Hi Guys,

 

Firstly, let me start with the obligatory disclaimer that I am a total noob to this stuff and am reaching out for some valuable advice from those much more experienced and knowledgeable than myself. My name is Jason, I am 31 and based in North Parramatta, which sits (near as makes no difference) in the geographic heart of Sydney, Australia.  I have an interest in geography and history, and all things geospatial and live adjacent to some of Australia's most significant built heritage items.  BTW - I don't facebook, I don't blog and this is my first forum post in a decade, but i thought it may be worth sharing my experience, and hoped to draw on the feedback of others to help guide me forward.

 

For some context, I have had a few electric gliders, I have never flown a heli heavier than 500g and the last time I held an RC transmitter the Revo 2.5 had just hit the shelves. (>6 years ago).

 

About 3 months ago I stumbled across this video.

I had to google what the FPV stood for but was immediately captured by the concept.  This kicked off a period of about 10 weeks watching countless videos, reading blogs and absorbing forum threads to effectively bring me up to speed on what is possible and what, perhaps, my first FPV airframe might consist of.

 

Initially, I had my heart set on building a solar assisted wing not unlike that which features in the video that inspired my pursuit.  Something that might be able to reliably stay aloft from sun up to sun down.  I came up with a design from the HS522 profile with a wing span of 3-metres (3000/900/600mm) and wearing 140W (17VDC@~8A) worth of PV which i call 'Mithra'. Renderings below.

There are also images of an early gimbal design for adapting JVC's venerable Everio series camcorder for aerial use (making use of it's excellent optics - 40x optical/70xdynamic/200xdigital zoom with both optical and digital image stabilisation.  This gimbal design was so early, i had yet to discover the virtues of brushless gimbal motors.

By the time I got to the point of resolving things like ground station requirements and designing a catapult capable of launching the 3-metre wide craft I realised that, considering my existing experience with UAV FPV tech and primary geographic location, i should completely reconsider my entry point.  After specing out a smaller but similarly complicated X8 with Range Video based electronics, I realised that even this was all too much to start with, so I ultimately decided that a multirotor would be a much more accessible platform upon which to build initial experience working with the various aspects of the craft.  Also relevant is the fact that I live just a stone's throw from a convict nations earliest and longest serving Goals, one of the nations oldest stone arch bridges, the first Government House, The People's Park/Governor's Domain (a UNESCO World Heritage listed site), one of the last intact fully landscaped Edwardian gardens, Australia's first observatory, and a bevy of historically and culturally significant structures designed by a respectable list of Government Architectects - dating from Georgian, through Victorian, Edwardian/Federation and later period designs (that's really old in Aussie terms).  I even have an 11ha lake held back by a stone arch dam dating from 1855-56 and surrounded by 300-acres of remnant woodland virtually on my doorstep... The allure of getting above it and getting amongst it (so to speak) is all to great to ignore, and only possible at low altitude via a multirotor.

 

Hence I commenced the obligatory research of multirotor focused forums, parts and suppliers, spent about 15 hours moving things around in ecalc, settling on the below parameters.

and ordered the following list of parts.

 

 

QUADCOPTER PURCHASES

 

TOTAL COST AUD

$1,208.13

 

 

TOTAL SHIPPING AUD

 

$104.12

JAYCAR ELECTRONICS

Product description

Price

Qty

Cost

Shipping

Liquid Electrical Tape - Tube - Red Handy 28g tube (1oz)

$12.95

1

$12.95

 

Heatsink Compound - Syringe - 50gm

$9.95

1

$9.95

 

Mains House (Twin Earth) Wiring Cable (1-metre)

$1.25

1

$1.25

 

 

SUB TOTAL

USD

$24.15

$0.00

 

 

 

 

 

 

 

 

 

 

3DROBOTICS.COM

Product description

Price

Qty

Cost

Shipping

APT-KIT-0006 APM 2.5 Case (Cables enter from top)

$4.99

1

$4.99

 

 

SUB TOTAL

USD

$4.99

$34.53

 

 

 

 

 

 

 

 

 

 

HOBBYKING.COM

Product description

Price

Qty

Cost

Shipping

#T2650.3S.1C/18569 Turnigy 2650mAh 3S 1C LLF Tx Pack (Futaba/JR)

$13.41

1

$13.41

 

#402000001/39293 Gyro / Flight Controller Mounting Pad (10pcs/bag)

$2.32

1

$2.32

 

#9210000019/35552 Turnigy nano-tech 8400mah 3S 40~80C Lipo Pack

$84.00

1

$84.00

 

