Technology for Defense
How to Build an FPV Combat Drone to Defend Your Country
This story highlights our collaboration in creating and donating an FPV (First Person View) combat drone for military use in Ukraine to protect our nation from attackers.
Editorial Note: This story contains content that could raise legal and ethical concerns, especially regarding military donations in different countries. Before engaging in any military donation efforts, please obtain guidance from legal experts or authorities in your country to ensure compliance with relevant laws and ethical standards. This proactive step helps ensure adherence to legal requirements and promotes transparency in your actions.
As you may have heard from the news, Russia initiated an attack on Ukraine in February of 2022 and is still attempting to occupy as much Ukrainian territory as possible. The United States, the EU, and the entire civilized world have been assisting the Ukrainian army in every possible way since the beginning of the aggression and continue to do so.
My friends and I also did not stand aside but decided to support defenders of our country in every possible way, using money, various technology devices and equipment from the very beginning until now.
Please note that we are defenders, not attackers. This story is not an invitation to war but an invitation to peace. As Ukrainians, we know how terrible war can be for a nation. We look forward to peace desperately.
I am a software engineer with a wide background in different areas. I use my knowledge for good purposes: to help humanity achieve peace. My country is badly suffering from this war. Therefore, recently, my friends and I decided to build and donate a combat drone to the Ukrainian army to support them in protecting our country.
In this story, I introduce a reusable drone for bombing the occupiers’ trenches to protect us from offenders. God is with us, and I believe we will win this war. Glory to Ukrainian defenders. If you wish to help, I hope this story inspires you to build and donate such drones to defend Ukraine.
I know this platform serves many countries, so building and using drones might not be legal in some countries. Therefore, I provided some insights to guide you about legal and ethical issues for consideration at the end of this story. Please follow the rules of your country and don’t get yourself into trouble.
First and foremost, I would like to express my appreciation to my brother and to my friends for their support and contributions. Also, I thank myself for my passion and patience throughout the fundraising process, component procurement, drone assembly, and overall configuration and trials to donate valuable tools to our army to defend the country.
Hardware Part
Let me introduce the components and appreciate their donators first before giving the instructions.
Drone components
Pavlo Sazonov, for financing Mark 4 7'’ frame, video-camera Caddx Ratel 2 12000 TVL and 915 MHz receiver Express LRS Nano
Alex Pollard, for flight controller SpeedyBee F405 V3 Stack BLS 50A and video transmitter VTX AKK Race Ranger 1.6W
Igor from Itera, for 4x EMAX ECOII Series ECO II 2807 6S 1300KV
Fedor Khomenko, for financing FPV antenna Lollipop 4 V4 SMA 10cm
Mister S, for financing Propellers HQPROP 7035 7x3.5x3
Drone Kit
Alexander Skachkov, for Li-ion Long range pack 6s2p — 9000 mAh
Yaroslav Rudiak, for financing 5.8G FPV Goggles 40CH X BAND
Roman Malko, for financing RadioMaster Bandit Micro ELRS 915 MHz Radio Adapter
Volodymyr and Vadym Vysotskyi, for financing RadioMaster TX12 Mark II Radio Controller
Add-ons
Lemur Cat, for financing Beitian BN-220 GPS module and Buzzer
Mariupol’, for financing Drop system for FPV on Mark 4 frame 7"
Speedy Bee F405 V3 Stack
A few months ago, I discussed various projects with friends aimed at supporting Ukrainian defenders with FPV drones. This discussion led me to select the best ones. Among them, I want to highlight a few: Social Drone UA and E-Drone. Both offer comprehensive video guides on how to build an FPV drone from scratch, and both utilize a Speedy Bee F405 V3 Stack as the drone core, which has become frequently used among amateurs. So, it is commonly used, and that’s why I also choose to use this core.
The Speedy Bee F405 V3 is a flight controller and power distribution board designed specifically for FPV drones. It is equipped with an F4 processor, which provides fast and efficient performance for controlling the drone’s flight and with variety of ports and connectors for easy integration with ESC, receivers/transmitters, and the FPV camera. You will later see how easy it is to use.
