Quadrysteria Mini Mamba Review

Mini Mamba (Final Version)

A while back, I bought a 250 racer style kit from Quadrysteria called the Mini Mamba.  It is high quality in general, with Sunnysky motors, true carbon fiber frame, SimonK ESCs, etc.  The kit included the frame, motors, ESC, integrated BEC/power distribution card, and instructions.

I initially elected to use a Mobius FPV system, spare mini-APM controller, and Lemon DSMX receiver to complete the build.  I started trying to use the instructions, which are well written, but not very useful.  Unfortunately, there are no pictures and you are left wondering which plate is the top, what is the front, exactly what standoff is required etc.  Fortunately, there are video instructions here, and they show you exactly what to do.

In the initial build, I ran into a few problems, some of my own making.

1. The mini APM may have been defective, it did not consistently stabilize the unit.
2. The integrated power board from the kit was defective.  It did not supply proper 5V for the receiver and APM.  I had to replace it with a power distribution board and use one of the ESC BECs.
3. The wiring for the mini-APM and rest of the electronics was not reliable, probably due to the crummy wiring supplied with the mini APM.  The ESC BEC was probably not the best choice as well.

The Mamba flew, but not well, I did crash it badly enough that I had to repair it.  One of the advantages of the Mamba is that will usually just break the props and/or the nylon bolts that hold the motor mounts to the carbon fiber arms, and this is easy to repair.  Previous quads tended to break arms, props, and frame plates, necessitating major repairs that takes hours and hours.

Based on this experience,  I stripped it down and rebuilt it with an Orange receiver that I had used before, a separate BEC, and a Hobbyking mini APM and Hobbyking GPS.  The wiring was much more straightforward as the Hobbyking units came with better cables and I was using a separate BEC. It takes some work to figure out where to stick the ESCs, cabling, BEC between the top and bottom plates.

Side view

Performance is much better but there is still a lot of tuning required as it is very sensitive to pitch and roll, but very insensitive to throttle.  Some other pictures are shown below.

Arm assembly which is set up for easy repair after crashes

Mobius FPV setup with integrated mount and transmitter.  This will be reviewed in future.

Short Review: Olympus Air as Drone Camera

As a dedicated Micro 4/3 Mirrorless camera user, I thought it would be great to try the new Olympus Air A01 camera.  This is similar to a product put out by Sony which attached a photo-quality lens to a Smartphone.  However, the unique ability of the Olympus Air is that it will take any interchangeable Micro 4/3 lenses.  Price is low: approximately $299 street price in USA for body only.

Olympus AIR A01

I received the AIR yesterday and rushed to get it charged (about 4 hours) and get it set up.  It is not a perfect product and there are a few warts, some of which could be fixed in future software.  The cylindrical body of the AIR is quite small and light, and it communicates with your IOS or Android device via Bluetooth and Wifi.  This has some issues as you disconnect from your home wifi to access the AIR wifi, as the AIR sets itself up as an access point.  You also have to download the correct Olympus AIR app, and set a few things up.  The normal mode of use is to clip your smartphone to the back of the AIR and use it as a viewfinder and remote control.  I tried this and it works as advertised.

The AIR has the following useful qualities for drones:

• Professional quality sensor (16MP) and lenses, Full HD at 30 fps
• No added functions, buttons, screens, & grips which are normally part of a photo quality camera - you don't have to lift a whole DSLR to get Photo quality
• Tripod mount - invaluable as you can easily adapt it to existing gimbals and mounts
• Interchangeable lenses
• Autofocus, image stabilization, face detection, long list of DSLR type features
• Ability to turn off wireless connections so they do not interfere with drone radio control
• Built-in battery
• Light - I measured 368 gm for the AIR with a Panasonic 14-42mm zoom lens, which is not the lightest 4/3 lens by any means.  The AIR alone is about 150 gm.
• Open API interface so software could be written to control the camera and lens in flight

I rushed to get it installed on my test mule drone, an SK450 Deadcat.  I found a tripod mount that attached to my existing Gopro mount, but it was not ideal as it mounted the AIR too high and too far forward, but it sort of worked (see photos).

