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mike_kelly's blog
Posted by mike_kelly | Oct 26, 2014 @ 12:32 PM | 1,666 Views
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 the Phantom could not carry the cameras I needed to use.
...Continue Reading
Posted by mike_kelly | Oct 26, 2014 @ 12:27 PM | 1,552 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/...Continue Reading
Posted by mike_kelly | Oct 26, 2014 @ 12:19 PM | 1,557 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 @ 12:07 PM | 1,521 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.

Most motors are very...Continue Reading
Posted by mike_kelly | Oct 26, 2014 @ 11:59 AM | 1,567 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 @ 11:39 AM | 1,511 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 @ 11:25 AM | 1,454 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 @ 07:35 PM | 1,983 Views
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!
BO640 (2 min 12 sec)

Posted by mike_kelly | Sep 26, 2014 @ 10:01 AM | 2,041 Views


I choose APM over other flight controllers because of the ability to do waypoints (cheaply). This is dependent on the telemetry link, usually provided by the 915 mHZ 3DR radios that keep your computer in contact with the aircraft and can upload changes to the flight plan and receive status information about the location and speed etc.

But if you start to get into long range radio control systems like Dragonlink or EZUHF the telemetry radios may not be able to keep up with the range of the UHF radio control.

So I have been looking for a long range solution for telemetry that will keep up with a UHF (LRS) long range radio control system.

One inexpensive long range solution for radio control is the OpenLRS system designed by Flytron (http://flytron.com) an Open-Source Long range radio system running on 433mHZ. This system was copied and produced in high volume by Hobbyking marketed as the HK Orange OpenLRS 433. They make modules to fit Futaba and JR radios. Since the Hobbyking 9XR and FrSky Taranis also support JR transmit modules this includes those radios too. Hobbyking makes OpenLRS modules that are 1 watt or 100mw. http://www.hobbyking.com/hobbyking/s...mpatible_.html

So Hobbyking drove the price down to the point the modules go for less than $30 each. Very attractive compared to other LRS systems that go for $200 a module.

Then came along FlipFlap, an RCGroups member in...Continue Reading
Posted by mike_kelly | Sep 16, 2014 @ 09:14 PM | 2,317 Views
I live in a heavily forested area so I need to travel a ways to get to a flying field. After reading the threads on ground stations on various forums here is my idea. I used a rolling tool cart. It has 7" wheels so it will roll on uneven ground. It has a folding pull-handle like travel airline baggage. It is modular and you can disconnect the top tool box from the base and use it separately.

I am an APM/Mission Planner user and will always have my computer with me.
In the lid I put my computer monitor and next to it a second monitor for dual-computer displays. This way I can undock the mission planner windows and put the Heads up Display in one and the maps in the other. The second monitor can also be used for composite video out of the FPV Video Receiver.

The keyboard is bluetooth and stored in the drawer under the top tool box but there is room under the keyboard for tools and parts.

In the bottom is a big car battery that can charge my lipos and run the system. In the middle drawer space for my radios and goggles.

I am not finished yet but I am having a lot of fun with it.

Posted by mike_kelly | Aug 30, 2014 @ 08:13 PM | 2,629 Views
There are some nice thrust tests on RCGroups but I wanted to evaluate relative quality. It is hard to do but the sound and vibration the motor makes is an indication of something. When the motor is spinning you can see the winding quality better and although it may not make a performance difference it sure seems it indicates the care in assembly.

You make your own judgement. The end of the arm was taped to the table so the motor would not wander across the table but it can vibrate and make noise if it is not balanced. These are raw from the vendor not balanced yet by me.

Mini Motors (2 min 10 sec)

Posted by mike_kelly | Jul 24, 2014 @ 10:43 AM | 3,188 Views
There is a lot of discussion about mounting ESCs out on the ends of the arms. The issue is that the high current flowing thru the power lines feeding the ESCs can form an electric field around the wires. This electric field creates something like a resistance, called an impedance, to the flow of power to the ESC. Unlike pure resistance, which there is nothing you can do about it, you can mitigate the effect of an impedance by balancing the effect of the two contributors to impedance - capacitance and inductance. Since the high current flowing in the ESC feed wires creates an inductive impedance you can reduce the effect by adding capacitance.



If you research the discussion on RCGroups , there is a whole thread on the subject, you will find the recommendation that if you want to put ESC's further out than about 10cm you should add some capacitance.

"As a rule of thumb, for every 4inch/10cm extra length/distance between battery and ESC, add an 220uF extra capacitance near the controller (electrolytic condensators, voltage the same as the capacitors already installed, low ESR type)"

Most ESC's come with a capacitor on the input lines. My solution, and it is only my choice not nessarily the recommended solution for everyone, for my Tarot 680pro what as follows.

I decided to add capacitance and insert the capacitors in the tubes. I wanted the...Continue Reading
Posted by mike_kelly | Jul 20, 2014 @ 05:04 PM | 3,361 Views
What you say, no way! I know all your images of the Blackout is screaming through the woods dodging branches. Well hear me out.

Like probably the majority of folks now on RCGroups I am a noob. I did not know how to spell RC last year. The year before I got a Hawkeye delta wing RC kite for an aerial photography project. But I really had a hard time with the change in orientation as the plane returned. I gave up. It really was not the right platform for me because I need to hover to compose images.