Procurements
In the very beginning, I discussed with friends their contributions and what we could build for the army this time, and fortunately, we agreed to supply not only the Drone but also the Drone Kit and Drop System. The full list of the components included can be seen in the appropriate list in the beginning of the story. It’s a comprehensive set that functions as a complete battle unit. However, it includes many more items for procurement.
During wartime procurements, especially in Ukraine, can be challenging. I spent two weeks and $840 to purchase all the necessary components for this project. The drone itself cost exactly $320, and the remaining amount was spent on Drone Kit, Li-ion Battery and Drop System.
Mark 4 frame assembling
The first step is the easiest one. You simply unfold all the items from the Mark 4 frame package and assemble it like a constructor in your childhood. Everything you need is just a screwdriver (M3) and the Mark 4 7" Schematic.
Professionals recommend not tightening the bolts at this stage. You will do that later, after soldering and assembling the entire drone. Simply screw the bolts softly with a hex-screwdriver M3 and enjoy the process.
EMAX motors installing
When the frame is ready, the next step is preparing and installing the motors. I used EMAX ECOII Series ECO II 2807 6S 1300KV and a special protective coverage for the motor wires, look at the picture below.
At this step, it is recommended to use a hex-screwdriver (M3) to install the motors without tightening the bolts. We will do so later.
Look at the picture above. This is what we should have so far before starting soldering. All 4 EMAX ECOII motors installed on Mark 4 7" drone frame. Let’s continue to build our warrior device.
Power supply cable soldering
And here we are. This is perhaps the most challenging part of the job — soldering the power cables. It’s beneficial if you have any experience in soldering, otherwise, I would recommend searching on YouTube and watching the video ‘How to solder the power supply wires to FC’.
Remember to solder the 1000uF low ESR Capacitor included in the Speedy Bee F405 V3 Stack package. Connect the Red wire to red (+) and the Black wire to black (-). This is necessary to protect the ESC board.
EMAX motors soldering
Before this project, I had never had any experience in soldering, and it became a challenge for me. This is my very first attempt at soldering, as you may see from the picture below, where I soldered all four motors to the ESC board.
After finishing soldering the motors to the board, you need to use a multimeter to test all the contacts. Please note that contacts from different motors should not be connected or show continuity.
At this stage, you can already connect the ESC to the FC with an 8-pin cable and link the entire device to a computer with Betaflight Configurator (using a USB cable) to pre-test the motors. However, I will explain this step later on in the section ‘Betaflight configuration’.
VTX and camera setup
According to the wiring diagram on the official website of Speedy Bee, the Video Transmitter VTX AKK Race Ranger 1.6W should be connected to the 9V, G, VTX, and T1 pins on the first UART port of the FC. T1 means that this is a TX from UART1. Look at the picture above.
Always double-check all the pins when connecting any peripheral device to the flight controller because they may vary from device to device. For the VTX, we use red (1) and black (2) wires, as well as yellow (5) and green (6). The internal red (3) and black (4) wires should not be used. I have isolated them. These may be used to connect to the video camera directly, but we will be using the FC to connect with the camera through that.
Video-camera Caddx Ratel 2 12000 TVL connects to the flight controller using 5V, G, and CAM pins as shown on the picture above. Red (1) to 5V, Black (2) to G, and Yellow (3) to CAM.
After soldering all the necessary connections, you can proceed to connect the FPV system either to your computer or directly to the battery for testing. If there is no smoke, congratulations, you have completed the work correctly. From this point, you can even turn on your FPV glasses and search for the channel to search your FPV drone. It should already be operational by this point if UART1 is configured correctly. [Read later on].
And don’t forget to connect your FPV antenna, Lollipop 4 V4 SMA 10cm, if you power on the VTX. Otherwise, there is a chance it could burn down.
ELRS receiver setup
The ELRS receiver is used to connect your drone with the Radio Controller. The operator manages the drone’s direction, speed, turns, altitude, and everything else using this radio controller. It is the primary device for controlling the drone.
According to the official documentation, it should be connected to UART2 on the FC board. Double-check which one you use and connect it according to the specification. In my case, as I am using Express LRS Nano, so that I connected Black to G, Red to 4V5, White to R2, and Yellow to T2.
