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LFR-Nano Control Board Placement Guide

Board assumptions: 100 mm × 120 mm rectangle, coordinate origin at board center, +X to the right, +Y toward the front. Board extents are X = -50 to +50 mm and Y = -60 to +60 mm. Use a 2-layer stackup with the bottom layer treated as the main GND reference/fill.

Placement intent

Front-heavy sensor distribution: put the IR sensor header on the absolute front edge and keep the IMU near the board center.
Keep user/service access at the rear: Arduino Nano USB, toggle switch, and buzzers should be accessible from the rear.
Keep 11.1 V / motor power physically separated from 5 V logic and analog sensor routing.
Keep high-current motor paths short and wide, with motor connectors on side edges.

Recommended placement map

Table

Function / part	Side	Recommended location	Orientation / how to place	Why
8-pin IR sensor female header	Top	Front-center edge, around X = 0 mm, Y = +56 to +60 mm	Pins parallel to front edge; cable exits forward/off-board	Puts the front line sensor mass and cable at the robot front; keeps analog sensor wires short and away from rear motor/PWM cluster
GY-521 / MPU6050	Top	Geometric center, around X = 0 mm, Y = 0 mm	Align module axes with robot axes; keep flat and away from buzzers/motor driver heat	Best inertial reference point; minimizes vibration/tilt bias from off-center placement
Arduino Nano	Top	Rear-center, around X = 0 mm, Y = -35 to -45 mm	USB connector facing rear edge; leave finger/plug clearance behind it	Rear USB access and short runs to IMU/I2C and driver control pins
Toggle switch	Top	Rear-left or rear-right edge/corner, around X = -38 mm or +38 mm, Y = -55 mm	Actuator faces rear/outward	Easy access; keeps battery/11.1 V entry localized at the rear power zone
Buzzer 1	Top	Rear-left corner, around X = -35 to -42 mm, Y = -45 to -52 mm	Face sound port outward/up; keep away from IMU	Rear corner placement avoids blocking sensors and reduces mechanical/acoustic coupling into IMU
Buzzer 2	Top	Rear-right corner, around X = +35 to +42 mm, Y = -45 to -52 mm	Face sound port outward/up; keep symmetric if possible	Balances rear mass and keeps top center clear
TB6612FNG motor driver	Bottom preferred if requested; otherwise top	Mid-rear between Nano and motor connectors, around X = 0 mm, Y = -15 to -25 mm	Orient VM/motor output pins toward motor connectors and logic pins toward Nano	Short motor current paths; good separation between motor power and logic/control
TB6612FNG VM decoupling capacitor(s)	Same side as TB6612FNG	Within 3–5 mm of VM/GND pins	Put directly beside VM pin with shortest GND return	Reduces motor supply transients and protects logic from VM noise
TB6612FNG VCC decoupling capacitor	Same side as TB6612FNG	Within 3–5 mm of VCC/GND pins	Place between VCC and nearby GND return	Stabilizes 5 V logic supply at driver
Arduino Nano VIN decoupling / bulk capacitor	Top	Near Nano VIN/GND, rear power side	Do not let a tall capacitor obstruct the top/front sensor surface; move tall bulk cap rear-side or bottom if possible	Supports VIN input while keeping top surface clear
11.1 V / power cluster	Rear power quadrant near toggle switch	Around the selected switch side, Y = -45 to -58 mm	Keep VM/VIN routing on one side corridor; avoid crossing center analog area	Isolates battery/motor supply from 5 V logic and sensors
Motor output connector left	Edge	Left lateral edge, around X = -48 to -50 mm, Y = -10 to -30 mm	Cable exits left; align with TB6612 output pins	Short, direct high-current trace path
Motor output connector right	Edge	Right lateral edge, around X = +48 to +50 mm, Y = -10 to -30 mm	Cable exits right; align with TB6612 output pins	Short, direct high-current trace path
M3 mounting holes	Both / mechanical	Four corners: approximately (±44 mm, ±54 mm)	Keep ≥5–6 mm from board edges and clear copper/parts around holes	Stable mounting with edge clearance on a 100 × 120 mm board

Routing zones

Use these zones as a practical mental map:

Front analog/sensor zone: Y = +25 to +60 mm. IR header and A0–A7 sensor nets live here. Avoid routing motor/PWM traces through this area.
Center motion-sensing zone: Y = -10 to +20 mm. GY-521 stays here; keep copper and tall parts symmetric around it if possible.
Rear logic/control zone: Y = -25 to -50 mm. Arduino Nano, buzzer signals, and Nano-to-driver control lines live here.
Rear/side power zone: Y = -10 to -60 mm, biased toward switch side and lateral motor connectors. Keep 11.1 V and motor current paths here.

How to route it

Route GND as a continuous bottom-layer reference/fill wherever possible. Avoid cutting the GND return under the Nano, IMU, and TB6612FNG logic side.
Route 11.1 V only from battery/switch to Arduino Nano VIN and TB6612FNG VM. Keep this net out of the front analog/sensor zone.
Keep 11.1 V / motor traces wide and short, mainly in the rear and side corridors. Maintain at least 0.5 mm clearance from A0–A7 analog traces.
Route A4/A5 I2C directly between Nano and GY-521 with short, parallel-ish paths over the GND reference. Keep them away from motor outputs and buzzer drive traces.
Route A0–A7 IR sensor nets from the front header back toward Nano in a bundle along the front/center logic corridor; do not interleave them with PWM D3/D5.
Route PWM/control lines from Nano to TB6612FNG in the rear-center area. Keep them away from A0–A7 where practical.
Place decoupling capacitors before routing: caps should sit beside their IC power pins, not wherever there is leftover space.
If TB6612FNG is on the bottom, use short vias for logic/control and strong GND stitching around the driver area.

Practical placement sequence in Flux/manual layout

Set board to 100 mm × 120 mm, 2-layer stackup.
Place the fixed mechanical/edge parts first: IR sensor header, motor connectors, toggle switch, USB-facing Nano position, and M3 holes.
Place the GY-521 at center and lock its orientation to match robot forward.
Place the Nano rear-center with USB toward the rear.
Place TB6612FNG between the Nano and motor connectors, optimizing VM and motor-output paths.
Place decoupling capacitors next to TB6612FNG VM/VCC and Nano VIN/GND.
Place buzzers in the rear corners after confirming they do not block USB/switch access.
Route in priority order: GND/reference strategy → 11.1 V and motor outputs → I2C → A0–A7 sensors → PWM/control → buzzers.
Run DRC and fix overlaps, off-board placements, and clearance violations.

Notes for automated placement

The placement workflow should be specific rather than generic: define functional grouping, fixed edge parts, layer preferences, and optimization goals. The placement guidance should be applied only after the board dimensions and stackup are set, because the placement agent cannot resize the board. Also verify that schematic nets exist before placement; placement without net connectivity cannot optimize real signal paths.

Placement intent
Recommended placement map
Routing zones
How to route it
Practical placement sequence in Flux/manual layout
Notes for automated placement