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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.
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