DIY 5" Archer-Match Racer — Detailed Build Guide

What you're doing:

Bolting the carbon fiber plates and arms together to form the drone skeleton.

Procedure:

1. Lay out bottom plate, 4 arms, and standoff hardware on a clean flat surface.
2. Slide arms into bottom plate slots. Align motor mount holes outward.
3. Thread M3 screws through bottom plate into arm mounting holes. Finger-tight first — don't torque yet.
4. Check all 4 arms are parallel and the assembly sits flat on a table. Twisted frames cause vibration that's impossible to tune out later.
5. Once aligned, tighten screws gradually and evenly. Apply Loctite Blue 243 to each screw.
6. Install the stack standoffs (the threaded brass/nylon posts that hold the ESC and FC). Make sure all standoffs are the same height.

What you're doing:

Mounting 4 motors to arm tips and routing motor wires back to the ESC.

Procedure:

1. Place each motor on its arm tip. Align the 4 screw holes (16x16mm pattern).
2. Check screw length before tightening. Screws that are too long puncture the motor windings inside and short-circuit the motor. Hold a screw next to the motor and verify it won't reach the stator.
3. Apply Loctite to each motor screw. Tighten with M3 hex driver — snug, not gorilla-tight.
4. Route the 3 motor wires along each arm back toward the center. Secure with cloth tape or zip ties every 3-4cm.
5. Label each motor position: Front-Right (M1), Front-Left (M2), Rear-Left (M3), Rear-Right (M4).

What you're doing:

Installing the 4-in-1 ESC, soldering motor wires, battery lead, and capacitor. This is the hardest step.

Procedure:

1. Mount the 4-in-1 ESC board onto the bottom stack standoffs (30x30mm pattern). The battery pads (+/−) should face the rear for clean wire routing.
2. Dry fit everything first. Place the Pixhawk, Jetson, and camera roughly where they'll go. Measure wire lengths. Cut motor wires to length — leave 1cm slack, no more.
3. Tin all pads first. Apply flux to each ESC motor pad, then melt a small dome of solder onto the pad. Let it cool. Then hold the tinned motor wire against the tinned pad and touch the iron to melt both together. This 2-step method gives much cleaner joints than trying to do it all at once.
4. Solder all 12 motor wires (3 per motor × 4 motors) to their respective ESC pads.
5. Solder the capacitor across the ESC battery pads (+ and −). Watch polarity — the negative leg has a stripe. The capacitor suppresses voltage spikes from the motors that can damage your Pixhawk and Jetson.
6. Solder the XT60 battery lead to the ESC power pads. This is the hardest joint — use a larger chisel tip, set iron to 420-450°C, and use flux paste generously. The pads need a lot of heat because they're large copper areas.
7. Also solder XT60 pigtails for the PM02 power module and UBEC input from the same battery pads (or use a Y-splitter).

First power-on test:

1. No props installed. No FC connected yet.
2. Use multimeter in continuity mode: touch + and − battery pads. If it beeps, you have a short. Do NOT power on. Find and fix the short first.
3. Connect battery through a smoke stopper. If the bulb glows brightly, there's a short. Dim glow or no glow = safe.
4. Remove smoke stopper and connect battery directly. ESC should chirp its startup tone.

What you're doing:

Installing the flight controller that runs PX4 autopilot — the brain that stabilizes flight and accepts MAVSDK commands.

Why Pixhawk and not Betaflight?

Standard FPV drones use Betaflight flight controllers, but Betaflight cannot accept MAVLink flight commands — it only supports MAVLink for telemetry output. PX4 on a Pixhawk is required for autonomous offboard control via MAVSDK. This is the same interface the AI Grand Prix simulator uses.

Procedure:

1. Apply vibration damping gel pads to the center of the frame (on top of the ESC stack).
2. Place Pixhawk 6C Mini on the gel pads. Arrow on the board must point forward — this sets the IMU orientation. Wrong orientation = wrong attitude estimation = crash.
3. Secure with nylon standoffs or double-sided foam tape. Do NOT use metal screws directly — they transmit vibration to the IMU gyro.
4. Connect PM02 V3 power module cable to Pixhawk POWER1 port.
5. Connect ESC signal cable to Pixhawk MAIN OUT ports 1-4 (or use direct DSHOT pads if supported by your wiring setup).

What you're doing:

Wiring two separate 5V power supplies — one for Pixhawk (PM02), one for Jetson (UBEC). They share the same battery but must be electrically isolated from each other.

