[DaveL]

Well, I don’t need sonar, or a tricopter, or a hobby for that matter. It’s my choice, so stop poking holes in it. And yes it’s also about the challenge, is that a problem? Especially here, in a diy drone community built on curiosity, generosity and collaboration?
If it helps you to understand, I’m a curious tech-hobby-geek who loves to tinker and chose a cool-ass rcexplorer tricopter as the base platform for my rc explorations, not some six-motor’d flying toilet brush with wires and guts hanging off of it 🙂
So we have much in common, even more so if you can help us learn how to do these things that we want to do.

[DaveL]

So, given a couple of months, I might figure out how to github myself a hex file with certain pins assigned for trigger & echo, and figure out where on the F3FC board to solder wires to connect these pins to a sonar gizmo, but I know this stuff is child’s play for some forum members, whereas I’m a mechanical guy. So please lend a hand with this so I can get back to drawing mechanical stuff like a canopy/rollcage 🙂

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[DaveL]

From my post over on the iNav thread:

Regarding sonar connections on F3FC frame, I did some digging around in github and found target.h for the RCEXPLORERF3 :

#define SONAR
#define SONAR_TRIGGER_PIN           PA6   // RC_CH7 (PB0) - only 3.3v ( add a 1K Ohms resistor )
#define SONAR_ECHO_PIN              PB1   // RC_CH8 (PB1) - only 3.3v ( add a 1K Ohms resistor )

Is this a useful lead?

Some smart & creative guy suggested looking into PA13 and PA14, which have solder pads marked SWDIO and SWDCLK in the middle of the board. Don’t know if these can be subverted for sonar connections but would be much better than tacking wires to fine pitch leads on the microcontroller!

And here is the pinout for the STM32F303CC:

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[DaveL]

Hey Marlon, keep an eye on the iNav thread, these guys are working on the position/altitude tools that everyone secretly wants.
And which I certainly need!
You and I can contribute, by testing the software each time it is updated.

DaveL

[DaveL]

I need my arms to swing, for the inevitable collisions with large spinning balls of rock!

Regarding sonar connections on F3FC frame, I did some digging around in github and found target.h for the RCEXPLORERF3 :

#define SONAR
#define SONAR_TRIGGER_PIN           PA6   // RC_CH7 (PB0) - only 3.3v ( add a 1K Ohms resistor )
#define SONAR_ECHO_PIN              PB1   // RC_CH8 (PB1) - only 3.3v ( add a 1K Ohms resistor )

Is this a useful lead?

Some smart & creative guy suggested looking into PA13 and PA14, which have solder pads marked SWDIO and SWDCLK in the middle of the board. Don’t know if these can be subverted for sonar connections but would be much better than tacking wires to fine pitch leads on the microcontroller!

I’m curious about the sonar if easy to hook up and try out, but not sure that it’s worth spending much time on.

[DaveL]

I’m still following iNav with high interest, and if my gps/compass arrives in time I’ll install it and test fly this weekend.

Question: Can I use sonar with iNav and F3FC Frame?

Does the current build for F3FC [inav_1.2.1_RCEXPLORERF3.hex] have sonar pins assigned or available to assign?

If no-one has tried yet, I’ll give it a shot, but will need to know where to connect it.

I’m a mechanical guy so I’ll need a bit of help with this.

In return I’ll make and test a vibration isolating motor mount which uses a two-piece clamp over a short length of black latex rubber tube, which in turn is slipped over the ends of the arms. The pieces can be 3d printed or machined easily. I may be able to include a cylinder feature on the bottom to make durable landing gear out of vinyl tubing or fuel hose.
Isolating the rear motor will be more complicated but do-able.

A quick solution to making VHB tape arm/frame isolation more durable is to peel the top liners off and apply some kind of thin sheet material, cut up plastic packaging window or cardboard maybe, it is double-sided tape after all !

DaveL

[DaveL]

Hey Marlon, check out the behind-the-scenes work going on, there’s a small army of coders building the software we want.

The CleanFlight team is working on new stuff for v1.14 and beyond.
The tricopter tuner-meisters at TriFlight are making specialized tuning that will get rolled back into Cleanflight.
There’s iNavFlight working on gps, rth and altitude hold. <<I need!
And the mad scientists at BetaFlight testing out all kinds of innovations!

For each of these projects, click on the “issues” and “pull requests” tabs where you can read about the stuff they’re fixing or new features they’re building, it’s just awesome.

[DaveL]

I came across this Logic Level Shifter today, just a couple of dollars (small rcexplorer dude not included).

[DaveL]

Hi lauka, do you think it would improve flight behaviour if you disabled active braking in the ESCs ?

[DaveL]

I’m still pre-noob, but this caught my eye:

set tri_servo_feedback = VIRTUAL
.
.
servo 5 1000 2000 1500 40 40 100 -1

So I wonder – if no feedback wire, does it just use default values?
Are some of these servo values the endpoints and can you edit them manually?

[DaveL]

You have a very good understanding of this, and I am reminded of the term ‘aliasing’.
I’m stuck doing an urgent job, but please look at these explanations and see if they fit…

Definition: Aliasing

Anti-Aliasing (Sound and Vibration)

[DaveL]

I haven’t completed my V3+F3FC so I can’t test yet, but when it’s ready, I’ll set it up on riser blocks under each motor and somehow tap in to the Z axis accelerometer to evaluate the Z resonance without battery, then with each of the two battery sizes that I have, and finally each battery with damping foam.
I have an ADXL321 accelerometer around here somewhere, which can be used with a scope or loudspeaker test software like Arta. Or some way in Cleanflight that I am about to discover 🙂

[DaveL]

Also there will be beat frequencies from the almost same motor rpms, just like when tuning guitar strings, and these may get into the airframe through prop downwash, so isolating the motors may not help enough. Go after the frame vertical stiffness and damping (or cut the arm lengths down!)
😀

[DaveL]

Great work!
I’m not at all surprised by the Z vibrations. The airframe is supported in flight by the three thrust vectors, effectively hanging on the motor shafts, and has some natural resonance frequency in Z.
This natural frequency is determined by the mass of the central part of the airframe and payload, and the stiffness of the structure which acts as a spring. A lower mass and/or a stiffer structure increases the natural frequency; a higher mass and/or a softer structure lowers the natural frequency.
The degree to which motor/prop vibrations will excite the airframe Z natural frequency depends on the frequency of these forcing functions, as they’re called, and the damping (or lack of damping) in the structure.
I’m running out of time at the moment, but think about frame stiffness (tighter screws, lateral stiffener on frame), payload mass (try different battery size), or increased damping (sorbothane/latex foam pad under battery) to mess with the vibration until it ceases to be a problem.
Cheers and thanks for the great work you’re doing!

[DaveL]

Hey thanks for responding Donny, I agree that 3S makes sense.

Can the current draw in constant hover or lazy flight be predicted well enough to choose between the 3S1P or 3S2P batteries? Anyone have similar motors and some current draw measurements?

I realize that battery specs are only on paper but should be useful to compare within the T-Graphene product range, which I homed in on for apparent better than average durability.

So to compare some choices:
The 4000/3S2P/15C-30C (on paper) does 4Ax15C=60A sustained and 120A burst, and weighs 296g.
The 3000/3S1P/65C is weight comparable at 301g, and no doubt will crank out all the amps I could hope for.
But how about predicted flight time? And the price difference which means the 4000/3S2P is buy-three-get-one-free.

I’m just trying to optimize my purchasing where I can, because I’m starting out from scratch, gave away my old-tech rc stuff decades ago. Sooner or later my wife’s going to audit me …

[Author]

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