AnyLeaf Blog

Parts you need for a quadcopter in 2022

Written on Feb. 24, 2022, 7:46 p.m.
Updated June 17, 2022, 3:36 a.m.

Overview

Getting started with building a custom quadcopter can be intimidating. There are a number of guides available online - this article is intended as a summary, and reference. If you prefer video format, check out this video by Joshua Boardwell. His channel includes a number of nice intro videos, including how to build quads.

One of the biggest challenges to getting started is learning what parts are required. It's easy to think you have all you need, then discover what you're missing one by one. This article doesn't go into details about what each part does - we'll go over each category of required parts, and review the most important points and terminology. Bottom line: Make sure you have one part from each category, and that they're compatible with each other.

This article is geared towards DIY FPV quadcopters, eg racing and freestyle, but applies more broadly.


Frame

The frame provides a stable platform for the rest of your components. It usually includes a central structure that contains the aircraft's electronics, and 4 arms extending from it to house the motors. For racing quads, the distance between forward and backwards arms may be longer than that between left and right arms (H config). On other quads, the arms may all be equal length, or may have a longer left-right arm distance (X config).

Frames are often made of carbon fiber, due to its combination of strength, light weight, and low cost. They're often manufactured by cutting flat carbon fiber plates with a CNC machine. Different parts of the frame are usually attached with hex/allen M3 (3mm diameter) screws. They usually have mounting holes for flight controls and ESCs are well, in one or both of 20mm, or 30mm spacings.

Frames come in different sizes, often described by the arm spacing, in inches. Larger frkvames allow for more electronics, and larger batteries and motors; smaller frames can be faster and more maneuverable, or be suitable for indoor spaces. Frame size is usually described by the largest propeller size it can accommodate, using the prop's diameter in inches. 5" frames are a good starting point for outdoor quads, and 2-3" frames for indoor. Small quads (and their frames) are referred to as "whoop", "tiny whoop", or "cinewhoop" - these have ducts surrounding their rotors, which protect both the propellers, and whatever they might collide with!

There are some open source frame designs available, like the Source One. These allow anyone with a CNC machine to mill their own, and pair with suitable screws and standoffs. Frames built from these designs are often available for purchase at a low price.

Make sure your frame can fit the components you want. For example, if you're using a DJI digital video system, check that there's an additional (20mm) square mounting pattern in addition to the main one. Some frames have more robust mounting systems than others. Ie, frames that include a front camera mount with adjustable angle (instead of a simple set of screw receptors mounted on support standoffs, for example) may make your build easier and more robust. Some frames include built in mounts for GoPros, antenna supports, and cable management (like raceway on the arms to conceal motor cables, and brackets to route battery cables).


Motors

Choose motors suitable for your drone size and use. Consider frame size, battery size, propeller size, and what performance characteristics you expect from your quad. There are two broad categories of motors: brushed and brushless. Brushless motors are more powerful for a given weight, and last longer. Brushed motors are cheaper. Other than for small indoor aircraft, choose brushless.

Motors are often described by their stator size, with numbers like 1306, 1806, and 2204. The stator is the main stationary part of a motor; it contains copper windings, which create a magnetic field that drives the rotating parts. The first two digits in those numbers are stator diameter in mm, and the last 2 are height, in mm. So, larger numbers here correspond to larger motors, and usually more power. A 2204 motor has a stator with a 22mm diameter, and 4mm height.

Another measure is back EMF, often referred to as kV. This is a measurement of electromotive force (voltage) generated by the motor, and is associated with how fast a motor rotates, with a given voltage applied. This is measured in kilovolts-per-RPM, so the full unit is \(\frac{kV m}{rotation} \). Motors with lower back-EMF (kV) are generally more efficient, and use less current to spin at a given speed. A lower KV motor uses thinner wire with more windings - it can produce more torque and power, and drive bigger props. This article on Drone Nodes goes into detail on these parameters, and other details about motors for quadcopters.

Consider motor torque as well. Higher torque allows more rapid response to control inputs. Generally, larger stators provide more torque.

As a starting point, consider the following stator sizes for a given frame size: 2204-2206 for 5". 1806 for 4". 1306 for 3".

Compare motor maximum thrust with the weight of your quad. At least a 4:1 thrust : weight ratio (By adding the thrust of all motors) is a good rule of thumb. 8:1 or higher may be suitable for racing quads. For context on these numbers, a thrust:weight ratio of 1:1 means at full power, the quad can hover in level flight, but can't gain altitude, or move laterally without losing altitude.

