How to build an FPV drone step by step

What we’ll build

A 5" 6S freestyle drone, with DJI O4 Pro digital video and an ExpressLRS receiver. It’s the most common setup today and the one with the most spare parts. If you prefer analogue video, the steps are the same: only the camera and the transmitter change.

Allow a couple of afternoons. Don’t rush: a clean build flies better and is easier to repair.

First build? Do the Build course first: 97 animated lessons, from the multimeter and soldering to the radio, Betaflight and Blackbox, with an exam and a certificate. This guide is the complete, detailed version.

Want to see it in 3D? In the 3D Workshop you can build this very drone part by part, rotate it, pull it apart in an exploded view and click on each component. Each step in the viewer leads to the full explanation on this page.

Before you start: read Tools and soldering. All tests are done without props, and the first battery connection is always made with a smoke stopper.

Parts list

Want to use other parts? Check them with the compatibility checker: it tells you whether they fit together and draws the wiring diagram for you.

You’ll also need the radio, DJI goggles compatible with the O4 and a balance charger. The tools are the ones from the workshop: a 60 W or higher soldering iron, solder, flux, multimeter, smoke stopper, Allen keys and cable ties.

1. Prepare the frame

1. Check every part

   Count the screws and make sure no arm is cracked.

2. File the edges

   Run fine sandpaper along the carbon edges that wires will touch. A sharp edge can strip a wire and cause a short circuit.

3. Assemble the base

   Fix the arms to the bottom plate and put a drop of threadlocker on the metal screws that don’t use a nylon lock nut.

2. Mount the motors

Place each motor with its wires facing the centre of the frame and fix it with four M3 screws. This is where the most expensive mistake of the build happens: a screw that’s too long touches the windings and burns out the motor.

If the screws that come with the motors are too long for the thickness of your arm, use shorter ones or add a washer.

3. Prepare the ESC

Before mounting it on the frame, solder on the battery lead (XT60 pigtail) and the capacitor. It’s much easier with the board in your hand.

1. Battery pads

   They’re the biggest and need lots of heat: a chunky tip and 400–420 °C. Tin the pads and the wires separately before joining them.

2. Polarity

   Red wire to the positive pad, black to the negative. Check it twice: if you get it wrong, the electronics burn when you plug in the battery.

3. Capacitor

   As close to the pads as you can, with the white stripe (negative) on the negative pad. Protect it with heat-shrink tubing.

4. Mount it on the frame

   With the rubber grommets and the arrow on the board pointing forwards. Don’t overtighten the nuts.

4. Solder the motors to the ESC

1. Cut to length

   Run the wires under the arm and cut them so they reach the pads without tension, but with no wire to spare.

2. Strip and tin

   Strip about 2 mm from each wire and tin them. Put a little solder on each ESC pad.

3. Solder

   Rest the wire on the pad, heat both at once and remove the iron when the solder flows. The order of the three wires doesn’t matter: the spin direction is fixed later in software.

4. Inspect

   Look for solder bridges between neighbouring pads. A good joint is shiny and volcano-shaped.

5. First power test

Before adding anything else, check there’s no short circuit.

1. Continuity with the multimeter

   With no battery, put the probes on the XT60’s positive and negative. If it beeps continuously, there’s a short: don’t plug anything in.

2. Smoke stopper

   Connect the battery through the smoke stopper. The ESC should play its startup tones and the bulb should go out or glow very faintly.

3. If it stays lit

   Disconnect straight away and check for solder bridges, stripped wires and motor screws.

6. Mount the flight controller

1. Connect the ESC–FC cable

   Use the cable that comes with the stack. Check that the wire order matches at both connectors: some brands aren’t compatible with each other.

2. Orientation

   Flight controller arrow pointing forwards. If you have to rotate it so the USB is accessible, you’ll correct it in Betaflight.

3. Test it before closing up

   Connect it via USB to Betaflight and check that the 3D model moves like the drone. If the firmware needs updating, now’s the time.

7. Connect the ExpressLRS receiver

1. Solder the four wires

   5 V, ground (GND), TX and RX to a free UART on the flight controller. Note down the UART number: you’ll need it in Betaflight.

2. Antenna

   Route it out of the back of the frame, away from the carbon and the props, held with a tube or a printed part.

3. Protection

   Wrap the receiver in heat-shrink tubing and fix it with double-sided tape so it doesn’t vibrate.

4. Bind it

   Set the same binding phrase on the radio and the receiver. See Radio and receiver.

8. Install the DJI O4 Pro

1. Power

   Better from the flight controller’s 9 V regulator than straight from the battery: that way the transmitter is protected from voltage spikes.

2. Data

   TX and RX to a free UART, crossed. This is how the voltage, flight time and the rest of the OSD data reach the goggles.

3. Camera and antenna

   Fix the camera in the frame’s mount, at whatever angle you like (20–30° to start). The video antenna goes at the back, pointing up and backwards.

4. Activate and bind it

   Activate it with DJI Assistant 2 while powering the drone from a battery (USB alone doesn’t work). Then put the goggles in binding mode and press the O4’s bind button until the LED turns green.

Never power up the video transmitter without the antenna fitted: it can burn out in a few seconds.

9. Close up the frame

1. Tidy the wires

   Secure them with cable ties or tape so they don’t touch any prop or get pinched between plates.

2. Top plate

   Fit it without overtightening and check that no wire is squashed.

3. Battery

   Stick an anti-slip pad on the top plate and thread the strap through.

4. Antennas

   Fix them with the frame’s mounts or 3D-printed parts, pointing backwards.

10. Configure it in Betaflight

Now for the software. It’s explained step by step in Betaflight. For this build, pay special attention to these points:

• Ports: Serial RX on the receiver’s UART; the DJI UART set up for the OSD.
• Receiver: CRSF protocol and check every channel.
• Digital OSD: apply the DJI OSD preset, choose the UART connected to the O4 and the HD video format.
• Motors: with no props, check the order and spin direction, and enable bidirectional DShot.
• Modes: arm on AUX1, beeper and turtle.
• Battery: calibrate the voltage with the multimeter and, after the first flights, the current sensor so the OSD’s mAh reading is reliable.

Want to go long range? Add an M10 GPS and set up GPS Rescue so the drone comes back on its own if it loses signal. The build course has a whole module on setting it up and testing it safely.

11. Fit the props

1. Check the direction

   Before fitting them, make sure in Betaflight that each motor spins as in the figure.

2. Each prop on its motor

   Props have a marking or a mirrored profile: the thicker edge must lead in the direction of rotation.

3. Tighten the nuts

   With the 8 mm socket, firm but without overdoing it.

12. Before the first flight

Go through the pre-flight checklist, especially the failsafe: switch off the radio with the drone armed and no props, and the motors must stop.

At the field, start with a short 30-second flight. Land, touch the motors (they should be warm) and check the image isn’t shaking. If all is well, you can start enjoying it.

Most common mistakes