Sunday, December 21, 2014

WLT v262 problems

Tried to fly my v262 the other day and even at full throttle, it doesn't have enough power to take-off. Fore-Port motor is especially weak. Sprayed motors with contact cleaner and lots of black dust came out. It didn't help. Sprayed Tri-Flow inside ... still no help. Removed foam body and now quad flips over on take-off. Eventually, Fore-Port stopped turning completely.

Motors 3,4 run CW. Motors 1,2 run CCW.
Each red prop is build different and rotate opposite
each other. Same with black ones.
 
Brushed motor
Open in a new window and then click to Zoom-In

One brush is fair. Other is ground-down to nothing and missing (only part of wiper-arm remains).

Should I fix a $60 quad? Probably not, but I really like my v262 because it's impossible to crash it or damage it with body left on (it just floats down to earth). It was my first quad trainer. Motors aren't too expensive so I currently have some on order BG's US-Warehouse.

To repair my first v262 motor failure, I ordered 4 of these from BG USA-Warehouse at $6 each. I ordered on Saturday and got them on Tuesday  :cool:. This was with Free-Shipping via USPS.

All 4 have a large sticker on plastic bag that says "V262-16 Motor"

Smaller sticker:  SKU088984 ClockWise EVK 1028-0
Inked on motors themselves: N50-3124, 2014-10-22

Smaller sticker:  SKU088984 CounterClockWise 0925-2558
Inked on motors themselves: LV-N50-3027/34.5, 2014-06-06

Even though they are supposedly the same, I ordered 2-CW, 2-CCW ... and will replace as such. Unlike the store pic, gears are mounted towards the middle of the shaft like originals.

Repair went fine, I replace Motor #3 with a ClockWise-motor. Gears mesh-together a little loose (a fraction of a millimeter off) but there isn't really a way to easily adjust that. CW means red-positive-wire goes to + sign on motor. Once the bad motor is replaced, controller board now spins all motors at full speed (which it wasn't doing before when it detected a bad one). LEDs on 2 front red-prop-ed motors are white. LEDs on 2 rear black prop-ed motors are red/blue.



I also made a better battery mount. Battery holder is turned upside down to accept spare slightly larger (but exact matching) $5 battery from HobbyKing. Added a loose wire-tie for a little middle-support, and then a velro-strap from junk-box.

Compass holder cracked, oh puck

Flying around in the backyard today. It's confined and has plenty of obstacles, but was mostly just light flying, hovering, and  AutoTrims. Also testing GPS on cold, overcast, cloudy day with high Kp-Index of 5-6 (was mostly getting sats=7/hdop=2.2 ... pretty surprising actually. Eventually went to 8/2.0).

During a fair landing, I kinda landed on one LandingGear skid and quad flipped over upside down. It wasn't even that bad a landing and really surprised me. Anyway, as it came to rest I heard a cracking sound.

 
It was the compass puck. So, Prop-Guards won't save the puck. I "glued" it back together with Plastruct solvent. 

 

Installed new double-sided foam tape on bottom. I did a new mount with a Plastruct strap (and small single-sided foam tape cushion) and tiny metal screws.

  


After Compass Calibration, new Compass Offsets are -118, 9, -1 . One of those is significantly higher than before, but still well within recommended range (-150 150).

Also recalibrated the Accelerometer while I had MP running.

EDIT 2015: Ended-up changing to this mount after cracking puck. Simpler and no extra metal screws near compass. Compass Offsets are a little better now at -99, 17, 15.

Sunday, December 14, 2014

Telemetry Radio - Moved inside aircraft

Telemetry radio has been working fine attached to bottom of Nova. Therefore, I bought a 15cm SMA cable and moved radio inside Nova and the antenna comes out the side of body. It's a tight fit, but radio is in channel between PowerBoard and shell. Only thing cable is really touching is the slight edge of ESC white nylon socket.
 

EDIT 2015-01 : This is the my old Internal layout. It has since been changed and optimized.

EDIT 2015-05 : Since the above pic, I had moved the 915mhz radio back outside/underneath Nova. I have now tried moving it back inside again (during gimbal install). I didn't want it in old location because GPS is over there now.

This is the new location. Notice FrSky antenna moved to top of RX (still at 90 degrees to back one). If this all passes interference and RSSI testing, it stays here. I will just add a bit of foam tape to prevent vibrations between radio and case.

 
 
Verified 3DRobotics 915mhz Telemetry radio settings. ECC is on. While slower through-put, official docs say it is recommended and supposedly it has better distance range. Yes, you can change settings on the slave radio from MissionPlanner (without removing it from quad).
 
 
 


Monday, December 8, 2014

Repairing GPS & Compass Modules and Cables

I cleaned away black tarnish and corrosion from pins of PicoBlade socket on the BS-126 GPS-Module (HK Nova stock one). The blade-pins appeared to be made from a solid/non-plated metal. Tarnish and pitting (causing the poor electrical connection) was pretty deep and hard to remove, but I managed. I carefully scraped with a small/dull hobby-razor knife, used a special file for cleaning/ burnishing relay-contacts, and cleaned with "CRC QD Plastic Safe Liquid Contact Cleaner". As usual, this was all done under extreme magnification and lots of light. I got all surfaces of blade-pins nice and shiny again (and able to conduct electricity). 

I ordered parts to build a new GPS-Module cable and they arrived in a few days. Wires appear to be 30 gauge with thin flexible silicone-type insulation. Pins were much better than original ones and didn't have any strange plating on them. Crimps also looked fine. I carefully removed the Dupont (RC Type) pins from included single-position plugs and installed new pins/wires in a good 4-pin-position black Dupont plug from spare-parts box. Connection seems to be 100% now and not susceptible to drop-outs during basic flexing of cable or vibrations. During back-yard testing, I was getting a fast GPS-3D-Lock and good sats/hdop numbers. I'm calling it fixed.

New GPS-Module cable installed. Pic is good enough to see pin-outs.

I replaced the foam tape to be similar as shown above. I used 4-5 layers to make it as high as possible. The ceramic antenna on top is just barely touching the top plastic body cover (when fully installed) and seems to get the best reception this way (for this entry-level GPS Module that means just "acceptable").