This guide on Quad Questions goes into detail on choosing suitable motors.


Flight controller (FC)

The flight controller (FC) is a circuit board that acts as the central electronics hub for the quad. It's usually a square shape, with mounting holes spaced 30.5mm or 20mm apart (along an edge), to fit different size frames. Some have mounting holes for both of these forms, or others.

The FC contains a number of components on it - the most important of which is a microcontroller (MCU). The microcontroller is a small computer that includes a CPU, memory, and small circuits(peripherals) such as communications buses, and analog-to-digital converters. The most popular MCU for FCs is the STM32. There are many STM32 models, and they're grouped by family named such as "F4", "G4", and "H7". When you see a FC labeled with one of those categories, it's referring to the type of MCU. They all work in a similar way, so here's a rule of thumb: F-series MCUs are older (But still popular). H7 is a high performance, expensive MCU. G4 is a medium-performance MCU that's cheaper than H7. You can find details in our MCU comparison article.

The MCU is responsible for storing and running firmware like Betaflight, and communication with the other components.

The FC also contains an Inertial Measurement Unit (IMU) - this is a small IC (integrated circuit) that contains a 3-axis gyroscope, and 3-axis accelerometer. The gyro is critical to all quads, and is required for stable flight. If using a control scheme other than Acro (manual) mode, you need the accelerometer too, to find the attitude. Other sensors may or may not be included on the FC, such as a barometer (for estimating altitude). Note that some sensors like GPS, time-of-flight (TOF) sensors, and optical-flow cameras are unlikely to be on the FC directly, since they need to be on the outside of the quad. The FC usually includes an on-screen-display (OSD) IC, which adds a flight-data overlay to the camera feed.

FCs contain a number of connectors to power, and communicate with other electronics. These are usually pads (expposed copper you can solder wires onto), or pin headers. The pin headers are usually JST SH (1mm between pins), or GH (1.25mm between pins). Pin headers can be more convenient - especially when removing or reconnecting wires. However, since few standards exist for wire ordering, pads are more flexible. Sometimes "pre-crimped" wires are included with flight controllers and other electronics, that plug into pin connections in any order.

Common connections include power and ground, UART, I2C, and SPI. Power is often available as raw battery voltage (Vbat), 5v, , 3.3v, and sometimes others like 10v. UART is a flexible digital communication system - each UART Rx/Tx(receive/transmit) pair can connect to one device. Radio receivers, ESC telemetry, camera control, and other features commonly use UART. I2C and SPI are similar, but can connect multiple devices using the same wires. Sensors usually use these, including the onboard ones.


Electronic Speed Controller (ESC)

The ESC accepts signals from the FC to control power to each of the motors, and applies corresponding amounts of current to each rotor. The battery is usually connected directly to the ESC - the FC and other components are powered by a battery connection between the ESC and FC.

The ESC generally has a digital connection to the FC for each motor. The FC send data using DSHOT (Or a related protocol) on these lines. An additional line may be provided, for which the ESC send data (called telemetry) back to the FC. Current-gen ESCs usually run one of the following firmwares: KISS, BLheli, and Simonk.

The ESC might include a capacitor that can be connected between battery terminals to help filter electrical noise. If it doesn't include one, you can add one. This article provides details on why you might want one. Good capacitance value are between 100µF, and 1,000µF. If buying a capacitor not specifically designed for quads, make sure its voltage is rated high enough: At least 20% higher than your cell's voltage.

ESCs come in 2 common form factors: A separate ESC for each motor (Generally mounted on the frame arms), or a "4-in-1" ESC, that includes circuitry for all motors on a single board. 4-in-1 ESCs are increasing in popular, and usually mount directly below or above the FC, using the same 30mm or 20mm mounting screws. Check out the selection at RDQ.

ESCs provide 3 connections for each motor - usually solder pads. The order you connect the wires from your motor doesn't matter: Any config is acceptable. Swapping any 2 wires reverses the direction the motor spins, but this is something you'll configure on your FC, eg with Betaflight.

Some ESCs are larger than others, for a given hole spacing. If the one you're considering extends past the mounting holes by more than a few mm, check that it'll fit your frame.


Camera

The camera is used for FPV flight, eg so you can see where the quad's going! It's powered by a connection on the FC (usually at least 5v), and connects to the FC. The FC accepts its analog signal, adds an on-screen-display (if desired), then sends the signal to the video transmitter.