But before that, I also soldered these wires to the ELRS receiver exactly and double-checked that TX from the receiver should be connected with RX (R2) on the controller. At the same time, RX on the receiver should be connected to TX (T2) on the controller.
Once you have done this, you can power on your FC and pair the device with your RadioMaster TX12 or analog radio controller to check its functionality and readiness.
Software Part
Betaflight Configuration
Alright, we’ve completed the soldering, so we’re good to move on. Next up, let’s configure the parameters for our Drone. To do that, you’ll need to download the Betaflight Configurator for your operating system and connect your drone to the computer via USB.
On the first screen you will likely see the image of your drone and some general information. We skip this page and go to the ‘Ports’ tab to properly check and setup parameters.
Since we’ve soldered the VTX on UART1, we need to select one of the VTX-related types from the list under the ‘Peripherals’ section. In my scenario, since the Race Ranger VTX utilizes the SmartAudio protocol, I’ve opted for ‘VTX (TBS SmartAudio)’. In your case just try one of the VTX here.
The next page is the ‘Configuration’, where we need to enable the following:
- Enable ‘Accelerometer’ and ‘Barometer’;
- Set up your craft’s name instead of ‘UA-914’ displayed on my screen;
- Enable arming even under angle (180 degrees);
- Enable ‘RX_LOST’ and ‘RX_SET’ for audible alerts.
Later, when setting up the Drop system with servo drive, we’ll also enable ‘SERVO_TILT’ in the ‘Other Features’ section to enable the drone to work with servo drive (for bombing).
In the ‘Power & Battery’ section, you’ll likely need to configure the following settings:
- Minimum cell voltage: 3.0
- Maximum cell voltage: 4.2
- Warning cell voltage: 3.1
These settings are ensuring correct operation with the power supply.
PID (Proportional-Integral-Derivative) profiles determine how the flight controller responds to various inputs and disturbances during your flight.
By adjusting these PID profile settings, you can optimize the flight performance of the drone, achieving better stability, maneuverability, and responsiveness.
I recommend configuring all the settings highlighted in red on the screen above to optimize performance. If you need any explanation about that, you can hover over the question button in front of each parameter.
‘Rate Profile Settings’ control how sensitive and responsive the drone is to stick movements, particularly regarding its rate of rotation or change in direction. These settings essentially dictate how quickly the drone reacts to pilot inputs. The default value for parameters highlighted in red is 620, but let’s set it to 490 to increase performance.
By adjusting ‘Filter Settings’, you can effectively reduce noise and vibrations in the sensor data, resulting in smoother flight performance, improved stability, and better control responsiveness.
I suggest changing only three parameters highlighted in red. Remember to save changes on each page to apply them. Otherwise, they will not take effect.
The ‘Receiver’ section is used to configure how the flight controller communicates with the receiver unit, in our case ELRS 915 MHz Nano, which receives commands from the RadioMaster TX12 radio controller.
Since we’ve soldered our receiver to UART2 as configured in the ‘Ports’ section above, we only need to adjust a few parameters on this page:
- Receiver mode: Serial via UART;
- Serial Receiver Provider: CRSF;
- Enable ‘Telemetry’ to display key data on the radio controller;
- Channel Map: AETR1234.
Please note that when setting up the RadioMaster TX12, choose the CRSF protocol, which we have configured in the flight controller.
Adding an ‘ARM’ mode in the ‘Modes’ section allows you to control when the drone is armed or disarmed. To set this up, you need to bind your RadioMaster TX12 Radio Controller with the drone during configuration. Then, click on ‘Add Link’ next to the ‘ARM’ command, and toggle the switch on/off on the Radio Controller that you want to use for ARM/DISARM. This action configures it accordingly.
Also, using the yellow scroll, as shown on the picture above, you can specify the tumbler state in which the drone will be armed. And don’t forget to save changes in the right bottom corner of the configuration page.
The ‘Motors’ section has tools for testing and resolving issues with the motors on your drone. It enables you to individually activate each motor to confirm their proper functionality and configuration.
