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Posted by mike_kelly | Jun 09, 2015 @ 08:36 PM | 9,681 Views
I just reviewed the Pixhawk LITE a low cost small form factor Pixhawk clone offering from GoodLuckBuy. It seems like it will serve well as a replacement for APM.

But for my big multicopters I am more and more looking for reliability. I have learned a few things from my first builds and the top three are:
1. The quality control on the common parts we buy is poor.
2. You are going to crash and break things.
3. Because of #1 & 2 you better be able to fix your aircraft without tearing it down to bare bones because you will be doing it often.

If you don't want to be frustrated think reliability from the start of your build.

That is where the Pixraptor comes in for me. You might think why do we need another Pixhawk clone, especially one that is more expensive than other clones? Well this new Pixraptor is not your take-a-picture-and- copy-it-exactly type board. Somebody really took a look at what could be improved and tried to make a better product. I won't know if they met those lofty goals until the build is finished but the attempt was definitely made.

First thing I notice is the connectors all come out the sides. I like this. It is hard to make a build with clean wiring if all the connectors are pointing straight up. Next they used molex connectors instead of Df13. Some people hate DF13 connectors. The deal is the DF13 connectors require you to tilt the connect on edge and kind of rotate into the socket. If you don't do that installing and removing you risk...Continue Reading
Posted by mike_kelly | May 20, 2015 @ 05:49 PM | 29,167 Views
************************ Notes or errors and omissions **************************
NOTE There is a new version of this board GLB is calling V2. They fixed the power module connector. It now conforms to the Pixhawk standard. But all the other problems talked about below still exist.

The following information concerns V1 of the board.
GLB Pixhawk LITE version 1.
Whomever created the pinout pictures on the GLB website got a number of things wrong, at least as of this date. Hopefully they will correct it.
The order of at least the Power Module and I2C pins are backwards from the same connectors on the 3DR Pixhawk. So instead of using the standard cable for all Pixhawk and APM power modules a custom cable will have to be made! Scoopdreams noticed that the 6 pin cables provided with the Pixhawk LITE are not straight through but reversed. So using one of those cables does allow connection to a standard power module but don't use the normal cable provided with the power module.

Left image is the standard APM and Pixhawk power module, the same connector orientation in both pictures, grounds are on the left and 5v on the right. Note in the Right picture the Pixhawk lite is the opposite.

Since the I2C connector is backwards, but there is an expansion board for more than one I2C device, (I2C devices are compasses, LED external lights etc) jesmail suggests using a reverse cable from the Pixhawk LITE I2C port to the I2C expansion board. This has the
...Continue Reading
Posted by mike_kelly | May 19, 2015 @ 08:38 PM | 2,892 Views
Tarot T shaped landing legs are pretty common throughout their line, as well as many other brands. Tarot uses hollow carbon tube skids. If you land at an angle and touchdown on only one of those legs first, they tend to break off right at the T joint. It seems like a pretty common problem. Some people put wooden dowels inside the carbon tubes but I did not want anything rattling around in my skids.

I first tried some fiberglass skids but I was concerned that with something much stronger it would just transfer the implact further up the landing gear. Sure enough the next flight with the fiberglass skids I did not break the skid but instead broke the T Joint and the landing leg and the attachment at the top for the landing leg.

Not a good trade-off.

Then I found some nylon 10mm rod on Ebay. It comes in just about the right length. It bends, unlike the fiber glass and will absorb some shock. I dont know if it will be enough but time will tell. It flexes under stress but is not too soft.

If you have a better idea please post a comment, thanks.
Posted by mike_kelly | Apr 13, 2015 @ 11:22 AM | 4,088 Views
************************** Mis-labelling *******************************
I think I have figured out what is wrong. THESE ARE LABELLED WRONG!! I am so tired of products with sloppy incorrect documentation. On each quick detach is an arrow, which you might reasonably assume indicates the direction of the motor they are designed to go onto. Nope the labels are backwards and the description is backwards.

