I have been reading with interest the sonar usage (right sensor, etc.) because I had already purchased the previously recommended sensor (EZ0) but had yet to add it to my quad. After reading the posts by Maxbotix and others, I went ahead and took the plunge. I added a 100uF capacitor directly to the board (photo above) as recommended and put a 100ohm resistor on the +5V line.
I created a cable and hand-braided it in an attempt to eliminate as much noise as possible. I know Maxbotix recommends a shielded cable but I didn't have any. The cable is also a little too long. I also temporarily mounted it to a paint stir and put it on the opposite side of the air-frame from the receiver. But as you can see from this photo, it is darn close to one of the prop tips too. But enough of that - how did it perform?
Here is the result of a test flight in pretty high wind.
The red is the sonar height, the green is the barometer height. At no time did the actual height get above 10m during my test.
First, I am continually surprised at how accurate the barometric height is. Second, the sonar trace has some decent readings for much of the flight, but sometimes is has crazy readings. I can't tell exactly what is going on here yet, but I'm going to track it down. I know the sonar I have is ultimately too sensitive and is probably picking up things like the mailbox (which was certainly nearby). Additionally, I wonder how likely it is to be hindered by heavy winds?
I'm going to do some more testing soon. I want to shorten the boom to get it further from the prop. If anybody has any testing methods they think are good for sonar units, please let me know.
Comments
Scott, I would recommend that you put in the recommended 10 ohm resistor as that is what makes it an R/C filter circuit that is tuned to effectively damp particular frequencies of electrical noise that are picked up on the power leads. 1/4 or even 1/8 watt carbon is sufficient as power draw is minimal.
@Tom - I read that and modified my MB1000 with the recommended power filter circuit as seen in the photo (well, except for the resistor). Since I had already purchased it, I wanted to give it a try rather than buy the MB1240. Of course as Gary has said it might not be worth it. If I can't figure out some way of making the MB1000 more effective I will give up.
@Hugues - I would like to see the sonar data graph from this if you've got one.
@Christian
Hello, this is Tom Bonar from MaxBotix.
Christian, the article also applies to fixed wing UAV's with the biggest change being the direction of the prop wash. Unlike a multi-copter with vertical prop-wash, a fixed wing UAV will have horizontal prop wash. The MB1240 is the recommended sensor for both fixed wing and rotor wing (multi-copter) UAV's.
Our engineer's haven't tested the sensor on a fixed wing UAV, however they have stated the sensor they recommend is still the MB1240.
Please let me know if you have any questions.
Best regards,
Tom Bonar
Technical Support
of MaxBotix Inc.
Phone: (218) 454-0766
Fax: (218) 454-0768
Email: thomas@maxbotix.com
Technical support and sales are subject to
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website at http://www.maxbotix.com/ MaxBotix,
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Hello,
I have tried to follow Maxbotix recommendations (although I have the MB1260 which apparently is NOT recommended by Maxbotix, should have bought the less expensive MB1240).
I have moved the sonar to the bottom quad plate as far as possible from prop wash and ESCs.
I have shielded the cable with special EMI cable.
I then took a plastic drinking cup that i cut in half. I layed a thick aluminium sheet alla round it. The sonar is placed inside it (and the cup upside down to face the ground of course).
Then to follow the recommendation about noise and wind that could impact the sonar's measurements, I placed a microphone foam shield around the sonar itself.
This is the result in pictures :
First picture shows the "aluminium cup shield" :
Second picture shows the sonar inside the "cup shield":
Third pictures and following show the installation on the quad to avoid prop wash and be as faraway fro mother interfering electronics:
View from bottom of the quad :
View from above: (yeah I have lots of foam to protect my quad from me learning how to fly it... it is not an EMI shielding device ;)
Talk about technical support!
Is that article applicable to fixed wing aircraft, at least to an extend? Are there different considerations in that case?
Having read your tutorial (thx for that) I ordered an MB1240 some days ago. If the weather permits, I will mount it tomorrow and see what it does. We have only flown MB1200s until now, which we still had in use from two years ago.
Hello, this is Tom Bonar from MaxBotix Inc.
I saw your forum post and would like to lend some input. Like stated the MB1240, MB1340, and MB1242 are the only sensors that we recommend for UAV applications. We do not recommend the MB1200 or the HRLV-EZ series of sensors. The MB1200 is the most sensitive sensor that we sell, and because of the sensitivity it is the most likely to have interference. The HRLV-EZ sensors is not able to handle the high noise floor that UAV's tend to have between the motors, vibration, acoustic noise, etc.
If the MB1200 is to be used, it is highly recommended that the sensor is mounted as close to the center of the frame as possible. This will help protect the sensor from prop wash, and long runs of cable that can transmit EMI into the sensor's power or return signal.
If you haven't already read our engineer's evaluation of using a sensor on a UAV, I would recommend it. The article can be read here, http://www.maxbotix.com/articles/067.htm.
Please let me know if you have any questions.
Best regards,
Tom Bonar
Technical Support
of MaxBotix Inc.
Phone: (218) 454-0766
Fax: (218) 454-0768
Email: thomas@maxbotix.com
Follow us on Facebook at: http://www.facebook.com/pages/MaxBotix-Inc/125159384204938
Technical support and sales are subject to
the terms and conditions listed on our
website at http://www.maxbotix.com/
MaxSonar,EZ0, EZ1, EZ2, EZ3, EZ4, AE0, AE1,
AE2, AE3, AE4, WR1, WRA1, and WRLA1 are
trademarks of MaxBotix Inc.
Based on previous experience with the EZ0, for indoor use and another application, I 'd like to add:
The sensor behaves differently against surfaces of different texture. I believe that more rough surfaces give better responses, because they diffuse refractions better.
Thus flying over grass may result in better results than flying over concrete.
@Scott, I mentioned a specific instance, the medicine cup is thin stiff plastic and when it vibrates from external sound or mechanical vibration it actually produces sound itself.
I am sure if a softer plastic or more rubber like (sound damping) enclosure / horn could be provided it would actually help rather than compound the problem.
@All, However the main thing is switch to a EZ4 or 1243 type SONAR I know you already bought one of the others from 3DR but for multicopters at least they just won't work right and you will be chasing your tail.
You really need the higher noise rejection and narrower beam of the EZ4 for the uniquely noisy environment of the Multicopter.
And, unfortunately it really needs to be mounted as nearly under the center of the multicopter as possible to avoid prop wash turbulence noise.
Really hard to make that work with stabilizing / tilting under slung camera mounts, I know.
The best solution is to get rid of the noise, not learn to live with it.
BTW excessive prop noise (stalled props from dropping fast then hitting high throttle for instance) really tend to make these things spike.
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