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Home lock position question

Discussion in 'Phantom 2 Vision + Discussion' started by pjw73nh, Jun 16, 2014.

  1. pjw73nh

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    When (if at all) does Home Position get blanked, or reset?

    For example, I get home lock at "flight area #1" on Saturday, (fast flashing green then slow flashing green) and fly for a half hour. Then power the battery down, take it home, and go to flight area #2 a few miles away on Tuesday.

    Questions.

    1. Did the home position get erased when I powered down on Saturday at flight Area #1? Or is it held in some kind of NVRAM within the phantom or controller?

    2. If on Tuesday, I didn't get enough GPS sats for home lock (fast flashing green), and only got the slow yellow, is my home position still "flight area #1"? If not what (if any) IS my home position ?...

    3. What is RTH behavior in the situation proposed in #2?

    Thanks for your patience with these questions. I have read all manuals cover to cover numerous times, and viewed many videos and still can't seem to get ALL the details I am seeking.
     
  2. pjw73nh

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    Geert, I appreciate you taking the time to reply, but I don't see any direct answers to any of my questions. I worded them as simply and specifically as I could, because the answers to these questions would significantly increase my understanding of the flight systems.

    I HAVE read the manual. Several times as noted in the last paragraph. If I have searched the manual a dozen times and can't find the information, I have to find other resources. I thought this forum would be one of them.

    In many instances, the manual is not clear. For one, the authors interchange some of terminology throughout the manual making it confusing for a person new to automated flight to follow.

    For example is home lock the same as home position?
    Is the abbreviation Tx the same as controller?
    Is non-GPS mode the same as ATTI mode (whether attained automatically by lack of less than 6 GPS sats, or manually in NAZA mode and switch S1.

    You are correct, I DON'T UNDERSTAND HOME LOCK. THAT IS WHY I AM ASKING THESE QUESTIONS.

    Thanks to some of the folks in this forum, I am just starting to grasp some of the differences of GPS and non-GPS mode.
     
  3. pjw73nh

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    Thank you. That helps a lot.

    I understand this, but isn't home lock (above) just a manual means of setting home position (NAZA-M mode and S1). Or does it mean something else?

    I have no intention of flying in NAZA-M mode until I am very proficient with the craft in Phantom mode..

    Yes I do understand the Tx vs controller terminology, I was just giving examples of why the manuals can be confusing.


    Thanks.
     
  4. AnselA

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    No (re)setting home point (position, location) can be done as manual tells:
     

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  5. RPA

    RPA

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    I'd certainly emphasize the "OR MORE" bit. I won't be at all surprised if people start checking to make sure I'm alright while I'm doing this. I must look like I'm having a seizure or something.

    I've tried slow and steady, fast and frantic and all the procedures between but it's not obvious which works. Usually it just kicks in for no apparent reason.
     
  6. Dirty Bird

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    #1 is an interesting question, for which I do not have a definitive answer. To my knowledge, the Home Point location is NOT saved, however, there IS a small battery on the GPS board photos I have seen. This battery may be used by the GPS exclusively...perhaps for an onboard clock, or to maintain ephemeris data? Personally, I would want to allow the Phantom to obtain a new Home Point each and every time you fly. Else, what if you are flying in Kansas today, but flew in Maryland yesterday. Its gonna open up a big case of "SUCK!" if she decides to fly home to yesterday's Home Point! :shock:

    2 - Since I do NOT believe the Home Point is retained through power cycles, it means you won't have ANY Home Point, and you will be utterly homeless. Wait for enough satellites to set a Home Point ***BEFORE*** you take off!

    3 - If there is no Home Point set, I am not sure how she will behave. Will she just "land only" where she is, or fly to some undefined Home Point? You might want to peruse the user manual a bit and see if these scenario is defined?

    I apologize for not having a definitive answer. I strongly suggest you ALWAYS achieve a fresh satellite lock, with a bare minimum of 6 (preferably 7) satellites locked. Its an expensive gadget to lose.
     