There are a few drawbacks to the AIR, which I will list below, mainly concentrating on drone-specific items:

• The setup is complicated, you have to read the instructions carefully and follow them
• The app is not intuitive, some updates needed here
• Wifi video transfer to smartphone takes a long time for some unknown reason, about 10 minutes for a 3 minute video.  I recommend connecting the AIR via USB to your PC where the transfer took about a minute.
• You have to keep your smartphone hooked up to the AIR by wifi and bluetooth, and the smartphone will try to go back to its home network if you turn off the AIR or connection is lost, causing you to have to go back to the setup menu and reselect the right networks again.

Olympus AIR with Panasonic 14-42mm lens

SK450 Deadcat with AIR

Closer View of Not-So-Great Mount

Always Keep Two Quadcopters

I learned again that it is a good idea to have two quadcopters:

1. One to fly
2. One that you crashed and is being repaired

Another important lesson was not to fly near trees, as Quadcopters Love Trees.

Quanum Q-2D Brushless GoPro 3 Gimbal Test

Gimbal Mounted on S500 Quadcopter

Attached a 2D camera gimbal to the drone and did a quick test flight with my Gopro Hero3+ Black.

The included Gimbal mount on the S500 frame was not useable as there was only about 1-2 cm of clearance between the bottom of the gimbal and the ground and I was sure that the gimbal would be damaged in a hard landing (see previous review of the S500 frame).

The gimbal is the HobbyKing Quanum Q-2D Brushless GoPro 3 Gimbal.  I could not get it to work attaching the gimbal controls to the Pixhawk so I connected the servo cables to the FlySky i10 receiver directly.  The only adjustment was limiting the maximum throw on the transmitter for the gimbal controls to +/- 30%.  This makes the gimbal less sensitive to the movement of the rotary controls on the transmitter.

Successful indoor Test Flight is shown below:

Unsuccessful outdoor test flight (gimbal worked, quadcopter not so much) is also below:

First Successful Quadcopter Autonomous Mission

After all the adjustments to the Deadcat SK450, I took it out to the local "park" (remote muddy field) to try a mission.  It was a simple mission, fly to a few waypoints, circle at one waypoint, return to launch, then land.  It actually worked!  Here is the video:

Further Enhancements

After the exciting flight last week, I had to repair the Quadcopter as one of the arms broke in a landing.  So I decide to make a few enhancements:

1. Put in a new APM controller and GPS to fix the Loiter issue.  This did not turn out well as the new controller was defective but the GPS seemed to improve things.  The new GPS is Hobbyking brand, old one was a "no-name" with some mods to make the cable work.
2. Improve power feed to the controller and receiver by using a UBEC (battery eliminator) instead of the power feed from the ESCs.  This is recommended due to the interference from the ESC and I do think  it improved things.
3. Get rid of extra wires in the controller wiring harness.  Done.
4. Install new arm.  Did this, I learned from the dearly departed Flying Flowerpot quadcopter that it is almost impossible to properly fix a quad's arm and they are reasonably cheap.
5. Performed a test flight and analyzed logs.  Seemed to improve things with few glitches on barometer and GPS and more stable flight.  Testing will continue.

Don't Try Auto if You Cannot Loiter

Learned a new lesson yesterday, should not have needed to learn it, because it is obvious.

If your quadcopter cannot LOITER successfully, don't try an AUTO mission.

I headed over to the local "park" - more like a remote muddy field that the county calls a park - to fly my quad.  The plan was to check out AUTO mode with the program shown in the previous blog entry.  I forgot, or ignored the previous tests that showed that LOITER mode did not work well, the copter bobbed up and down and did not hold position.