In most ads the TL68B36 is described as a ccw and the photos have an arrow in the ccw direction. My Tarot prop adapters that are labelled as such go on the CLOCKWISE motors NOT on the ccw, in order to work correctly i.e. not spin off during flight.

Please see Post#59 at

Originally Posted by strips View Post
Unless you have a genuine foxtech prop mounts I would not trust the colour to be enough. Hold the prop and rotate the motor the way it would rotate when flying. It should fasten the prop.
Agreed - THIS IS THE ONLY SAFE WAY to proceed - with several different suppliers now selling these adapters in different colours - please do it the way suggested above by "strips" and several others. And then tighten by hand a little more once the props are on correctly.

Unfortunately if you look at the very 1st post on this topic the pictures with the prop mounted are WRONG ! Don't blame FoxTech for this though - the initial review was
...Continue Reading
Posted by mike_kelly | Mar 19, 2015 @ 05:15 PM | 5,644 Views
One of the most important build issues on a multirotor is reducing vibrations. The motors and props make a lot of vibrations and the flight controller does not like this. The flight controller has a number of sensors that are vibration sensitive. So if you want your multirotor to fly smoothly and loiter accurately you need to get those vibrations down. The problem is that the flight controller sensors need to be firmly attached to the multirotor to sense the movements. So you have a problem, you need to dampen the vibrations from the motors yet you don't want the sensors to get too isolated, using too soft a spongy foam/gel, from what the frame is doing.

That is why a lot of people spend so much time balancing motors and props to reduce vibration at the source.

Another way is to use anti-vibration motor mounts. I bought a set of Tarot TL68B33 (black) and TL68B34(red) to test on my Tarot 650 Sport quad and see if they would really be any help. They isolate the motor vibrations from the arm by adding a little rubber bumper between a motor plate and the motor mount. It did not look like it would do much.

But much to my surprise the reduction in vibrations is quite significant. Vibrations on an APM flight controller are considered acceptable if you can reduce the x-axis and y-axis vibrations to below +-3 units and keep the z-axs to -5 to -15 units. It is not easy to get your vibrations to this low level. I ended up using the RCTimer anti-vibration flight controller mount to...Continue Reading
Posted by mike_kelly | Feb 14, 2015 @ 03:49 PM | 5,853 Views
I just got through with my Tarot 650 Sport build. I was very careful to check that all the rotations are correct.

1. Motors are rotatiing in the right direction on each postion on the multirotor according to the 3DR wiki. Note that the motor numbers are not simply clockwise around the quad, but the motor test in Mission Planner does not follow the motor numbers and simply starts one motor at a time in a clockwise direction.

2. The Clockwise (CW) and Counter Clockwise(CCW) props are on the right motors A clockwise motor needs a clockwise prop. The reverse rotation props are the clockwise, sometimes known as "pusher" and sometimes marked with an "R" like 9045R. The so called normal props are the counter-clockwise.

3. The Radio Calibration is correct
in Mission Planner and the sticks move in the correct directions. Note that the Pitch must move the slider bar DOWN in Mission Planner when you move your pitch stick "forward". All the other sliders move in the same direction as the stick moves.
...Continue Reading
Posted by mike_kelly | Jan 27, 2015 @ 04:52 PM | 6,098 Views
>>> Feel free to post your Tarot travel case solution as a comment at the end of this blog post <<<

Now that I have my Tarot built I need a travel case. The aluminum ones from Asia are way too expensive for me and the Pelican cases are worse. After looking and following other posts I finally came upon the Plano 114400 Bow Case.

This case is 41"x17" x7" which is enough room for the Tarot 650i 650s 680 680 Pro and 690 even with extended arms. It is lockable and has room for my gimbal too.

It comes with a thin layer of pluck foam so I plan to put a layer of solid foam underneath the pluck foam.