Never again will I assume a connection is good, just because connectors are securely fastened (not on this model-aircraft anyway).

Upon inspection of Compass-Module, found the same problems. Luckily I ordered some extra parts to build more cables. New cable will end-up being about 1.0 inch shorter (but still reaches with length to spare). Like before, still had to carefully clean tarnish and corrosion from cheap imitation PicoBlade sockets themselves, soldered to the boards at both ends. Then, I installed the new cable.

New Magnetometer (Compass) cable
 
As you can see from the above pic, the pin-outs (for the stock Nova compass) are:
1-4
2-3
3-2
4-1
 
Update 2015-01: I have not had a single problem with GPS-Module or Compass since replacing these cables and cleaning away corrosion and tarnish (from the modules themselves).
 

Monday, December 1, 2014

No GPS (again)

Drove down to field to fly. Clear sky day, winds 10mph, Kp-Index is 2 (good). I flew my smaller v262 quad and then got the Nova out.

I couldn't get a GPS-3D-Lock at all. DroidPlanner was reporting sats=0/hdop=100 after 15 minutes on flight line. Tried power-cycling and even a new battery.

Apparently, with GeoFence turned on ... if you have no GPS-3D-Lock you can't Arm at all or even fly in manual (I couldn't Arm in Stabilize either). You can't change settings like that with DroidPlanner-1. Without my laptop at field (to turn it off) ... no flying for me today. I packed it up and drove home.



In MP/Terminal/test/gps it gave me the response "ublox ok". ScottFlys (from RCGroups forum) helped me and pointed-out that my Logs revealed the GPS-Module seemed to be communicating with APM-FC but there was no satellite data. GPS Status codes were all "1" (trying to acquire sat data) after many minutes. It was acting like maybe the ceramic gps-antenna was bad or broken.

I considered turning-off GeoFence for now in case problem re-surfaces while at field. However, instead I will just fix problem. As long as I have a minimal GPS-Lock, it will still Arm. On second-thought, just turn GeoFence off while trouble-shooting GPS problems (on less variable).


BeStar BS-126 with ubx-g6010-st U-Blox chip

Upon opening the Nova, I found everything looking visually ok. The GPS-Module's blue-led was flashing (so it was getting power). The gps-module cable was plugged in all the way on both sides (the Molex PicoBlade side at gps-module and RC-Plug side at FC). I removed cable and did a rudimentary continuity test (using only exposed outer contacts) with my ohm meter ... all 4 wires passed. It's a simple cable... GND-TX-RX-VCC.

 
I re-connected it (didn't really do anything to it) and GPS-3D-Locked in seconds after powering Nova on. I was getting sats=11 and hdop=1.3 very easily. However, if I wiggle the wires and connectors it goes to sat=0/hdop=100 again. Appears to be a good old-fashioned intermittent bad connector or wire. I'm thinking on the RX or TX lines since the GPS-Module is getting power the whole time (it's blue-led is always flashing).

Inside APM FC
Let's start at the beginning. I opened the FC and checked the 4 gps header pins. All clean and shiny metal. Their solders to PCB also look ok (not great, but acceptable). All these examinations are under heavy magnification with lots of light.

Cable: RC-Plug/Dupont (FC side)
After documenting the whole cable's pin-outs, I carefully backed-out the pins and examined the crimps under magnification. They looked fine. I didn't see any corrosion or tarnishing (contact points were shiny). I couldn't really find anything wrong so I just adjusted (very slightly bent contacts) the pin-sockets in this end of the cable to be tighter and cleaned with contact cleaner. Pins do appear to be fairly low-quality metal but ok.

Cable: Molex PicoBlade (BeStar BS-126 GPS-Module side)

First thing I notice is that the white nylon plug is poorly made/moulded and not a genuine Molex part. It is also missing the Molex patent marks. I carefully backed-out the pins. Second thing I notice is that the pin-sockets are very low quality clones. They are obviously not genuine Molex parts either. They also appear to also be poorly Chrome-Plated ? Since when are contacts chrome plated? Shouldn't it be something like gold or even tin ? There is also a black tarnish inside them where the contact points actually touch the socket's pins (appears to be a bad "un-like metals" reaction). Surprised it was making any contact at all. Looks like I have found the root problem.

Zoom-in the see spots of black tarnish on pin blades.
It's the same on other side of pins.
BeStar BS-126 GPS-Module (PicoBlade socket)
Found similar black tarnish on both sides of pin "blades". But only on the 4 pins that the cable uses (so it's obviously a unlike metals reaction). Comparing to some new genuine Molex PicoBlade sockets (direct from DigiKey), it's obviously a cheap clone. The pin's actual shape is a little different and you can let the blade-pin's composition metal is not the same as the genuine part.

**************************************


I have ordered parts to make a new cable. I will try to clean (poorly cloned) PicoBlade socket's blade-pins on GPS-Module and salvage it.

**************************************

I only have about 8 flight-sessions on my Nova. During that time I have experienced 2 complete failures of the GPS-Module (to find ANY satellites) and 2 attempted fly-aways during GPS dependent RTLs. At the time, I chalked them up to sun-spots, CME, and/or poor Kp-Index (general GPS glitches). One I even thought might have been me flipping the wrong switch (and/or incorrect FrSky radio switch programming) while trying to invoke FailSafe condition. Due to the intermittent nature of this problem, it's taken a while ... but it looks like I have finally found the root cause of those failures.

 
GPS Module Trouble-Shooting:
Here are some notes. I will flesh-out these notes if I ever have to do more GPS-Module TS or decide to replace/upgrade mine completely.
 
Prerequisites:
  • Test GPS-Module outside (on a clear-to-partly-cloudy day) so it's ceramic antenna has a clear view of sky (and satellites). One less variable to worry about.
  • Give it at least 30 minutes to acquire a signal before you give up.
  • Verify cables and pins are good with a multi-meter (voltage and ohms)
  • I think GPS works on radio frequencies 1.2ghz and 1.5ghz . Nothing else should be running on those frequencies or you will get interference.
GPS Module's Blue-Led: Means GPS-Module is getting power and I think (maybe) also initialized and ready/working. Can't go much further without this.
GPS Module's Red-Led: This led is mirrored by Nova's external Green-LED. Flashing for "trying to obtain a GPS 3D-Fix" and solid for a proper 3D-Fix.
 