So I try taking off in AUTO mode with no luck, then do a manual takeoff and flip the switch for Auto mode.  At first, things seemed OK, then the quad headed for the river, gaining altitude.  Before I could react, it was over the Potomac at about 75 feet, then it dipped below the tree line and I could not see it.  I flipped back to manual (Stabilize) control and thought "that quad is gone".  I hit the throttle to try and bring it back up above the trees and it appeared as a little speck in the distance.  I then was able to bring it back with some skillful (lucky) stick work and land it.  Was I ever lucky!

The saving grace is that it took some great video footage while on its semi-controlled mission.  Also, this is why you should not fly near people, as this could happen to you and someone could get hurt.

Here is the video:

Quanum FPVplus Wide-Angle 1080P HD FPV Camera with 5.8GHz Transmitter Review

I recently purchased this camera from Hobbyking with the intent of using it for video recording on my quadcopter and perhaps FPV operation.  The camera takes still photos, videos, and real time video and incorporates a transmitter so you can use it for FPV flying.  It is an integrated alternative to using an FPV camera and separate 5.8 GHz transmitter and it follows the GoPro form factor to a large extent.

After some use, here are my views on this product.

Positives

1. It uses the Gopro form factor, so it can use Gopro accessories.  It is lightweight.
2. You need to do some work to adapt this to your quadcopter:
1. You have to adapt the supplied cable to provide a 12V supply to the camera.  It has no internal battery so it is useless without power.
2. It has no included mount or tripod threaded hole so you need to adapt a Gopro mount to your purpose.  This can be done with the usual hobby tools.
3. The video is of acceptable quality, quite good in fact, see the video sample below.  This was taken with no gimbal, a shock absorbing mount, and reasonably balanced props, so it still has some shake.
4. Construction seems rugged.
5. With the included transmitter and antenna, it is easy to set up for FPV operation.  I was able to connect the camera to my RX LCD5802 7 inch monitor in about 5 seconds - truly easy.
6. Downloading the videos to a Mac or PC is easy using the microSD card.  Note that the camera will not work without a card.  Also note that the developers seem to have used Huawei phone software as the base for this product - you will see some directories and files that are unusual for a standard digital camera.
7. I recommend always connecting the antenna when the camera is powered up.  Some RF transmitters can burn out if they have no load like an antenna.  Don't know if that is the case here, but better safe than sorry.

Negatives

1. It is difficult to know what mode the camera is in as there is no LCD display and only one LED to provide status.  Spend some time with the very brief instructions on your workbench to familiarize yourself with operation before flying.  Otherwise, you may take off with the camera turned off.
2. The MicroSD card sticks out and can be easily ejected.  You may want to put some tape over it temporarily so you don't eject it at an inopportune time.  You also need to consider this when you adapt the camera to a Gopro accessory.
3. You cannot adapt an onscreen display (OSD) to show quadcopter telemetry on your ground screen as the video to transmitter inteface is within the camera and cannot be accessed to insert an OSD card between camera and transmitter.

In summary, I recommend this camera as a simple to set up FPV camera and transmitter system for quadcopters and other UAV.  It is easy to set up, provides good video, and is rugged.

Rear View

Side View with antenna removed

Side view with MicroSD slot, mode switch, connector

Gopro mount modified to accomodate antenna, cable, switch, etc.

Latest flights - SK450 Deadcat

Got three flights in last week and the quadcopter is still in one piece.  The video from the quad is cleaner than before as there is less vibration, but still a bit of jello.

Balancing a Quadcopter

After a short break, I am back to working on the Deadcat SK450 quad.  One thing I am learning is that balancing the quadcopter is important.

Model aircraft are very sensitive to their point of balance, but I did not realize quadcopters had a similar tendency.

If your quadcopter, properly calibrated with the trims set at 0, tends to go forward or backward slowly after takeoff in Stabilize mode, you are likely nose (forward movement) or tail (backward) heavy.  If your quadcopter is not symmetrically built (left to right across the centerline), you could also see a consistent movement left or right.

