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Archive for October, 2014
Posted by mike_kelly | Oct 26, 2014 @ 11:32 AM | 24,879 Views
This is a 7 part series, skip ahead if you like:
#2 Battery Technology
#3 Motors and Electronic Speed controllers (ESC's)
#4 Propellers
#5 Flight Controllers
#6 Radio Control Transmitters
#7 Learning to Fly

Introduction part 1

There is a stampede of new users storming the gates of RCGroups. This is understandable because there are exciting new things happening at a rapid pace, especially in the multirotor category. When you have new technology, there is often a delay in getting out basic information because of the rapid rate of change. I thought I would put down some notes in my blog about what I learned upon entering this new world. These notes are designed to be an overview to get someone started but there is a lot of detail not covered and some ideas are generalized in order to not lose a newcomer.

I started this adventure a couple of years ago because I needed to do some aerial photography. I found the Hawkeye Delta wing aircraft designed for aerial photography:
Hawkeye Thread

It was, and is, an excellent platform but I found that the photography I needed to do could not be done in flight. I needed to hover but, at that time, RC helicopter and multicopter platforms seemed very complicated and way out of my reach. That is why my notes are multirotor-centric because that is my need.

Like so many other people, when the DJI Phantom came out I jumped on it thinking it would solve all my problems. After getting it, I discovered how small and light a GoPro is and that...Continue Reading
Posted by mike_kelly | Oct 26, 2014 @ 11:27 AM | 21,174 Views

Radio Control (RC) models have been around for many decades. They started out with fuel-based engines because the battery technology was not available to store enough energy to enable electric flight. With the invention of the Lithium Polymer (LiPo) battery, electric flight blossomed because it was able to not only store a reasonable amount of energy but it was also relatively light weight. But Lithium Polymer battery technology must be understood by the new RC enthusiast because it can be dangerous if not treated properly. LiPo batteries are made up of multiple cells joined together to create a battery of a certain total voltage. Each cell is about 4 volts, thus two cells (2S) equal an 8-volt battery and three cells (3S) (3x4v=12v) equal a 12-volt battery, etc. You will see people refer to batteries as 2S, 3S, 4S, 5S, or 6S; they are all multiples of a single lithium polymer cell joined together to form a higher voltage battery. If you join two batteries or cells in series the voltage increases; if you join two batteries in parallel, the voltage stays the same but the total energy capacity available increases. If you have six single-cell LiPo batteries in series, it is called a 6S battery with a voltage of 6x4v=24v. If
you have two 3S 1000milliamp (ma) (same as 1 amp) batteries wired in parallel, you have what is referred to as a 3S 2P battery (P=parallel) at a voltage of 3x4v=12v and a capacity of 2x1000ma=2000ma, which is the same as 2 amps.
http://www.rclab.info/2012/...Continue Reading
Posted by mike_kelly | Oct 26, 2014 @ 11:19 AM | 22,690 Views
The batteries supply power to a number of components but the common ones are the motors for every craft. RC hobbyists use a direct current (dc) brushless motor most commonly. This motor is controlled by sending it dc pulses that turn electro-magnets inside the motor on and off in a pattern that gets the motor spinning. There is a round cylindrical housing that is lined with permanent magnets and rotates. This type is called an "outrunner" because the outside of the case rotates. Some are the reverse and they are called "inrunners".

In an Outrunner there is also a fixed star-shaped assembly, called a stator, that has wires wound around a form that, when powered with an electric current, causes a magnetic field to form. You turn on one set of windings to cause a momentary magnetic field which attracts the winding to the next magnet on the housing, and the rotating part then moves toward the next magnet. Then you pulse another winding and cause it to move toward the next magnet on the housing. By turning the windings on and off, that form multiple temporary magnets, we can get the rotating part to begin spinning. We need to have a controller that will send pulses to our motors in a precise fashion.
...Continue Reading
Posted by mike_kelly | Oct 26, 2014 @ 11:07 AM | 19,224 Views
Motors and propellers need to be matched to the purpose. Each motor is designed for a particular purpose for optimum efficiency. A high KV motor is designed to spin faster with small props and is used primarily for acrobatic aircraft. Low KV motors are designed for large props and heavy load applications.

Propeller specifications are noted as the diameter and the pitch. The pitch is the twist in the blades and is measured as the distance in inches the propeller would travel if it were like a screw being screwed into a wood block. Each turn of the screw would move the screw so far into the wood, depending on the twist. Same for a propeller; more twist and it goes further through the air. A propeller for a small mini-quad might be a 6 x 4, sometimes written 6040, which would be 6 inches in diameter with a pitch of 4 inches per rotation. A large prop for an aerial photography aircraft might be a 17 x 3.8, or 1738, which would be 17" in diameter with 3.8" of pitch.

