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FPV 101

First Quad

Introduction

The purpose of this article is to be the ultimate go-to guide for a beginner to start getting an understanding of the parts that they’re going to need to be able to build their quad. Included is a checklist, and a brief explanation of each part on the machine, including links to learn more about each part. By following through this article, you should have all the information that you need to have a successful first build. With the growing popularity of mini racing quads, what we’ve found is that a lot of people (like many of ourselves) are starting cold into the RC community as a hole, having no experience building, soldering, researching, etc. This article should serve as an all-hands-on-deck exposure to the hobby, and will tell you the ins and outs of what you need to know to get started.

 

Frame

(A QAV210 with 30 degrees of camera tilt) 

Generally, when considering working on a racing quad build, the first thing that people consider is the frame size that they are going to use. In general, frames are classified by the maximum length (in inches) of propellors (or “props”) they can “swing.” The current popular sizes for propellors are 3″, 4″, 5″, and 6″. In general, we recommend a 5″ quad as a starter build. It will generally have more room available for you to build inside of, and it will allow you to expand in the future to different/more electronics on the inside. Our recommendation is to go for an “H-quad” or a “freestyle x-quad”. These classifications refer to their shape: “h quad” placing the arms towards the end of the main body of the frame, and “freestyle x-quad” having a large main body, but the motors are arranged in an X formation. Both options will fly perfectly well for a beginner, so don’t get hung up on the distinction. Just pick a frame that is sturdy and appealing to you. In general, we like to see the base/bottom plate/arms of the quad to be made out of 4mm thick carbon fiber. From our testing, 3mm can hold up, but we generally prefer to see more advanced pilots flying 3mm because they’re less prone to crashing than beginners.

One more note about frame sizes is that they will usually have a measurement in millimeters with their name or in their description. 250, 220, 210, 185, 180, and 130mm are all common measurements. Airframe measurements are diagonal from motor to motor. In general, 250 H quads, and 220 X quads will fit 6″ propellors. In general 210H quads and 180X quad will fit 5″ propellors, and 180H and 160X will fit 4″ propellors.

  • QAV210
    • 4mm base plate, and plenty of room for a first build. It only goes together one way, so it’s a very smooth assembly for someone that’s just getting started.
  • Falcon 185
    • Do this build only if you’re a ready for more of a challenge. It is a true X quad, but not a freestyle x quad. It’s small and light, and can still swing a 5″ propellor.
  • ShenDrones Tweaker 5″ or Shendrones Mixuko

 

Motors

 

(Broken in Emax "Red Bottoms" 2205/2300kv)

Once you have chosen your frame, you are now ready to choose motors that would be appropriate for the size of propellor that your frame is capable of swinging. With motors, there are two measurements that you need to be aware of, and then there are recommendations on prop size based on those measurements. When you are looking at a motor, there will always be at least two numbers listed: the motor size and the motor “KV.” A popular motor size, for example, is 2204 / 2300kv. The 22 refers to the outer diameter of the “bell” the part that spins around on the outside. The 04 refers to the height of the “stator,” which is inside part of the motor that is bolted to the frame and doesn’t spin. Thus, a 2206 motor would be slightly taller, while an 1806 motor would be thinner AND taller. On the other hand, the second number “Kv” refers to the speed at which the motor spins. The actual measurement is basically “revolutions per minute per volt.” One thing that you’ve probably been exposed to is that racing quads will run on different voltages of batteries. 12 and 16 volts are popular voltages for batteries, so when you see a 2300kv motor, it’s really saying that it rotates at 2300 * 12 (or 16) RPM. So a 2300 kv motor with no “load” (i.e. in a perfect situation) will spin at 27,600 RPM on 3S.

