Every drone needs a flight controller to do the work to keep the motors spinning and the board aware of where the aircraft is. Continue reading as we explore what a flight controller is, why it's important so you can choose the right one for your project.
This article is part of a series that covers the entire concept of quadcopter parts, how they work, and how they come together. For further reading, see the master article: Components & Anatomy of an FPV Quadcopter
A flight controller (FC) is commonly referred to as the brain of your copter. This important piece of hardware takes user input and sensor data to keep the craft in the air. The flight controller works to spin each motor at the appropriate speed to create the desired result. This is done by real time processing translated into outputs.
The FC is also a hub to connect external peripherals like radio receivers, GPS, and even auto pilot. These are connected via UART ports or Universal Asynchronous Receiver/Transmitter ports.
Modern flight controllers all run an on-board configuration firmware and are configured via software. You might have heard some of the popular software/firmware combinations like CleanFlight, BetaFlight, or RaceFlight. This software provide a graphic user interface (GUI) which allows you to configure, tune, and change settings on your flight controller. Some companies like Fly Duino offer custom firmware and software for their products (KISS in this case).
Multiple types of firmwares can usually be loaded on a single FC and the appropriate software will then control it. Other than being aware of the type(s) your FC supports - this shouldn't weigh into your purchase decision too much.
As we spoke about already - a flight controller is constantly processing inputs and sensor readings. The calculations for these inputs are very complex. Having a faster on-board processor helps handle these calculations quickly. Higher processor power allows higher looptimes. A looptime is the amount of time it takes for the processor to complete a PID loop. A higher looptime reduces the amount of delay and smooths out the flight characteristics.
Modern FC's are using one of a few versions of the STM32 processor - F1, F3, or F4. Starting with the early F1 flight controllers, most have now shifted to the more powerful F3 version. F4 processors are just beginning to make their appearance on new models. As of the time of writing, either an F3 or F4 processor will do the trick.
Built in to the board of your FC will be several sensors. These sensors enable your flight controller to understand the orientation, movement, and even location of your copter.
Lets dive into the use for each sensor:
Sensors for FPV Pilots
When browsing flight controllers you will often see two models. Often described as Acro vs Plus or Deluxe. For short range FPV flying you really only need the two sensors found in the Acro version - a gyroscope and accelerometer. You will find additional sensors like a barometer, GPS, and magnetometer on flight controllers designed for long distance flight - the Plus or Deluxe version. In short, if you plan on flying FPV or LOS, go for the Acro version.
Flight controllers allow recording of the inputs and sensor readings through an on-board blackbox recorder. This allows pilots to review flight data after the fact to tune their copters. Some boards feature on-board memory for storing recorded data. Others offer a micro SD card slot for recording to external flash memory.
Blackbox recording is a power user feature allowing someone to get in and fine tune their copter. If this sounds like something you're interested in - make sure to get an FC with on-board or external memory support.
An external radio receiver must be connected so the flight controller can receive inputs from a radio transmitter. The flight controller needs to support your radio receiver and protocol in order to receive communications. Be sure to cross reference this before purchasing.
UARTs - these ports allow you to connect external peripherals to your FC. Commonly you will connect your radio receiver and telemetry to UART ports.
USB Port - In order to update settings on your flight controller you will connect it via USB to your computer. You may also use the port to do firmware updates. Most FC's include a micro USB connector on the board.
Connecting external parts like ESC's or radio receivers to your FC comes in a few different styles. Each connection type has its unique advantages and disadvantages which we will cover here. Also note that you may find multiple types of connectors on different boards.
This connection type has two main styles - pins or direct soldering. By soldering pin headers onto the board you can connect wires with servo connectors. By direct soldering you simply run a wire through the hole (hence the name) and solder it on the other side. This popular connection type is a favorite of many pilots due to its multiple connection options and strength.
Pads sit on the edge of the board allowing you to solder wires flat to the board. This type of connection first appeared on the KISS and Lumenier LUX FCs. Since that time other manufacturers have adopted the style. A specific example being the Furious FPV RADIANCE.
The SH connector series is the most compact offering from the popular JST connector brand. This small connector type can be seen on FC's like the SP Racing F3 board. Rather than soldering the wires directly to the board, the FC will include JST-SH connectors with wires. You then connect these wires to your parts directly or by joining wires.
This connection type has the benefit of being disconnected easily.
Some flight controllers feature a built in BEC which allows you to connect the FC power directly to the battery. This can make things easier as you then don't need to rely on the voltage regulator on your PDB.
As an example the KISS flight controller features an integrated 500mA 5v BEC. This allows you to power external devices like the radio RX or race transponder right from the FC.
Most controllers will have a boot mode. This mode is used when you update the firmware of your FC. Boards without a button require you to create a connection between two tiny pads on the board using something metal or soldering. This connection must be made when booting and running the FC in boot mode.
Boot buttons remove this tedious process by adding a small button which you can press with your finger. This is a very nice-to-have feature.
As miniquad technology improves parts are becoming smaller and smaller. This has enabled the addition of other common peripherals right onto the FC board. These advances have enabled smaller and cleaner builds.
Power Distribution Boards
Normally found on a separate board, PDB's are now starting to show up as an integrated part of the flight controller board.
By adding IR LED's to your FC, this allows you to remove the need for an external transponder. This can easily save you $50 and the extra wiring/mounting needed to add a race transponder to your build.
By adding an OSD chip to the FC you can display information over your video feed. This again saves lots of space and wiring by removing the need for an external board.
Built-in VTX's have grown to popularity with FC's like the Singularity FC. Adding a video transmitter to the FC makes the build more compact and allows you to control it from the chip.
Here at Controller Craft we catalog every drone product from around the industry. Visit the flight controller section to find the right flight controller for your next build.
Hopefully this article helps you understand flight controllers and helps you choose the right one for your next build. Please leave questions and comments below.
Last updated on February 6, 2017