So last year I saw someone's Phantom and was really impressed by the flight controller, this should solve me problem I thought. So I rushed out and bought a Phantom. Then I discovered how small a gopro was and that I was not going to lift my cameras with a Phantom. So I decided to canabalize my Phantom and build an F450. Not a good idea. It worked but it was difficult to troubleshoot problems with the Phantom receiver and transmitter which were never intended to do any job other than the Phantom.

I started over reading. I followed advise to get a little hubsan or a proto and learn the feel of the sticks. I still had trouble with orientation changes. The little guys also did not quite fly the same as the bigger cousins.

Then I discovered the APM with it's autonomous flight capability and open source community. I read all I could find on RCGroups. Then I read some more.

I realized I was not going to get what I needed without a much much bigger lift platform. I concluded,...Continue Reading
Posted by mike_kelly | Jul 20, 2014 @ 02:07 PM | 2,800 Views
Just some images of what came in the kit and the notes from Marek on how to space the larger 4.3" monitor away from the back. The shell is the same size as the 3.5" kit but the buttons are on the opposite side to match Marek's Cyclops monitor which indeed does not blue screen when signal is lost.
Posted by mike_kelly | May 06, 2014 @ 03:04 PM | 7,998 Views
I have been concerned with the purchase of FPV goggles that my eyes may not land in the range that the optics of most mass produced goggles are designed. They are an expensive option and if they don't fit, or work for me, I would be stuck with them.

As an alternative to commerical goggles, I came across this post
about a kit made by a fellow in Poland. It uses a single 3.5" lcd monitor mounted in a custom made case. The virtures of this approach, for me, are that there is no inter-pupal distance to be concerned about, there is only one screen not two. Next I can use my own glasses, which I needed to do in addition to the supplied Fresnel lense.

I received my kit today and I am very impressed. Marek has produced a brilliantly simple product. Very carefully thought out with everything I needed, except the LCD screen, to assemble the goggles in about 20 minutes following Mareks Youtube video:

I used the recommended lcd monitor linked to at his website(http://napolskimniebie.pl/_oferta/oferta.htm#rwd13).


I don't believe this monitor is actually 640x480 as indicated by the ebay seller. It looks closer to 320x200 by counting pixels. But it is a sharp lcd and works fine. I think the issue is what your FPV camera is actually sending to the ground station. It doesn't do any good to have a higher quality...Continue Reading
Posted by mike_kelly | Feb 20, 2014 @ 12:35 PM | 3,454 Views
Brand new out of the bag.
Posted by mike_kelly | Feb 17, 2014 @ 09:21 AM | 3,816 Views
In the first tutorial we discussed using eCalc to get some basic answers
about a multirotor design. How long will it fly and can I lift that
camera and gimbal I want to use?

But eCalc can tell you much more. Let's talk about the limits and
warnings when looking at eCalc results. The mistake I made when I first
started using eCalc was to think the warnings were something I had to
stay way away from. I wanted to make sure I did not come close to those
warning limits in a design. But Markus pointed out that you want to use
your motor fully. You don't want such a powerful, and heavy, motor that
you never really use the full capacity. If you are selecting a 480 watt
motor, but the eCalc results show that, for the combination of parts you are
using, the maximum electrical power the motor is using is
only 150 watts, you are not using much of the potential of the motor. It
means that even at the highest throttle setting you can not get the full 480
watts of power.

Your design always needs to be tempered by the type of flying you do.
Are you an acrobatic (acro) flyer who really pushes your motors to the
limit with flips and fast climbing? Do you do Aerial Photography (AP)
and hover most of the time? Are you doing videography and need smooth
even passes? Each type of flying puts a different load on the motors.
ECalc tells you something about the performance for each type of flying.

For a given motor and payload combination, eCalc estimates...Continue Reading
Posted by mike_kelly | Feb 09, 2014 @ 10:26 PM | 6,947 Views
What is eCalc anyway? It is a web-based program to take multirotor design data and calculate some valuable information about the design. It was written by Markus Mueller.

eCalc is a powerful tool to answer questions like "will that motor work" or "what will my flight time be"? You can use it as a "what if tool" to design your multirotor. For example, what if I change the props from 13x4 slow-fly to 14x5.5 E props?

Although DJI, for one company, has introduced some very popular ready-to-fly multirotors, many other brands are still custom built by forum members from parts and most are very different builds from each other.

So, let's design a multirotor from scratch. We want to lift a Sony Nex5n camera.
The first thing to realize is that we need to know the weight of every part of this project. When you ask forum members "will this motor be good for me?" it is really hard to answer because you have to enter all the data into eCalc to find out. Unless somebody runs that exact set of parts in their own multi-rotor you probably won't get an answer - because other members honestly don't know.

So, let's start with a Tarot FY690 frame. A frame that can handle the wieght of the Sony Nex5N camera. There are, of course, lots of other frames that will work just as well. I'll also pick out a complete set of parts, somewhat arbitrarily, and then we can play with substitutions to see if we can improve our design.
1-Tarot TL68C01 (FY690) =...Continue Reading