#D2830-111000/24529 D2830-11 1000kv Brushless Motor

$9.87

5

$49.35

 

#HLFT-01/41037 Polyester Velcro Peel-n-stick adhesive side V-STRONG (1mtr)

$4.33

1

$4.33

 

#IMAXB6/25873 IMAX B6 Charger/Discharger 1-6 Cells (GENUINE)

$28.37

1

$28.37

 

 

SUB TOTAL

AUD

$181.78

$20.48

 

 

 

 

 

 

 

 

 

 

RCTIMER.COM

Product description

Price

Qty

Cost

Shipping

GCP1038 (4Pairs) 10x3.8" Carbon Fiber CW CCW Propellers GCP

$34.99

1

$34.99

 

P25253 Gyro / Flight Controller Mounting Pad (10pcs/bag)

$0.98

1

$0.98

 

UAV-APM433 433Mhz ArduFlyer UAV GPS Flight Control System

$137.99

1

$137.99

 

MAVLink-OSD RCTimer MAVLink-OSD V1.0 (Suit AIOP, ArduFlyer, APM)

$24.99

1

$24.99

 

VCS RCTimer Voltage & Current Sensor 90A (suit MultiWii, APM, etc)

$15.99

1

$15.99

 

 

SUB TOTAL

USD

$214.94

$8.49

 

 

 

 

 

 

 

 

 

 

EBAY.COM

Product description

Price

Qty

Cost

Shipping

SMA Female Nut Bulkhead To U.FL / IPX Pigtail 1.13 Cable ... (300906891940)

$2.16

1

$2.16

 

FPV ANTI-Vibration Multifunction Landing Skid Kit F450 F5... (190853928072)

$33.99

1

$33.99

 

Newest MWC MINIUSB FTDI TOOL USB PC Firmware Programmer B... (261244921736)

$8.54

1

$8.54

 

15CM Micro USB B Male Left Angle To USB A Female Data Cab... (180844465762)

$1.68

1

$1.68

 

Right Angle Micro USB Type-B Male to Male Extension Phone... (261131169887)

$2.04

2

$4.08

 

1PC 3V-5V HMC5883L Triple Axis Compass Magnetometer Senso... (200940132520)

$1.59

1

$1.59

$0.89

New 20CM Male to Male Servo Lead (JR) 26AWG x5 (271242603780)

$8.90

2

$17.80

 

FPV 5.8G 200MW 500MW 9db Aerial High Gain Omnidirectional... (281099846150)

$8.82

1

$8.82

 

1pc TV AV Audio Video Cable for #18 HD camera, external p... (221256466006)

$4.34

1

$4.34

 

AU1786 4pairs 10x4.5" 1045L/R CW CCW Nylon Propeller,Mul... (290883335930)

$9.99

1

$9.99

 

FrSky DFT 2.4GHz Two Way Transmitter for Futuba Hitec (271100019825)

$34.84

1

$34.84

 

ePacket to USA FrSky 2.4G V8FR-HV 8 CHANNEL RC Receiver H... (310669652701)

$31.85

1

$31.85

 

E-Flite Blade SR Hook and Loop Battery Strap B400. - EFLH... (251282819916)

$1.50

2

$3.00

$1.20

ZAP Z-42 Thread Locker Lock Screws Buts from Loosening... (390384775289)

$8.85

1

$8.85

 

Antenna Tube Base Speing Mount (2pcs) #02612A (360659561969)

$4.95

1

$4.95

$3.30

HKRC Mulitcopter GPS Antenna Mount (151061386124)

$6.49

1

$6.49

 

DJI GPS Mounting seat MultiCopter GPS Fast Installation M... (271194524470)

$12.99

1

$12.99

 

Windscreen Car Mount for Google Nexus 7 (small) (160881336677)

$11.39

1

$11.39

$3.36

Black Plastic Cover Case Shell for GPS Antenna Neo6m 6H M... (130939687288)

$6.47

1

$6.47

 

1/4" Split Ring Camera Screw Bolt fr Tripod Quick Release... (271015691626)

$7.32

1

$7.32

 

50PCS Mini Micro Jumper for 2.54mm Male Pin Header For Ar... (181085286314)

$3.28

1

$3.28

 

12in RP-SMA right angle to right angle plug both female p... (150778654559)

$3.63

2

$7.26

 

3M 10FT WiFi Antenna RP-SMA Extension Cable Cord For Wi-F... (251106734418)

$2.59

1

$2.59

 

30cm RP SMA Male to Female Pigtail WLAN Network RF Antenn... (280790816746)

$1.29

2

$2.58

 