You can connect Nova's stock uBlox GPS-Module directly to laptop with an Arduino FTDI-to-USB adapter. Use uBlox's u-Center for Windows software. This will verify GPS-Module is good without any help from Flight-Controller. uBlox GPS-Module must have APM config file loaded (only needs to be done once ... unless it gets corrupted somehow).
 
If you ever connect VCC power to GPS-Module backwards (reverse polarity) you have likely fried it completely. You might try removing the battery (or is it a super-capacitor) or otherwise master-reset it's memory.
 
To estimate what GPS you should be getting:
 

Thursday, November 13, 2014

GeoFence and Current Config

Turned on the GeoFence. The aircraft is small and I'm currently only flying LineOfSight (LoS) with no FPV (yet). So, I think this is reasonable.

GeoFence (current settings):
Type: Altitude and Circle
Action: RTL or Land
Max Altitude: 120m (400 ft is current suggested AMA Limit in USA)
Max Radius: 200m (656 ft or 1/8 mile)
RTL Altitude: 20m (65 ft. Note that this is the normal RTL altitude parameter)

http://copter.ardupilot.com/wiki/ac2_simple_geofence/

Note: (added after later GPS trouble repaired): With the GeoFence enabled, the pre-arm checks will require you have GPS lock before Arming the vehicle (at all, in any mode). Consider controlling it with a TX switch or take laptop with MP to field every time. Leaving it enabled for now because I only fly Nova outside, and never fly without a minimal GPS-Lock. If I need to Arm it inside house for some reason, I'll have to switch GeoFence off first.

FrSky Taranis:
Switch B: Flight Timer-A
Switch D: Loiter, Stabilize, Altitude-Hold
Switch E: Off, Simple-Mode, Super-Simple-Mode (GPS)
Switch F: Off, RTL (ReturnToLaunch)

Android 4.x Tablet running DroidPlanner 1.x (GCS)

MissionPlanner: v1.3.11
ArduCopter: v3.1.12 (Nova stock)
FW: v120
FC: APM_v252_v2.0
Props: 8045 stock (8in x 4.5 pitch)
Battery: Turnigy LiPo 11.1v 2700mah 3s 20-30c (102x35x28mm)

Addons:
Prop-Guards
Soft camera mount
Mobius 1080p camera
HK 3DR 915Mhz Telemetry Radio v2

Monday, November 10, 2014

Flight Testing

Due to the way our house is constructed, I never get any GPS satellites inside the house. I when into back-yard to test re-assembled Nova (like I usually do) before driving all the way to flying field. Out in the open, I couldn't get a GPS-Lock for 30 minutes (as in 0 sats and 100 hdop). Since I had just had quad apart, I thought problem might be on my end. According to other forum pilots, looks like today was bad day for good GPS. According to www.swpc.noaa.gov , there was a MCE that's going to be disrupting things for a while.

To estimate what GPS you should be getting:

After 30 minutes of sats=0, hdop=100 ... it just started working. I finally got a GPS-3D-Lock but hdop was still too high to Arm in Loiter Mode. Depending on yard location ... Sats 5-7 & hdop 2.3-6.7. I just Armed in Stabilize, did some AutoTrims and hovers and flew around in back-yard "obstacle-course" :)

Backyard hovering and flying.
GPS still not good, but at least getting something now.

The good news is that the vibration problems appear to be fixed (and hopefully also WobbleOfDeath). I didn't fly very much and wasn't very high, but no WoD was observed. For reference, the X-Y (red & green) Acceptable Range is -3 ~ +3. The Z (blue) Acceptable Range is -15 ~ -5.

All vibrations are well within acceptable levels. "Landing spikes" can be ignored.

Zoomed into a period (from above graph) for a closer look

Friday, November 7, 2014

Quadcopter and Multi-Rotor videos

They say a picture is worth a thousand words ... so how much for a video? I keep finding cool multi-rotor videos, so I thought I would link to them in this post. Most of these are geared toward sales and marketing. Videos geared toward "how-tos" are usually linked in the relevant posts themselves, throughout the blog. Most of these are better in HD with sound.

Here is the HobbyKing Quanum Nova marketing video.

You can tell Walkera has a large marketing budget, and wins the award for flashy/polished product videos. Be sure the sound is on and crank-up the YouTube resolution (gear icon) for these.

Hitler reacts reacts to a DJI Phantom flyaway. Remember that Quanum Nova is Arduino-based and RTC is short for "Return-to-China". After loosing 3 Phantoms, he decides to try a Blade 350. These are funny (sorta like Hogan's Heroes) and he reacts strongly to lots of things on YouTube (I never knew).

DHL is using quadcopters for deliveries. Video-1Video-2 and Video 3 (wish I had a team of people helping with pre-flight and watching my Telemetry).

The multi-rotors fly so well, the Internet is loaded with fly-away videos. Here is a Phantom fly-away over water and last minute RTL. Here is a Phantom-2 fly-away and eventual recovery. Here is a bunch of Fly-Aways in an Yahoo article (don't try this at home boys and girls).

RCUK edited this video with iMovie. Footage from his (custom APM-based) Walkera Scout X4 & GoPro.

Tuesday, November 4, 2014

Troubleshooting Wobble of Death (WoD)

With the help of the multi-rotor pilots in the RCGroups forums, it appears my WoD might be related to excessive airframe vibrations affecting the APM FlightController. While not much, as I've been adding extra weight to Nova (Camera Mount, Mobius Camera, Telemetry Radio, and finally Prop Guards) it seems to be getting worse and more frequent during flights. While I originally thought the WoD spells were a new development, as I review my flight-log-posts ... it has been occurring as far back as Flight #4.

Here is an IMU graph from Flight #7.


