Projects

Take Flight With H4WK

The Complete DIY Quadcopter Project

Anthony Feizi

Issue 10, April 2018

Part 1: The Basics

BUILD TIME: 8 hours
DIFFICULTY RATING: INTERMEDIATE

Building your own drone might seem like the exclusive domain of hardcore flight enthusiasts. But you can do it too - we show you how!

Have you seen those epic videos on YouTube of a multirotor flying through a valley, or circling around the edge of a cliff face? Multirotors (aka drones) have been around for ages now, but in recent years they have become a lot more popular due to the vast amount of consumer options available.

Thanks to the increased availability of parts, the price of making your own drone has decreased signficantly. Couple this with today’s access to amazing open source control software, and it’s never been easier to build your own drone.

With mountains of information available, and significant choices regarding parts, it may be a slightly intimidating task when getting started. However, this article is designed to arm you with the right information, and will make the process as simple and smooth as possible.

The first half of this guide will cover how multirotor aircraft work, and the parts required, and then we will have some fun so you can build our own!

IMPORTANT SAFETY NOTES

Ah yes, everyone’s favourite word for ruining the fun! In all seriousness though, getting injured with drones is not fun – trust me; these blades can spin at over 5,000RPM and I’ve seen my fair share of clean slices and hospital visits, so please always be sensible and take care.

Here are some things to take note of:

  1. Read the laws before flying – I can’t stress this enough. You must realise that you are flying an aircraft that can do serious damage. Visit the Civil Aviation Safety Authority (CASA) website casa.gov.au/ to get up to speed with the laws surrounding Remote Piloted Aircrafts (RPAs).
  2. Stop and think before flying. Yes, building your first drone is exciting and you will want to fly it straight away, but common sense goes a long way when operating drones.
  3. Download the Can I Fly There? app from CASA. It is a very handy app to check if an area you will be flying in is safe to fly. The app also has rules and guidelines to make sure you are flying safely.

Checklists

Checklists are a great thing to have and use before heading out to fly, and when you arrive at your location. Here is a useful set of checklists that I follow before flying.

Pack list:

The Drone:

Check aircraft is in flight worthy condition, including:

At the site:

Check the site for possible hazards:

Consider psychological issues such as:

Check weather elements:

Examine wind speed:

Other considerations:

Part 1: The Basics

Types Of Drone Frames:

Tricopter

This type of drone has three arms separated at approximately 120 degrees from each other, with a motor connected to each arm. The back motor typically has an RC servo attached to it, to swing the motor to provide yaw movement. Due to its design, tricopters are more agile and fly more like a plane, instead of something like a quadcopter, so they tend to be more popular for freeflying and racing.

PROS:

  • Very agile
  • Lighter than other multirotors
  • Cheaper due to minimal motors and ESCs
  • Longer battery life

CONS:

  • No redundancy if a motor fails
  • More complicated due to the servo
  • Only allows for a small load
  • More vulnerable to wind

Quadcopter

Quadcopters are the most popular style of frame and are usually the first thing that springs to mind when someone refers to a drone. It has four motors, one on each arm, which are either set in an “X” or “+” configuration. The “X” configuration is the most popular setup for a quadcopter. Quadcopters tend to be the Swiss army knife of the drone world, due to their simple design and as they have one of the most versatile frames.

PROS:

  • Easy to fly
  • Can lift larger loads
  • Lots of different frame designs for different use cases
  • Simple to build

CONS:

  • No redundancy if a motor fails

Hexacopter

Hexacopters tend to be more popular with heavy lifting applications; for example, they are quite popular in the film industry for carrying video cameras. Hexacopters have six motors, one on each arm, and come in two variants: the one above is the standard layout for a hexacopter and the second one is called a “Y-6”. Y-6 multirotors look like a tricopter but have two motors on each arm in a coaxial configuration.