RP-SMA male to RP SMA male RF Pigtail Coaxial Cable RG316 (320877776826)

$2.30

3

$6.90

 

SMA male to male plug RF Pigtail Coaxial Cable RG316 #K (170816353522)

$2.30

3

$6.90

 

edge mount PCB board receptacle RP SMA female plug connec... (140620036239)

$1.19

6

$7.14

 

5x SMA Female Plug Center Solder PCB Clip Edge Mount RF C... (330909095334)

$4.37

2

$8.74

 

10Pcs AMS1117-3.3 LM1117 3.3V 1A SOT-223 Voltage Regulator (130750978645)

$1.25

1

$1.25

 

New 10pcs X DIP switch 3 Position 3p 2.54mm Pitch Throu... (330758987979)

$3.84

2

$7.68

 

10 x 470uF 16V 105C Radial Electrolytic Capacitor 8x11 (250851988762)

$1.10

4

$4.40

 

50x SMD Chip Surface Mount 1206 Resistor 1.8k ohm 182 (110787970509)

$2.20

1

$2.20

 

50PCS 1210 226K 22uF 16V 10% SMD Capacitor (220983887749)

$7.70

1

$7.70

 

Murata 1210 4.7uF/16V X7R GRM32RR71C475KC01L, 100pcs (160605719497)

$13.19

1

$13.19

$7.15

2 pairs 10" Blade Propeller 1038 RC 4-axis X-axis Aircraf... (251101579508)

$10.99

1

$10.99

$2.00

AU1792 8x 11x4.7" 1147pro Balck L/R CW CCW left right Pro... (290883336784)

$12.99

1

$12.99

 

HD 1080P DVR 808 #26 Full HD Mini Action Camera Recorder... (221239585941)

$99.99

1

$99.99

 

1pc TV AV Audio Video Cable for #18 HD camera, external p... (221240572122)

$4.40

1

$4.40

 

SanDisk 8GB 8G Class 10 MOBILE ULTRA Micro SD Micro SDHC ... (271026926167)

$12.70

1

$12.70

 

Hobbywing Quattro Skywalker 25Ax4 Brushless Speed Control... (151063810316)

$39.75

1

$39.75

 

5.8g 3&4 Leaf Antenna&Skew Planar W/L RP-SMA type connect... (161041084624)

$12.99

1

$12.99

 

FLYCAT MWC X-Mode Alien Multicopter Quadcopter Frame Kit ... (251285685675)

$57.23

1

$57.23

 

Handheld Non-Contact IR Laser Infrared Digital Temperatur... (360632643721)

$12.12

1

$12.12

 

NEW 500g 0.1 gram Precision Digital Pocket Scales Jewelle... (130933176003)

$9.00

1

$9.00

$6.95

1pc Shield Adhesive Aluminum Foil Duct Tape 20mm X 50m (300671863515)

$6.99

1

$6.99

 

Dubro TRU-SPIN Prop Balancer DU-BRO 499 (181137895690)

$35.00

1

$35.00

$6.95

AV Video Input USB Adapter with Software for Laptop/PC (140969002429)

$13.43

1

$13.43

$5.03

5.8G 200mw Wireless AV Transmitter Module+5.8G Video AV ... (251282845279)

$32.98

4

$131.92

 

 

SUB TOTAL

AUD

$762.45

$36.83

Approximately 4 weeks later this shows what I had came up with (note - I was still waiting for the M2.5x16mm hex bolts required to fit the 10mm upper plate extensions at this point so the battery is not yet fitted).  The current airframe and related ground station components can be viewed here.  Video flight log can be found here.

 

Assembling the various components was reasonably straightforward and rather rewarding, and integrated a range of techniques which I picked up through my online research.

For interconnections, I did my best to minimise path lengths, maximise distance between sensitive data lines and power cables (primarily by maximising the opportunities offered by the vertical layout - with noisy at the bottom and sensitive higher up.  All wires were also platted in an effort to maximise rejection, and ALL unnecessary power and ground wires removed to eliminate redundant weight and risk of ground loops.  Overall, I think it makes everything nice and neat, but it also minimises the need for fasteners and dampened movement.