For our setup, we should select the following options:
- Mixer: QUAD X;
- Motor protocol: DSHOT600.
As a part of motor testing, it permits you to confirm the functionality of each motor, adjust their output as needed, and ensure they spin in the correct direction for optimal flight control. Remember to utilize this feature safely by conducting tests without propellers installed on your drone to prevent any potential damage.
The OSD (On-Screen Display) section allows you to configure and customize the on-screen display settings for your FPV (First Person View) video feed displayed on your video monitor or goggles.
I would recommend to setup the following:
- Altitude (without decimals);
- Artificial horizon sidebars;
- Battery usage (graphical remaining);
- Craft name;
- Flight mode;
- Link quality;
- Warnings.
In addition to displaying various parameters on the screen, you can also drag and drop them to the specific location on the screen.
Overall it provides essential flight information at a glance, enhancing your situational awareness and overall flying experience. Properly configuring the OSD can help you monitor important telemetry data and make informed decisions while piloting the drone.
The VTX is responsible for transmitting the video feed from your drone’s onboard camera to your FPV (First Person View) goggles or video receiver. As you remember we have soldered our video transmitter to UART1 on FC.
Our AKK Race Ranger 1.6w has a specific VTX table which you have to download from the file. Look at the example below:
{
"description": "AKK Race Ranger VTX Config file",
"version": "1.0",
"vtx_table": {
"bands_list": [
{
"name": "BOSCAM_A",
"letter": "A",
"is_factory_band": true,
"frequencies": [
5865,
5845,
5825,
5805,
5785,
5765,
5745,
5725
]
},
{
"name": "BOSCAM_B",
"letter": "B",
"is_factory_band": true,
"frequencies": [
5733,
5752,
5771,
5790,
5809,
5828,
5847,
5866
]
},
{
"name": "BOSCAM_E",
"letter": "E",
"is_factory_band": true,
"frequencies": [
5705,
5685,
5665,
5645,
5885,
5905,
5925,
5945
]
},
{
"name": "FATSHARK",
"letter": "F",
"is_factory_band": true,
"frequencies": [
5740,
5760,
5780,
5800,
5820,
5840,
5860,
5880
]
},
{
"name": "RACEBAND",
"letter": "R",
"is_factory_band": true,
"frequencies": [
5658,
5695,
5732,
5769,
5806,
5843,
5880,
5917
]
}
],
"powerlevels_list": [
{
"value": 0,
"label": "200"
},
{
"value": 1,
"label": "400"
},
{
"value": 2,
"label": "800"
},
{
"value": 3,
"label": "1600"
}
]
}
}If you have any other VTX, you should find an appropriate VTX table and load it in this section by clicking on the ‘Load from file’ button. Once you’re done with this, you can proceed to choose the following settings:
- Band: RACEBAND;
- Channel: 1;
- Power: 200.
Also, enable ‘Low power disarm’ to conserve energy when the aircraft is disarmed and stay on the ground surface. Each time you do any changes don’t forget to save them clicking ‘Save’ button usually located in the right bottom corner of the configuration section page.
Propellers installation
When you are done with all the configuration in Betaflight, you are ready to tighten bolts, install the battery onboard, and attach the propellers. Installing propellers is crucial for a successful flight. Installing them in the wrong direction can cause the drone to flip or sustain damage on its first flight. So, be careful.
In our configuration, we use the direct mode for motors. This means that the front left and back right motors rotate to the right side as [clockwise]. The right front and left bottom motors rotate [counterclockwise] to the left side. This is shown in the picture below.
Each blade on the propeller has two sides: the side forming the top and the one at the bottom. The propeller should be installed on the motor so that the upper part of the blade faces the direction of motor rotation.
As shown on the picture below, I am tightening nut on the left bottom motor (3), which rotates counterclockwise. As you can see, upper part of the blade faces the left direction.
Tighten the nuts securely on all motors, but be careful not to over-tighten, as this can damage the motor or propeller. When done, ensure that everything is installed correctly, open the camera, bind with Radio Controller and Goggles, and you are ready for the first flight.