According to: http://copter.ardupilot.com/wiki/ac_measuringvibration/

The X-Y (red & green) Acceptable Range is -3~+3. The Z (blue) Acceptable Range is -15 ~ -5. Even ignoring what appear to be "landing spikes" ... all vibrations are beyond acceptable levels.

The following items will be checked:
  1. Flight Controller mounting location
  2. Flight Controller mounting material and isolation from airframe
  3. Propeller Vibration and Balancing
1. PASSED. Currently, the Nova's FC is mounted Aft of CenterOfGravity or CenterOfFrame by about 10mm, and Port about 20mm (away from CenterLine). The FC still has the indicated side Forward. That side is parallel to the front side of quad, and is perpendicular in the aircraft. This was done in the beginning to facilitate mounting everything (FC, RX, and GPS) to PowerBoard without them touching each other, or any raised components on PowerBoard. While nothing is declared in official docs, according to some knowledgeable pilots in APM forum, there is no reason to re-mount FC in exact CG middle of quadcopter. After normal calibrations (including Accelerometer/Gyro) due to quadcopter's size and speed, there should not be a performance or dependability penalty for this slightly off-set mounting location.

Edit 2015-01: This turned out to be a FAIL. While it doesn't show as good on above graph (as others on this blog) ... X and Y should originate at 0. I think this can only happen when FC's gyro/accelerometer chip is in true middle of quad.

2a. PASSED - FAILED. Mounting needs to be around 10mm thick so that the side USB plug clears the RX, yet FC does not touch the top of body shell. As I examine the current layers of thin white foam tape, it seems very rigid. I have replaced it with a more appropriate material. I used two 1-inch sections (one on each end) of thick/plush (5mm) foam gyro mounting tape, two layers for 10mm thick. The FC mount is now plush and flexible (but still secure) and should be much better at isolating vibrations from FC and it's on-board instrumentation.



2b. PASSED - FAILED. Since the FC boards are not actually screwed down inside plastic case, there is some movement. I'm not sure, but I think the PCBs (and attached sensors) might have been vibrating inside case. Added small pieces of gyro foam-tape inside case (on sides ... not on top where barometer-foam piece is). Seems to work fine.

2c. PASSED. Inside the FC, (with it's two-PCB construction) I noticed the grounding metal case of the Micro-USB plug (on upper-PCB) is dangerously close to pins hanging-down from main power-header (from lower-PCB). Added a small piece of electrical-tape (3 layers thick) to prevent a short circuit or arcing.



3. PASSED. Balanced stock-white CX-20 8045 props with Dubro Prop Balancer. They needed little if any balancing so I really doubt they were causing any significant vibrations.

Other things I have done to Nova in this maintenance cycle:
  • Did another Accelerometer calibration since FC was moved. Hold quad very still and level/perpendicular at each stage.
  • Motor Test via MP/Terminal. They all run and sound ok.
  • Upgraded MissionPlanner to v1.3.10 and then to v1.3.11 a few days later
  • Set THR_MID parameter to 550.

Saturday, November 1, 2014

Flight #7 - Return to Flight

I took the repaired Nova to larger middle-school field to fly it. Winds were 10mph (with gusts) on a clear day. Flew 2 batteries (about 20 minutes total) and Nova survived with no damage. However, I seem to have a re-emergence of an old problem (now more frequent and pronounced) ... I think it's called Wobble of Death. It's not Ground Effect because I'm high-up, usually trying to hover. As I describe flights, assume all is ok (no wobble) unless I mention it. It happened about 5 times.

First flight was an AutoTrim. It seemed to really need it, so I did it twice (to finish with a good landing) and it worked fine.

Had a quick dhop of 1.8. I'm really liking the new Prop-Guards since if it tips over on landing a prop-strike is prevented. Even if it flips on landing (in short grass) it doesn't really bind props/motors.

Flight 1


Colors are the different Flight-Modes

On first battery I tested Stabilize, Loiter, AltHold, and RTL. I'm trying to remember now when the WoD happens. It seemed the Mode didn't matter (saw it during most of them). Wind gusts seem to cause it and while it almost flipped completely over a few times, it never actually did. Switching to Stabilize and making a course correction seemed to cure it.

On second battery I did another AutoTrim (just in case it would help WoD, but it didn't). Ran though all modes but I also tested Simple-Mode for the first time. Generally kinda weird but works fine and might come in handy. It works in Stabilize as well as AltHold (a welcome surprise).

I have Mobius video and logs to analyze. So, what causes Wobble of Death?

Sunday, October 19, 2014

Nova Repaired

I called it "repaired" and screwed body back together. It was only on the bench for one week.

I upgraded to MissionPlanner 1.3.10. I re-did all calibrations (Radio, Compass, Accelerometer, and ESC) and everything looks fine in MissionPlanner, DroidPlanner, and with Taranis control. First flight will be an AutoTrim.

CH-7 is already assigned to a 3-Position switch at Taranis. In MissionPlanner, changed CH-7 to be Super-Simple Mode. Middle position (or first click) ends up being Simple-Mode (non-GPS but directional) and Down should be Super-Simple-Mode (GPS required but even works "behind" pilot). When bench testing radio, there is no indication in MP or DP that SM or SSM is engaged. Even though it's just a Mode-Modifier, I find it strange that the only way to know if it's setup properly is to fly quad and see what happens (especially for a Mode that changes what the sticks do).

I really liked the Prop Guards (for the short time I had them) so I installed a new set. If you drill a small hole in them, you can leave them installed while opening the quad. This way, you don't have to remove the 8 prop-guard/motor screws. With them only being Phillips-head who wants to be removing them just to get inside the quad (not to mention the fact that they hold the motors securely in place). Be sure to only use these 8 special-longer screws with the prop-guards. If used incorrectly, them will touch/scratch the internal motor windings and kill the motors (and possibly the ESCs).



I already have a set of genuine DJI Phantom (P330/SPN9) 8045 props that I picked-up at LHS. Best I can tell, the stock props were clones of these (and these will continue to be my "spare-set"). I ended up just getting a new set of stock white 8045 props from HobbyQuad.com along with my Prop Guards.

If I do anything else to it before next flight, I'll document it here.