 

For transmission duties I reinvigorated an old Futaba FB-T8AUF, which I had lying around from approximately a decade ago, with a 2650mAh Lipo battery and DFT FRSky 2.4Ghz transceiver.  After a quick internal repair of a fatigued pot wire, a bit of a clean up and a few other mods like removal of the metal carry handle to allow for better reception and signal propagation and removal of the racket on the throttle axis (by sanding it smooth and increasing tension of pressure plate - I am really happy with what I spent here! All up it was less than $100 for RCTX radio gear (including the V8FRII and I am wanting for nothing at this stage (other than maybe a 2W upgrade, which will likely be added soon).  It even offers full 6-way mode control via combination of 2 and 3 way switches, while the air brake function and other programmable offset options fulfil other duties like RTL and tuning functions.  Channels 6, 7 and 8 are also on pots, which will be useful for gimbal control in the future.  Also gives my setup a retro feel - as the transmitter is very dated!

 

For AV RX and RX duties I really needed to better understand the various elements of this, so I opted to build my own.  Bruce Simpson's helpful videos sold me on this concept, and proceeding the with assistance of Tim Creque's (see this thread for more info) Eagle CAD board designs, I am very happy with the results so far (learning lots).  Note - I am using 3.3VDC version TX purchased from infinitegadget on ebay. Making antennas is also an art I am keen to hone, with average results so far (my 5.8Ghz clover leaf performs as well as purchased item, but my Skew Planner leaves much to be desired.  I am yet to try a helical, but might wait until I have a CNC bench for that.

 

Hoping to simplify installation and interconnections, I opted for Hobbyzone's 25/30A 4-in-1 ESC, which is located underneath the frame.  This was mounted upside down (with the heatsink radiating heat from below the surfaces it is cooling, rather than from above), however it doesn't get overly hot with this configuration, so i expect this is not going to impact on reliability to much (I could simply flip the ESC, or add a tin heatsink extension, if it was of greater concern).  The 3A BEC in this unit also seems to be quite clean in comparison to a few UBECs i purchased, and it runs everything with ease including the AV Transmitter, with plenty of headroom to spare.  I cant recommend this enough to anyone wanting a cleaner frame setup.

 

To give me something to receive the live video feed I dug out an old portable DVD player i had collecting dust, made some internal space by removed the disc carriage, and installed a receiver which I spliced in to the main board via it's composite AV input and switched 5VDC rail.  To this I intend to add recording capability via the SD DVR available from HK, which will complete this item (Actually, I will likely add antenna tracking GS to this unit also for compactedfunctionalitiness).  It provides 1hr45minutes of operation on the original unaltered 7-year old 2800mAh NiMH battery pack which is excellent, but these cells will eventually be replaced with li-ions offering 9000mAh capacity. Telemetry is received via 433Mhz link via PC or (for increased portability) my little nexus 7.  Both the AVGS and Android telemetery GS with mounts, antennas and accessories all fit neatly into the travel pack provided with the DVD Player (now the AV GS), and the RCTX clips conveniently to the back to provide a small single handled package for all relevant equipment no bigger than a small shoebox.

 

Not wanting to stretch for a gopro, at least until my ability to build a reliable airframe had been evidenced, I decided to opt for something cheaper - hence the modified #26 808 1080 HD camera.  This was chosen for it's compact size, low weight, full HD capability and it's relatively affordable price.  Not happy with it's comparatively (to the gopro 3 black) narrow field of view, I decided to have a go at improving it.  The current lens is a cheap 0.47x wide angle taken from a 3-in-1 lens adaptor designed for the iPhone5 (cost $6 shipped).  It gives a great live output, the recorded files are sharp and of good quality and it records continuously for just over an hour between charges (recharge is quick too). It appears to have great potential, however wont be useful on the airframe until I learn how to deal with the jelly effect (Made more difficult by the fact that the camera itself has such a low mass in comparison to the airframe it sits on).  It does get very hot though, as the case is a rather undersized heat sink.  In winter this is not a huge concern, but i am pretty sure that this thing will go into thermal shutdown if operated in the Aussie summer for more than a few minutes.  I am planning to sandblast the case back to bare aluminium (removing the black paint finish) in an attempt to mitigate this issue to a small degree.

 

My idea to increase the height of the top plate (hence the name Quadzimodo - the hunchback) to make room for the 8400mAh 11.1 Turnigy Nano-Tech pack seems to have worked a treat.  It not only fits wonderfully, but also provides the following:

 

1. Exceptional protection in the event of a collision (2 crashed now have done no damage to anything but the rotors (other than some scratches on the receiver and prop mount tips).

2. An easy way of accurately and repeatedly placing the battery in the exact position for ideal balance.

3. Plenty of flexibility in movement forwards or backwards to counterbalance a wide range of payloads.

4. Facilitates a reasonably neat and tidy layout.

5. Due to tight fitting tolerance, the craft acts as a shape monitor, immediately identifying any swelling of the cells.

6. In combination with the choice to position the ESCs under the frame, the battery functions and a shield between the ECSs below and sensitive electronics above.

