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Old Mar 04, 2013, 10:20 PM
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Brushless RPM sensor false readings

Hi. I bought am almost complete suite of EagleTree electronics recently. I finally got everything installed today and was doing the first OSD testing. Everything appears to be working fine except the RPM sensor, which is periodically showing a non-zero figure (~3-4k) while the motor is off but armed. Now, I read the FAQ and it suggests either the arming tones or brake pulses, but this is well past arming and I have all brakes off (plus its not that regular). One weird thing is I can force it to "blip" by engaging AUX2. Whenever I use the AUX2 switch, the blip happens. But I don't need to do that... just sit and wait and it will do it (non consistently) every say 4 to 20 seconds. Thoughts?
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Old Mar 05, 2013, 11:00 AM
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I am also getting spurious RPM readings with the brushless rpm Sensor plugged in but not hooked up to a motor and only a battery has been attached to eLogger V4 and no ESC. Just found it doing a battery "test" recording. Appeared on all battery tests with both 13+ volts and 21+ volts input.
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Old Mar 05, 2013, 02:25 PM
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Hi, are these pulses happening outside, or indoors? If they are happening indoors, and especially when connected to a PC, they are most likely AC line noise (either 50Hz or 60Hz) that the sensor is picking up. There is some line noise filtering in the eLogger firmware, but it is not able to filter it all.
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Old Mar 05, 2013, 11:11 PM
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In my case it was a field test... not hooked up to a PC.
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Old Mar 06, 2013, 08:33 AM
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Mine was not connected to a PC, just setting on my kitchen counter.
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Old Mar 06, 2013, 02:31 PM
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s_mack, do the pulses occur if the ESC is unarmed? If not, most likely the ESC is generating some noise pulses when armed that the sensor is picking up. One additioanl thing to try would be to use both sensor wires (one per motor pole) if you are not already, or try disconnecting "wire 2" if both are connected.

Ken, what are the values of spurious readings you are seeing? If they continue outside your house, and the readings are greater than the normal readings your motor produces, you can click "Advanced, Set Min/Max Values" and cap the RPM value to the max that you would normally see. This will hide the spurious pulses.
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Old Mar 06, 2013, 11:43 PM
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Quote:
Originally Posted by billpa View Post
s_mack, do the pulses occur if the ESC is unarmed? If not, most likely the ESC is generating some noise pulses when armed that the sensor is picking up. One additioanl thing to try would be to use both sensor wires (one per motor pole) if you are not already, or try disconnecting "wire 2" if both are connected.

Ken, what are the values of spurious readings you are seeing? If they continue outside your house, and the readings are greater than the normal readings your motor produces, you can click "Advanced, Set Min/Max Values" and cap the RPM value to the max that you would normally see. This will hide the spurious pulses.
I am having the same problem with my brushless RPM sensor - when ESC is connected it intermittantly jumps in values, the RPM does increase with throttle, so it seems to work properly. It is only at idle that I notice these spurious pulses. It stays at 0 when I disconnect the Elogger V4 from the ESC, but of course the ESC no longer has power then.
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Old Mar 07, 2013, 12:16 AM
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Quote:
Originally Posted by billpa View Post
s_mack, do the pulses occur if the ESC is unarmed? If not, most likely the ESC is generating some noise pulses when armed that the sensor is picking up. One additioanl thing to try would be to use both sensor wires (one per motor pole) if you are not already, or try disconnecting "wire 2" if both are connected.
The pulses are there when unarmed, but that's expected because my ESC emits a periodic "tone" (yes, I know its no the ESC that's singing to me) to warn that its not armed (I guess). It expectedly goes haywire during the arming tones. But its after arming that I don't expect it to do that and it does. Ie. its "jumping" when there's no tones at all.

I'm not going to worry about it though. I tried a different ESC and it still jumps during any tones but is steady when armed but zero rpm... as expected. So it is something to do with that ESC. Even though I have brakes set to off, there's obviously some sort of pulse that's going through.

Just to address your other comment: It is currently connected with both wires. I suppose I can give it a try with just wire #1.

Thanks for your help. I'm satisfied that its my ESC causing the behavior. It appears accurate during use otherwise.

- Steven
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Old Mar 07, 2013, 07:49 PM
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Thanks for the update. Yes, it sounds like the one ESC is just noisy. I'm guessing removing a wire won't affect it, but it won't hurt to try.
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