(Left to right: 1806, 2204, 2205, 2206)

Why does all this matter to you? Well.. basically, these numbers impact performance tradeoffs between props, sizes, and rotational speeds. The GENERAL rules of thumb are these:

  • Higher KV will draw more current from the battery because it will push more and more amps out through the motor, but they will spin faster. In general, higher KV motors require propellors that are smaller and don’t have extremely high angle of impact (they’re flatter, instead of biting at the air more). Example: 3100kv/1306 motors are perfect for 3″ propellors, because they are small props that can be spun very fast, but not draw too much power.
  • Lower KV motors will draw less current, and swing larger propellors more efficiently.
  • Smaller motors (in terms of 2204/1806/2208) etc will be lighter, but they may lack the torque required to spin larger props.
  • Larger motors will in general have higher torque, but in general can’t spin propellors as fast.
  • Popular motor specs include:

Our recommendation for the 5″ frames listed above would be some sort of 2204/2300 kv motor. It will give you great performance on both 3s and 4s batteries, and you’ll be able to experiment with many of the different kinds of props available on the market.

 

Electronic Speed Controller/ESC

(A well loved FVT Littlebee 20 mounted on a quad)

The next choice that you’ll need to make is that of the electronic speed controller (ESC). This is an electronic device that sits between the flight controller and the motor. The flight controller tells the ESC how fast to spin the motor, and the ESC then measures how to spin the motor that fast and does it. In addition, the ESC is connected directly to lipo (battery) power, and converts the D.C. Current of the battery into Tri-phase A.C. power to spin the motor. ESCs all have at least 7 connections: 3 wires for motors, two wires for power/ground, and two for signal/ground. With the three wires that go between the speed controller and the motor, you can directly solder each wire to the pads. When we power the motor later, you can reverse the direction of the motor by swapping the soldering point of any two motor wires. Generally, people de-solder the wires from the ESCs, and solder the wires of the motors directly on to the ESC after mounting on the frame.

When choosing an ESC, here are the things you need to pay attention to:

  • Max/Burst Current
    • You need to pay attention to the maximum and burst current capacity of the ESC that you choose for your build. Most ESCs will list their max continuous current as part of the name of the item: I.e. Littlebee 30A, XM20s, etc. And the burst current is usually around 10A higher than the max continuous current. So, if your motor/prop combination per motor is around 25A at max throttle, you’ll be fine with a 20A ESC, since you’ll on average be drawing less than 20A, and only above it at the top 10% of your throttle range.
  • Firmware
    • There are currently 4 popular firmware available for electronic speed controllers. Two are open source, and two are closed source. BLHeli is the most popular by a landslide, and is generally recommended as the best balance between good/cheap. SimonK is the other open source option, but it generally doesn’t perform as well as BLHeli in many aspects, and is not nearly as configurable. Next, KISS is the first of two popularish closed source firmwares. KISS is regarded by many as one of the best on the market, but it comes at a price. Finally, VGoodESC/Firefly ESCs have another closed source firmware that is attempting to replicate a similar feel to KISS, and is generally cheaper. However, limited support and configurability is available.
  • Bootloader
    • When it comes to BLHeli and SimonK ESCs, you generally want to make sure that the BLHeli bootloader is on the speed controller you choose. As technology has been advancing, it’s become a lot easier to work with BLHeli with ESCs that have the BLHeli bootloader. Technologies are coming for SimonK ESCs, but we would still recommend choosing ESCs that come with the BLHeli Bootloader. FVT Littlebees and XM20s are examples of BLHeli Bootloader ESCs.
    • If you have an ESC with a BLHeli Booatloader, you are able to use “cleanflight passthrough” to easily connect to and configure your speed controllers, which is one of the most useful techniques ever for someone that has had to change their settings.
  • Supported Communication Protocols
    • This is a minor sidenote, and in general not something you should have to worry about unless you are really, really future proofing your machine. But, just as a sidenote, some ESCs support different communications protocols and others don’t: available protocols are PWM, Oneshot125, Oneshot42, and Multishot. You need higher end/faster/more powerful ESCs to run Multishot, so if that’s a long term goal, keep it in mind when selecting your ESCs.
  • Chipset
    • The final note about speed controllers is that you’ll want to choose a more advanced chipset. As time marches on and hardware continues to improve, more advanced processors are coming out for speed controllers. In general, look for an ESC with an “F390” chip or above, when choosing a BLHeli-based ESC.

