Espritmodel.com Telemetry Radio
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Old Mar 05, 2008, 08:47 PM
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Brushless RPM Sensor FAQ

Q: I am seeing erroneous readings my Brushless RPM sensor. What can I do?

A: There are three classes of problems that can occur with the brushless sensor:

1) Erroneous readings that result from the "song" that the ESC causes the motor to produce, normally at powerup, but sometimes whenever the throttle is opened. This should NEVER have an effect on the readings when the motor is actually spinning. If your motor is playing a tune or beeps during startup, this will show up as readings on the brushless sensor, even though the prop is not spinning. The firmware attempts to screen these out of the logged data, but this is not always possible. If you are seeing RPM readings due to the song at powerup, one way to eliminate it is to use the "logging triggers" option. You can set a logging trigger that will not log if the current is below a threshold, or you can set a time delay trigger that keeps the unit from logging for a few seconds after powerup.

2) If you see constant, non-zero RPM readings when the motor is not turning, but no song is being played, most likely your ESC is sending brake pulses to the motor. The brake pulses show up as non-zero RPM. The firmware again attempts to screen these out of the logged data, but this is not always possible. If you see these, and you have ESC braking enabled, one solution is to set a "don't log until X amps" logging trigger which will keep data from being logged at zero amps. Again, this problem should NOT affect logged data when the motor is actually spinning.

3) Spikes or dropouts when the motor is actually spinning. This is a more complex issue, and we can most likely resolve it for you, but need to collect more data from you. Email us a .FDR file at support@eagletreesystems.com.
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Last edited by billpa; Mar 05, 2008 at 10:23 PM.
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