PROS:

  • Can carry massive loads
  • Can fly if two or less motors stop

CONS:

  • Expensive due to the extra parts and larger battery required

Octocopter

With motors on each of the 8 arms, octocopters have some serious thrust so are ideal for heavy lifting. This style of multirotor is typically suited to more experienced users, due to its complexity to build. Octocopters also come in two styles: the one above is the standard configuration and the second configuration is an X-8. X-8 multirotors look like a quadcopter but have two motors mounted on each arm in a coaxial configuration. They are quite popular when a compact frame with lots of thrust is required.

PROS:

  • Can carry massive loads
  • Can fly if four or less motors stop

CONS:

  • Expensive due to the extra parts and larger battery required
  • Not the best frame to start off with as a beginner

Pitch, Roll And Yaw Like other flying objects, drones operate the same way. Remembering the axis of movement will help make debugging and piloting easier. In this guide we’ll be building a 500mm quadcopter, as it’s a good size when getting started with multirotor building.

Pitch, Roll And Yaw diagram
DIAGRAM Credit: http://xybernetics.com/2016/04/08/tech-talk-quadcopter-basics/

Common Construction Materials:

Carbon Fibre: Carbon fibre is definitely one of the best materials to use to build a drone. It’s tough and extremely lightweight, so if you can budget it in, carbon fibre is a good choice. This will make your build fly better and consume less energy. When working with carbon fibre, make sure to wear PPE when cutting, sanding or machining it. Carbon fibre also impedes RF signals so keep that in mind when mounting your electronic components such as antennas.

Aluminium: Aluminium is quite useful for the arms, frame and landing gear. It’s flexible, lightweight (though it is heavier than carbon fibre), and relatively easy to work with. Aluminium is inexpensive and readily available in comparison to carbon fibre which makes it a popular material of choice when drone building.

Wood: Wood is a good choice when making a frame on a budget, as it has a high strength-to-weight ratio. Plus with wood, you can make spares cheaply.

G10: G10 is a variation of fibreglass and is often used as an inexpensive alternative to carbon fibre. G10 is also used in PCB (printed circuit boards), so its quite popular for drones under 600mm to use a PCB as the base plate, with etched tracks for power distribution from the battery to the ESCs.

Plastic: Plastic sheet and 3D printed plastic parts are quite popular amongst DIY drone enthusiasts. Do take note that 3D printed parts are not durable and can be heavy, so more thought is often required to ensure the design is light and strong.

Parts That Make Up Our Multirotor:

Parts that make up our multirotor

Motor

Brush versus brushless? This is an age-old question. The short answer is, for anything larger than a 65mm frame, brushless motors are better. However, the downside to brushed motors is that their brushes can wear, thus leading to a shorter lifespan. That said, they are cheaper and require less electronics to get working.

motor

Brushless motors are almost always used for multirotor builds, due to their versatility, durability and ability to generate lots of power. They tend to be more expensive than brushed motors.

Brushless motors come in two styles:

Inrunner: where the coils are fixed on the outer casing and the magnets spin on the inside of the case.

Outrunner: where the magnets are on the outer casing and are spun around fixed coils inside the motor casing.

Inrunners are generally exclusive to RC helicopters, airplanes and cars due to their high speed. They tend to have less torque than outrunners, which is why outrunners tend to be more popular for multirotor builds.

The motor size is usually noted in a XXYY format and are measured in millimeters. The first two digits refer to the diameter of the stator, and the last two refer to the height of the magnets. Typically, the larger the numbers are, the higher the torque the motor is able to produce - the drawback being the mass of the motor.

What are KV ratings on motors?

KV ratings refers to the number of revolutions per minute that a motor (with no load attached) will turn when 1V is applied. Basically, it refers to how fast a motor is able to spin at a specific voltage.

Generally, a low KV rating will give you more torque, but at the cost of less top speed; going higher will increase your top speed but at a reduced torque. Most average builds will use a KV rating between 500 to 1000. Keep in mind the right KV rated motor for your build will depend on the size of your frame, purpose, battery voltage and propeller size.

