Hi all! After some pid tuning, but require further adjustment, today i made the first real flight with my "heavy ArduXOcto", i open this thread for sharing my experience if someone else wants build a similar  "heavy configuration" using ArduPiloltMega 2560, IMU, GPS and Baro, etc.
I have previously tested more expensive systems like Mikrokopter and Wookong, and unfortunately i think there is still much hard work over the code for make this electronic flight like the competition, but considering the price i would say  that goes too well.
I'm still quite satisfied, even though my copter in some aggressive maneuvers tend to wobble a lot, and in the Loiter mode some circles is inevitable because I believe that the management of the accelerometers correction is not optimized or inactive.
Over the baro range i've a good altitude precision, max 20/30 cm of excursion.
This is my hardware configuration:

- APM 2560
- OilPAN IMU
- Mediatek MT3329 GPS V1.6
- XL-MaxSonar MB1200 (with active filter and "thermal mods", 4 x 10 ohm resistor around the case)
- ESC HiModel Pro 30A, in high timing mode
- Two switching BEC 6V 5A (connected to electronics through two diodes 3A, the tension output is 5.33V)
- Motor TigerMotors MT2814 710 kv (mounted with 3° inclination for increase YAV control)
- Props APC 13x6.5 "E" (X8)
- Two-Way telemetry "Mikrokopter Wi232" (890 MHz)
- Six led strip connected to APM (pins AN8<->AN13 through ULN2003), thanks to u4eake for the code
- Homebuilt frame, mixed aluminum / vetronite (by AleBS, thanks dude! :P) + homebuilt hood
- Lipo 4s2p 5000 mhA 40c
- TX Futaba T12FG
- RX Futaba R6008HS

Total weight (with 2 lipo pack): 4.3 Kg...i forgot something or not? :-)

I'm uploading the video on my youtube channel, post them soon, for now I leave you some pictures.
I enclose
the parameters used for the flight test in a soft wind, but there's one error, the real "Rate Pitch I" is set to "0".

Best...

Marco



NOW IN "X8 COAX" CONFIGURATION...



One of the first flight:




New video with "X8" frame and "ArduCopter V2.4"


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In addition to the material that i wrote in the configuration i wrapped the sonar with soft sponge to keep the heat generated the resistor, i got used shielded audio cable with a toroid to the "sonar side". A little piece of sponge is also over the baro.
See photo for the detail...
Attachments:

Wow, that's a lotta foam on the baro!  I used a tiny little dot, the same size as the baro chip, and it didn't work well.  I'll use more!

 

What did you use as foam on the sonar?  I got a tiny, thin little thing from an earphone/headphone.  It barely fits over.  I don't know if it's thick enough, haven't tested yet.

 

Also, I notice now that I read your original specs, that you are supplying the APM with 6V through a diode to drop voltage to 5.3V?   And that's working fine for you?  I ask because I was thinking of doing the exact same thing. But wasn't sure if 5.3V was ok for the IMU.

Yes Robert, try with more foam,  but pay attention to not isolate the external noise, the cover foam for big microphone (in Italy is called "ice cream") is perfect!
The IMU and APM work fine from 4.5 to 5.5V.
Never use the bec inside the esc,
even though they are Castle Creation and similar!!!

I've only found REALLY big microphone foams.  Way too big.  Can't find a source for small ones. :(

Well, I think I have a solution anyway.  Just picked up a CC BEC rated at 10A.  That should be plenty for the servos and APM.  Also picked up some diodes, epoxy rectifier diodes (what's the difference? anybody?) and a 5V 1A voltage regulator which might do the trick.  In fact, the voltage regulator is rated at up to 35V input, so why can't I use it to directly power the APM?

You can use CC and the other one, set the CC to 6V and go to APM with a classic diode (5A min), and with other little bec (for emergency) go to APM with schottky diode.
Anyway 1A is too low, but for emergency (if CC fail) is good if you don't use servo, because you must consider 1A for servo.
My experience save me to some crash, i never use the same bec for servos and APM, i take the 5V for each servo from the eight bec inside the esc, in fact i've 8 bec on board and if fail for supply the servos is not important... :P
The rule is: 2 bec with two diodes for APM, some bec inside esc for each servos... only if you have an heavy config, hexa or octo (LOL).

Hmmm... I've got 2 3A "Epoxy rectifiers", and 2 1A "micro diodes".  I did see some even bigger rectifier diodes, I think 6A each. There's not a lot of selection at Circuit City anymore. :(


I thought 1A would be more than enough to power the APM and receiver.  Or, I could use the 3A rectifier diodes, but I don't know how those compare to normal diodes... nor do I know what Schottky means. Hmmm... more research.

I don't see much point having redundancy for the APM but not the servos.  If the servo power supply fails, the heli will crash.  If the APM power supply fails, the heli will crash.  So either have double redundancy on both supplies, or none at all.

One of the main reasons that I want to use the diodes is because I am going to have a large capacitor bank on the APM power supply for noise and to prevent any possibility of a brown-out.  But I want the cap bank to supply ONLY the APM.  If the servos brown-out, that's not a big problem. (as long as it's brief).  Without the diode, I think the capacitor bank will quickly drain back into the servos.

Am I making any sense?  I'm fairly new to electronics. ;)

What camera did u use to take the pics of your apm and sonar???

Sony HX9, the little monster... :P
I use the same camera for the published video...

I've got a WX10, the little brother to the HX9.  I'm also REALLY impressed with it!

Yeah, it's a good alternative at low cost with the same important features.

It takes better pictures than my Canon 350D with the kit lens!

I've got a really nice 3-axis gimbal designed, the whole thing is only 5" wide, the same as a bare DSLR.

Wow! Can you share it or PM me? :-)

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