 

The technique used to lift the top plate is super simple and could no doubt be implemented into any DJI arm based multirotor such as a hex 550 or TBS quad to achieve a simular result.

 

With almost everything ready to go including the AV link, camera, APM Autopilot, RCTX, ground station components all sorted, I was left waiting for the boom stand mount for the GPS receiver and the external magnetometer (the latter was ordered because an external mag is recommended for 3.0.1 update of arducopter).  Burning to get in the air, I resoldered the onboard mag and temporarily mounted the GPS above the APM (a position partially obstructed by connecting wires) and decided to persevere with some preliminary flights.

 

The first 3 flights worked a treat, with no problematic issues and just about everything working as I would expect.  I was truly astonished at just how capable the APM 2.5 with 3.0.1 is straight out of the box with default settings.  As is evidenced by the flight video log, it seems pretty idiot resistant. Flight 2 was particularly enjoyable and revealed that the 1147 props are not too big for the airframe.  I was elated by how smooth it was, and surprised the rate it gains altitude via small momentary throttle pops. Interestingly, while ecalc estimated hover time to be up around 26-minutes and at 34% throttle, I estimate (based on my first 3 flights or approximately 30-minutes of flight time) it's hover flight time is a slightly more modest 21-minutes and approximately 50% throttle is required for hover.  Average current consumption is around 400mAh per minute.  I am still happy with this though, with the battery working well within it's constant 40C rating and unlikely to ever get a chance to challenge the burst limit of 80C for more than a fraction of a second (unless, of course, I go and load it down with another 1.5kgs attempt to do battle with the wind.

 

The one exception at this early stage was the current sensing capability, which was way off and over reading by approximately 100%, meaning that the APM would think it had expended 8400mAh when in fact it had only used approximately 4400mAh (Gauged based on how much the charger could put back into it after each use - B6 genuine from HK on 5A balanced setting).  I am yet to track down the issue here, but while it fails on correctly reporting the current consumption (both real time and cumulative) it does report voltage with absolute accuracy, so i am not at any real disadvantage until I fix it (other than continuous flights being limited to 10, rather than 20-minutes).

 

By flight 4, I had build enough confidence to head to the end of the street and take advantage of a space larger than my backyard to stretch the legs a bit more.  While the first 10 minutes or so went great, it appears that the GPS gave a false location which hit the eastern most edge of the 150m geofence i had set, which triggered a failed LAND sequence, then RTL mode - which (based on the fact that it didn't know where it was) caused it to rather violently make a beeline for the treeline.  I thank my lucky stars that all I hit were trees before it realised what it was doing.  Frankly, this episode really put the fear in me, and totally reframed my respect for these things - they really are dangerous in the wrong hands!  Amazingly, the only damage sustained was to a single propeller blade - which was replaced and the new set of 4 rotors rebalanced.

 

Still waiting for my GPS boom to arrive, i tweaked my failsafe settings a little and headed back out into the backyard.  Flights 6 and 7 went great, but again, flight 8 went bad - with the craft again triggering into FTL mode and heading (at speed) to the place which it thought it should be (which happened to be on the other side of my Barbeque (a collision which can be witnessed from no less than two perspectives via my video flight log referenced above).  Well... this is what I think is going on based on the kmz file from the park fly - as can be seen below.

and evidence of the GPS behaviour - as can be seen below.

This stuff really pulled the wind from my sail, and I resolved not to fly again until the boom stand for the GPS receiver had arrived.

 

Luckily, both the magnetometer and the GPS boom stand arrived the next day, so I didn't have to wait long.  However, have now lunched 5 1147 props, i was forced into wearing something smaller.  I had 2 sets of 1038 carbon fibre from RC Timer and few sets of 1045 plastics from ebay... I chose to balance and fit the plastic items due to safety concerns (I expect that carbon does way more damage than plastic) while I wait for more plastic 1147s to arrive.

 

I noticed an immediate improvement in the speed at which the APM would establish a 3D fix after relocating the antenna, and the cheap (less than $2) 3-axis mag I purchased worked great hooked in via the IC2 port.  However, errors in the location are still happening, especially indoors (sometimes it thinks it is over 1km from here, which I just don't understand).

 

I also do not like the performance of the craft on the smaller diameter props, and I don't like the idea that they require more current to hover.  It seemed to prefer flying on the 1147s, and I actually plan to order a few sets of 1238 props and a set of arms extenders (unfortunately adding 80grams to the frame in the process), just to see how much more efficiency I can extract from this configuration.  I am a big fan of efficiency over power, thus I see the size of the props as the most obvious area to maximise - as just as cone area relates to the efficiency of a loudspeaker, so does the prop area to a multirotor.