Thus, for our 5″ quad build, we would recommend any of the following:

 

Flight Controller

(an assortment of Flight Controllers of various shapes and firmware)

The next part of our quad that we’ll need to choose is the flight controller. This is the “brain” of the operation — it controls the speeds of the motors to maintain stability on the quad. In addition, it converts signal from your receiver and relays your commands to the motors, etc. There are many, many flight controllers available on the market, and many different variances within different products and versions. Thus, all we can really do is tell you what we like to see in flight controllers, and let you make the decision based on price point after that. Here are the things you need to keep in mind when choosing a flight controller:

  • Processor
    • The primary differences between flight controllers is the processor that they carry. They’ll have one of: F1, F3, or F4 processors. In general, F1 boards will do everything that you’ll need on a racing quad, but as technology and software improves, they are starting to struggle to keep up, so it is our recommendation that you find a flight controller with an F3 chip or higher. F4 boards are generally reserved for larger machines that need to do mission planning, or are running lots of sensors and GPS, etc. In addition, one firmware, RaceFlight, is making advances that take advantage of the F4 boards for racing.
  • Firmware
    • In the same way that there are many options for flight controllers, there is also a wide variety of firmware available for the flight controllers. The firmware is the software that controls the hardware on the flight controller. Currently, there are 4 primary optiosn available for racing quads:
      • Baseflight (extremely outdated)
      • Cleanflight (the go-to standard for a long time, but starting to fall behind)
      • Betaflight (the current most popular, bleeding edge firmware)
      • Raceflight (Focused on ease of use and higher-end hardware) 
      • KISS (closed source, but very popular)
    • It’s our recommendation that you find a flight controller that supports Beta flight, as it makes tuning/setup/learning much much easier than with baseflight/cleanflight.
    • You could also go KISS with your first build, but it’s hard to find replacement parts if something gets broken, and they tend to be more expensive.
  • Flash Memory 
    • One feature that we like to see on flight controllers is onboard flash memory. A current feature of clean/betaflight is the ability to log data to to an onboard flash device. This will allow for finer-tuned builds because you can see the actual motor output data in a graph format and refine your tune and PIDs based on the visual information. While there are options for logging this data without an onboard flash chip built into the flight controller, it’s a huge convenience to be built in, and is quickly becoming an industry standard.
  • Form Factor
    • Just a quick note that most flight controllers come with 32x32mm mounting holes, which is a standard mounting setup for flight controllers. That being said, some will have cutout sides (Lumineire lux, KISS FC) and some will be smaller than 32×32 (Naze Afro Mini rev3). Generally, people use the 32×32 size, but be aware of other options for your builds.
  • AIO vs Full vs Acro
    • We wanted to make another sidenote on types of mini flight controllers. AIO (all in one) is a board that contains a power distribution board, on screen display, and flight controller all stuck together. There are not many of these available on the market, simply because they aren’t as popular, and they’re much trickier to work with for a limited benefit. A “Full” board generally contains more sensors than you’ll need for flying a racing quad, like a barometer. Often, full boards will be a slightly bigger size and have a different mounting pattern, making them tricky to fit into most racing frames. Finally, an “acro” board is usually a barebones board that has only the bare minimum that you’ll need for racing.
  • Voltage Regulation
    • Finally, the only other thing worth mentioning that can be a major difference when you’re building your quad, is that some flight controllers have on board voltage regulation and others don’t. Flight controllers need to be given 5v power input — no more, no less. Some flight controllers have an on-board 5v regulator, which makes builds a little bit simpler, but many flight controllers do NOT have a 5v regulator, so you’ll need something separate. Not a huge issue, but something to keep in mind. It is definitely not a deal-breaker when choosing a flight controller.

