Replies to This Discussion

Permalink Reply by estebanflyer on February 7, 2013 at 9:56pm

Hello Mark,

I have been trying to understand the differences between 3DR and FrSky and which one is more reliable or works better with the APM 2.5. I am considering buying the ready to fly hexa kit that comes with the FrSky and the 9ch TX/RX, but I want to know if the 3DR is better.

I know... you will probably say: research more. and you are probably right. But nothing compares to the word of the guys that know.

Thank you!

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Permalink Reply by Drone Savant on February 7, 2013 at 11:21pm

Are you are talking about *flying* with the 3dr 433 or 900mhz radio alone as a replacement for the Turnigy JR Style Radio module? That sounds like you are cutting into unknown territory if so. 

I believe Mark was referring to using the 3dr radios for telemetry. 

It would be nice if you could do this with the 3dr radios, alas I don't think they are anywhere remotely near this with the firmware - http://forums.openpilot.org/topic/13487-my-openpilot-pipx-copter-tr...

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Permalink Reply by estebanflyer on February 8, 2013 at 7:34pm

I needed to know what each did better. I wasnt sure what the FrSky did. now I know.

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ModeratorPermalink Reply by Mark Harrison on February 8, 2013 at 12:48am

Hi estebanflyer,

The two radios are used for two different things:

• FrSky for flying, from the transmitter ("remote control") to the aircraft.  The transmitter needs a FrSky module to transmit to the receiver on the aircraft.
• 3DR for telemetry, downlinked from the aircraft to the PC.  It's pretty much a replacement for the USB cable.

Both FrSky and the 3DR radio are excellent and I can recommend both.

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Permalink Reply by estebanflyer on February 8, 2013 at 7:32pm

I see!! Frsky is for flying and telemetry, while 3dr is only telemetry. great. thank you!

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DeveloperPermalink Reply by John Arne Birkeland on June 4, 2012 at 2:24pm

Having demonstrated a properly working failsafe on an expensive radio apparently being blocked by the APM PPM encoder behavior, could someone please explain this to me because I'm confused - this demo is in direct contrast to all the bashing I have received lately.

Not entirely true, the demonstration shows the PPM encoder having a design weakness by keep the last known value when there is a physical signal wire loss.

The price of you radio has nothing to do with it simply because the throttle channel of the receiver is disconnected, preventing any failsafe value from reaching the APM board. When the throttle channel is reconnected the Spektrum failsafe clearly works as intended again.

The only radio receiver I know of that supposedly stops sending a signal on the throttle channel (same effect as physical wire loss) is the 9X. And even here there are conflicting reports depending on firmware and receiver revisions. All other radio systems that I know of, will either transmit last known or failsafe throttle value when the radio is turned off.

So to make it clear. The design flaw (I will admit that, but it was by design for technical reasons mentioned in the failsafe thread) is only in effect when there is a broken throttle wire, or with certain 9X radios/receiver combinations having uncommon failsafe throttle handling.

Anyways, with the new firmware the wire loss/9X throttle problem should be solved.

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Permalink Reply by Chris Huitema on June 4, 2012 at 5:50pm

I have experienced this as well, had a loss of control that saw my quad fly away. I am on here almost every day and knew of the issue and have been following it closely, yet i still continued to fly with my stock 9x.

the wakeup was when i lost my quad, i was very lucky that when i walked (kinda running and panicing) to the way the quad dissapeared i got the signal back to the xbee's then after working out where it was from the GPS i drove till i got the video signal back too. found the quad undammaged on someones front lawn, luckily it didnt hit their BMW in the drive.

Who knows how far it would have gone if the battery had more charge left i guess i was lucky on more levels than one!

Since then i have modded my 9x and set the failsafes. and i guess another thing is having the xbee's and making sure the battery is secure so it doesnt get ripped off in a crash.

I have been considering getting a GSM GPS tracker, they are small and light, independant battery etc. 1 quick sms and it will send you a sms back with its gps position speed etc. they have about 48hr battery life (rechargable) and work almost everywhere.

http://www.ebay.com.au/itm/Vehicle-Realtime-Mini-Spy-Tracker-GSM-GP...

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Permalink Reply by Jake Stew on June 4, 2012 at 9:34pm

Another option along those lines... There are quite a few people on ebay selling "GPS trackers" which are simply Boost Mobile phones with a GPS tracking app (free).