Just got back from 2 flights (batteries) on small WLT v262 quad. Good to go flying again.

The Texas daytime temps are now more reasonable. It's been 3 years, so I am starting the rather time consuming process of cleaning and staining my back wooden deck. I'd rather it didn't, but most of my free time will be spent on this project (instead of quadcopters) so I can finish before winter comes.

Deck is 12 year-old white-pine. This pic after 30 man-hours of cleaning prep
and staining with 6 gallons of Defy Extreme stain (Light Walnut) ... 2 coats.

Wednesday, October 15, 2014

Nova ESC and body Repairs

Repaired (red led) ESC and it tests good. Saved some down time and $35. I am using (normal) leaded solder and have iron set to 360c.

Notice PWM signal from chip, thru resistor and then to top of board where it uses PCB Via to jump to other side.

 
 
I verified that the 5v trace (with usable solder-pad) is indeed not connected to anything else (notice a 5v component is intentionally not soldered in). All the Vias are the same size and very tiny. As other blog pics show ... the only PCB traces (on this side) that still carry the PWM signal is the PWM's Via's circle. So that it will accept solder, I used finger-nail buffing-pad to carefully buff-away the green paint from the Via circle pad AND a 2mm section on adjacent 5v trace. After fluxing this small area, created a solder bridge between the two. The tiny blob of solder pictured here (where "W" used to be) is covering the whole via top surface as well as the whole 5v trace cross-section. Checked work with ohm-meter.
 
So, now the previously un-used 5v pad becomes the PWM pad. Since we now have a solder-pad large and sturdy enough to handle a 26awg wire, soldered the PWM wire to it.
 
The "PWM detection for LowVoltageAlarm & LED control circuit" wire gets a proper connector (so whole ESC can be installed or removed without soldering). Soldered it to it's own pad further along this new hi-jacked trace. I suppose it should be noted that it was this short red hard-soldered wire (with no slack) that lead to the pad being ripped from the board in the first place.
 
The repaired version was tested in the quad with a battery and works fine.
Three strips of Plastruct (added in a second phase) 
A new frame/body/shell is about $40 (shipped) but currently Back-Ordered at HK. Repaired cracked styrene body with Plastruct Plastic Weld Solvent-Cement and then some thin strips of Plastruct (# 90739), were layered inside for reinforcement (on side-edges and middle). They also sell "dowel-shaped" pieces that might work. Over the years, I have gained experience with various glues and materials. I know that using the right glue for each material is important. The Plastruct Solvent "wicks-into cracks" and melts the plastic back together. It the end, the cracked pieces (and any reinforcement pieces you add) all become very close to "one piece" again. I was impressed how well it worked.

Basic Testing
IIRC, you can test motors and ESCs via MissionPlanner option and/or Terminal without arming motors (or pre-arm checks). Be sure props are removed first.

Troubleshooting "All ESCs are beeping"
  • ESCs are getting main (hard-wired) run voltage from main LiPo battery, but ESCs can tell they have no PWM control (control signal that tells them to stay Off or stop, Arm motors and start them, speed-control, etc.)
    • Check in this order
    • This can be caused by no BEC (+5v) voltage being connected to RX radio (and therefore, also no power being passed to FlightController).
    • FC might not be getting power (usually via CH-1 Aileron connection) 
    • FC might be damaged or malfunctioning
      • FC might have a corrupted firmware and needs to be reset and Firmware re-loaded with MissionPlanner.
        • Followed by loading of Default params & complete calibration.


Trouble-Shooting visibly fried or damaged PowerBoard, Motors, or ESC after a crash or LiPo battery problem.
I've never had to do this, but I have wrote this procedure to help a forum member. I think it might come in handy in the future. Seems to fit on this post.
  • Unplug all ESCs and RX.
  • Connect LiPo and check PowerBoard for BEC +5
  • Check PowerBoard for +11v output at each corner (ESC Input motor-run voltage)
  • Connect one (non-fried) ESC
  • Connect one (non-fried) Motor
    • You can test the motor's 3 phases with a LCR or LC meter. It measures the inductance of the coil-sets. All 3 should be similar. The motor should not be connected to ESC or anything else during test.
  • Use MissionPlanner Motor Test and try to get this set working.
  • Keep testing at this location the rest of motors and/or ESCs.
    • Remember that testing a fried motor might destroy a previously good ESC and vice-versa. I would just write-off any obviously blown parts and try to check and/or save the rest.
ESC Replacement Notes:

I've never had to do it, but according to forum reports, different version ESCs can be mixed. Be warned that the orientation of the solder-pads is reversed on some models. If in doubt, use a meter to check volts and/or ohms before connecting. As I stated before, there doesn't appear to be a 5v generation circuit (aka +5_BEC) on these ESCs.

There are 3 heavy-gauge (thick) Power-Input wires:
Red - 12v +
Black - GND
White - 5v+ (for LEDs)

There are 2 thin PWM motor-control wires (black Dupont/RC-Type plug):
White - Signal
Black - GND

There are 3 wires for brushless motor connection:
Red, Black, and Yellow

The PWM signal only needs White (Signal) and Black (GND) wires ... for each ESC. If there is also a red wire in that set, it should not even be there. But, it seems that at the Cheerson plant, pre-made 3-wire Dupont cables (RC servo type) are plentiful. So if it is there, either heat-shrink it or leave it soldered down to the ESC with the other two (actually used) wires. If you trace the ESC's PWM red-wire solder pad, you will see it actually goes no-where. You can also just remove it (back-out pin, etc.) on each end.

The 5-volt power for the LEDs comes from the PowerBoard, but is only sent to the LEDs when the quad wants each of them to light up. If you think about it, it must be this way. Otherwise, you would have separate control lines going to each ESCs ... to control the LED lighting.

There is one other thin (usually red) wire, but only on the Forward-Port ESC. That is something different.

http://quadcopter-robotics.blogspot.com/2014/07/b-power15-2nd-circuit.html

Motor Troubleshooting:

Haven't done much with Nova motors, so no dedicated page yet. Seems to fit here for now. You can easily open motors and check inside (glued-on magnets, etc). If you ever mounted motors with wrong screw (too long) windings are likely permanently damaged underneath (just takes a scratch). Electrically, they can be checked with LCR Meter (aka LC or Inductance Meter). A basic Volt/Ohm meter is usually not sensitive enough.
 
