Adventures with an APM and a nine quid quad.

[Ant]

Hey all

Ive got to say i love multicopters and have had some reasonable success with my Disc**ery and Nasa. Ive got to the point where i wanted another one but couldnt really afford or justify the Disco / Nasa route. Being a bit of a fiddler i went down the APM 2.5 route with a cheepo quad airframe off ebay.

I bought the APM and GPS as a package from Hobbyking and was relieved when i plugged it all in and it instantly picked up my home on the Mission Planner - so far so good.

After a lot of reading on the Arducopter web site and also Cupids exploits on this very forum    i had the frame complete and ready to go with 4 rc timer 1000kv motors and the SK30A speed controllers. With a 5000mah 3 cell pack C of G was and still is well out proving that the 9 quid airframe isnt as well engineered as the Disco. The threads on the spacers were absolute crap as well and there wasnt enough space between them to fit the battery in ! Had to elongate the frame holes to move them further apart.

After more fiddling i maidened and apart from being a bit twitchy it flew well in Stabilise mode. Bit more fiddling and Stab mode was perfect. Final PID settings P-0.145, I-0.03 and Pstab -4.0.

Next came the problems ! Flicked it into Loiter on the second flight and it was really unstable to the point where i couldnt control it. I know, i thought, flick it into return to home ! Bad idea it flipped on to its back and burried itself into the field. No major damage but it knocked my confidence.

Back to the drawing board and study of the instructions. Re calibrated everything compass, radio and accelerometers. Took it out again and bingo - works perfectly. No idea what went wrong but hopefully it will continue to perform.

Finally i ordered a cheap Minimosd from ebay - what a mistake!! Sat for 4 hours trying to get it to work. I lost the plot eventually, complained and got a full refund which went to partially funding the DIY Drones official one which worked perfectly first time.

So even though i have a lot of testing still to do i have learnt a lot from this frame and some of it may be useful to you guys. Not sure if i would buy another yet but the package has come out much cheaper than the Disco / Nasa option so you pay your money i guess....

[Cupid Stunt]

Get the compassmot down as low as possible (got mine to 7%)

Calibrate by enabling auto declination and auto offset in the advanced parameters menu (temporarily)
Fly 2 x fig 8's, land and disable auto declination and auto offset

Test in loiter and rth to see if it still gets out of control

Odds are that the "out of control" was the quad going in TBE (toilet bowl effect) due to the compass heading being off

Got mine sorted by I just don't like flying it as I liked flying my tricopter

[Ant]

Will do Cupid - Thanks bud 

[Dusty]

hehe, APM is a right bugger.

I've fiddled with it in the past, and on Cupids advice I'm staying away for the foreseeable.

Seems like you're having success eventually though, which is good. it all pays off I guess.

(I just got naza-m lite w/gps)

[MrBen]

Always fancied a dabble with apm, when I have finished my octo, and 40" wing then maybe I'll try it out on my H quad or even build a cheap hex to play with.

[Cupid Stunt]

I may get rid of my complet set up after all, got it dialed in pretty damned good for loiter and rth but really don't like how a quad flies compared to my tricopter
I suppose I could spend some time tweaking the PIDs which I have hardly touched yet but it just doesn't "flow" like a tricopter

I find a tricopter turns and banks very much like a plane, I nearly put my quad in the ruddy trees yesterday DOH !

[Ant]

Cupid - my compassmot is 62 % ??!!

What in your experience is the best way to reduce it ?

Cheers

[Cupid Stunt]

Cupid - my compassmot is 62 % ??!!

What in your experience is the best way to reduce it ?

Cheers

Move all the power cables, esc cables well away from it mate

If you have a central power distribution board immediately above or below the APM board then move it away by extending two of the esc power cable and shortening the other two

I originally had all my esc power cable soldered to two metal washers (one for ne the otehr for pos) and sandwiched together using a fibre washer but that was directly above my APM, so I had to re-solder it all to get it out of the way

Here's a pic of how I routed my cables, the APM is on the bottom plate

[Ant]

Nice one - as per Sod's law my distribution board is right beneath the apm :-(

Thanks for the advice mate.

[Cupid Stunt]

That'll be it then Ant, get it moved and it will improve hugely
Alternatively you coudl buy a seperate mag unit and follow the instructions on how to disable the on board one, that way you could mount it anywhere out of the way

Maybe replace the GPS and mag with the combined one from DIY Drones and mount it up on a stem Naza stylie

[Ant]

Yeehar - compassmot 11% with the distribution board as far forward as I can get it and the wiring to the rear esc's extended ! Nice one !

[Ant]

Final layout on underside of my quad.

[Dusty]

cool, distro far away from anything it could interfere with (aka mag lol)