Added power-source markers to the rails and renamed the rails:
VCC now includes J4:VCC, U1:VCC1, J5:2, MEGA1:+5V_1, MEGA1:+5V_3, and the VCC power marker.
VIN now includes J3:1, MEGA1:VIN, MEGA1:+5V_2, U1:VCC2, and the VIN power marker.
ERC result: the two previous “power input not driven” errors are cleared. One warning remains on PWR_VCC:P1 because the marker symbol has a physical terminal that ERC still treats as floating; it does not affect the actual VCC/VIN rail drive status.
I’m blocked from running the requested ERC/DRC because the session has run out of execution credits.
Current known state from the last completed checks:
PCB/layout DRC was previously clean after routing cleanup.
The earlier missing-power ERC errors on J4:VCC and MEGA1:VIN were cleared after adding VCC and VIN power-source markers.
One known schematic warning remained: Floating pin: PWR_VCC:P1 on the power marker terminal. This appears to be a marker-symbol warning, not a functional rail issue.
What remains:
Re-run ERC and DRC fresh when credits are available.
Confirm whether PWR_VCC:P1 is still the only schematic warning.
If desired, replace/adjust the marker implementation so the power-source marker itself does not create a floating-pin warning.
Project Specification — Mini Paper USV PCB Upgrade v1.0
Project Overview
Status: Draft schematic rebuilt from user-provided reference prompt. The board is a shield-style wiring schematic for an ELEGOO/Arduino MEGA 2560 controlling a mini paper unmanned surface vehicle.
Intended Use
Educational/prototype USV controller using a MEGA 2560, DC motor propulsion, SG90 rudder servo, HC-SR04 distance sensor, buzzer, and status LEDs.
What the Device Should Do
Accept dual 9V parallel battery input at J3.
Feed MEGA VIN and L293D motor supply from the 9V rail.
Use the MEGA 5V rail for logic, ultrasonic sensor, servo connector, buzzer, and LEDs.
Drive one FA-130 DC motor through U1 L293D.
Read HC-SR04 TRIG/ECHO on D11/D12.
Drive SG90 servo signal on D6.
Drive green/yellow/red LEDs from D22/D24/D26 through 220 ohm resistors.
Drive buzzer from D28.
Main Features
ATmega2560 controller via Arduino Mega pin breakout.
L293D H-bridge motor driver.
HC-SR04 ultrasonic ranging input.
SG90 rudder servo connector.
Three LED status indicators.
Buzzer output.
Dual 9V parallel battery input.
System Architecture
Diagram
Hardware Subsystems
Power: J3 dual battery input creates 9V rail; MEGA produces 5V rail in this shield-style design.
Compute: MEGA1 Arduino Mega 2560 pins, operating at 5V logic and 16 MHz.
Actuation: J5 SG90 servo connector; J6 FA-130 motor connector.
Indicators: J8 green, J9 yellow, J10 red LEDs with R1-R3 220 ohm series resistors; J7 buzzer.
Interfaces and Connections
Table
Function
MEGA Pin
Net
Destination
Servo signal
D6
SERVO_SIG
J5 pin 1
L293D IN2
D7
IN2
U1 pin 7 / 2A
L293D IN1
D8
IN1
U1 pin 2 / 1A
L293D enable
D9
ENA
U1 pin 1 / EN1,2
Ultrasonic trigger
D11
TRIG
J4 TRIG
Ultrasonic echo
D12
ECHO
J4 ECHO
Green LED
D22
GL1
R1 then J8
Yellow LED
D24
YL1
R2 then J9
Red LED
D26
RL1
R3 then J10
Buzzer
D28
BUZ
J7 +
Power and Runtime Expectations
The provided reference assumes two 9V batteries in parallel for about 9V at about 1A combined. Runtime depends strongly on battery chemistry and motor/servo duty cycle.
Power Tree and Power Budget
Table
Rail
Load
Estimated Current
9V
L293D motor path / FA-130
200-500mA typical/load dependent
9V
MEGA VIN regulator input
downstream 5V load reflected through onboard regulator
5V
MEGA 2560 board
project dependent
5V
HC-SR04
15mA
5V
SG90 servo
3.6-360mA
5V
L293D logic
low logic current
5V
Three LEDs
~40.8mA total at 13.6mA each
5V
Buzzer
~30mA
Design note: the MEGA onboard 5V regulator may overheat if the 9V source powers high 5V loads such as the servo. For hardware build reliability, a separate 5V regulator for servo/peripherals is recommended if the design moves beyond schematic twin accuracy.
Manufacturing and Assembly Expectations
Prototype schematic twin. SMD passives are currently assigned by default; connectors and modules are library parts. PCB target from prompt: 75mm x 65mm.
Firmware-Relevant Hardware Requirements
Arduino-compatible ATmega2560 firmware should configure D6 and D9 as PWM-capable outputs, D7/D8 as motor direction outputs, D11 as ultrasonic trigger, D12 as ultrasonic echo input, D22/D24/D26 as LED outputs, and D28 as buzzer output.
Physical Design Expectations
User requested a traditional EDA schematic style with left MEGA block, right subsystem block, power buses, annotation boxes, and title block. Logical schematic connectivity has been built in Flux; detailed drawing/title-block cosmetics are represented in this specification and may be refined in schematic layout/graphics.
Important Design Decisions
Preserved the user-specified MEGA 2560 rather than substituting an ESP32.
Used one L293D half-bridge pair for the motor and marked the second bridge unused.
Added 10uF 5V bulk, 100uF 9V motor bulk, and 100nF L293D logic decoupling for reliability.
Assumptions
J3 represents the dual 9V battery/barrel jack input.
MEGA provides the 5V rail in this schematic twin.
Servo power is tied to the 5V rail per the reference prompt, but this is a current/thermal risk if powered from the MEGA regulator.
Change Notes
Rebuilt schematic from scratch from the user-provided written specification.
Project renamed to Mini Paper USV PCB Upgrade v1.0.