Calculations

RPM = KV * Battery Voltage

For example, if we power a 1000KV motor with a 3S LiPo battery (11.6V), the motor will spin at 11600 RPM without propellers on. However, if we use a 4S LiPo battery (14.4V), the motor will spin at 14400 RPM without propellers on. The RPM will decrease due to air resistance once you have a propeller mounted onto the motor.

A motor that produces a high thrust may be good as it gives you faster acceleration, but you need to consider the efficiency and current draw, to make sure it’s not drawing a ridiculous amount that exceeds what your hardware can support. To give to you the best response and handling, your thrust will ideally be two times larger than the mass of the drone.

PROPELLERS

We typically see propeller sizing in the format, AxY.Y. The first value is the diameter of a propeller (virtual circle that a propeller generates) and the second value is the pitch (the amount of axial travel per revolution). Both values are in inches and generally a shallower pitch provides more torque, while a steeper pitch allows for better agility and a higher top speed.

PROPELLERS

They can be manufactured from a number of materials, such as:

Plastic: Plastic is the most popular material for props. It’s cheap and has good durability, but will most likely damage if you have a crash.

Wood: Wood is not that common for multirotors but is extremely durable, although expensive, due the intricate machining required. It tends to be more commonly used on RC planes.

Carbon fibre: Carbon fibre propellers are the cream of the crop. They are super high quality and extremely durable; but they’re expensive, so are not recommended for your first build.

Whenever you are designing a multirotor, make sure you include the weight of the propellers, as this is often overlooked or forgotten.

The number of blades has an effect on the overall thrust and control of the aircraft. Two and three blade propellers are the most common, but you can get up to six blades. Keep in mind when you increase the number of blades you will increase current draw, and reduce the top speed.

THE ELECTRONIC SPEED CONTROLLER (ESC)

These components provide the ability to control the direction and speed of the motors. You will need one ESC per motor or you can get a four-in-one ESC solution for quadcopters, if space matters.

ELECTRONIC SPEED CONTROLLER

You must consider the amp draw of your motors i.e., the maximum current draw of the motors. The ESC’s burst current needs to exceed this value, or it can send your latest build plummeting to the ground while on fire - I’ve seen this happen!

There are three core parts to each ESC:

Three-bullet connectors: The three-phase AC output that connects to the brushless motor.

Black and red cable: Takes the power input from the power distribution board.

Three-pin RC servo connector: Takes the RC signal from a source (like the flight controller).

ESCs are quite intelligent and can run different software. BlHeli_s and KISS ESCs are the most popular firmware available. Simon K and BlHeli, used to be popular ESC firmware, but this is now outdated.

ESCs can also communicate with the flight controller through various protocols. There are six protocols available, but the current standard is Dshot due to its stability and reliability. If an ESC doesn’t support Dshot600 or higher, it’s not worth considering. Most hardware made after mid-2017 will support past and current protocols.

Battery Elimination Circuit (BEC)

BECs are designed to convert the raw battery voltage to a fixed regulated voltage. Some ESCs have BECs installed on them but sometimes you may need to buy a separate BEC to power your flight controller and other components that require regulated voltage.

FLIGHT BOARD (BRAINS)

The flight board is the brains of your multirotor. It takes into account the position of your multirotor and control input, and calculates how fast the motors should spin and sends the signals to the ESCs.

flight board

Most flight controllers are built around a specific software such as Ardupilot, Cleanflight, Betaflight, Raceflight or iNav, so your preference in software may affect your decision.

Ardupilot: If you are looking to build something that can fly autonomously, Ardupilot is the way to go. The Ardupilot is an open source, uninhabited vehicle autopilot software suite that can be used for multirotors, fixed wing, vertical takeoff and landing (VTOL) aircrafts and ground vehicles. The community is quite large and there are a lot of developments happening. It’s also great for general flying, GPS-assisted flights and aerial filming.

