Building an FPV Drone

Most drones consist of 7 main parts that are integrated to maximize efficiency and effectiveness:

Flight Controller: The brains of the drone, it knows where it is, where it needs to be and figures out the best way to close that difference. Most contain accelerometers, a barometer (for altitude), and some even have an electronic speed controller integrated into it. In my build I used the SpeedyBee F405 V3 stack which includes the flight controller and ESC in a stacked position.

Electronic Speed Controller (ESC): This device receives power straight from the battery and is built to handle a certain amount of voltage. The ESC is tasked to provide a certain amount of power to each motor based on commands from the flight controller. In my build I am using a 6 cell battery(6s), so I had to make sure the ESC was rated for that large amount of power.

Frame: The frame holds all of the parts and protects them from damage in a crash. Most are made of carbon fiber to decrease weight while also keeping it durable. I used the TBS SourceOne V5 and it is in perfect condition even after crashing countless times. It is made to be used with 5" propellers.

Motors: The motors spin the propellers creating lift. Choosing a motor can be difficult because there are so many options. I chose the T-Motor Velox V2.0 V2207 1750KV motor. The V2207 indicates the size while the KV indicates the power in RPM/Volt. For 5" drones with 6s, anywhere between 1600 and 1800 should be sufficient. On a lower cell battery, such as a 4s, you can go from 2300KV to 2700KV because the lower voltage means you need more RPM/Volt. If the motor spins too fast (by using too high a KV on high voltage) they may overheat and be damaged. The motors are soldered directly to the ESC.

The Build

Receiver: The receiver, or RX, gets paired to your controller/remote, receives signals from it, and sends them directly to the flight controller. It consists of a small board with a T-shaped antenna. There are many options for RX protocols (of which your remote and RX have to be the same type), but you should generally use either TBS Crossfire or Express-LRS. For my build I used ELRS, so I bought an ELRS remote and RX.

FPV System (Camera & VTX): FPV drones transmit real time video from an onboard camera. This is done by connecting a camera and video transmitter (VTX) to the flight controller. The VTX transmits data at 5.8ghz which is captured by the fpv goggles on the ground. There are two options for an fpv system: HD or analogue. HD systems generally include the camera and VTX as a single unit and require special goggles, one example being the DJI Air Unit. For my build I went with analogue because it is cheaper and easier to set up. I used the Foxeer Razer Micro 1200TVL camera paired with the Happymodel OVX303 VTX. Video transmitters have different power levels measured in milliwatts (mW). The OVX303 can transmit at power levels 25mW to 400mW. Switching to a higher mW increases range and penetration of signal, but consequently, increases power usage and therefore heat levels. I use 100mW because it can keep cool while also transmitting at a decent range.

GPS: The GPS uses satellites to triangulate its location. It then communicates this information to the flight controller and unlocks many features such as return to home. I chose the HGLRC M100 Mini because of its extremely small size and lack of compass. I preferred a GPS without a compass because it can cause interference with nearby electronic components such as the VTX. This can lead to poor video quality and other issues with the flight controller. I mounted it using a 3d printed mount I designed and printed. It works well and can lock onto up to 15 satellites in under 20 minutes.

Remote, Goggles, Batteries: For a remote I use the RadioMaster CC2500 ELRS and for goggles I use the BetaFPV VR03. These are budget-friendly options and work great. Unlike the remote, the goggles do not need to pair to the drone, instead they just need to be on the same channel/frequency. For batteries I use Ovonic 6s 100c 1000mah/1300mah Lipo batteries. The 1300mah lasts longer but also weighs more, but, for my flying style, the 1000mah last around 5 minutes which is plenty of time. To charge the batteries I use an HTRC C150 Lipo battery charger 1-6s. Lipo batteries are dangerous, though, and mishandling of these batteries can lead to fire, explosions, and toxic smoke inhalation. Make sure to do your research before buying or charging these batteries.

3D Printed Parts: After getting my GPS and new VTX antenna, I needed a way to mount them securely to the drone (I tried tape). There is a very large FPV community so there are countless mounts, modifications, and other 3D models available, especially for the TBS SourceOne V5. I used ThingyVerse and looked for a mount that would fit my GPS and antenna, but could not find anything that I liked. I decided to design my own mount so I took one of the available mounts as a template and built on onto it. I made a few designs until I created one I felt good about. I posted the design on ThingyVerse.

Click to Maximize

Betaflight Software

Betaflight is a software your flight controller runs and it is also what you use to configure your drone from a computer. There are a multitude of options and tabs so I recommend watching a tutorial on YouTube if your are planning on building your own drone. A good Youtuber to watch for all things FPV is Joshua Bardwell.

Within Betaflight, in the failsafe tab, I was able to set up a very privative version of return to home. With a bit of tweaking of the options, I was able to make it work well. It lands within a 10ft radius of it's home point and holds its position despite heavy wind.

Return To Home

The Crash

On my first test flight, it was my genius idea to fly it in a parking lot next to the water. Turns out I didnt really tighten my motor screws very much; I was using a broken screwdriver I had to improvise. So after a bit of flying, the motor flew off and the drone splashed into the Chesapeak about 50ft from shore. It was the week of the SAT so I just tried to forget about it.

The day after the test I went back with a metal detector, a wet suit, and 40 degree weather and started wading in the frigid water. Luckily, my dad had captured a video of the crash so we screenshotted the frame with the splashed and aligned it with the horizon. He gave me directions with a walkie-talkie as I walked around. It had not been 5 minutes of searching when suddenly my metal detector started vibrating frantically. I felt extreme joy as I lifted my lost treasure out of the water.

If it hadn't been for that video, it would be lost forever. It would have become a permanent home for the shrimps within the drone's circuits and wires. Most of the parts still worked despite being submerged for over 5 days. The only thing broken was the ESC and, of course, the battery, which began smoking when we took it home. I washed everything to get the brackish water and shrimp corpses off. There was even a shrimp living inside the lens, on the sensor of the camera. The camera, though, still worked perfectly.

First thing I bought after, was a good screwdriver.

"Everything is a learning experience, both good and bad that happen to you. You take what happens and learn from it. That's how I look at everything, the good and bad. You learn about it, and you improve." - Markelle Fultz

Summary

This was a very fun project to make and I learned a lot about technology integration, GPS, and UART and the exchanging of data between devices. I recommend this project to anyone interested in engineering because it is a really fun way to problem solve and design modifications like I did with the GPS mount. Other than the drone crashing, this was an exciting experience that assured me even more that engineering is the place for me.

If you are interested in building your own drone, feel free to ask me any questions.