Got a very strange one here that I am hoping somebody will have encountered before.
This project uses an 8" cube with a brushless electric ducted fan (EDF) as a thrust source. I have an MPU-9150 to keep the balance. The EDF is powered by two 3P lipo batteries, controlled by a Turnigy AE-100A Speed Controller with BEC. Because of suspected interference caused by the ESC when the EDF is powered up, I put everything else on a separate 3rd battery. So the micro servos that run the directional fins, the Arduino, and the radio receiver are all powered by a separate battery with a Pixnor Multirotor Power Distribution Board providing the power to everything. There is even a large 12V relay that is operated by a switch to provide power to the EDF so that I do not have to keep plugging/unplugging a battery connection. The input to the ESC is just the signal and ground (common ground between the ESC and the Arduino) so the BEC of the ESC is not even being used.
When I power up and calibrate the 9150, I am getting degree readings on two planes of very low values - e.g. it is on a flat surface. As soon as I power up the EDF, the readings go crazy.
Attached is a text file showing the output of the Arduino. The column that starts 26(LJUD) is the value read from the RC Left Joystick Up/Down, which is the thrust control of the EDF, so you can see when that goes above my activation value for the EDF of 80 is when the EDF is being kicked in. In the beginning of each line are the angle readings and if the cube thinks it is flat (+/- 5 degrees from calibrated flat) the word UP is at the beginning of the line. When I powered up the EDF, I was holding it down to the table, so the angle of the cube never changed (other than small vibration amounts). The angular readings from the 9150 MPU go crazy! I even have it taking an average of the last 3 readings to try to smooth the transitions.
So the question is, am I still somehow getting an electrical feedback from the ESC, or - since the EDF is brushless and drawing as much as 100A when it is at full power - could it be giving off an electro-magnetic interference that is screwing with the MPU?
I am attaching a picture of where the MPU is in the cube. It is hard to tell the depth with one picture, but the ledge/platform the MPU is mounted on is at the very bottom of the EDF where the air is coming out; but it is nonetheless only about an inch away from the housing of the EDF.
Thanks for any suggestions you may have!
Problem_Readings.txt (2.6 KB)