 

Following the crash which ended flight #4, and when i switched away from the 1147 props, i have had a problem with unwanted yaw (rotating in a clockwise direction).  The yaw now drifts gradually under normal hover and is rather more pronounced under increased thrust or normal manoeuvre.  In an effort to eliminate this, I have recalibrated both the accelerometer and compass a number of times, changed the external mag board to a different type, and even switched back to the onboard mag, but nothing seems to eliminate the problem.  Next, I will try reloading the firmware and if that doesn't address the issue, i will start swapping out motors to see if i may have an issue there.  However, i have my doubts that the latter will help, as all motors appear to be working just fine and perfectly consistent with the way they were originally (however the crash ending flight #4 appeared to strain them pretty hard and the crash that ended flight #8 actually dislocated 2 props along with their rotor mounts and shattered the remaining 2 props to pieces).

 

For Flight 10, which is not uploaded yet, I took my disabled mother with me down to the local cricket oval on a particularly windy day.  It flew fine, but the unwanted yaw issue is still present and problematic.  While flights 1-9 were all under 13-minutes of flight time per charge, for this trip I logged a little over 20-minutes on this charge.  The voltage (under hover load) at which I ended the flight was 9.45V, which came back up to 9.7V after the flight and prior to charging.

 

Unfortunately, after flight #10 I noticed an ever so slight bulging of the battery pack.  We are talking less than a few millimetres on each side (if it came like this, it would have seemed fine), but it was enough to a difference in shape in the hand.  Upon charging, it actually accepted 8656mAh - meaning that I over discharged it by approximately 3%.  Upon sliding it back into the frame, my suspicion of it's slight bulging was confirmed, as it is now about 1-3mm (total/cumulative) wider than it was (although still fits great).  Considering I had only cycled 10 charges through this battery, always charged it on balanced setting and in all but one instance only pulled between 50-75% capacity - is this normal?

 

Anyway, with 10 flights and 2 pretty hairy (yet forgiving) crashes under my belt in as many days, I have the following questions:

 

1. Can anyone help me understand why my GPS isn't perfect?  And if it's behaviour is normal? My iphone, android, ipad, navigation unit never think there a km from where they are, so why would my APM? Or to be Expected?  Should I invest in a more expensive GPS?  Could it be the fact that I have extended the length of the coaxial wire joining the ceramic antenna element to the Ubloc board? (it was about 30mm, it is now 250mm)

2. Anyone got any ideas why my current sensor isn't behaving as expected?

3. Based on the evidence above, can anyone confirm that my theory as to why it went rouge in flights 4 and 8 is accurate?  or perhaps, if my theory is wrong suggest what actually happened? Is there anything obvious I can do to mitigate the risk of this happening again, that I haven't already addressed?  Has this happened to anyone else?

4. Have I lunched the battery?  IE - is it dangerous now it has deformed (even though it is deformed to such a small degree?).  Should I discard it, speak to HK who supplied it, or should i simply persevere with it?

5. Can anyone see any issue with my approach to the wiring?

6. Can someone help with identify the cause of the unwanted yaw?

6. I would greatly appreciate any other input or feedback!!!

 

Thanks so much,

 

Jason.

Note - log file is of recent flight were yaw drift issue is present, while the kmz files are from the day of my Park Crash (flight #4).

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Replies to This Discussion

Hi Monroe,

Compass is actually mounted up underneath the GPS antenna on the 250mm boom stand, so am not sure the problem can be liked to battery proximity. Also, I used onboard compass for flights 1-8, and have only moved to external for flights 9-10. I have also tried reverting to onboard and switching to different external mag board (also mounted up with the GPS and away from other electronics) and this provides no difference (which makes me think that it is something else). Perhaps my apm 2.5 board is too firmly mounted to the frame, could this cause the accelerometers to drift?

Excuse my ignorance, but I lack the knowledge of RF to be able to check for harmonics in any range really. Is there a non-cost-prohibitive solution that could help me expand my ability to do this? Device wise?

I will add the relevant log file to the post above shortly, so you may take a look at it if you like.

Thanks,

Jason.

Great write up! That was an enjoyable read.

I'd be very concerned about having the GPS and video TX effectively back to back, and not too keen on the long coax from the GPS antenna. Have a look at this as an alternative, the whole thing will fit in your GPS enclosure:

http://coolrc.wordpress.com/2013/09/08/check-out-how-small-this-u-b...

