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Spektrum DX8 and AR8000 Failsafe setup

Posted by Crispin on March 29, 2012 at 2:30pm

I've been struggling to understand how to get the APM failsafe working properly and have yet to find some clear instructions that a noob like I can follow. It suddenly dawned on me how to get it all setup.

Here is my normal zero throttle output:

3689450214?profile=original

Here it is when the radio is off:

3689450232?profile=original

The AR8000 can be taught what to do if it looses contact with the mothership. The default is to leave or move the throttle to zero. As you can see, zero is normal and not enough to invoke the APM failsafe. (see here for more info on the APM Failsafe: http://code.google.com/p/arducopter/wiki/AC2_Failsafe)

What you need to do is tell the AR8000 to go below zero when the radio is lost and here's how you do it:

  1. Turn on the radio and go into servo setup.
  2. Find the throttle travel setup (on the DX8 it's the first screen)
  3. Scroll down to negative travel (Left hand 100%). Change that to as high as it'll go. 140% in my case.
  4. Confirm in Mission Planner that throttle input is now around 920uS
  5. Turn off radio and receiver.
  6. Insert Bind plug into RX and turn on.
  7. Remove bind plug from rx. Light should continue blinking.
  8. Ensure throttle stick is down.
  9. Turn on radio while holding down bind button. Radio should rebind.
  10. Turn everything off.
  11. Turn radio back on and change the throttle throw back to 100%
  12. Turn on quad and connection with MP
  13. Confirm that minimum throttle is back to around 1100.
  14. Turn off radio and throttle should now drop to around 920uS (or whatever it was beforehand)
  15. If not, start again.
  16. Now go to parameters in MP
  17. Find THR_FAILSAFE and set it to 1.
  18. Find THR_FS_ACTION and set it to 2 (1 = continue on Auto mission, 2 is RTL)
  19. Click on the write params.
  20. Click on Refresh to ensure it wrote it.

What you have done is told the receiver that when you loose contact, this is the new throttle position. It is of course, way lower than normal range. The low value is enough to trigger the APM failsafe which will RTL and land.

This all works in theory for me and MP seems to agree, I'll be out testing it tomorrow but just wanted to get it all down on paper so to speak.

Tags: ar80000, dx8, failsafe, spektrum
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Comments

  • Mike R. October 17, 2012 at 8:18pm

    Great post, Thank you! - I have a DX8 with a happy failsafe setup now..

  • Stephen R Mann October 17, 2012 at 7:22pm

    Wow - thank you.  This is exactly the information that I was looking for.  (Why this was never found when I searched for "failsafe" - frustrating).

  • Crispin September 7, 2012 at 11:35pm

    Hi Rick,

    I think there was already a log raised for it but it was a low priority. 

    Regards,

    Crispin

  • Rick Eis September 7, 2012 at 8:48pm

    Hi Crispin,  

    You said, "An idea might be to only enter failsafe if armed AND there is movement in the sensors (i.e. you;re in flight). Will add a note to devs."

    This sounds like an excellent idea ....  Did you send anything to anyone about this?

  • ootktk September 5, 2012 at 12:34am

    I thought of this last thursday but didn't implement it that night as I don't usually fly out of range. On friday I flew behind some telecommunication tower at close range and the inteference caused a signal loss when it was out of LOS, quad fell like a rock. Lesson to self: TRUST THE INSTICT

  • 100KM
    Hein du Plessis August 20, 2012 at 2:26am

    Ok, over the weekend I let it circle (for I guess 20 seconds..) and RTL kicked in. What an awesome thing this :)

  • 100KM
    Hein du Plessis August 15, 2012 at 6:15am

    Brilliant, makes so much sense now that I understand.. Thanks Crispin. I'm flyinf Arduplane, I don't seem to have a THR_FS_ACTION. Setting THR_FAILSAFE to 1 or 2, just causes it to go into CIRCLE mode, how can I get it to RTL?

  • Barry Nash June 1, 2012 at 12:32pm

    does anyone feel like going through the steps on a "Futaba FG8 Super"?

  • Crispin May 31, 2012 at 12:23am

    A worthy note. It did happen to me. After flying I had the quad in front of me on the ground and still armed (stupid, I know) and turned off the TX. It tried to shot up but due to low batteries, was rather sluggish and I managed to get my face out the way. Could have been interesting.

    An idea might be to only enter failsafe if armed AND there is movement in the sensors (i.e. you;re in flight). Will add a note to devs.

  • Knut Graf May 30, 2012 at 6:37pm

    One side effect to watch out for, with failsafe set to RTL, is that if you accidentally switch off the TX while your quad is armed, the quad will think "RTL !", and climb to come home. While that is exactly the desired effect in the middle of a mission, it is less so when the quad is sitting on the ground while you are fiddling with the TX (which should not happen, but might.)

    I tried this with the quad tied down, so nothing happened to man and machine. Always pay attention.

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