Stock Radio Notes:

Since I purchased a PnF Nova (without radio), I have never owned the stock white radio set transmitter or receiver (TX or RX). However, I know many of you visiting this Blog might have them, so here are some notes from the RCGroups forums.
 
Here is the basic wiring, showing where the Ground, Positive-5v, and Signal rails are located on RX. In a stock config, power comes from BEC on PDB to Battery (B) socket on RX. Then (since all the "power-rails" are connected) the power gets to FC through standard 3-wire Dupont (servo-like) cable connected to Aileron (A) channel.
 

Please note that (like any electronic machine or vehicle) through-out the whole aircraft ... proper power polarity must be followed (for all standard voltages ... like +5, +12, etc.). If any component's power is connected with reversed polarity, it will short-out when power is applied. It might destroy several components when the "magic smoke" escapes (as components fry and burn-up). If unsure of voltage or polarity of a "power supply point", check first with voltmeter before connecting. Verify plug and socket polarity (with docs or pics), and power requirements before connecting anything.
 
The stock white RX/TX radios work as a matched set. Only this Cheerson RX model will work with this TX model. It might be FlySky protocol (not to be confused with FrSky) but I don't know it's ever been proven. If you need a new one of either, you can get them at HobbyKing (for Nova) or BangGood (for CX-20) ... or if serious about hobby ... use a better, more hobby-grade radio.
 


Monday, October 13, 2014

Flight # 6 - Crash Landing - Damage Evaluation

The good news is that all electronics seem to still be working. On the bench, I connected a LiPo and used the Taranis and DroidPlanner. I can Arm and spin motors, instrumentation sensors are all working, etc.


Lower shell only 60% cracked (but mounting point is damaged). Notice oval copper solder-pad ripped from ESC.

Upper shell 100% cracked. Screw mounting point compromised.


Top and bottom body-shells are pretty much trashed unless I try to glue them back together. I would like final repair to look acceptable, but more worried about structural integrity since it is a motor arm and shell is also the frame.

ESC damage. Not sure what PCB Revision this is, but I think it's older (ie v1.0).

Scratched SMT micro-trace and soldered on jumper wire for testing. It worked but didn't hold. Notice trace lifted from board but stayed connected long enough for testing.


The PWM solder-pad oval got ripped right off the ElectronicSpeedController (ESC) PrintedCircuitBoard (PCB). I did a very-temporary micro-solder-hack to make sure ESC was still working, and it is. However, all the PWM traces are SMT form-factor, so re-acquiring that trace (on either PCB side) will be tricky. There appears to be several different "MFL1218" Nova/CX-20 ESC PCB Revisions and but the word in the forums is that they can be mixed in the same aircraft and work (calibrations, actual operation, etc.). Appears to be a simple 2-layer PCB.

PWM detail. Under the letter "W" signal uses a hole-thru Via to other PCB side. All the way back, PWM trace is about 50% width of a normal trace like the 5v one pictured here.
Not sure what is risky-er ... trying to fix this one and use it or trying to integrate a different revision one. Also, a new ESC is $35 shipped (from Hong Kong and the wait). One possible way to fix this one (and it be durable enough) might be to cut the 5v trace toward middle of PCB, jump to it near Via hole, and use it's pad instead (5v trace/pad isn't being used). Actually, as I examine under the QC-1 sticker ... this version doesn't appear to have 5v capability, so the 5v trace isn't connected to anything on either end.



It came to rest like this. It was still on and knew it had landed. I don't think landing in the tree caused much damage, rather it was the Nova hitting the ground under the tree. In addition to the Body and ESC, one prop-guard was broken and twisted beyond repair. Three of the props were nicked but none had broken blades. Prop-guards seem to do their jobs ... absorbed crash energy, and likely prevented even more damage to delicate parts (ie motors).

Wednesday, October 1, 2014

DroidPlanner (GCS) on Android tablet

I lucked out and just managed to get IceCreamSandwich 4.x installed on my old (circa 2012 with GingerBread 2.x) Chinese Android 7" tablet (iView 760TPC). It is dual-core with 512mb RAM, and supports USB Host Mode (for 3G cell dongles, etc.). The tablet came with a little OTG USB adapter cable that allows you to plug in normal-sized USB flash drives (while I don't use it much, it goes work). The tablet's native USB port is Mini (not Micro) so I can't use the OTG cable supplied with HK 3DR v2 Telemetry radios. Therefore, for now, I will use the iView OTG cable, and the normal USB cable that I use with the radio on the laptop.

At first, DroidPlanner didn't seem to work (radio lights weren't flashing quite right, and DroidPlanner would not Connect). I checked the page at DroidPlanner GitHub, and it mentioned trying the USB Host Check app. Sure enough, the checks all failed (which I thought was strange ... since old OTG USB Adapter was already working for Flash drives). I went ahead and clicked the "Fix It" button and rebooted. I still had the 915mhz radio connected. After it booted up, it detected the radio and ICS asked me if I wanted to use it with DroidPlanner. This was a sure sign that things were looking better. Sure enough, after starting DroidPlanner, it connected with no problems. HUD is working nicely.



I was then getting a "Unfortunately, TTS has stopped" (crashed) on every startup. I clicked OK, and the app worked fine. The error went away completely after the Google Play Store offered a "TTS Update" and I let it install. Now, TTS (Speech Prompts) work fine in DroidPlanner.



I used this mount from HobbyKing. I also upgraded to this 5inch USB Mini-Micro male OTG cable for a much cleaner look.

Edit: In March 2015, I upgraded to a better Android tablet.

Troubleshooting:

USB-OTG cables are asymmetrical (only properly communicate when connected in proper direction). It has more to do with internal wiring than connectors that might be soldered on each end. USB-OTG port should at least work with USB flash drives or "wired" computer direct-connected storage (as a starting point).