Betaflight: It is experimental but has the most up-to-date features. Updates happen almost weekly. It’s not as advanced as Ardupilot but is perfect for small size drones. It also runs on a lot of flight boards.

Cleanflight: It’s like Betaflight but the code is slightly more stable and has the best bits merged into it. The updates are slow and it’s supported on less boards.

Raceflight: Raceflight is specialised for racing and has removed stability and GPS features to increase loop times.

iNav: iNav sits between Ardupilot and Betaflight in terms of features. It’s mainly used for aerial filming and GPS assisted flights.

Currently, F3 or F4 flight controller chips are the most commonly used. Anything lower such as the F1 is not worth investing in, as they are outdated and their support is being phased out. F7 chips are slowly becoming available; however, there is currently no software taking full advantage of this.

In order to keep your multirotor flying smoothly, flight controllers get lots of data from various sensors. These include:

Accelerometer: Measures linear acceleration on the X, Y and Z planes.

Gyroscope: Detects angular changes on three angular axes.

Inertial Measurement Unit (IMU): A small module that contains the gyroscope and accelerometer.

Compass: Gives headings information of the drone.

Barometer: Measures atmospheric pressure and provides the height of the drone.

GPS: Gives the geographic coordinates of the drone.

Usually, the more sensors you have the more expensive your flight controller is going to be. A flight controller designed for racing is going to be cheaper than a flight controller designed for autonomous flight.

For our build, we are going to be using a Pixracer with Ardupilot. The Pixracer is a great board if you want to get started with an autonomous flight, as it is good value and packed with features.

TRANSMITTER, RECEIVER AND TELEMETRY

RC transmitter and receiver

In order to control the multirotor you need some sort of connection from the ground to the aircraft. Most of the time you will use an RC transmitter and receiver, but if you want the best value remote, get the FrSky Taranis X9D. It’s the most popular among pilots around the world and is often recommended in forums. It runs the Open Tx firmware, which allows you to customise absolutely everything you can think of. If it’s out of your price range, then the FlySky FS-i6 is a great alternative, especially for beginners.

When choosing a controller I ask myself how does the controller feel in my hand? My favourite saying is “if it doesn’t feel good in your hands, you will never use it.” This also applies to picking the right remote so test and try different remotes to see which one feels best. Also check the quality of the gimbals in the remote; the smoothness will affect the way you pilot your multirotor.

Make sure the receiver has the appropriate protocols to communicate with your flightboard. Remote/receivers that support the following tend to work with most flight boards:

  • SBUS (FrSky)
  • IBUS (FlySky)
  • DSM2 and DSMX (Specktrum)

Remotes that have lots of receiver options will be helpful in the long run. As you build more aircraft, you will find that different sized receivers have different applications and will suit different frames.

Telemetry transceiver sets allow you to send and receive commands and important aircraft data. For example, this can be receiving battery information to your ground station computer or sending waypoints to your multirotor for an autonomous mission.

BATTERY (AND CHARGER)

batteries

A majority of multirotors are powered by Lithium Polymer (LiPo) batteries. LiFePO4 is another battery chemistry that’s used, but its very rare in this application. LiPos are great because they have a high energy density, high current discharge rate and are lightweight. However, the cost in comparison to other batteries is higher, and they can become a safety hazard if not handled correctly.

s: The “s” stands for the cell count of a battery pack. 3S equals three cells, 4S equals four cells, and so on. To get the voltage of your battery pack, you multiply the voltage of a cell by the number of cells.

Voltage: The battery’s voltage should match the motors you have chosen or you will run into issues such as overheating.

Capacity: The capacity of a battery pack is usually measured in amp-hours or “Ah”. As a general rule of thumb, the higher the capacity, the more flight time you will get.

C rating: The C rating refers to a battery’s discharge rate.

Calculations

Discharge current = C * Capacity.