The solution is to move equipment to counteract the imbalance.  The battery is usually the easiest thing to move.  The process is like this:

1. Take a short test hop inside or in very calm winds and note which way the quad wanders.
2. Move the battery back if you wander forward, or move the battery forward if you wander backward.  Mark the battery's new position with masking tape.  See figure 2 for battery installation (farthest to rear) on my quadcopter when camera is installed.
3. Try another test hop, see if the quad will hover in one place.  If yes, the balance is OK.
4. If it still wanders, move the battery as in step 2. and also move the tape.   Take a test hop, see if it is fixed.  Repeat until you get a nice stable hover, something like you see in the video below.  My problem was the quad moving forward consistently, which is now fixed, it still moves from side to side due to my clumsy control inputs.
5. Once you have the battery in the right spot, leave the tape in place and mark it so you know where to put the battery next time.  See figure 1.

Figure 1 Tape markings for different quad configurations

Figure 2 Battery installed in camera configuration

You may have to do this for different configurations, like with and without camera, so you would have two markings for where to put the battery.

Don't add weight to get a balance unless you really have to.  Adding weight just decreases flight time and dynamic stability.

New Drone is Down, Debugging Now

The new Deadcat drone no longer works.  I cannot figure out why and have spent about 6 hours trying everything.  It seems to be related to the Pixhawk flight control unit interacting with the ESC (speed controllers).  Below is a summary of the problem that I sent to 3DR, the designers and manufacturers of the Pixhawk.  I will let you know what happens.

--------------------------------------------------------------------------------------------------------------------------

I might have a bad Pixhawk autopilot.  I bought it in December and it worked fine for about a month.

Here is my config:

SK450 frame

4 x Turnigy plush 30A ESC (red power lead is disconnected - Pixhawk is connected to signal and ground only)

4 x Turnigy Multistar 2216-800kv motors

Pixhawk

3DR GPS module

3DR battery sensing module

Spektrum DX6i Transmitter

Orange R615X receiver

Various turnigy 2200mah batteries

Mission Planner on a PC for ground station

It worked like a charm before, reference this Youtube video (excuse the lousy quality).  Deadcat SK450 Test Flight 1

				Deadcat SK450 Test Flight 1
				View on youtu.be	Preview by Yahoo

No crashes, I was still test flying in the basement as it is 20 degrees outside with snow.  I was upgrading it as the R615X receiver has limited range.  So I  tried a new receiver, the Orange R800X, and never really got it to work, then I went back and did the following:

- reloaded arducopter 3.2.1 by first loading the plane software, then reloading the quadcopter software, also pressed the reset button on the pixhawk

- recalibrated all my ESC s manually one by one

- did many full setups: compass, accelerometer, radio, .. calibrations

- checked a lot of the parameters and adjusted them, then set them back if there was no improvement

- verified the radio was working by connecting servos to the receiver and also by doing the manual one by one calibration of the ESCs

- verified the pixhawk was seeing the radio inputs, and was putting out the correct outputs, such as increasing throttle on all 4 output channels when the radio throttle was advanced after arming

Here are the problems that I am seeing:

1. The USB connection fails 50% or more of the time.  I have to power cycle the pixhawk and/or plug and unplug the USB cable.  I tried two different USB ports on my laptop, no difference.  This is pretty consistent for the past 5 days.  It worked fine before.

2. The ESCs continuously complain that the initial throttle input coming from the Pixhawk is not low enough.  Here is a phenomenon I saw today regularly:

1. I calibrate the ESC by connecting it directly to the throttle output of the receiver, and go through the calibration procedure.  The ESC responds with OK tones.  
2. I try the motor still connected to the receiver, and it revs up and down with the throttle input.
3. I move the ESC input over to the Pixhawk, arm the Pixhawk, and then the motor responds properly after arming.  Note that I did not power down the pixhawk or receiver.
4. I power down the quad (radio, pixhawk etc.), and start it back up.  I get normal startup tones from pixhawk and the ESCs complain that they have no throttle input (this is normal as the safety switch is off)
5. I turn on safety switch, arm the pixhawk and get OK tone, but the ESC complains that the throttle input is not low enough again.  Motors will not function.
6. WEIRD!
7. I also tried calibrating one ESC through the pixhawk instead of connecting to receiver (step 1).  The ESC seems to calibrate successfully.  I execute step 3 successfully.  I get the same problem at step 4.