Drop system installation
The Drop System is the final step of configuration which transforms our standard drone into a military-grade tool, enabling the deployment of bombs. From a technical prospective, it includes a servo mechanism capable of holding and releasing bombs when the operator switches the toggle to the bombing position.
I’ve connected the servo mechanism to the flight controller as follows:
- Red wire of servo is soldered to the 5V pin on the top right corner of FC;
- Black wire of servo is soldered to the G pin on the top right corner of FC;
- Yellow wire of servo is soldered to the S9 pin on the FC.
Once you done with soldering you have to configure these last things in the Betaflight Configurator as shown below.
As we are using the 5V and G pins from the LED strip of the FC, we also need to enable them in the configuration by enabling LED_STRIP. Additionally, enabling SERVO_TILT allows us to configure the servo mechanism on one of the toggles.
As shown on the picture above, I have selected mid (1500), min (1100), and max (1900) values for Servo 1, determining its angle of rotation. Additionally, I’ve configured A2 (AUX2 toggle) to serve as the bombing function.
Remember to save changes in all sections once you’ve finished configuration. Now, disconnect your drone from the computer, connect it to the battery, insert a tennis ball into the servo mechanism instead of a bomb, and test it using your RadioMaster TX12 radio controller.
Ready for combat operations
As I mentioned in the beginning of this story, a lot of my friends took part in this project by purchasing different components for drone and drone kit. Some of them helped me with soldering, as it’s my very rare attempt to solder something. And finally, we assembled the comprehensive Combat Unit comprising all the necessary elements for fighting with enemies.
As you may see from the picture above, the FPV Drone Kit is now ready for combat operations. It includes: 7" Drone, Li-Ion battery 9000 mAh, 5.8G FPV Goggles, RadioMaster TX12 Radio Controller, ELRS 915 MHz adapter, and Drop system attached with a tennis ball instead of a bomb installed. The operator will change it later, on the frontline.
As the final part of the project, this equipment was handed over to the Ukrainian military, who heroically defended the eastern border of the country. It will reduce risks of injury for soldiers involved in combat missions on the frontline, thereby attaining tactical superiority.
Support Ukrainian frontline
Since 2014, when the RF first invaded Ukrainian territory, Ukrainian defenders have continued to be a symbol of resilience, fighting with unwavering determination. Their commitment to protecting the Homeland is truly remarkable, and we are proud of their bravery and sacrifices.
As Ukrainian defenders face military challenges from insidious adversaries, it’s crucial for them to receive appropriate equipment and support. By building your own FPV drone using resources like this article or projects such as E-Drone, you can contribute to protecting the current world order based on law rather than the law of power.
Legal and Ethical Considerations in Other Countries
I know this platform is global, and building and using drones might not be legal in some countries. Therefore, I want to guide you through legal and ethical issues.
While building and donating a drone itself may not be illegal in some countries, there are several legal and ethical aspects to consider:
Exporting military-related technology or equipment, even if donated, is subject to export control regulations.
The International Traffic in Arms and Export Administration Regulations govern the export of defense articles and dual-use items. Depending on the technology involved, compliance with these regulations may be required.
The operation of drones, especially those intended for military purposes, is subject to regulations set by the Federal Aviation Administration (FAA) in the US.
These regulations cover various aspects, such as registration, airspace restrictions, and operational limitations. Therefore, it is crucial to build a drone that complies with FAA regulations to ensure legal operation.
The use of drones for military purposes, including combat operations, is subject to domestic and international laws, including laws governing armed conflict, human rights, and the laws of war.
Transferring military technology, even in the form of a donation, may have implications for national security and foreign policy. Depending on the nature of the technology and the recipient of the donation, approval or oversight from relevant government agencies may be necessary.
Given these legal complexities, citizens and organizations considering similar initiatives should seek legal advice and ensure compliance with applicable laws and regulations.
Additionally, transparency, accountability, and adherence to ethical principles are essential when engaging in activities involving military technology and defense efforts in your country.
Thank you for reading my story. I hope you find it helpful. As usual, if you have any questions, please leave a comment on this article or ask me on Twitter I will be happy to answer.