Digital camera systems like DJI digital, HDZero, and OpenHD are also available. These provide much higher quality realtime video, and have different degradation characteristics at max range. They're more expensive than analog, are bigger and heavier, and few options are available. They can be added to any FC that has an available UART connector.

Currently, analog cameras and video transmitters are more popular, but digital is gaining ground. DJI Digital systems like the Caddx Vista provide the best video quality, but have slightly more latency than analog and HDZero, and are expensive. HDZero systems have lower latency than DJI, and better video quality than analog. If you're building a new quad, seriously consider a digital camera and Vtx. For best quality and signal penetration, choose DJI. For low price, go with HDZero. The HDZero Freestyle has better range and signal penetration than other HDZero models.

Cameras come in different sizes. Ones labeled "micro" are lightweight, and suitable for racing. Ones labeled "nano" are suitable for 2-3" (eg whoop) frames, but provide worse video quality. Larger ones provide better quality video, but weigh, and cost more.

For recording high quality (eg 4K) video, mount an external camera, like a GoPro, on your frame. These don't transmit live video for flying, but provide the best video quality for sharing after landing. Note that adding a GoPro adds weight. Some frames include mounting hardware on the front specifically designed for them.


Video transmitter (VTx)

The video transmitter is powered by your FC (Usually with at least 7v), and accepts a video signal - this is usually the analog camera data, with an OSD overlay added by the FC. It sends a radio signal to your receiver/display on the ground. For the digital systems listed above, these usually come with (And are attached to) the camera.

Common operating frequencies are 1.2Ghz, 2.4Ghz, and 5.8Ghz. 5.8Ghz is a good choice to start with, since it's popular, and uses a small antenna. VTxs may have fixed, or adjustable power output. Higher power allows longer range. For example, 25mW is suitable for indoor flying, 600-1000mW is good for long ranges, and choices in between are useful for short-range outdoor use.

This article by Oscar Liang goes into details on VTxs, and how to select one. Considering choosing a VTx that has a square mounting pattern, so you can mount it in top of your FC, or on a secondary mount if your frame has one - this will make assembly and wire-management easier.

If using a digital system like DJI digital, make sure both your camera and transmitter are compatible. They're often sold together. These usually mount using a 20mm square pattern, often behind or in front of the main FC+ESC stack. (Or on the main stack for 2-3" frames)


Radio receiver

The radio receiver accepts signals from your radio controller, and uses it to control your quad. For example, signals for throttle, pitch, roll, and yaw. Quads also use auxiliary functions, controlled by switches on your controller. These are often used to change flight mode, and arm the quad.

Some flight controllers instead a receiver, and some require a separate one. There are a number of radio protocols to choose from, and your receiver has to use the same one as your transmitter.

ExpressLRS (ELRS) is an open-source protocol gaining popularity due to its long range, and low latency. Some new FCs have built in LRS receivers, but you usually need a separate circuit board. ELRS is a good default protocol to use for new setups, but its newness may be a hassle, eg due to rapidly-updating firmware that needs to be kept in sync between transmitter and receiver. ELRS is compatible with 900Mhz, and 2.4Ghz transmissions. 900Mhz offers longer range, and 2.4Ghz lets you use a smaller antenna. As a default, use 2.4Ghz, and make sure the transmitter and receiver both use the same frequency.

Other radio protocols include FrSky, and TBS Crossfire.


Radio controller

The radio controller (Sometimes just called "radio") accepts control inputs - usually from 2 sticks and a number of switches - and transmits them to your quad's receiver.

Radio controllers often run open source firmware - OpenTx, or EdgeTx. Of these, choose EdgeTx; it's a newer, updated version of OpenTx. If your radio comes with OpenTx installed, consider switching.

A popular model, and great starting point, is the Radiomaster TX-16S. The Radiomaster Zorro is nice for one in a smaller form-factor; similar to a video game controller. Smaller models like the Zorro may have smaller batteries (ie shorter battery life), but can be more comfortable, and easier to transport. Cheaper models are available as well, that include fewer features.

Radio controllers can also be connected to a PC over USB, to use with drone sims like Liftoff.

Consider buying a lanyard for your controller. Most controllers have an attachment point on their front for these. If you drop your controller while flying, the lanyard can help avoid a crash.