Thank so much for your kind words Chris.

Thanks for your feedback. I was yet to really do anything much with the logs at that point in time.  As a result, I was effectively blind to the presence of excessive vibration.

As it turns out, I had at least 1 bent rotor assembly (no doubt associated with earlier crashes).  Damage was either in the alloy prop adapter or in the steel motor shaft (replaced both).  I actually only noticed this by accident, while sitting twirling the rotors with my fingers one afternoon prior to a flight (and noticing the tip of the rotor assembly being off axis). I then replaced the motor, and this immediately eliminated the unwanted yaw issue.

Subsequent flights have given no issues caused by vibration or magnetic interference.

G'Day Matt,

Yeah, your concerns regarding my GPS configuration are well founded. The errors I am getting must be seen to be believed.

I have since upgraded the coaxial link between the UBlox and the antenna to RG178, and i have also shortened it's length. I also modified the angle of the VTX board and it's antenna mount. But, I am yet to notice any improvement in the performance of my GPS.  Clearly, a new approach is needed.

I found the cased version of the GPS you suggested here, and have one on it's way.  With any luck, that should be what i am after.  Thanks so much for the suggestion.

Why use a long coax between the GPS board and antenna, that's prone to signal losses and interference and not use a longer serial cable between the APM and the GPS ? If you want twisted and shielded cable, any piece cut from the data cable of an old phone will do.

 

Now, on external interference. It can come from where you least expect. I once maidened an APM 2.5-based quad for AP at our weekend flight field. and I ran into two problems. The roll servo for my gimbal (identical to the pitch servo) was too weak and caused camera oscillations, and GPS would go from 8 to 5 then 0 sats and loiter would turn into a mad dash in a westernl direction. Being a flight field, I wrongly blamed the GPS behaviour on the people blasting the sky with watts of RF for long-range FPV airplane flights.

Going home, I replaced the roll servo with a bigger one, and I flew AP missions happily for a couple of months, until one photoshoot in high winds which depleted my LiPo faster then expected, resulting in not having enough throttle to stop the high-speed descent and landing gear flexing on touchdown enough to hit ground with gimbal's bottom and wreck the pitch servo. No biggie, I thought, camera is OK, gimbal is OK, went home and swapped the old roll servo in. First test flight in my backyard, loiter turned into a mad dash into the optical fiber bringing the internets to my home, flip, ground, all four CF props with shredded tips.

After analisys, it turned out that that particular servo was playing havoc with my GPS.

Hi Para,
The reason for the use of the long coax instead of a long serial line is due to the fact that the antenna/U-Blox sandwich combo would not fit inside the antenna mount I had selected to use. Hence the choice to separate the two boards and extend the coax joining the two.
Hopefully, the solution out forward by Matt above will address the issue.

hello

a very nice project.

I got inspired from the exact same video by Alex (80km fpv flight) and started working solar assisted uav project, still am trying to gather as much info about the things to be considered and taken care of before buying stuff and starting building it.

it would be great to know your research work and method. I am a scratch builder so will be building my own wing. my aim is to keep the budget as low as possible as i dont have much money to spare.

here are a few problems I am still facing:

Solar cells
1. choice of solar cells, was very interested in the a300 by Sunpower, but they don't seem to be available anymore.
2. methods to glue solar panels on the wing.
3. protect the solar panels from environment (i checked a few sample mono crystalline cells and each cells is about 200 um thin and very delicate)
4. how would these cells take the shape of the wing profile,

5. is there any method to calculate wing dimension from peak power available from solar cells and estimated payload of everything needed to fly the plane?, e.g mppt, autopilot, motor, servos etc

6. selecting, calculating and soft testing the dimension of the wing

7. selecting the right airfoil for the wing

i would love to know about your research, characteristics and design specs of the wing.

thanks and regards

Electronics inc

Thanks for your interest in the solar wing. As you can see, it is not a huge deviation from Alex's bird... Much like what I imagine he would build as a 3.0 version. Many problems to deal with to get it right though, as you realise.