You must make sure the maximum current of your build does not exceed the discharge current or you will end up with puffed lipo batteries, or it may even cause a fire.

Chargers

LiPo batteries will require an intelligent charger to manage the voltage as it charges, to prevent damage to the cells.

Read reviews of chargers that have balance charging as a feature before you make your decision. I strongly advise against buying cheap, unknown chargers as they can overcharge your cells.

POWER DISTRIBUTION BOARD (PDB)

POWER DISTRIBUTION BOARD

The PDB splits your battery voltage into multiple points of access so you can connect all of the electronics neatly. Some PDBs have built-in regulators so you can power your low voltage electronics such as the flight controller and camera. Before buying a PDB, make sure your PDB can handle the maximum current draw of your build.

ON SCREEN DISPLAY (OSD)

ON SCREEN DISPLAY

The OSD either comes on your flight controller or can be purchased separately. They display useful information such as battery voltage, current draw and even an artificial horizon on your video feed.

FPV CAMERA, VIDEO TRANSMITTER (VTX) AND RECEIVER (VRX)

FPV Cameras (AKA the eye of of your drone) need to be perfectly clear or there’s a chance you will crash your pride and joy. Consider the following when selecting a camera:

Sensor type: CMOS tends to be the cheaper option, however CCD will give you a better result.

Lens: Each sized lens will provide a different field of view (FOV). The smaller the focal length the wider the FOV but you will also get a fish eye effect that you will need to deal with. 2.8mm is quite narrow; 2.5mm is the best all-rounder size, and 2.1mm is great for freestyle flight, but for racing it may be too wide.

Resolution and latency: The higher the resolution the more latency you experience. It’s best practice to use a camera with the same resolution as your goggles or screen.

Meanwhile, the VTX transmits your camera feed to your RTX.

Power output: In Australia you are limited to 25mW @ 5.8GHz. Make sure your radio is within that limit.

Channel options and switching: A variety of channels allows you to fly in groups without getting interference in your feed as you can switch between channels. As long as the VTX channel list is compatible with your RTX you are set.

Signal quality: Cheaper VTX and RTX will be more susceptible to noise and can cause interference in the video gear of other pilots. More expensive boards have better filtration electronics which means you will get a cleaner signal, and won’t cause issues with other pilots.

You can either get VTX goggles, screen or a module that can plug into other displays or phones.

CAMERA GIMBALS

Camera gimbals are used to stabilise your camera while flying and prevent the video from looking like it has been through a washing machine. Camera gimbals usually have two parts: the gimbal itself and the gimbal controller. The gimbal controller plugs into either your RC receiver or flight controller to receive inputs from you.

How Do Quadcopters Move?

Now that we know what all the parts do, let's look at how they move

Hover

Hover: All motors run at the same RPM. The lift generated from the motors must be enough so that the quadcopter counteracts its weight but not enough to climb in altitude. The torque affect from each of the motors that are acting on the quadcopter should cancel out, or the quadcopter will want to yaw left or right.

Pitch

Pitch: Pitch control relates to the quadcopter moving forwards and backwards. In order to move forwards the back two motors must increase in speed. This pitches the nose of the quadcopter downwards, thus resulting in forward movement. Conversely, backwards movement is achieved by increasing the speed of the front motors.

Roll

Roll: In order to fly to the left, the right two motors increase in speed, which lets the left-hand-side dip, resulting in a sideways movement. To fly to the right, the left hand motors increase in speed, which lets the right-hand-side dip.

Yaw

Yaw: In order to yaw (or rotate), quadcopters increase the speed of diametrically opposing pairs of motors. Since the pairs rotate in the same direction, the quadcopter rotates in the direction of the increased torque.

Before you commence your build, it is recommended that you check out the resources below for information and additional assistance regarding laws in your area, other build guides to learn from other people or to get a better understanding of the Ardupilot software.

NEXT - PART TWO: Construction

Part Three: Software & Setup

Part Four: Repairing Your Drone