Sonar ALT_Hold Issue


Hello there,

Yesterday, i added a new senor onto my quad, MaxSonar MB1260 XL for better altitude hold. Before attaching and re-uploading the ArduCopter 2.7.3 onto the APM 2. I erased and reset the board. And then attached sonar as described in the wiki manual. And uploaded the code and followed all initial steps (Of course i enabled the sonar). Everything went smooth. 

Next step, time for test fly. It flew great in Stable mode. However, as soon as i toggled the ALT_Hold switch ON. Quad started acting strange. It kept climbing higher n higher and suddenly dropped out of nowhere. Luckily i managed to control by toggling the switch back to stable mode.

I have checked everything couple of times now. All connection looks good. Mission Planner looks ok. I don't know what the problem. Your help would be so much helpful. I have attached couple of videos below. Please take a look at them. If you need any other information let me know. Thank you.

Quad Setup:

  • DJI F450 Frame
  • HackerStyle 20-22L Motors
  • Turnigy TY-P1 25Amps ESC (Flashed with SimonK firmware)
  • ArduCopter 2.7.3
  • MB1260 XL - Sonar 
  • 4000mah 20C 3Cell Battery
  • DX7 with AR7000 
  • Using one of four ESCs to provide power to the APM 2. 








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  • @Kur,

    We saw your posting and wanted to offer some assistance also. As some have recommend, placing the power filler on the sensor will help your performance. This will help remove any issues from dirty power and ensure the sensor has a clean power supply which results in the most stable range readings.


    Also, we have noticed upon further investigation, there is a chance that the signal line from the sensor to the ADC may be getting noise injected on the line . This noise could be EMI from your radio controller, or electric motors or from running your signal line next to items that emit a lot of power or EMI such as a wireless send/receiver. We recommend using shielded cable similar to the MB7954 that we sell. One consideration is to ensure you do not solder the shielding at the sensor end, you only solder the shielding at the ACD end. You can follow the recommended connection method as displayed in our diagram at this link


    @ R_Lefebvre You made a statement that you have never gotten the sensors working and that you don't understand. We would like to work with you to find the solution that will allow the MaxSonar sensor to work on your drone and others. Once we work through your specific issues, we would like to complete a detailed writeup on what it takes to use a MaxSonar sensor on a Drone. We would like to work with you to provide some detailed information on the why things have to be done a specific way in order to attain success. Please contact me at so I can assist you with finding the right solution.


    If anyone has any questions, please feel free to email me at


    Best regards,


    Scott Wielenberg

    Technical Support & Sales of MaxBotix Inc.

    Phone: (218) 454-0766

    Fax: (218) 454-0768



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  • I've had success using aluminium foil as a shield around the cable. It also helps to keep the sonar/cables away from any of the high-current lines and ESC's.

  • I've used an MB1260, and now an MB1200.  I've used that sonar mount from 3DR.  No luck.

    I even bought an MB1240 for it's noise rejection, but haven't tested it yet.

  • i have the same problem with you.  I m using MB1260, when i switched to alt hold, the quad raise continuously.  I will going to buy 10k resistor, 1500uf 6.5v cap and shield 3pin cable to replace it.  Let see did it improve!

  • I've been pulling my hair out trying to get my MB1200 to work as it should.

    So far I've added a shielded cable, ferrite cores on both my 3DR radio and 5.8ghz video transmitter. (The ferrite cores did the most noticeable change for me.) I've yet to implement the power supply filtering but I am assuming that I should do that as well. Just need to find the time to do it.

    A problem I had once was the quad continually rising as you described. I didn't fly it, I just left it on the ground, and looked at the telemetry data. Without even moving, the height started at 0.2m and slowly crept upwards.

    I then checked the Sonar in CLI and realised that the Sonar was reading a constant 7+m distance, i.e. it was faulty. I resoldered the connections and it worked as it should again.

    My most recent flights in Alt hold mode seemed OKAY at slow to moderate speeds... but once I made the quad fly faster then it would dip down and touch the ground. I just crashed my quad yesterday trying a low altitude (<5m) FPV flight over an undulating terrain. The quad didn't correct for the changes in the terrain and hit the ground.

  • I agree with R_Lefebvre. My best solution for the sonar was to remove it from the system. Last time I trusted it I was testing loiter, it was working alright until suddenly as soon as I turned loiter on the quad plummeted to the ground. my best altitude hold is my throttle stick.

  • airmamaf, Good catch. You were right. Both cables were touching the carbon fiber plate. I have added rubber washer. Now they are not touching the plate. However, i still didn't get to fly today since it was raining. So i couldn't say, if that was the issue. 



    Geoffrey, Thanks. ;) I already have listed all the details here. But i will message you all product links. :) Lets keep this blog on the track so people can refer to it in the future. 

    R_Lefebvre, Yucks!! :( Many people are having this issue with their sonar sensors. I hope, its the hardware not the software. BTW, which sonar sensor are you using? I am gonna buy this Sonar Mount because i think, my sensor is very low to the ground and it could be the problem. 


  • You know, all this being said, I have NEVER been able to get the sonar to work.  I just don't understand.

    I just checked my latest data, thinking it must have worked finally, and nope... still no go.  the data is just pure garbage.  I've got the filter, the shielded wire, and now it is riding on my vibration damped platform on my quad.  The platform has ZERO vibration, no jello video on a Contour HD.  And it's just garbage.

    I just don't get it.

  • Hi Kur, Sorry this one is off topic, kindly provide details of your build (motors, props, esc etc ) and where you bought them cause I am interested in having a similar setup. How much pay-load does it take. I liked your quad!

  • Maybe a simple reason, carbon is conductive and your carbon plate touch gnd and vcc of your sonar ... so there's a shortcut

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