Today I'm test sonar my Arducopter in ALT Hold Mode. I use USB HUD cable (Have Shield) connect to Pitot port IMU and receive signal from AN (pin 3) the Sonar. It perfect not noise in test.
Now, I use code ArduCopter2.0.39b
Wiring shield to ground at Sonar.
And connector to Pitot port IMU.
Installer to sonar mount under main frame.
Red line is Sonar Alt , Green line is Baro Alt
Comments
I have two of the Maxbotix MB1240s and I have used shielded CDROM cables to transfer the signal from the sonar to the APM2.5. I also installed the recommended resistor/capacitor power filter right at the sonar connector. This has resulted in a reasonably noise free sonar signal. This blog post shows how to install a connector and power filter on the sonar input: http://diydrones.com/profiles/blogs/sonar-quick-connector-and-power...
Regards,
TCIII
Old conversation I know, Twisted pairs would help a little with the power line, but not so much with the signal line. You would be better off with a shielded cable salvaged from a broken usb hub or microphone cable, etc.
I just solved my last remaining sonar noise issues and it turns out the last problems that persisted were caused by the sonar location too close to the power distribution wiring, in spite of shielded cables. Locating the sonar properly (far from power wiring or ESC's or oriented so that equal emissions are received from opposing current flows) is just as important.
What're you have sonar graph ?
Becuase, I be used ferrite cores but It have some noise. TT_TT
A real shielded cable is of course the way to go.
I just wonder...
Can any of the electronics guru´s tell us if a twisted three-wire lead would give the same or sufficient shielding effect?
Twisted servo leads is a common technique used in the RC world and said to diminish RF interference in longer leads by a cancelling effect. Many also use ferrite cores that the servo leads are wound through a few times.
Twisted wire example Ferrite core filter example
It's work.
I use a shielded Microphonecable as well :)
I use cable shield from old USB Hub. I'm solder Shield line to GND in sonar and IMU Port (Pitot Port).
When, I change ALT Hold Mode. It high performance and rather Stable level. Yeah !!!!!
In Log I change ATL Hold Mode in period 1200 - 2200 line number on the graph
That looks really good - it is so important to use the sonar/baro alt logging function to check your sonar noise performance and not just trust the CLI's sonar values. Until my sonar's plot matched my baro plot like yours does, I was getting very intermittent alt hold performance.