How Drone Controllers Work (Explained for Beginners)

Whether you’re new to drones or have been flying them for a while, you must have wondered how drone remote control works. Remote controllers are the reason you can fly your drone to a distance ranging from a few feet to several miles away from you without relying on cables. And knowing how they work helps you make the most out of them.

So, how do drone controllers work?

To put it simply, it involves sending a signal from a transmitter in the controller to a receiver in the drone. The flight controller and ESC help interpret and execute these signals while maintaining a stable flight.

Remote controls also send instructions regarding cameras, sensors, and any other payload the drone is carrying.

Please keep reading to learn more about drone remote control.

What is a drone controller? #

A drone controller is a device that allows a drone pilot to control a drone from the ground wirelessly. Drones have other controllers, such as the ESC and the flight controller. But in this case, we are referring to the device the drone pilot holds when controlling the drone.

You may sometimes see this device referred to as a radio controller or RC. Some might also refer to it as a transmitter or a remote controller.

A brief history of radio control #

While consumer drones gained popularity quite recently, the whole concept of Radio control dates back to the 19th century. This was when the idea of remotely controlling devices for military purposes was pursued extensively. 

As a result, the military invented remote-controlled torpedoes, missiles, boats, teletanks, and anti-jamming systems. This was to minimize the risk of losing soldiers in combat. Radio-controlled devices were widely used in both WWI and WWII.

Over the years, various nations refined their RC systems by making them smaller, inventing transistors, and even enabling them to communicate in several channels. These improvements made it possible to use RC systems in model aircraft by the 1950s.

Fast forward to the 21st century, where every Radio manufacturer produces RC systems that can be used on a wide range of devices, including toy cars, model aircraft, and drones. 

For those who’d love to build their own drones, you can buy an RC system for as low as $30.

How drone controllers work #

Drone controllers work by sending instructions to a drone via radio signals. To understand how they work, let’s look at the main parts and how they all function.

Drone transmitters #

The drone transmitters are located on the drone controller and are the piece responsible for converting the controller’s commands into radio signals, which are then sent to the drone.

Drone receivers #

The receivers are antennas that receive the signals from the controller and convert them into electronic data that the flight controller can act on.

Flight controller #

This component acts as the drone’s brain or the central nervous system. After receiving the interpreted information from the receiver, it determines the power necessary to carry out the instructions sent from the controller. 

The flight controller also combines data from sensors that make the drone aware of its surroundings. 

These include:

• Accelerometers – These sensors measure the rate of rotation and determine the drone’s orientation by determining the tilt and angular velocity.
• Magnetometers – These sensors help a drone orient itself in relation to the magnetic north.
• Gyroscopes – Gyroscopes also measure the rate of rotation, allowing a drone to remain stable when hovering or when in flight.

ESC (Electronic Speed Controller) #

After the flight controller has simplified the instructions into voltage, now it’s up to the ESC to execute these commands by minimizing the power on some motors and increasing the power on other motors depending on the task or direction you need the drone to take.

Parts of a drone controller #

Below are the main parts of a drone controller.

Right Stick #

This is the stick on the right, and it’s responsible for Roll and Pitch movements.

Left Stick #

This is the stick on the left and parallel to the right stick. It’s responsible for yaw and throttle.

Antennas #

These are the transmitters that send the radio signals to the drone.

Other features #

Below are more features you’ll find in most controllers:

• Trim Buttons – These buttons help you align a drone in case it starts drifting to one side or is unstable when in flight.
• RTH (Return To Home) – You’ll find this button in most controllers and in various locations. It’s used to “call” the drone back to the take-off point or another preset location if there’s an emergency.
• Camera buttons – For drones with cameras, you can start recording, take still images, or control the gimbal using the controller.

Basic drone movements #

Below are the main drone movements and what happens when you push the controller’s sticks.

• Roll – This is the movement that allows the drone to move to the right or the left along the roll axis that runs from the front of the drone to the back of the drone. It’s accomplished by pushing the right stick left or right. For a drone to roll, the ESC will reduce the power of the motors on one side of the drone (left or right).

• Pitch – This movement allows a drone to speed forward or backward along the Pitch (X) axis. It’s achieved by pushing the right stick forward or backward. The ESC reduces the power of the back propellers and increases the power of the front motors to make them rotate faster. That’s why the drone’s front section tips downwards when the drone is speeding forward.

• Yaw – This is where the drone turns clockwise along the Yaw axis that runs from the top to the bottom of the drone. On the controller, you push the left stick left or right. To accomplish this, the ESC minimizes the power of the motors in a diagonal pattern.

• Throttle – This is where the drone increases or decreases in altitude. In this case, all motors are rotating at the same speed. The faster they spin, the higher the drone moves.

How drones communicate with the controller #

Below are the main communication channels used in drones and controllers.

Radio frequencies #

This is one of the most common ways that drones communicate with controllers. Radio frequencies are invisible waves that form part of the electromagnetic spectrum. For them to work, there has to be a transmitter and a receiver, which I’ve already described above.