1. The a300s look ok, but you can buy cells claiming 3.8-4.1W per panel on eBay which are affordable. Might be worth a look - search for grade A solar cells.
2. EVA encapsulant film is what is used for sealing conventional roof mounted solar panels, and would probably be the best solution. NOTE - you need to be able to heat cure the film and this general requires access to a suitably sized temperature controlled oven or kiln (DIY or otherwise). There is also a liquid compound designed for doing the same job, and popular among the DIY solar panel guys - but this, I think, is a far less attractive thing to be using on an airframe.
3. See above... And I think they should be pretty safe once mounted to the wing. If not, slice and halve the size of each cell.
4. You can align and slice the panels to best follow the wing surface, or you could fully or partially counter sink the cells into the wing, or you could install the panels inside the wing with a clear wing surface material... It will be important not to deform the shape of the upper wing surface though - as that is where all your lift is coming from.
5. Not really, everything changes whenever you change anything else. Best thing to do is focus on maximising wing area, maximising use of that wing area, maximising use of associates electronics.... And keeping your wing loading as low as humanly possible, as efficiency and endurance is obviously the #1 goal if going to the trouble of integrating solar.
6. There are various web based calculators available to help you here - eCalc is great, and I used a delta wing calculator to find cg, etc for my model. Check the forums, plenty of useful stuff out there.
7. I picked the HS522 because it seemed the most efficient in terms of volume verses area and, due to the large 3m wingspan of my model the relatively thin profile was no problem.

Had a quick look through my files to see if I could post something quick for you, but it has been a while since I fiddled with this project and I couldn't find the spread on this. There really is no difference between calculating the weight and flight characteristics of a solar plane verses a conventional plane, just that the extra weight of the added hardware must be accommodated (hence the focus on wing loading). I chose to stick with the Delta wing, seems best suited for solar due to efficiency of design and huge ratio of usable surface area.

I have kinda moved my focus over to multirotors while I get properly familiar with the APM and all the other hardware involved... But will inevitably come back to this at the appropriate time, when I am better equipped to make it happen.

dear quadzimodo

thank you so much, i really appreciate you taking time to read and replying to my comment.

i am no aeronautical engineer and i am still struggling or rather finding a short cut method to design and build the airframe. so up till now i have learn t that there is no short to this. before implementing everything i want to calculate each and every aspect of the project with the basic aim to check if by adding solar panel and mppt charger would it be able to achieve longer flight time as compared to:

1. no solar cells and mppt

2. more battery about the weight of the solar cells and mppt.

there are so many variables in this. some times i just think of gathering the required equipment and making it to check whether it would fly or not.

well thanks again for your reply and good luck with your projects.

electronics inc

I am also a bit of a greenhorn when it comes to aerospace engineering, having only discovered the joys of sUAS in the past year.  I come from a background in journalism focused on automotive aftermarket, consumer electronics, science and DIY electronics... My passions covering sustainable systems, GIS, human geography, heritage, photography, so I kinda think that sUAS dovetails into this list quite nicely. I am riding a steep learning curve at the moment, but that is half of what makes this so captivating as a hobby.

With regards to finding the short cut method to design and build the airframe, I am not sure that such a thing exists.  The closest thing to it would be to gleam as much valuable knowledge from pioneers like Alex, cherry-picking the very best ideas, and improving what you can.

I am speaking very generally here but I think it is pretty evident, by looking at the success of others, that solar (based on easily and cheaply sourced 6x6-inch 4W 0.5V poly cells) certainly has it's merits in this application.

If you wanna run some numbers, you could use Alex's 80km flight as a case study.  The full 3.5hr flight is up there, as is all the live telemetry data - including input and output voltage and current.  You could run the video, and set a screen capture program to take a screengrab every second, then crop the screengrabs around the current data, then run the screengrabs through an ocr to convert the screen info into text based data table.  This would allow you to calculate exactly how much energy went in and how much came out, and what the averages, peaks, etc were.  I think all the weight info for the solar and mppt is on the associated forum posts as well (something like 440g for the cells and 200g for the mppt, I think... plus 4 x 5000mAh zippy lipos).  I think the solar and mppt weigh about half what the 20Ah battery weights... and that, on a sunny clear day, the solar and mppt is more efficient use of available weight allocation.  But you would have to do the numbers to see just how much more efficient.

My approach was to calculate the wing area needed to make <140W (dictated by the weakest link in the solar chain - the selected mppt) from the solar cells i selected (the 4.1W 8A 0.8V 6x6in cells I mentioned), then select a suitable wing profile (HS522) from which to build a perfectly sized delta wing (3m) to provide the minimum amount of usable wing area to accommodate the resulting number of cells (combining to deliver 17VDC at <8A).  I compared the Wing span, Root chord, Tip chord and Sweep of other large delta wings like the Queen Bee and did my best to match proportions and ratios.  I then worked out the best way to orient the solar cells on the wing for easiest connection, best use of space and best performance after slicing cells (so that no area of the remaining cell is cut or made ineffective by relevant cutting lines), and also considered the best path for series/paralleling the cells for desired final voltage.

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