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Always start at Step 1...
#1
I made a vague reference to a wild goose chase in my Tricopter build thread.  I thought I'd share it here because between Professor Google and myself I spent 4 hours stuffing things up and getting more and more frustrated.

See the thing is, every single part of these craft is a complex device, usually built and bought for prices that distract us from exactly how much technology and capability we are buying.

Now in hindsight of having wasted around 4 hours fault finding a non-existent fault and ruining some quite neat build work I'll share the whole story in the hope it helps some other person forgot this ritual of silly mistakes:

What I did Good:
  • I had previously "bench" tested and run the F/C for several hours, flashed the target firmware (iNav).  I knew that the board powered up and "worked" although I hadn't tested the motor outputs.
  • I had checked the power fed by the PDB - both the 5.3v and the Battery voltage
  • I had checked the function of the GPS, the Receiver and the ability to use the "yaw" control to tilt the tail.
  • I had run up the ESCs on the bench and updated to the latest BLHeli available for them.
Essentially at each stage of the build I went through I would get the function.  If something wasn't right I stopped until I resolved the issue.  Everything had gone well with only my inexperience with the hardware causing issues.

What Happened:
After getting my motors mounted and connected to the ESCs I plugged in the USB cable, a battery and fired up iNav configurator.  Moving straight to the motors tab I activated the motor outputs and pushed up the sliders one by one.

The tail motor spins up smoothly, sure it had done that before when I had previously tested it and now it still worked.  Win!

The right-hand motor spins up with a bit of a stutter at first.  No big deal I think and it's even turning in the "correct" (CCW) direction.

It all goes wrong on the last motor.  Motor three on the left-hand arm.  It stutters forwards a bit, then backwards,  and after a few seconds the ESC beeps a few times and resets.  Uh Oh!

Naturally I jiggled the cables and uttered profanities as is customary in these situations but somehow reverting back several steps in the evolutionary path failed to yield results.

So I did the next worst thing.  I doubted myself.

Herein started the stupids.

I looked at the wiring and decided the servo signal line wasn't soldered neat enough at the ESC.  I redid that.  Twice.

Then I decided the power wiring looked iffy.

Then I thought maybe the motor didn't like the ESC wiring order so I changed that.

Then I thought the ESC had failed.  Lucky it's a tricopter because that meant I had a spare ESC!  So I swapped it.

Then I thought the signal wire was maybe pinched up and broken in the folding arm system.  So I bypassed it.  

Then I thought maybe the Flight Controller had a bad output.  So I swapped it with the right-hand one.

Then I thought the power feed was bad, so I bypassed it.

Then I thought the ESC wiring order was wrong.  So I changed it.

Then I  thought..... ..... .....

Well you get the picture.  Nothing worked though.  That damn motor kept stuttering, the ESC (two by this point) kept beeping like a deranged Star Wars Droid and I was no closer to the problem than a Storm Trooper is to shooting a target.

Time to watch some TV and contemplate a more passive hobby, and the addition to my wardrobe of a nice snug jacket with extra long sleeves that do up at the back.

Later that day
Sit down in my study/workshop/home office 
  • Plug USB into Tricopter
  • Fire up iNav
  • Engage Motors - set to max throttle
  • Connect Battery
  • Wait for melodic Beeping
  • Move master slider to 0 throttle
  • Wait for Melodic Beeping
If you don't recognise the above sequence then let me share with you the joy of ESC Calibration.  This is where the BLHeli software on the ESCs does a bit of a mating ritual with your Flight Controller so everyone knows the rules and boundaries of the relationship.  It's what ensures that 1000rpm really means 1000rpm, and somewhere in there I'm sure there's an exchange of safe-words for special times.  

It's also THE FIRST THING that must be done when you finally introduce your motors to their ESC and your ESC to you Flight Controller.  You want a consenting 3-way relationship between these components.  Any other way ends in disaster.

It's also what I didn't do.

I have no idea why that one arm wouldn't spin up despite changing everything - even out of sync with other motors it's unusual for a no-spin situation, I probably shouldn't care, but the hours of glorious sunshine that I could have been out in breaking props instead was spent redoing a perfectly good build.

My biggest mistake though was reaching for the keyboard and doing a Google search instead of a simple "Step by Step" guide on preparing for a maiden flight.  Sometimes we should remember no matter how complex this gear is, most of the time the problem isn't firmware or hardware its the fleshware putting it all together.
Builds: Mini-Quad  -  Tricopter 
A Blog

[-] The following 4 users Like Aaron's post:
  • unseen, Tom BD Bad, fftunes, sloscotty
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#2
Its always the same! Humans always expect the worst! 
I spent about $200 trying to fix the turbo on my van, took it to 2 mech friends, then to the turbo specialist who... pulled a piece of tape out of the turbine! Turns out the mech who did my last service decided, that rather than replace the 'pipe' clip that secures the air filter...
the only way I can think to describe this, is when a 5 year old expresses derision by putting their tongue under their bottom lip and groaning 'Un Un!'
Windless fields and smokeless builds
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