3. Parameters do not seem to be reliably stored in the Pixhawk.  It keeps resetting the battery failsafe settings and sometimes when I try to write a parameter change via mission planner I get an error "Bad Number", which is not very useful.

4. Now, I cannot get the Pixhawk to connect to either receiver, the previously used and flown R615X or the new R800X.  The radio calibration screen shows no activity, but the receiver is definitely connected to the transmitter as I test it with a servo or connect it to an ESC and can throttle the motor up and down.

I am stumped.  If I had my trusty Tektronix oscilloscope from EE school, I would check the signal on the pixhawk ouputs but alas, I don't have one.

Deadcat SK450 Test Flight

Test Flight Successful

Finished the basic build of the quad and was able to get a quick successful test flight in the basement after about 5 hours of messing around with the quad, my radio, and Mission Planner.

Finally worked out all the little issues and had a successful test flight:

1. The Deadcat needed to be balanced as it was naturally nose heavy.  Moving the battery allowed me to balance the quad.
2. I played around with ESC calibration and radio settings for hours because the props kept spinning when I armed the quad.  My old APM equipped quad did not do this.  Well it turns out that the default for Mission Planner with Pixhawk is to make the blades spin slowly when armed.  I did manage to program the ESCs to play tunes when they power on, but that is not much use.
3. Turning on the throttle failsafe is a waste of time as it is triggered as soon as you arm the quad, causing the arm function to fail.
4. Use loctite on all bolts, the one place that where it was skipped (landing skids), a bolt came loose.
5. Need to make up a cheat sheet with the meaning of all Pixhawk and ESC sounds and lights.  It is hard to understand failures otherwise.
6. Had to reverse all the RC channels except throttle.
7. It seems smoother than the last quad as the props are balanced but it is more twitchy on the controls, so will have to do some more tuning.

RIP Flying Flowerpot

Pre Flight

The Flying Flowerpot has gone to the great beyond, aka the garbage bin.  It was a great first drone to build, I learned a lot, but it had its share of problems.

For the last flight, I programmed it via Mission Planner to fly a rough polyhedron at 60 feet over the River Mills Park near the Potomac River.  It accomplished this and then loitered.  When I switched it back to Stabilize mode, it somehow became unstable and did a death dive.  This broke the internal frame, two arms, two propellers, one motor, the battery mount, and the flower pot.   The basic electronics are fine, but I will have to get a new frame kit and motor at least.  The video is below.

The new build will take some time, so postings may be sporadic.  Have a Merry Christmas and a Happy New Year and Happy Hannukah.

Flying Flowerpot 2.0 -- SK450 Quadcopter Rebuilt

Flying Flowerpot 2.0

I finished the Flying Flowerpot quadcopter rebuild and had a successful basement test flight in the new configuration.  Changes since the last blog posting:

1. Moved the camera mount again, to the upper level but with a new mounting bracket so the camera is out front between the props.
2. Moved the receiver slightly.
3. Tidied up the wires.

The following photos show the Flying Flowerpot 2.0:

Top view, no flower pot

Note the receiver attached to top level with double sided foam tape

New camera mount

Front view

Rear View

Rebuilding The Flying Flower Pot Quadcopter - The Six Million Dollar Man

Partially Rebuilt Flying Flower Pot (Pot removed for clarity)

One of the advantages of building your own quadcopter is that you know how to fix it if it breaks, and you can make improvements at the same time.  It is kind of like the Six Million Dollar Man TV series:   "We can rebuild him. We have the technology. We can make him better than he was. Better, stronger, faster."  The Flowering Flowerpot, after its last flight and crash (see previous blog post), needs this treatment.

