Connected up the new XL-MaxSonar EZ0 (MB1200) which turned up in the mail today and I'm testing with the motors running and the motors off while holding it about 150cm off the carpet.First log attached is with the motors running. The sonar data starts off by going up to 700 and then as I pick it up with the motors running and carry it over to a clear area about 150 cm off the floor it goes down to about 50cm and spikes until I kill the motors and set it back down with the sonar hard against the floor. At this point it goes back up to 700.In the second log I did the same thing but without the motors running. This time it started off by going up to 360 and then as I lifted it up and carried it over to a clear area 150cm off the floor it seems to settle in at about 185 on the log and there are no spikes in the data while I held it there.The sonar is placed dead centre of the frame under the hub embedded in the foam and the two core shielded cable is about 12cm up to the APM pitot connector. ESC sit out at the end of the arms near the motor and all the high EMF noise gear is up the top away from the sensor.Needless to say my alt-hold while 2m off the ground went badly. Went up briefly followed by a decent to the ground and then up and down near the ground.Only thing I can think of is that the foam shakes too much. EMF issues just don't appear to be possible with the shielded cable not going near the noisy electronics.I will attach a long stand-off near the edge of the centre hub and stick the sensor on the end of that with two sided foam tape to see if that improves it.
Maxbotics also recommends that you use noise filters on the cable, so we may provide those with the sensor going forward. I think the things to really avoid are the ESCs, but there may be noise coming from the wires, too. Basically, these ultrasonic sensors are really sensitive to electromagnetic noise, so shield them as best you can.
I get very poor sonar readings when over carpet, but they become rock-solid when over a hard surface like paving/concrete/wood. I don't know if that's normal, as I haven't got my quad to a point where I have tried to use sonar-altitude-hold.
I normally fly over long grass, which I assume gives a worse reflective surface than carpet, but I've not looked at the figures for it yet either.
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http://code.google.com/p/arducopter/wiki/AC2_Sonar, Now it's rock solid.
Maxbotics also recommends that you use noise filters on the cable, so we may provide those with the sensor going forward. I think the things to really avoid are the ESCs, but there may be noise coming from the wires, too. Basically, these ultrasonic sensors are really sensitive to electromagnetic noise, so shield them as best you can.
I get very poor sonar readings when over carpet, but they become rock-solid when over a hard surface like paving/concrete/wood. I don't know if that's normal, as I haven't got my quad to a point where I have tried to use sonar-altitude-hold.
I normally fly over long grass, which I assume gives a worse reflective surface than carpet, but I've not looked at the figures for it yet either.
BUzz.