Thread: Discussion G sensor not reading correctly
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Old Jan 29, 2013, 09:18 AM
BobW99 is offline
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I wrote this before seeing your post. It explains everything.

OK I have done a bunch more testing and figured out the problems. If I am wrong on this I will surrender my engineering degree to Eagletree.

All tests were run using a 2 pole, 2100 Kv motor running at 7.5V. Expected peak RPM = 15,750

First the Brushess RPM Sensor
I have compared brushless RPM measurement between Flight and Ground mode and get different measurements between modes. I suspect there is an issue with the post processing of the signal in car mode since changing the number of motor poles in car mode has absolutely no effect on the output RPM. In flight mode changing the number of motor poles has the expected effect.

Flight Mode Motor RPM = 16,200 RPM
Car Mode Motor RPM = 13,200 RPM

Now for the Optical and Hall effect sensors. There are two issues here. First the Number of magnets or light strips entered in while in Car Mode has absolutely no effect on the RPM calculation. This is the same issue noted above for entering the number of poles for the Brushless sensor. Both sensors work perfect for the values entered in Flight mode. The good news is if you are using two magnets with the Hall Effect the measured RPM is correct. For the optical sensor the RPM will be Ĺ of the actual.

The next issue is two of the radio buttons for selecting the location of the optical or hall effect sensor are reversed. If your sensor is located on the spur then select the radio button for sensor mounted on motor/pinion. If your sensor is mounted on the motor/pinion then select the spur. This will produce correct RPM and speed readings. If you sensor is mounted on the axle then selecting the Axle radio button will be produce correct readings.

I installed my old hall effect sensor with two magnets mounted on the spur and I get correct readings using the above procedure.
Motor RPM = 16,200 RPM
Speed = 47 kph

Saving g sensor readings does not work in car mode. It works fine in flight mode. It would be nice to be able to look at Zaxis readings in Car Mode since the data is already there.

Thatís all for me. I can fudge the output to get correct readings now. Hope this helps someone else.
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