Add-on radio transmitter

If using a radio protocol your controller doesn't support, you may need an add-on transmitter. This attaches to your controller, and includes its own transmitter and antenna. For example, if your receiver uses Crossfire or Express LRS, (a popular protocol), you may need this. For example, if you wish to use ELRS on the TX-16s, you plug a small transmitter module and antenna into the top bay on the back of your controller. Some controllers, like the Zorro can come with ELRS included.


Display or goggles

These receive video signal from your VTX, and display the resulting feed. Common form-factors are small, battery-powered displays, and goggles that take up your whole field-of-view.

Goggles are ideal for racing, and FPV use in general. Keep in mind, it's best-practice (and often a legal requirement!) to maintain line of site with your quad - so when using goggles, bring a friend to keep an eye on the drone. And to make sure no one stages weird photos with you while you're in The Metaverse.

If using a digital system, you need a special display or goggles that's specifically designed to work with it. Again, expect to pay more, for better quality video. Eg, DJI's goggles.


Batteries

Batteries not included! You need a rechargeable battery for your flight controller, and one for the radio controller (Usually not included). These are usually Lithium Polymer (LiPo) chemistry. LiPo battery packs contain one or more LiPo cells, wired in series. Each cell has a nominal voltage of 3.7v. At full charge, expect around 4.2v. When empty, expect 3.2v. LiPo is used instead of the Lithium-ion batteries common in phones and laptops, due to lower weight for a given amount of charge. (Li-ion batteries are smaller, but heavier.)

A battery with 1 cell is called "1S". 2-cell batteries are called "2S", ad infinitum. More cells mean longer battery life, but higher weight and cost. Since the cells are wired in series, voltage is proportional to number of cells. So, the nominal voltage of a 4S battery is 3.7v × 4 = 14.2v. Its fully-charged voltage is 4.2v × 4 = 16.8v.

Name / # of cells 1S 2S 3S 4S 5S 6S
Nominal voltage 3.7v 7.4v 11.1v 14.8v 18.5v 22.2v
Fully charged voltage 4.2v 8.4v 12.6v 16.8v 21.0v 25.2v
Empty voltage 3.2v 6.4v 9.6v 12.8v 16.0v 18.2v

Letting a LiPo cell discharge below 3v can permanently damage it. Optimal voltage for long-term storage is 3.8v per cell. So, to maximize shelf life, don't store fully charged, or empty. Check out this page for tables on expected voltage across the charge/drain cycle.

You likely want more than one battery, so you can swap them out without having to recharge.

4S or 6S is a good starting point for your quad. 6S will add weight, but offer longer battery life, and lower voltage sag. Small ("mini", "whoop") quads may use 1S, 2S, or 3S. Large and long-range drones may use 5S or 6S. For your radio controller, check the size of the battery box. 2S is common. This article goes into details on quad batteries.

You should choose higher cell count for more powerful quads- higher power use needs higher voltage to prevent an increase in current draw. If you draw too much current, LiPo voltage will temporarily drop (voltage sag).

Battery capacity (electric charge) is usually listed in mAh (milliamp-hours), and WH (watt-hours). When comparing battery hours, mAh is only directly relevant when comparing batteries with the same number of cells. WH is a more universal measure of capacity. Watts = Volts × Amps. For example, a 1500mAh 6S battery has more capacity than a 1500mAh 4S battery: \(1500mAh × 4.2V × 4 cells < 1500mAh × 4.2V × 6 cells\)

Batteries generally have one of 2 types of connector: xt60, and xt30. Make sure this is the same type of connector on your ESC. xt60 is more common on full-size quads, and xt30 is common on whoops.

If while charging, your LiPo starts puffing up like the Stay Puft Marshmallow Man, run. Or unplug in.


Battery charger

Buy a battery charger designed specifically to work with LiPo batteries. There are many options available. Chargers that include a GUI with settings can be easier to work with. These let you specify number of cells (eg 4S), desired voltage, and charge mode. Ie, they may let you automatically charge to a full voltage of 4.2v per cell, or maintain a voltage suitable for long-term storage (to maximize life), eg 3.8v per cell.

An example of a reasonably priced charger that has these features is the ISDT 608AC.


Propellers

These spin, and are usually made of injection-molded plastic. They usually have between 2 and 6 blades each. The more blades, the higher the thrust, but lower the efficiency. This can result in subtle tradeoffs - For example, whoops tend to use 5 or more blades, since this lets they get away with a smaller, lighter frame due to the higher thrust. The increased blade count decreases efficiency compared to a 2-blade prop, but the weight savings from the smaller frame increases efficiency. To get started, Choose a 2-4 blade prop for 5" quads, and a 4 or 5 blade prop for whoops..

