and remote parameter tuning without reflashing firmware

Motor Driver ICs

Two DIP-package dual H-bridge motor driver ICs handle the four motor outputs:

  • One IC drives the left and right differential drive motors, enabling forward, reverse, and steering by varying relative wheel speeds
  • The second IC handles the crane lift motor, controlling extend and retract of the boom arm

DIP packages were deliberately chosen for the competition build — they are hand-solderable, replaceable in the field, and survive the rough handling of a competition environment better than fine-pitch SMD parts.

Passive Components

The through-hole resistor array visible on the board provides:

  • Base resistors for any BJT-buffered control signals
  • Pull-up/pull-down resistors on ESP32 GPIO pins to define safe default states (e.g. motors off) at power-up before firmware initialises the outputs
  • Current-limiting resistors for status LEDs indicating motor direction and enable state

Wiring Harness

The colour-coded wire harness connects the board to the full vehicle:

Colour Function
Red / Black LiPo power and ground
Yellow / Orange Drive motor A and B
Purple Crane lift motor
Brown Servo signal
Red / Yellow striped Sensor power and signal

PCB Fabrication

PCB Reverse — Trace Layout and Through-Hole Soldering

The board was fabricated using the toner-transfer chemical etching process:

  1. Layout exported from EAGLE as a mirrored top-copper PDF
  2. Toner heat-transferred onto cleaned copper-clad FR4 board
  3. Board etched in ferric chloride solution to remove unmasked copper
  4. Toner stripped with acetone, leaving clean copper traces
  5. Holes drilled for all through-hole leads and board mounting screws
  6. Components hand-soldered, starting with ICs then passives then connectors

The reverse side of the board shows the characteristic hand-etched single-layer trace layout — the two large DIP IC footprints dominate the left half of the board, with the ESP32 header spanning the right and the passive component field filling the centre.

Autonomous Control Logic

The competition run sequence implemented in firmware:

  1. Initialise — zero all motor outputs, run self-check on sensor readings
  2. Navigate — drive toward target using distance sensor data to correct heading
  3. Position — slow to a stop at pick-up distance; use fine sensor data for final alignment
  4. Deploy crane — PWM ramp-up to extend the boom arm at a controlled speed
  5. Grip — trigger the gripper servo at the target extension position
  6. Retract — retract boom with object secured
  7. Return — navigate back to the drop zone and release

Wi-Fi telemetry logged each stage transition in real time, allowing post-run analysis of where navigation errors occurred.

Outcome

The assembled robot successfully demonstrated autonomous crane operation in competition conditions. The custom PCB provided reliable motor drive and servo control throughout, with the ESP32’s dual-core architecture allowing navigation logic to run on one core while motor PWM outputs were managed on the other — avoiding the timing conflicts that arise when both run in the same execution loop.

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