It is not a perfectly rigid case like the Pelcan cases. It flexes a bit and it is definitely a cheaper build quality but it is lighter and a lot less expensive.

I got mine off Amazon for $75 shipped.
Posted by mike_kelly | Jan 26, 2015 @ 09:07 PM | 7,430 Views
I have been wrestling with this issue for weeks and I thought I should document what I discovered. Many people these days need to use more channels to control external devices like Gimbals, Lights, Retracts, Camera Shutter and Video switches. For more traditional buillds it is not hard to take the pwm outputs of your reciever and directly connect them to your devices, by-passing the APM flight controller...until you run out of channels. But for newer builds with PPM or S.bus receivers you may not have any pwm outputs to use directly from your receiver. Yes with many Frsky receivers you can do both s.bus and pwm but that is a different story.

So if you are using ppm input to your APM how do you control extra devices?
Mission Planner provides a optional hardware page in setup for APM, it is labeled "Camera Gimbal". It allows you to map input channels from your transmitter to an output pin on the APM board. This is where the documentation gets a little tricky. First APM does not support more than 8 channels. Pixhawk does but not APM. Second the documentation is poorly written and uses duplicate names/labels to refer to multiple different pins.

On the gimbal hardware page there are three control options for gimbal tilt, roll and yaw. But these control options can control other devices than a gimbals. This is not clear in the 3DR wiki.

You can control from your RC Transmitter on channels you have assigned to certain tasks. Say you want to control lights from your...Continue Reading
Posted by mike_kelly | Jan 22, 2015 @ 10:32 AM | 6,377 Views
One of the fun things about multirotors right now is that we are at the very beginning. Someday soon there will be mostly RTF (ready-to-fly) multirotors out there with all the problems solved. But right now we get to figure it out ourselves and have the fun of designing and solving problems.

One of those problems for me was how to get a video and shutter control cable connected to my Canon S100. I went to Gentles in the UK, who makes lots of different shutter video solutions for RC and he said it was not possible with the Canon S100. What?

So I did some digging and this is what I found. The Canon Powershot series uses a mini USB cable for connection to a desktop computer and for video out. They make a cable for video out, the Canon AVC-DC400 and the Canon AVC-DC400ST. The only difference is the 400 is single-channel audio and the 400ST is two-channel stereo. But why do they also make the USB Cable IFC-200PCU? Why two cables? It turns out that our favorite connector, the mini USB, has many versions. The typical cable that we use for connecting our flight controllers only needs to use a few pins. It needs power and ground and transmit and receive. But the mini USB can have up to 11 pins. It has five on the top side and six on the bottom.

11pin mini USB connector

This is what Canon does; they use the top five pins like any normal USB for communications with the PC and they use the bottom six for video out....Continue Reading
Posted by mike_kelly | Dec 27, 2014 @ 11:17 AM | 5,985 Views
I have been troubleshooting why my 2.4ghz video transmitter and receiver were acting so wierdly. I got video on different channels than are illustrated in the documentation. I searched the internet and found many other people who are confused, but some people seem to do fine with the same documentation.

I finally figured out my problem and it is because I am a "half-empty" guy rather than a "half-full" guy. This is one of those interesting situations where two people can look at the same thing and see two entirely different things. An RC inkblot test.

The whole array of Boscam video transmitters and receivers use dip switches to change the channels for transmission or reception.
...Continue Reading
Posted by mike_kelly | Oct 26, 2014 @ 11:32 AM | 7,521 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 | 6,677 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. Reading
Posted by mike_kelly | Oct 26, 2014 @ 11:19 AM | 6,869 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 | 6,672 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 versatile and...Continue Reading
Posted by mike_kelly | Oct 26, 2014 @ 10:59 AM | 7,026 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 | 6,542 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 | 6,549 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 | 6,118 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)

Posted by mike_kelly | Sep 26, 2014 @ 09:01 AM | 8,383 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 ( 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.

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