Propeller sizes are listed by rotor diameter. Choose the largest propeller you can for your frame size. Generally, propellers designed for 5" frames are labeled 5", for example. Make sure the props are small enough to stay clear of each other, of your frame, and of everything mounted on it - with a comfortable margin that account for blade flexing.

Props are usually labeled on their top side with the direction they're designed to rotate. You need 2 clockwise, and 2 counter-clockwise props on your quad. Make sure these coincide with motor direction, and that your ESC, and/or FC are set up so the motors spin in the correct direction. Props on opposite corners must spin in the same direction, and ones on the same side must spin in opposite directions.

Different props have different pitches and, variations in blade length. Make sure the blade isn't too long for your frame. To start, don't worry about pitch.

It's a good idea to keep extra props around - they're one of the most easily-damaged items in crashes.

Some propellers are designed to minimize noise.

You might also find carbon-fiber props. Compared to plastic, these are lighter, stronger, and quieter. They have fewer efficiency losses from blade flexing due to their high stiffness. However, they're usually not used in FPV quads due to their increased wear on the engine, increased damage to the engine in event of a crash, and the danger they pose to soft tissue in the event of a collision.


Mounting and connecting equipment (Likely included with above parts)

It's important to assemble your quad in a way where all component are secure, and the propellers are clear of wires and other obstacles. Your frame and other components usually come with mounting hardware - this may or may not be sufficient, depending on the items, and how you'd like to mount them. Flight controllers, and (4-in-1) ESCs usually mount on the same set of 4 screws, with holes built in to your frame. You may want to include rubber grommets around their screw holes, silicone spacers to absorb vibration from the frame, and other spacers to keep these circuit boards a suitable distance from each other. If your VTx (or other electronic components) can mount on the same holes, you may have an easier time.

For circuit boards that don't mount on the main stack, you may need to secure them using a combination of zip ties, and shrink wrap.

Wires should be secure, and as short as possible. Make sure there's no risk of wires or antennas getting in the way of props! Test your final setup with props attached before flying, and ensure you have sufficient clearance.

Secure motor wires along the arm the motor's mounted to. Electric tape can work in a pinch. More robust solutions include shrink-wrap, or plastic housings that secure the wires to the arm.

Batteries are usually mounted with cloth straps. You may also wish to use adhesive velcro strips (Like 3M Dual-lock) along the bottom (or top) of your battery, and the top (or bottom) of your frame. This, combined with one or more straps, is very secure. Like with other wires, make sure the battery's wires are clear of props.

Common attachment locations for batteries are above, and below the frame. Battery placement changes the center of gravity (CG. This choice depends on your frame, and flying style. Generally, batteries on top are more suitable for general use and freestyle, since it puts the CG near the center of thrust. (Ie, aligned with props). Racing drone sometimes place the battery on the bottom. Position the battery forward and aft, so that the CG is as close to the center as possible. Ie, your quad's natural balance point should be as close to the center of the propellers as possible.

Antenna mounting depends on the size, shape, and number of antennas. Small wire antennas (Like from ELRS receivers) may be taped or secured on frame arms, terminating near the motors. VTx antennas are usually secured in a way to extend out the rear of the frame.

Camera mounting depends on the specific camera, but usually frames including mounting pieces the camera screws into, that can be secured near the front. You may wish to buy additional mounts, or 3d-print ones to your specifications.


Beeper

Beepers (also known as buzzers) are small speakers that use either piezo oscillation, or magnets to make a loud tone. Beepers can sound when the battery is low, or to indicate other problems, like a lost connection to the controller, or disconnected battery.

There are two categories of beeper: Active, and passive. Active buzzers have 2 or 3 wire connections to the FC, and passive have 3. For passive buzzers, the FC outputs a square wave (ie, alternating between 3.3v and 0v) over a signal line, and uses a dedicated 5v power line: The beeper makes a tone at this wave's frequency. Active beepers are on or off from the FC's perspective, and generate their own wave.

Some beepers have a built-in battery - this is useful for finding your quad if the battery falls off. Beepers are optional, but are useful for finding lost quad, and as a safety feature. This Oscar Liang article goes into details.


Where to buy

Here are a few reputable sources to buy these from:


Conclusion

Wow, that was a lot of shopping and money!

References