Our recommendations for flight controllers for our 5″ build are as follows:

 

Propellers

(a collection of props of various sizes, shapes, blades, brands, and pitches) 

Another early consideration that you should make is propeller type/size. While in the past there hadn’t been a ton of options here, but props are starting to come in many different shapes, sizes, and have different features. The first thing to understand is how propeller (prop) measurement works. If you look at information on props, you’ll see the following: 5045, 5040, 6030, etc. The First two numbers refer to the length of the prop’s diameter in inches: 50 = 5″, and 60 = 6″, and so forth. The second set of numbers refers to the angle of the pitch of the prop. A higher number means it’s angle is higher, and a lower number is a lower angle. The number is a measurement of a distance in inches that the propeller would travel in a perfect viscous fluid. Obviously, that doesn’t make sense in terms of quads, but it can be used as a comparative measurement.

The larger the prop and the higher the pitch, in general the more thrust it will provide, but it will also draw more current, so you have to find a balance between efficiency/power. In addition, you need to pay attention to the speeds/torque of your motors, because it’s very easy to accidentally overprop your motor, and cause it to overheat. In addition, if your motor doesn’t have enough torque, it will have trouble bringing the prop up to a high enough RPM speed to take advantage of the propeller’s thrust.

In addition, you can also get props with different counts of blades, each in of themselves carrying different values for efficiency and thrust. Props come in 2, 3, 4, and even 6 blades. In general, people fly 2 and 3 blades. You can get bis and tris in just about any pitch, length, but there are only a few quads on the market (at time of writing.)

Thus, in general, here are some examples to follow when choosing motor prop combinations. All would be compatible with 20A ESCs:

  • 2204/2300 kv motors — stick to 5″ props, any blade count, and any pitch. 5045 tri blades are pushing your luck, so tread carefully. You can get away with 6″ props on a very light build.
  • 2206/2200 kv motors — stick with high-angle 5″ props or any pitch 6″ props. 5045 tri blade and 6040 6″ bi blade fly very well on motors of this size.
  • 2208/2000 kv motors — 6045 only
  • 2204/2600 kv motors — 4045 tri blade, or 5040 triblade on a light rig (sub 300g dry)
  • 1306/3100 kv motors — 3045 tri blade

For our 5″ build, we would recommend 5045 bi blade, or 5040 triblade.

 

 

Power Distribution Board

Another brief consideration for your build is how you’re going to distribute power from the battery to all of the components. In recent years, many new options have come out for power distribution that will make your build easier and easier. Power distribution boards basically come in two variants — ones with regulators and ones without. Power distribution boards (PDBs) that do not have regulators are basically just pieces of copper that will “stack” with your flight controller using nylon standoffs that make it easy to solder wires together into a circuit. On the other hand, you can buy power distribution boards with built in 5v, 12v, or both regulators, which makes wiring up flight controllers and video transmitters very easy.

Some power distribution boards can also come with OSD (On screen display) built in. When assembling your FPV system, you would connect the camera and VTX to the PDB, and the OSD will be added to the video signal on it’s way out the video transmitter. We’ll cover OSD options in more detail, but it was worth mentioning that some PDBs have OSD support built in.

Our recommendation for our 5″ quad build would be Brotronics UberDistro board.

 

FPV Camera

(an HS1177 600TVL Cased, 25x25 mounted inside of a minimalist x-frame)

The FPV camera is the video camera on board that uses standard definition to capture the perspective of the quad. That video signal is passed through to the video transmitter, which is transmitted back to the pilot. FPV cameras currently come in three different styles: mirco, uncased,  and cased. Micro cameras are very small CMOS-based cameras with limited configuration options. They are very small, and are intended for very small builds. Uncased cameras have been around for a long time, and were the standard until about a year ago. However, they tend to be more fragile than their uncased brethren. If you ask just about any pilot, they’ll pretty much exclusively recommend the HS1177 model 600TVL cased camera.