Generally, high-pitch propellers are used for fast, quick low-torque applications like acrobatics. Low-pitch propellers are used for low speed, high torque, heavy-lifting applications. For acrobatics, you would most commonly choose a high KV motor with a high-pitch prop. For the other end of the spectrum, with a heavy aerial photography platform, you might choose a low KV motor and a large diameter low-pitch prop.
IT is a lot like the...Continue Reading
Posted by mike_kelly | Oct 26, 2014 @ 10:59 AM | 21,227 Views

The invention of the flight controller changed rotored RC flight dramatically. It began with those who took a small computer board and wrote a program to control multiple motors to allow multirotor flight. Let's use a simple quadcopter as an example. When you want a quadcopter to hover, all the motors must run at the same speed. If you want the quadcopter to move forward (away from you), the two motors farthest from you must slow down and drop the quad down in the front or pitch the quad forward. This allows the back two motors to drive the quad forward. Same idea to move left. The left-most two motors must slow down or the right-most two motors must speed up so that the quad can move left. The combination of the various speeds of the four motors moves the craft around. Can you imagine if you had to control all four motors manually to do this? That is what the flight controller automatically does for you. It takes your commands from your RC transmitter and translates your "go left" stick commands into what it takes to get the motors to move the quad left.

But a flight controller does so much more. The advent of smart phones was part of the sequence of events that led to the current crop of flight controllers. The large-volume sales of smart phones brought down the price of the accelerometer, compass, and barometer sensor chips. These chips sense where and what the quad is doing at any moment in time so the computer knows what to do next. The accelerometer chip...Continue Reading
Posted by mike_kelly | Oct 26, 2014 @ 10:39 AM | 19,847 Views
RC Transmitter

The last link in our control of the aircraft is the RC hand-held transmitter and the receiver it transmits to that resides on the aircraft. Each stick that you move or switch that you flip sends a command to the receiver on the aircraft and that information is in turn sent to the flight controller to execute your command. I found this very confusing at first because the names of things start to overlap. There are many radio transmitters and receivers on a modern multirotor. Getting them all straight can be difficult at first.

1. There is the traditional RC hand-held transmitter that has the sticks and switches and sends commands to the receiver on the aircraft.
2. There is often a telemetry transmitter that sends flight controller information back to a laptop on the ground with flight status information.
3. There can be a First Person Video (FPV) transmitter that sends video from a camera on the aircraft to a video receiver on the ground and then a viewing screen.

To make things even more complicated, most of these systems can now do double-duty and be both transmitters and receivers or a transceiver. Some telemetry radios can transmit data from the aircraft to the ground and also receive commands from the ground station. Many modern RC transmitters can also receive basic telemetry and display the information on their built-in LCD displays.

You will hear people talk about a RC Transmitter as being mode1 or mode 2. Some modern transmitters can be...Continue Reading
Posted by mike_kelly | Oct 26, 2014 @ 10:25 AM | 18,297 Views
I gained much wise advice on flying by reading through the pages of RCGroups. First, you need to get familiar with the way an RC aircraft changes its orientation while you fly. This can be quite difficult. As the aircraft is going away from you, left is left and right is right. But when the aircraft is returning to you, what was left is now right and what was right is now left. When you're flying at slight angles to your position, it can be even harder to figure out which way is which. A flight-simulator program on your computer is a great way to practice flying without damaging your equipment or hurting anyone else.

FMS free flight simulator

AeroSim at Hobbyking

I got a flight-simulator program that allowed me to hook up my actual RC transmitter to the computer so I was using the real sticks to fly the simulated aircraft. These flight simulators are quite good at giving you a real flight experience. I crashed a lot and I'm glad I used a simulator first. This allows you to get the feel of the light touch needed to move the controls, the sticks.

Next, I got a very small inexpensive quadcopter, the Hubsan X4 one of many small quads, to practice real flight. This little quadcopter is only a few inches in diameter and comes with its own miniature transmitter. Flying this little quad gives you a feel for the sticks and the light touch you need to not over shoot everything. During my first flights, I would move the throttle up gently, I thought, and my quad would shoot up...Continue Reading
Posted by mike_kelly | Oct 17, 2014 @ 06:35 PM | 9,920 Views
Blackout mini H quad
RCX-1806H motors
Mini-APM from GLB
ULRS 433MHz Long range radio with mavlink telemetry
2.4Ghz vtx

A short video of testing my Blackout with the ULRS radio system.

I have some tuning to do on the roll pids but ...

I'm a happy camper!

Blackout Mini H with mini APM ULRS RCT1806H (2 min 12 sec)