For a drone to communicate with a controller, they must all be ‘tuned” to the same frequency. But what happens if there’s another device in the same range and using the same frequency? That’s where the RFID comes in.

The RFID (Radio Frequency Identification) is an identification code assigned to the communication between a drone and a controller. And the drone will only respond to signals that contain that specific RFID.

Drone communications prefer lower frequencies since they can operate at wider ranges, allowing a drone to move further away from the controller. However, if the frequencies are too low, you’d need very large antennas. So, to strike a good balance, most drones operate in frequencies ranging from 800 to 900 MHz.

Wi-Fi #

Most drones now have Wi-Fi, especially those with an app and a camera. Wi-Fi makes it possible to stream the footage from a drone in real-time, giving birth to one of the most sought-after hobbies in the drone world, FPV racing. 

This is where you wear VR-like goggles and fly your drone like you’re in its “cockpit.” Unlike radio frequencies, Wi-Fi operates in frequencies ranging from 2.4 GHz to 5.8 GHz. Those are very high frequencies. That’s why Wi-Fi works best at shorter ranges.

Global Position System (GPS) #

GPS has greatly enhanced drone navigation. It does this through improving stabilization, enabling Return To Home, and identifying No-Fly zones. 

So, how do drones communicate with controllers through GPS? You directly send the coordinates to the drone, and the drone’s GPS will follow these coordinates.

Some drones are designed not to take off in No-Fly zones, but the communication about these zones actually comes from the drone’s app. Nowadays, it’s even possible to select waypoints in the form of coordinates, and the drone will follow them autonomously. This is a common application in the land survey field where you need to take aerial images of a place.

Satellite Link #

This is a more sophisticated method of communication and is only applicable to military drones such as the Hawk or the Predator drones. Communication through satellites allows the military to control their drones while they are thousands of miles away. However, they still need to have a ground station within the area the drone is operating to coordinate taking off and landing.

Fully Autonomous #

This aspect is still in development, but it’s already seeing some applications in the inspections and military sectors. Traditionally, a pilot has a controller to send signals to a drone. But for fully autonomous drones, you can give them an area of interest, and they’ll fly in these areas, gather data, determine the best route, avoid obstacles, and fly back to the take-off point on their own.

Why drone controllers are unique in the RC aircraft world #

Below are some reasons why drone controllers stand out.

The “RC” abbreviation #

As mentioned earlier, while radio control has been around for more than a century, RC model aircraft and vehicles have only been around since the 1950s. When the RC abbreviation was first coined, it meant Radio Controlled, but when it comes to drones, it often refers to Remote Controlled. 

Regardless, it refers to how a drone can be controlled remotely. The RC technology used in UAVs is also more sophisticated than other model devices.

Number of rotors #

Another significant difference is the number of rotors. Most RC aircraft only have one rotor, which makes it easy to control since all you have to do is control the speed of the rotor and the angle of their propellers to maneuver. 

On the other hand, drones come in four rotors or more. And the controller has to control all four rotors to make sure the drone maneuvers as it’s supposed to. The flight controllers and ESC make it possible for the controller to control the speed of each rotor without interfering with the drone’s operations. Imagine how hectic it would be if you had to control the speed of each rotor manually.

Troubleshooting #

If your drone won’t connect to the controller, below are some possible reasons, and ways to fix this issue.

You’re doing it wrong #

If you can’t connect your drone to the controller, chances are you’re doing it wrong. Each drone has instructions on how to do it, so make sure you check them and follow them strictly when setting up your drone.

» MORE: For more information on how to connect your drone to the controller, check out our guides:How to Connect a Drone to the ControllerHow To Connect DJI DronesHow to Connect Holy Stone DronesHow To Connect Snaptain Drones

Low battery levels #

Another issue that could cause connection problems is low battery levels on the controller, on the drone, or both. It’s important to check the battery levels of all your devices before flying your drone.

Make sure you’re using the latest firmware version #

Drone manufacturers often release firmware updates for drones, controllers, and apps. These updates often fix any underlying issues, but they can also interfere with the connection between a drone and a controller if they’re not all using the same version. Another way to fix it would be to uninstall the drone app and install it again.

Signal interference #

If you’re trying to fly in areas with electromagnetic interference, it may hinder the connection between the controller and the drone. If your drone connects to the controller and takes off, you risk losing it since you may lose the connection when the drone is in flight.

You’re flying too far away from the controller #

If after successfully connecting your drone to the controller, and after flying for some time, you get an error that you’re out of range, or the video footage loses quality or stops, you may be flying too far. 

Each drone has its limit. Some can fly a few feet from the controller, but some can fly as far as 6 miles, depending on the type of communication you’re dealing with. However, regulations in most regions require you to fly within the Visual Line of Sight (VLOS). So, always keep your drone in sight, and avoid flying past the drone’s limit.

» MORE: How Far Can A Drone Fly (From the Controller)?