From what I remember getting a prepaid Boost Mobile phone and using one of the free or pay apps is the cheapest way to do GPS tracking.  I haven't used them, but I think they're a lot cheaper ($35) and have longer battery life and better tracking capabilities (maps and internet location).

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Permalink Reply by Brad Hughey on June 5, 2012 at 5:05am

It would seem Zen's question about most stable/reliable/dependable gear has substantially been answered regarding R/C equipment.  However, I for one would like to know from this group what they think offers the most predictable baseline functionality for flight stability and fault-tolerance (or fault avoidance).

For example, I added the GPS and compass options to my APM 1.4 thinking that it would be interesting to play around with the navigation features at some point, but if those ancillary components increase the risk of anomalies in the basic flight control functions, should they be turned off?  Some have said that the DJI NAZA is a better turn-key control solution if you want basic stability and are willing to sacrifice some (most?) of the autonomy.  HK has a very basic unit too, and while it has almost no features at all, it's as cheap as dirt.

Let's face it: even in their most minimally functional configuration, these are complex devices, and it doesn't take much to send things askew during initial flying.  Perhaps it IS a good approach to vet the whole rest of the craft with a minimalist control solution before advancing to whole "tuning your loitering" thing.

What does that roadmap look like?  Is there a sans GPS basic stability configuration for the APM that removes most of the variables?  Should one start with the HK, and only if a stable hover can be established, then the APM should be implemented?  Is the DJI NAZA simply "the one to get", unless one DOES have a desire to extend the experimentation into the realm of true aerial robotics?

Considering the stated openness objective of both the APM platform and this forum, we owe it to ourselves to have a candid discussion of where the state of this art fits with the needs of the community.  If we don't have a fundamentally stable ship as a result of our efforts, nothing else really matters.

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DeveloperPermalink Reply by John Arne Birkeland on June 5, 2012 at 7:18am

The APM platform is by definition experimental. Meaning that new features and updates are constantly added. And as we all now, new features and updates means there will be bugs in the system.

The alternative is to have a stable branch with focus on code quality and a proven feature set. New features would be added much less frequently and only if they do not impact core performance and have been proven during extensive testing. More like how commercial products (from a serious manufacturer) is maintained. But a stable branch will not just spring into life by itself. it would require a lot of work making and maintaining. Compared to the experimental branch, development would move at a snails pace. And the resources required would most likely also affect general speed of development on the APM platform.

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Permalink Reply by Brad Hughey on June 5, 2012 at 7:49am

Mr. Birkeland: I agree with you completely.  In fact, I would even go one step further by saying that all non-turn-key solutions in kit form, and especially those cobbled together from piece-parts (frame from this guy, motors from someone else) are highly experimental.  

The guiding philosophy of "Do It Yourself Drones" perhaps is the question, and most specifically, what would provide the greatest good for the widest interests of the group?

Not everyone here is interested in bleading-edge robotics experimentation, where the risk of failure might be hundreds of dollars of lost investment.  I'd say Mr. Zen is just such an example.  Some are here to learn, experiment, and ultimately carve their own path to enlightenment, but I'm guessing they're a small minority.  Most want the functionality of a drone and are willing to put forth the integration effort to keep the price down below $5K USD.

A good analogy here is the manned EAA/experimental aircraft market.  Those folks aren't all aeronautical engineers, but rather pilots on a budget willing to devote lots of time to the project but not a lot of money.  The resulting product is still officially experimental, but not to the point where they have to worry about the wing shearing off in a 2G turn.

I am also not suggesting that DIYD (or 3DR) necessarily needs to have multiple coding paths for the APM; the basic "ultimate stability with training wheels" solution might not include the APM at all.  Rather, why don't we flush out what the options are, and the risks and benefits associated with each?

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ModeratorPermalink Reply by Mark Harrison on June 5, 2012 at 8:41am

Brad,  check out the Multirotor forum on RCGroups:

http://www.rcgroups.com/multi-rotor-helis-659/

Just about every multirotor controller project has a dedicated thread with lots of good information.  I've got a KKBoard (no hobby king version for me, this is back from when they were $150! :-/) and MultiWii, and it's been very interesting to compare and contrast the philosophies, designs, and flying results of the various models as you've said.

Here's the slides from a presentation I gave a while back... it was an arduino-centric group, so I included notes on all the above systems... you might find it interesting.

http://markharrison.net/drones/hackers-drones.pdf

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