  7. AnselA

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    But what happens if home location is not set (due to lack of enough satellites) and P2 is flown in non-GPS mode? Which value P2 memory have for home location after power up? Uninitialised variable values should not be used and home lock mode should not be allowed. RTH triggered by lost TX/RC signal is more problematic, what P2 can do? It does not know where it is and where it should return.

    EDIT: if not 6+ satellites in failsafe procedure, it just descends.
     
  8. Dirty Bird

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    What Geert was explaining to you is there is a difference between your Home Point (the location your Phantom considers Home) and Home Lock, which is one of the auxiliary features available in NAZA mode. In NAZA mode, S2 offers three control modes:

    Position 1 (up): Heading Lock - Right stick control inputs are locked to the physical FRONT of the Phantom.

    Position 2 (middle) Course Lock: Right stick controls are linked the the Phantom's nose direction when compass heading is read (first rapid green flashes in NAZA mode). i.e. If the Phantom's node is pointing due North when compass is read, Right stick FORWARD would direct Phantom North, right stick BACK would direct her South, etc.. The direction occurs REGARDLESS of the Phantom's orientation.

    Position 3 (down) Home Lock: Right stick FORWARD move Phantom AWAY from Home Point. Right Stick BACK brings Phantom back to Home Point. These movements occur REGARDLESS of Phantom's orientation. Home Lock does not function within 10 meters (or feet...can't recall off the top of my head) of the Home Point, and the aircraft reverts to Heading Lock within the 10 meter area.
     
  9. Dirty Bird

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    I agree completely that this would be problematic...there would be NO home for which to return! That's why you should NEVER take off without allowing a Home Point to be recorded. If you do, pray you don't lose control as I don't know what would happen to your Phantom in such a situation? I believe it simply lands where it is, but I am not 100% of that?
     
  10. Dadcat

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    #1 - Just to be clear, the Home Point is definitely not saved when the power is shut off. You're right about the battery on the GPS board. It's there to keep satellite data in battery backed RAM when the main power is off. Unfortunately the batteries tend to be dead on arrival. It's supposed to be between 1.8 and 3.0 volts. When I checked, mine was 0.014 volts. The battery is spot welded in place so not easily replaceable. I think there is a slim chance it's some sort of rechargeable battery intended to backup GPS RAM for a couple of days, but I doubt it since I had flown the day before I got the dead reading on the battery.

    #3 - Yes, with no Home Point set, it will start down from the point the control signal is lost. If there's no wind or if it has acquired the minimum 6 satellites after takeoff it will go straight down. In a wind, if it's currently seeing less than 6 satellites, it will be blowing downwind while descending.

    There is a corollary to point #3. Even if you had 6 satellites and a Home Point set before takeoff, if it drops to 5 or less visible satellites the Phantom goes into "Ready to Fly non-GPS" (which is identical to ATTI). In even a fairly mild wind, if you're looking at the screen instead of the bird, that thing can be a long way off before you notice and can respond. I've seen this happen but I caught it before it was out of sight over some trees - just barely.

    I personally think the default "Phantom Mode", with different names for identical flight modes than what they are called in "Naza Mode", just creates unnecessary confusion. The assumption on DJI's part, that new buyers of these things are too dumb to follow an instruction like "Put both switches in the Up position" is ridiculous. That is exactly the same thing as "Phantom mode", but with more control options to get yourself out of trouble.

    Well actually there is one significant difference between "Phantom" and "Naza". The LED flashes while flying are different so you have to download another manual just to find out what those mean.

    I sympathize with those who have read the manual, and have difficulty sorting out things like the difference between "Tx", "Remoter Controller" and "Controller" (Hint- they are the same thing). I had the same problem and this isn't my first rodeo.
     
  11. pjw73nh

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    Thanks for the replies. I just got to thinking. And I apologize if my over analytical mind is making this more difficult than it needs to be.

    What happens in this situation?

    1. Home point successfully recorded before initial take off. Then start flying.

    1a. If RTH/failsafe is activated, it should fly back to recorded home point. Correct?