First, I got rid of the battery monitoring module, which might be causing problems and I cannot figure out how to use it.

Second, I rewired the control module (APM) to receiver wiring to get rid of the servo extension cables and labeling.

Rewiring, receiver is on the left

Third, I repaired the damage to the quadcopter - a broken arm and a broken motor mount on the end of another arm using 5 minute epoxy, which smells like crap and gets everywhere.

Broken motor mount

Break in arm

Fourth, I got rid of the structure holding the GPS and compass and mounted them using nylon standoffs on the third level.

GPS remounted

Fifth, I removed the long landing gear and mounted the camera on top.  The long landing gear seem to cause a lot of damage in crashes.

camera mount

I also ordered a bunch of spare parts (arms, motor mounts, landing gear..).  Stay tuned for more updates as we get the Pot ready for its next adventure.

The Flying Flowerpot Flies and Crashes Again

Make Sure Everything is Tightened

Had a crash yesterday with some damage.  Nothing serious and I was able to repair it quickly.  The "Flying Flower Pot" seems quite robust.  The problem was a propeller that came loose, causing the quadcopter to fall from about 20 feet to the pavement.  I then checked all the bolts and screws and found a few that were getting loose due to the vibration, so check your quad before every flying session.

Storing LiPo Batteries

I am still coming up to speed on usng LiPo batteries in models.  The latest thing I learned is that you should not store the batteries fully charged, or let them fully discharge.  The prevailing wisdom is that you should store them at 3.85 volts per cell, or 11.55 volts for the 3 cell packs that I am using.

I don't have a fancy charger yet so I was not sure how to get them down to 11.55 volts.  Luckily I remembered enough of my old Circuits class and am enough of a pack rat that I could create my own discharge circuit.

Using an old 50 watt 7.5 ohm resistor, a homemade heatsink for the resistor, some wire, and my newly purchased XT60 connectors, I was able to solder together a discharge circuit.

              + ------------ resistor
 XT60                             /
              - -------------------/

I monitor the voltage with a voltmeter and was able to discharge my packs to 11.55 volts and then store them in a LiPo protective bag (good precaution) on the concrete floor in the basement away from combustible material.  Always stay close to and monitor your batteries continuously when charging or discharging them.

Note that LiPo batteries can be dangerous and you should follow ALL manufacturers' warnings on the use, storage, and charging of these batteries.  I am not an expert and you should check the Internet and the manufacturer of your batteries and charger for accurate information.

Review: UDI 818A Quadcopter

UDI 818A as it comes out of the box

This mid size low cost intermediate grade quadcopter is easy to fly and includes a camera.  It is a good trainer before moving on to more complicated and expensive machines.  The unit is fully assembled and you just have to charge the flight batteries, insert transmitter batteries, and then you are ready to go.

The UDI 818A is available from Amazon and others for about $65 to $85 US.  This includes the copter with camera, transmitter (mode 2), extra battery, USB charger, and extra props.  It comes in white (my unit) or black, they are identical except for the color.  All you need to add are AA batteries for the transmitter.

Design

The unit incorporates a horizontal plastic prop guard assembly to help preserve the copter when you bump into something.  You can hit an obstruction without damaging the quadcopter.  You can turn the camera on and off with the transmitter and it takes decent video (see the youtube link below). Other than that, it is a pretty standard 4 channel quadcopter with 6 axis gyro stabilization.

Documentation is terrible - a google translation from Chinese with some made-up words thrown in.  Read it to get some basic ideas and a good laugh.

Flying

Relatively easy to fly, the throttle is not too sensitive and the controls work well.  Flight time is about 7 mins on one battery and it takes about 1 to 2 hours to recharge.  The inevitable crashes do not seem to mar walls or ceilings, in case your wife or mother is wondering.

This can be flown outdoors if it is fairly calm, but be careful as it will be harder to control than in controlled indoor environment.

Accessories

There are no accessories and you cannot add any due to the small size of the unit.  You may want to buy extra batteries or props that can be found on Amazon or Ebay.