Hi guys, This is my first blog post. I thought I would share with you my hexacopter. I call it v2.0 because I crashed it after the first build. I believe I had some issues with the compass being interfered with by the integrated PDB.
My specs are as follows:
Flamewheel 550 clone frame
Jdrones 850kv motors
Jdrones 10x4.5 props
Turnigy Plush ESC 25A (BLheli firmware)
Fr SKY RX with telemetry
Jdrones ioboard for telemetry link to 9x TX
Jdrones Ublox GPS
FPV transmitter, camera and receiver. (yet to be installed)
Anyways here are my pics:
Comments
Liam,
I have a flamewheel knockoff like you, I use the PDB and love it because it keeps the weight down on the HEX. However, if you put the APM in the middle like you (and I) you will have to get an external mag sensor regardless of the use of a ground plate. The power line (either PDB or how you have it) running that close to the APM will cause enough of a problem that it will throw the mag way off. The mag sensor is real cheap (about $15) and will save you lots of time by allowing you to mount it where ever you want/need.
Also, I use some cheap China express 1000kv motors and 10x4.5 props (not the best) and it flys pretty good!
@Liam: Don't know about that dji power distru board, but twisting cables is always the right idea.
Never really understood that geofence effort anyway. An uppper hight limit may be ok for most occasions, and if everything goes that wrong that you can't control it anymore and triggering the failsave (or automatic FS kick-in fails) you are screwed anyway, I wonder what geofence will help then. IMHO it would be better to iron out the lowlevel fu** ups in the first place like this one: http://tinyurl.com/mkl2cr4 to make it safer instead of doing higher level stuff to compensate for those basic issues. Just my terrible 2cents.
Awesome guys. Ive now got some pointers to work on.
I just got one question thou, did I do the right thing by not using the inbuilt PDB? I used the cables to try and reduce the EMI. Or can I negate pretty much everything by just adding ground plates? I have been told the inbuilt PDB produces a EMF as big as the circumference of the PDB itself. I figured that running cables would make the EMF smaller.
FYI guys, The crash that I had previous to this build was caused by GPS signal loss and user error. The weather was bad, and I was a bit complacent about the 3d GPS fix. I thought the fix was easy to get under any weather conditions, since my car GPS works well when it rains. I have since learned that a 3d fix is harder to achieve.
What happened was the GPS thought it was way outside the geofence, and it decided to go home, even thou the craft was sitting next to me. The results were it went 15m into the sky and over my head and 2 streets over trying to make its way "home". Again this was a learning curve, I learned by reading the wiki that all I had to do was to flick the flight mode switch and I would have control again.
I havent had any issues with the GPS, but I will keep Crashpilot1000's notes in case I need them.
Thanks for the great help :D
Note the small item under the GPS sensor, on this image (follow the arrow for number 2).
Liam, You may also want to know that a cable can act as an antenna. If you search with 'GPS interference' or 'GPS shielding' in the search field after clicking on 'See all Forum topics' (from the main DIYD menu), you can find many threads, some of which may be relevant to your hexacopter rebuild. An example thread.
@Liam
2) The groundplates should be connected to GND but even if not it's better that without. There is a big thread about GPS shielding etc - it boils down to reducing multipathing (reflection of GPS signal) and disturbances form other onboard sources. It should be 5-6cm square or round - don't remember that exact lambda philosophy, I just cut out a 5cm+ square by hand... used doublesided tape to stick the GPS on and feathered up a wire that is stuck under the last tape... There are professional solutions available for just a few $. If you fire up Ucenter and watch signalstrength go up with a groundplate you will never want to miss it. The groundplate under the APM will short inducted electromagnetic fields (hope I got that right).
5) I am quiet happily using those: http://flyduino.net/9x47-Carbon-verstaerkt-AP-Propeller-Set-Schwarz... . You will loose thrust but the idea behind smaller props is that if you have small motors with relative big props the desired RPM change commanded by the flightcontrol is delayed because of the momentum of bigger props. Smaller props might improve depending on the copter weigth etc. Those graupner e props are also ok but from my perspective overrated. If you choose them stay with 10'' because they produce less lift (and also momentum for the motor) than your APC. Just my 2cents, hopefully not everything is wrong..
@david teles
I originally bought the frame from ebay, I have recently bought a pack of HJI booms from ebay to repair it from a crash. I dont know the weight, I will let you know when I do it.
Cheers everyone for the positive and constructive feedback :D
@Graham Harding
The HJI arms I have found to be heaps more rigid than the stock ones from this frame. They appear to be made of a harder plastic.
@Crashpilot1000
1) Cool, I may just do that with the bullet connectors, I only put them there for servicability.
2) By ground plate, do you mean a plate that is grounded to the - of the battery? I twisted all the wires to try to eliminate the mag interference.
3) Same ground plate? - of the battery?
4) I cannot put self locking screws on the props. They are Jdrones with the shafts coming out of the motors they are retained by collets. They hold down pretty well.
5) What 9 inch props would you recommend? 9x? and what brand? I dont have tons of $
I think this less points to fail is the one to iterate on, I have had bullets failing on me.
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