Our recommendation for our 5″ quad build is the HS1177 cased 600TVL.

 

Video Transmitter

(various video transmitters modified for different uses)

Video transmitters is a huge can of worms in of itself, so we’ll give a lot of brief overview information and then go into specifics as to what’s best for racing quads. Video transmitters use different frequencies to beam analog video information from the quad to a video receiver that’s on the pilot’s end. (we’ll talk about receivers next). Video transmitters work on different frequencies, bands, and channels. Frequencies are the highest level of differentiation — different frequencies could include 5.8ghz, 2.4ghz, and 1.3ghz, each which require different hardware. In general, racing quads are flown on the 5.8ghz frequency, with some minor exceptions. Then, each frequency has different “bands”. Bands are collections sequential variations of frequencies, broken down into channels. A “band” is a combination of 8 “channels” and that “band” lies inside of a particular “frequency.” So, at a race, for example, you’ll be in the 5.8ghz “frequnency, flying on the “raceband”, using a particular channel. Not all events will require raceband, but most modern video transmitters will have it among their collections of bands.

In addition to supporting different channels and frequencies, video transmitters also come in different variances of power. The standard for the United States races is 200mw video transmitters. We’ve found that these have a high enough power to provide a clear video signal around a course, but are low enough power that they don’t interfere with other pilots. Other common options include 1mw, 25mw, 200mw, 400mw, and 600mw. However, 200mw is plenty of power if your antenna/receiver system is good. Generally, you’ll get most gains in terms of video reception from upgrading your antennas and receiver instead of just adding more power to your video transmitter.

Our recommendation for our 5″ quad build is the FX799T Video transmitter. It comes  in 200mw, and has a nice push button for changing channels and bands, making it easy to change channels from one to another. We also recommend using an SMA pigtail cable to take stress off of the video transmitter in crashes.

 

Video Receiver

( An FR632 mounted on a groundstation )

A video receiver is a piece of technology that stays near the pilot and receives the video signal coming back from your video transmitter. It then converts this signal and pipes it through video output into either goggles or a screen. While there are a wide variety of different video receivers available on the market, the only two major differences that you’ll need to be aware of are these: Goggle Modules and Standalone receivers. Goggle modules are video receivers that plug directly into a port on a pair of Fatshark goggles. Otherwise, you can have a standalone video receiver that would run a wire from the receiver to whatever you are using to display your FPV feed. Many opt to build their receiver into a groundstation, which will raise up the receiving antennas, and make sure that the best reception is available at all times. Finally, one other thing to keep in mind is that some goggles/headsets/screens will have a receiver built in to them, but most do not.

Another major difference to be aware of between video receivers is that diversity. Diversity is a process by which the receiver will choose the best performing signal from between the two antennas, and that is the video feed that will be displayed to the user. The video feed will “switch” from one to another instantly, so the user will never know that the receiver has changed from one antenna to another.

Our recommendation for our 5″ quad build would be to use the FR632 Diversity Receiver from Boscam.

 

Goggles/Screen

( Dominator V3 Goggles

The next part of your FPV system that you’ll need is a pair of goggles, a headset, or a screen on which to display your video feed. There are also plenty of options for goggles/screen available, ranging from low to high prices. We would recommend that you choose goggles, and that you don’t try to cheap out on them; for FPV, good, easy to use goggles can make a world of difference when out flying. If you have any intent to stick in the hobby for a while, it will be absolutely worth investing in this part.

Our recommendation for goggles is the Dominator V3.