DroidPlanner (even DP v1) requires ICS v4.x or higher on Android device. Test with DP v1 first (it has smaller memory and lower resource footprint). If that works, you can uninstall it and try a higher version. DP v2 and v3 might crash or malfunction if your device is not up-to running them. DP v3 (Tower) might require a dual-core or better and 1gb ram (depending on what background apps you are running).

With the Nova's main LiPo battery connected, get Nova working with 915mhz v2 radios in MissionPlanner for Windows first. This checks telemetry radios (important step) and Nova. Always properly Disconnect MP with button (before disconnecting physical cable). Leave radio on Nova, but move laptop's radio to Android device, now using USB-OTG cable.

To verify the your Android device even has a functioning USB port, I like to first test it with a flash-memory device.

You can really only have one version (either v1, 2, or 3) installed at a time (to avoid conflicts). Be sure radio-dongle and/or USB-OTG cable is disconnected at first. Install Droid Planner and reboot device. After full boot, connect radio (it should be detected). Select radio as Default device for DP. Start DP and try to connect.

If radio is not detected, run USB Host Check App from TaurusLabs. If device abilities fail, click Fix button and run Check again. After Connect, move quad and see if Hud responds (this will check basic communications). Forum member Jester1964 reports that they had to enable "USB Debugging" in Developer options before it would work for them.
 

Monday, September 29, 2014

Flight #5 - Testing Nova and Mods

At the small neighborhood field and light winds. Overcast skies.

After making sure Nova would take-off and land ok, I did the AutoTrim procedure. No problem getting a GPS 3D-Lock ... Telemetry revealed sats=7 and hdop=1.8 . Tested currently assigned Flight Modes ... Loiter, Stabilize, Alt-Hold, Land and RTL.

This is also my first-ever YouTube video. The local edited 1080p file looks smoother than the uploaded YouTube video (even playing on 1080p). The YouTube video looks more like 20-25fps than 30fps. Overall, impressed with Mobius Camera. The sun-exposure glitch (pointed-out in video) has been mostly eliminated.



Everything on quad seems to be working fine after mods (see list in previous post). This includes Telemetry radios, which I have been wanting since I ordered the Nova. Nice having laptop and MissionPlanner at field, and not have to connect USB cable any more.

For the camera, I am leaning toward a FPV setup (therefore, the static camera mount), mainly because that's what many pilots say works best. I suppose Loiter assisted footage was acceptable for AP.

Here are some notes about GPS and Arming ... Green light on-steady means GPS 3D-Fix ... likely sats=5 or better (hdop is irrelevant). Allowing Arming in Loiter means hdop=2.0 or better. Number of sats is irrelevant (it's more about QUALITY of GPS signal as a whole). I always Arm in Loiter ... for best chance of GPS dependent functions to work. If at the flying field without your laptop, but having trouble, try this GPS App on your phone (just search by zip code).

Saturday, September 27, 2014

Testing & Setup of re-configured Nova

Since ...
- FC boards have been completely unplugged, removed, soldered on, and re-installed.
- FC, RX, and GPS Module re-mounted (with new foam tape).
- ESC PWM control cables disconnected from FC
- GPS cable connector broke and was replaced
- Way RX and FC get power was changed
- Taranis firmware upgraded
- Telemetry 915mhz v2 radio installed
- Mobius Camera installed
- Any number of other things changed

... this post will try to document the various tests and procedures that I deem required to get the Nova ready for flight.

Final Internal Config. Everything is close without actually touching.


Initial quick/easy tests and observations:

At this point, the FC, RX, and GPS-Module have all been re-mounted with new/fresh foam tape. Nothing is actually touching (not even micro-usb plug and RX below it).

In Terminal/Test/Motors ... Motors seem to spin in proper order and direction. Testing order is different that FC connection number.

GPS-Module seems to be working (tiny blue led on it's lower-pcb is flashing). Inside house, I get nothing (sats=0, hdop=100) but this is normal for my house. On the porch, I can get a 3D-GPS-Lock and sat=9, hdop=3.0 ... I think ok for an over-cast night.

Compass, Accelerometer, and Barometer (air pressure altitude) seem to be basically working ... according to MP-HUD (but will still re-calibrate).

Radio (as a set) seems to be working. Nova will Arm and spin motors. The sticks and battery meter have been calibrated at the radio itself (or at the "radio level"). Radio calibration can now be done in MP.

External LEDs are working.

Telemetry radios seem to work fine. Having on-board Telemetry radio On and/or in use does not seem to affect main RX reception (RSSI values don't really change or get worse).

Camera is basically stand-alone, but seem to work during testing.

Calibrations:

Done like before (see previous posts) in MissionPlanner. First center your radio's Trim-buttons, and then calibrate Radio. Then, calibrate the Compass ... point each of 6 surface-faces to the ground and slowly spin around with it for each one ( aka "compass dance"). The globe model will end-up having 6 small circles embossed on it. The wireless telemetry radios make this east now. Current compass offsets are -54, 25, 2. And finally, the Accelerometer ... hold very still perpendicular-ly as instructed or prop-up.

ESCs calibrated (All at Once) in case end-points changed (center Trims first). FailSafe doesn't need to be changed but should be tested (see previous posts).

Carefully, did a "Hold by Landing Gear Test" ... with other hand, Armed and tested basic directional controls with TX.

All completed and/or passed.

Settings:

In MissionPlanner/Config & Tuning/Extended Tuning ... give Opt 7 a function and also Opt8 (I set to RTL). In Taranis (Mixer), assign both to their own dedicated switches. Check all Modes on FailSafe screen.

Next Flight Objectives:

First, I will see if it will still take-off and land. Then re-do AutoTrim. Check currently available Modes (some new to me) ... Loiter, Stabilize, Alt-Hold, Land and RTL. Test Telemetry. Try to get my first flight-video with Mobius.

Re-Assigned Radio Channels

For the following reasons, I have decided to re-assign my available radio channels:
- I don't plan on installing a gimbal any time soon.
- Mobius camera has it's own battery. Might as well use it.
- I could use some extra FC Aux channels for dedicated Flight Mode switches.