Seek technical help #

If none of the above tips help, reach out to the drone manufacturer’s technical team, or ask a question in forums. You’ll most likely come across a member who has experienced a similar issue and knows how to fix it.

Notable advancements in drone remote control #

Below are some tech advancements to look out for.

OcuSync #

OcuSync is DJI’s state-of-the-art transmission system that provides some of the longest ranges in the drone world. Below is how OcuSync has advanced over the years.

• OcuSync 1.0 – This version was used in all Mavic drones released before the Mavic 2. These include the Mavic Pro and Mavic Pro Platinum. It was designed to transmit 1080p video quality for short-range transmission and 720p for long-range transmission, and it has a range of up to 4.3 miles (7KM). In optimum conditions, OcuSync will download videos at 40 Mb/s.
• OcuSync 2.0 – This version came with the Mavic 2 in 2018 and exists in most of the drones released after that. It came as an improvement to 1.0 since it transmits 1080p on both long-range and short-range transmissions. Another improvement is that the OcuSync 2.0 automatically switches between 5.8 and 2.4 GHz. This makes it perfect for areas with many sources of interference.
• OcuSync 3.0 – This is the latest version, and it uses a whole new video transmission system that uses 4 antennas instead of 2 like in the 2.0 version. DJI also improved the video transmission system, allowing it to transmit HD videos from a range of up to 7.5 miles (12 KM).

Smart controllers #

These are controllers designed to work with several drones. A good example is DJI’s Smart Controller, an advanced controller that contains a 5.5-inch display screen, the OcuSync 2.0 transmission system, a range of up to 6.2 miles (10 KM), and in-built app capabilities. 

You can use the DJI Go or Fly app or download other third-party apps. Better yet, it has a DJI Go Share feature that allows you to stream your photos directly to social media channels.

The DJI Smart Controller combines the functionalities of a smartphone or tablet and a standard controller. But it’s also improved to make it more durable and reliable than a standard smartphone.

Currently, the drones compatible with the DJI Smart Controller include:

• DJI Mini 2
• Mavic Air 2
• Mavic 2 and Mavic 2 Enterprise Series
• Phantom 4 Pro V2.0

BVLOS (Beyond Visual Line Of Sight) flying #

As mentioned earlier, most regions require drone pilots to fly their drones within their line of sight. But this limits how drones can be used, especially in applications such as food delivery and industrial inspections. However, of late, most drone manufacturers and stakeholders have been pioneering BVLOS to expand the scope in which drones can be used.

So how would it work?

The pilot would rely on sensors, telemetry data, and GPS navigation to know where the drone is and navigate it. Flying BVLOS needs more skills compared to VLOS.

Below are some of the benefits BLVOS has over VLOS;

• It’s safer – In areas where a drone pilot needs to fly in dangerous areas, such as fire zones and gas leaks, it would be dangerous for a pilot to enter the area and fly VLOS. But BVLOS makes it safer since the pilot can position himself or herself miles away at a safe distance and still manage to fly over the area.
• It’s cheaper – In areas where drones aren’t allowed to fly BVLOS, they have to use helicopters which are expensive and not flexible. But drones designed to fly BVLOS have longer flight times, meaning they could fly over the same area several times without costing as much as a helicopter.
• The data is more accurate – Drones can fly at very low altitudes, allowing them to take high-res images from which users can derive more data compared to using manned aircraft.

Unfortunately, there are still too many restrictions against BVLOS, especially in the US. You have to apply for several waivers, and there’s no guarantee that you’ll be allowed to fly. But drone laws are still evolving worldwide, so we can expect BVLOS to be allowed soon.

FAQS #

Can you connect any remote controller to a drone? #

Not really. In most cases, drone controllers aren’t interchangeable. For instance, you can’t use an Autel remote controller to control a DJI drone. But there are some cases where drones within the same series can use the same controller, such as the Mini 2 and Mavic Air 2. There are also controllers designed to control several drones, such as DJI‘s Smart Controller and the Autel Smart Controller.

Can you control a drone with a smartphone? #

Yes, you can. Most drones come with apps that allow you to control the camera, gimbal, take-off and landing, and some intelligent flight modes using a smartphone in conjunction with a controller. 

Some drones, such as the Tello, are designed to be flown strictly with a smartphone without using a separate controller at all.

Is there a universal drone app? #

Not really. Drone apps are designed to work with a specific drone model and brand. You can’t interchange them. However, there are apps like Litchi, DroneDeploy, and RainBow that work with most drones and can be used to extend the functionality of a drone. But not all drones are compatible with these apps.

Can you buy a remote controller? #

Yes, you can. If your controller is damaged, got lost, or you’re planning to build your own drone, you can buy a controller. It’s always advisable to get the controller from the drone manufacturer to prevent voiding the warranty. 

When building a drone, you can find third-party drone controllers, but building your own is still an option. The type of drone you have determines the drone controller you want to use. So, start by getting a high-quality drone.

References:The history of radio controlPhoto by William Bayreuther