Procedure:

1. Connect PM02 V3 input to battery XT60 (via Y-splitter or solder to ESC battery pads).
2. Connect PM02 output cable to Pixhawk POWER1 port.
3. Connect UBEC input to battery (same Y-splitter or parallel solder).
4. Connect UBEC 5V output to Jetson barrel jack (center positive). Secure with tape so it can't vibrate loose.
5. Test: plug in battery → Pixhawk LEDs light up → Jetson boots. Both powered independently.

Before mounting — flash JetPack on your desk:

1. Insert NVMe SSD into Jetson's M.2 slot.
2. Connect Jetson to host Ubuntu PC via USB-C. Hold recovery button while powering on.
3. On host PC: open NVIDIA SDK Manager → select JetPack 6.2+ → flash to NVMe SSD.
4. Boot Jetson on your desk with a monitor/keyboard. Complete Ubuntu setup. Connect to WiFi. Enable SSH.
5. Install all software packages (see Complete Build & Deploy Guide, Phase 3).
6. Verify camera works and MAVSDK installs. All software setup done BEFORE mounting on drone.

Mounting on the drone:

1. Mount Jetson on 8mm nylon standoffs above the Pixhawk. Use M3 nylon screws (not metal — vibration isolation).
2. The Jetson dev kit is larger than the 5" frame body. It will overhang — this is normal. Secure it to the top plate rails or use a 3D-printed mount plate clamped to the frame.
3. Route UBEC cable to Jetson barrel jack. Secure with tape.
4. Ensure adequate airflow around the Jetson heatsink — don't block it with foam tape or straps.

Camera mounting:

1. Mount RPi Camera Module 3 Wide at the front of the frame using a 3D-printed bracket or zip ties.
2. Angle camera 10-15° downward from horizontal — this gives the best gate visibility ahead of the drone.
3. Connect FPC ribbon cable from camera to Jetson CSI-0 port. Lock the connector tab firmly. Vibration will dislodge a loose ribbon cable mid-flight, killing your vision pipeline instantly.
4. Route the ribbon cable away from motor wires (EMI interference) and secure with tape.

Pixhawk ↔ Jetson UART link:

PX4 expects companion computers to connect via TELEM2 for offboard control. The port is configured by default for MAVLink at 57600 baud — we'll change it to 921600.

1. Plug USB-to-UART adapter (CP2102/FTDI) into Jetson USB port.
2. Wire adapter TX → Pixhawk TELEM2 RX pin.
3. Wire adapter RX → Pixhawk TELEM2 TX pin.
4. Wire adapter GND → Pixhawk TELEM2 GND pin.
5. Do NOT connect adapter VCC to Pixhawk. They have separate power supplies.

RC receiver:

1. Solder or connect ELRS receiver to Pixhawk RC IN port: 5V, GND, and CRSF signal (receiver TX → Pixhawk RC RX).
2. Bind receiver to transmitter before mounting (hold bind button while powering on, then start ELRS bind in EdgeTX).
3. Mount receiver somewhere with antenna pointed away from carbon fiber (CF blocks RF signal). Tape antenna to a nylon standoff pointing up.

Connect Pixhawk to PC via USB-C. Open QGroundControl (free, qgroundcontrol.com).

# 1. Flash firmware
Vehicle Setup → Firmware → PX4 Pro Stable Release → Flash

# 2. Select airframe
Vehicle Setup → Airframe → Quadrotor X → Generic Quadrotor → Apply → Reboot

# 3. Calibrate sensors (follow on-screen prompts)
Vehicle Setup → Sensors → Compass → Gyroscope → Accelerometer → Level Horizon

# 4. Configure TELEM2 for companion computer (921600 baud)
Parameters tab → set:
  MAV_1_CONFIG  = TELEM2
  MAV_1_MODE    = Onboard
  SER_TEL2_BAUD = 921600
→ Reboot

# 5. Configure RC
Vehicle Setup → Radio → Calibrate (move all sticks to extremes)
Vehicle Setup → Flight Modes:
  Channel 5 (switch A) → Arm / Disarm
  Channel 6 (switch B) → Stabilized / Position / Offboard (3-position)
  Channel 7 (switch C) → Kill Switch

# 6. Motor test (NO PROPS!)
Vehicle Setup → Motors → Test each motor individually
→ Verify correct spin direction (see motor map above)
→ If wrong, swap any two motor wires at the ESC, or reverse in QGC

• Battery charged, voltage confirmed with multimeter
• Props installed correct CW/CCW per motor map (match markings on props)
• All screws tight (check motor screws, arm screws, standoffs)
• Camera FPC ribbon locked, UART cable secure
• No loose wires anywhere near prop path
• RC transmitter on, bound, switches in safe position (disarmed)
• Kill switch tested on bench (arm → kill → motors stop)
• QGroundControl sensors all green
• Flying outdoors, open area, spotter present, wind < 15 mph