    2. While flying, the phantom loses GPS for say 60 seconds. I still have control of the bird, it's 1000 feet away.

    2a. If RTH/failsafe is activated, it will just descend and land wherever it happens to be, drifting with the wind while doing so.


    3. Let's say it "re-acquires" GPS mode while that far away.
    3a. Will it record that point (1000 feet away) as a "new home point"?

    3b. If so, can I assume that if RTH/failsafe is activated, it will then fly to that NEW home point and descend (still in the newly acquired GPS mode)?

    Thanks
     
  12. Dirty Bird

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    1/1a - Correct.

    2/2a - Correct.

    3a-b - If it reacquires GPS lock it will NOT record a new Home Point. It would then return to the original Home Point.
     
  13. pjw73nh

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    WOW !!!! Thanks DB. If that is the case, I am guessing the software is smart enough to NOT set a new home point when it loses and re-acquires GPS in flight (unless done manually via S2). That is would have to be grounded when it re-acquires GPS to set a new home point.

    Thanks.
     
  14. Dadcat

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    That's right. You actually have to cycle the power off/on and reaquire 6 satellites to get it to reset the home point (other than using S2).

    It probably says somewhere in the manual that you should land before turning the power off.
     
  15. Navman

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    Something that was explained to me on another thread here.

    I've had to lift off with only 5 sats. but acquired more after lift off.

    When Phantom gets 6 sats. it blinks fast green thus setting a home point (to return too)

    In the case of a 5 sat. lift off, better to go straight up as the home point will then be straight down from where it lifted off.

    Do I understand it correctly?
     
  16. Dadcat

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    That's right. Just remember, if it drops below the 6 satellites later during the flight, it will not be using the GPS for anything. Let's say you climbed to 100 feet to get that home point set (using S2 I assume). If you later do an RTH with 6+ satellites in view, it will climb to 166 feet, fly back to that home point and then descend. If it drops to 5 satellites on the way down, let's say at 90 feet, it reverts to ATTI (Ready to Fly - non GPS) so will be subject to wind currents for the minute or so it takes to reach the ground. You need to be prepared to take control.
     
  17. Navman

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    Thank you from Canby Oregon Dadcat!
     
  18. Dadcat

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    I want to correct my earlier statement about the GPS battery:

    I had read somewhere that there was 3 volts or so on the battery when the main power was on. I'm thinking, you would never do that with anything but a rechargeable battery. It was raining yesterday so I opened my Phantom up to check.

    Yes, it is a rechargeable device. That's why it's spot welded in place. I first tried leaving the main power on for an hour. It took almost 4 hours for the ram backup battery on the GPS board to go below the spec'd minimum of 1.8 volts. A more realistic test was turning the power on for 7 minutes. After 10 minutes there was still 2.4 volts.

    I'm not sure the thing is even a "battery". It might be some kind of capacitor, though it does take time to charge more like a battery and it looks like a hearing aid battery.

    This means that things like satellite positions and track data are maintained in RAM for a period of time, allowing faster acquisition of a GPS lock following a power interruption. The specs for the GPS receiver say 1 second to first lock if the data is in RAM. It also explains why a home point gets set faster after the first flight. It just doesn't save the data until tomorrow.

    Sorry for the earlier misinformation.
     
  19. Tails_Up

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    I've had a similar situation. Launched in a small clearing, barely got six and launched. Lost one while about 6 feet up and it dropped into ATTI mode (I was in Phantom mode). A little breeze (plus idiot at the controls) and it's going all over the place. Didn't end well. Moral: Launch out in the open.
     
  20. ElGuano

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    Home position is never saved between power cycles. If you restart and launch without it, it will be null until such point it acquires 6 satellites, when it will automatically bind. If you rush your launch in an area without clear view of the sky, it could very well mean you unintentionally lock a home point you don't want.

    The gps battery saves almanac and ephemeris data from the satellites, and NOT gps positional or Naza data, so it does not persist home point or anything related.