Hi guys,

I have a brand new MB 1200 sonar, but I cant seem to get it to work. What happens when I flick the Alt Hold switch at low altitude, (~2m) is that my quad will rise slowly and then at about 10m then the motors slow down and the quad just drops.  I have attached a log file from that flight as suggested by Randy and it seems that the baro and sonar readings don't tally.  Do I have a bad sonar? II have already installed the resistor/capacitor filter and use a 2 core shielded cable to connect everything up. And yes, I did choose the correct sonar in APM Planner.

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Your sonar is not working.  

Have your APM plug into the computer and look at the Flight Data screen.  In the Status tab, you should see the parameter updating live.  Look at the "alt" and it should starts at 20 (cm).  Move your sonar to point to a different places and see if that number update.

Hi Wesley,

Yes the 'alt' reading updates from 0.2 and varies when I point the sonar around.  It also changes from 20cm onwards when I use the CLI test-sonar function.

But according to your log file, as seen on the pic I posted above, it was not working at all.  If you have no problem doing a static test, it could mean that the power providing to the sonar is still not clean enough, or simply just not enough.

You can try again and do some very simple hover to a couple of meters high, and then land.  Download the log file and look at the Sonar Alt line.  You should see the line starting from 20, all the way up to a few hundreds, and then back to 20 when you land.

It should look something like this:

Is that your log from the MB1260? (XL-EZLO)

I could never get mine looking like that!

Yeap.  The MB1260.  Now that I have a separate power supply to the APM2, the signal are super clean.  It helps big time on the OSD as well.  Very sharp and clear pictures.

EDIT: but it is very sensitive.  It can pick up a log or a rock on the ground and cause the heli to jump up.  lol.

Hi Wesley,

I flew at low altitude and saw no change in the altitude in the log and tlog files. The graph stays at 20cm.

Thanks for you suggestion. I am powering the APM with one of the ESCs. I will put on a separate BEC for the board tonight and test tomorrow. Will keep you posted.


Yeah!  Thanks Wesley,  the separate power supply did the trick.  The low altitude hold now is rock solid. Do you think that shielding the baro with cotton wool of sponge will reduce the motor pulsing at > 10m?


gz!  :)

It depends if your baro is being affected first.  Plot the baro and see if it follow the Sonar Alt and see if it's close enough.  Mine is way off and highly affected by my blades.  I'll have to create a case surrounding it later on.

I just ran across your post.  I am glad that you have gotten the sensor working well on your quad.  As you had found, clean power is very important to our sensor. Checking the power to ensure it is strong, stable and clean is our first recommended troubleshooting step.  We have provided some recommended solutions by clicking this link http://maxbotix.com/articles/035.htm. Your solution of a separate power supply is a great solution.  Provided the power is clean, the XL-MaxSonar-EZ sensors have a very high noise tolerance which can be read about in our noise testing.  You can click this link http://maxbotix.com/articles/012.htm to view the noise testing data. Also, we recently released a series of I2C interface sensors that were designed with the DIY Drones community in mind.  You can click this link to view the sensors http://maxbotix.com/Ultrasonic_Sensors/I2C_Sensors.htm
@Wesley Chuen 
Exactly! The MB1260 is a very sensitive sensor and is designed to detect even tiny targets out to significant distances.  For some UAV users this is ideal because they hover over soft targets like tall & thick grass and in this instance it can provide better detection.  Many other users prefer the MB1240 because it is better suited for large targets and is more noise tolerant.  The best balance is found in the MB1220 or if you want an I2C sensor the MB1222.


I you have any support questions, please don't hesitate to send me an email.  


Best regards,

Scott Wielenberg
Technical Support & Sales
of MaxBotix Inc.
Phone: (218) 454-0766
Fax: (218) 454-0768
Email: scott@maxbotix.com

Could u explain how you set up a separate power supply for the 1260? I am getting 4.87 volts at the sonar, but it doesn't seem to be working. In the terminal screen test it shows a constant 438cm.


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