 X8R-RXAPM-FC
RC Cable 1CH-1 VerticalCH-1 Vertical
RC Cable 2CH 2-4 Horizontal (signals only)CH 2-4 Horizontal (signals only)
RC Cable 3CH 5-7 Horizontal (signals only)CH 5-7 (FC Aux 1-3) Horiz
A-JumperCH 8CH 8 (FC Aux 4)
BEC 5vSBUS

Notes:
  • BEC-5v goes to RX and then to FC. FC (Flight Controller) really gets 5v from CH-1 connection.
  • Vertical connections are the standard way, with standard RC-Cable radio plug (Gnd, Power, and Signal).
  • I used "black to the right" when plugging in horizontal "servo-like" RC Cables.
  • A-Jumper is a standard (single-pin) 3inch Arduino Jumper cable
  • While Channel-Signal-Rail is on FC bottom, it's on X8R's top (opposite).
  • By using previously unused SBUS socket for power, frees a standard channel. It shares the same power-rails.
  • At this point, I can't even see a reason to need BEC-5v routed to lower connection panel. If need arises in the future, I can just use a RC Y-cable.

Good pic that someone made.
The white boxes are where you connect Dupont (servo like) RC-Cables. Mine is mostly like this. Only difference is that I went ahead and connected CH-6 also to RX (in case needed later). Red VCC and Black GND drawn boxes are just informational.

Friday, September 26, 2014

FrSky Taranis - OpenTX 2.x Firmware upgrade from 1.x

Taranis Radio has been working fine with my Nova quad. I thought this would be a good time to go ahead and upgrade to the latest OpenTX firmware. Might as well be running the latest code. I also wanted to start using OpenTX Companion, which is software you can load on your computer that allows you to program the radio from a computer (instead of just the radio itself).

My understanding is that the radio ships with a special FrSky version of OpenTX. In my case, it was several versions older.

This example uses my Taranis (Original, Model-B). It's a few months old and running FrSky stock firmware.
SVN: opentx-r
DATE: 2013-10-18
VERS: opentx-x9d-v1.1.02

Taranis should be disconnected from computer and switched Off.
This is the initial procedure when going from stock FrSky v1.x firmware to OpenTX 2.x (there is no easier way at this point).
To read or write Firmware to radio, Taranis should be Off when connecting to PC.
To read or write Models (Eeprom) to radio, Taranis should be On when connecting to PC.
http://open-txu.org/home/undergraduate-courses/fund-of-opentx/

After reading, to get started ... download, install, and use the proper version of Zadig (to install Windows driver for Taranis)
http://open-txu.org/home/undergraduate-courses/fund-of-opentx/using-zadig/

Follow the rest of the steps from Open-TXU.org to get OpenTX Companion installed, matching firmware downloaded and written to the radio. The current version at this time is v2.0.12.

After you get the firmware written to radio, the first time you turn on the radio, the current Eeprom will upgrade itself to a version that works with the new firmware. In my case, all the Models programming was still intact (but first flights will be made with caution until proven).

I then re-did the sticks and battery calibration (just to be on the safe side). Center your Trims first.
http://open-txu.org/home/undergraduate-courses/fund-of-opentx/checking-out-taranis/

Here are some simple rules to follow while using OpenTX Companion (basic work-flow):
  1. Always start by reading the current models and settings (called EEPROM) from the radio.
  2. Save the models and settings to the computer as a backup.
  3. Make changes to the EEPROM directly or by copying from other EEPROMS.
  4. Save the EEPROM when all changes are made.
  5. Write the original (now modified) EEPROM back to the Transmitter.
In addition to having your models set-up, the EEPROM contains all of your individual radio settings and more importantly - your radio calibration settings.

There are more advanced tricks, but for now, I will stick to the core-rules and work-flow above. Seems like this prevents programming made at the radio itself (ie., at the flying field) from getting accidentally over-written. The radio will always be the "current live copy", with backups on the computer. In the even that I have to restore the radio, I just need to redo the battery and sticks calibrations, and I'll be back current.

Thanks to the helpful folks in this forum that helped me get through this easily.

Here are some newer Taranis general usage notes and tips for using OpenTX-Companion.

Taranis-Plus Notes:
I think the Taranis Plus also ships with a FrSky firmware, however, it's derived from OpenTX 2.x, so upgrading it's firmware to a true OpenTX 2.0 firmware will be easier than above (I was going from 1.x to 2.x). I think you just connect Taranis-Plus to Windows computer via USB with "3-Finger Salute" and go from there. Also, in OpenTX-Companion you must let it know you have a Taranis-Plus (and not a plain Taranis). Hope this tip helps, but I don't actually have a Plus to test it.

Sunday, September 21, 2014

Mobius Camera Install

Used most of the supplied mount to mount Mobius (Lens-A) camera. Drilled a 1/4inch hole in the middle of lower plate and used a (cut to exact length) 1/4in. nylon bolt to attach it. A little foam tape at front and back (just to make sure it doesn't turn and/or loosen). Between upper plate and body, I used two small nylon washers to help even-out upper plate due to rubber dampening ball's grommets in corners.



The wire-ties and fishing line are for emergency tethers (and are required ... balls won't hold in crash). One loop through all plates and parts. Even in this default position, landing gear does not appear to be in Mobius wide-angle lens.

Willing to give-up tilt to have camera up higher. Might adapt or hack a Mobius mount later. Obviously, no gimbal yet, but not really any "jello" either so stock mount is fine for now.

Current Settings (updated 2015-03): I just set my Mobius exposure to "Sunny" instead of "Auto". Just one flight that way but seems much better (especially when facing the sun). Instead of the camera temporarily making the rest of the scene dark, and then slowly transitioning back, it's more of a constant brightness. The sun just looks bright and there are some cool halos now. Anyway, thought this tip should go here.

Update 2015-06 Changed Primary recording mode to 1080p/30fps Narrow. Will decrease "fish-eye effect" when camera is pointed down. While the end-effect looks like a zoom, it's actually a pixel-matched 1080p recording from middle of lens. I also tried 720p/60fps/Narrow ... while it is smoother, it's not as sharp when played back on 1080p monitor. I have it setup as Secondary.