 

Antennas

(two VAS RHCP 5 turn Helical Antennas) 

The stock antennas that come with video receivers and video transmitters are not the best tools for the job, when flying a miniquad. With a system where both elements remain in a fixed location, the stock antennas will do a fantastic job. However, with miniquads, we find that we want to have a circular polarized antenna on the miniquad and at least a circular polarized antenna on the video receiver. If diversity is available, we would choose to have a circular polarized antenna on one port, and some sort of “directional” antenna on another. Circular polarized means that the signal that is blasted from or received to the antenna will be “omni directional,” in that it will most effectively “see” signal from any given direction. Conversely, a “directional” antenna would be an antenna who’s reception is “focused” on a particular location or direction. Most antennas can be polarized in one direction or another, which is why you will see “right hand” or “left hand” polarized antenna. So, for example, the most popular antenna that you’ll see available for mini quads (apart from the standard “dipole” antenna that comes with the vtxes) is RHCP — right hand circular polarized. It’s polarized to the right direction, and it will be circularly polarized. You have to match the directionality of antennas up on the receiving and transmitting end, but the type of antenna can change. I.e. a Right-hand helical (a directional antenna that makes a cone-shaped video signal) can match up with a right hand circular polarized, for example.

Our recommendation for a set of antennas to start off with would be the TBS Triumphs.

 

On Screen Display

An optional feature for your machine would be what’s called an On Screen Display (OSD). An OSD sits between your video transmitter and your camera, and is connected to your battery power and flight controller. When video signal comes out of the camera, it goes into the OSD. The OSD then takes data that it’s getting from the battery voltage as well as information from the flight controller. It takes all that information and converts it into text that is displayed on the video signal. The combination of video feed from the camera and text from the OSD is then sent off to the video transmitter to be sent back to the pilot’s screen, where the information will be clearly visible to them.

As far as technologies out there, there are currently three ways to get an OSD built into your machine. First, you can buy a standalone unit. Products like the micro minim OSD are cheap and easy to get, and they are widely supported. In addition, you can buy OSDs like the RROSD Pro, which is actually a power distribution board/on screen display combo, which makes setup/configuration easy. Finally, you can also purchase a flight controller, like was mentioned above that is an AIO flight controller. The OSD will be built in, and you’ll wire the video system up to the flight controller.

The last thing that we want to mention about OSDs is that they are often not simple, and they are not somthing that is 100% necessary. We would recommend that your first build not include one, just to make it a little bit more simple, and then later go back and add it when you’re a more confident builder. That being said..

Our recommendation for an OSD is the Micro Minim OSD.

 

RC Receiver

An RC receiver is a piece of electronics that is flown around with the quadcopter. It receives the RC signal from the transmitter or remote controller that the user will use to control the craft. There are a number of different protocols that these receivers support, and many different companies create their own receivers that are compatible with their transmitters. Generally, a pilot will have one particular brand of who’s transmitter/receiver combination that they’ll use: FrSky, Futaba, Graupner Spectrum, to name a few. There are four main main communications protocols between receivers and flight controllers, each that have their own different pros and cons, and you’ll have to choose a receiver that supports your chosen communication protocol. PWM, PPM, SBUS, and Satellite are the available options. Please see our other article about choosing the best protocol for your machine.

Our recommendation for an RC Receiver is the FrSky X4R-SB receiver.

 

RC Transmitter

Our recommendation for an RC Transmitter is the FrSky Taranis.

 

Batteries

We just wanted to briefly mention batteries. For miniquads, currently most pilots fly on 4s batteries, many fly on 3s, and some fly 5s or higher. There is lots to learn about batteries, so we’ve written another article that goes into a lot of depth about batteries.

Our recommendation is for you to use Tattu 4S 75-150C 1300 mAh Batteries on our 5″ rig.

 

Other Useful Tools

So that’s it, you now have everything you need to be able to build your first racing miniquad. In addition to the parts, here is a list of things that might come in handy as  you are building and maintaining your machines.

  • Soldering Iron
  • Helping Hands
  • Screwdrivers
  • Electric Tape
  • Heat Shrink
  • Servo Leads
  • Zip Ties
  • Lipo Charger
  • Power Supply
  • Battery Straps
  • Voltage Tester
  • Lipo Storage Bag
  • XT-60 Connectors
  • Nylon Standoff Kit
  • Heat Gun/Lighter