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Eagle Tree Systems Onboard data loggers, telemetry, and OSD support


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Old 09-13-2011, 11:47 AM   #1 (permalink)
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Default Data Logger on 450 Sport

Yesterday I noticed that one of my 450 Sports just didn't have the usual "umph" for some reason, and I barely cleared a tree that I usually get over without a problem.

So of course I am using this as an excuse to get a data logger. I'm looking at the Eagle Tree v4 with an optical sensor. The thought of putting magnets on the main shaft gives me the heebie jeebies and I want the actual rotor speed, not a calculated speed. My questions are, does anyone have pictures of how they implemented the optical sensor on a 450 Sport, and is the v4 the "optimum level of coolness" for a 450 Sport?

Thanks in advance,
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Old 09-15-2011, 04:23 PM   #2 (permalink)
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Can't say I had much success with the optical sensor (and this was on T-Rex 600 where I could move it around and test). Mainly I think the problems (bad RPM values) was from sunlight hitting the sensor.
As for the magnetic sensor, I have that one on my bigger helicopters now (600,700), works great. I think it could work also on a 450, there is actually a pre-made hole on the 450 main gear ( SEv2 version anyway) where the magnet can be glued.
Btw, there is no major issue with the brushless sensor, works well enough - the gear ratio needed for the calculation is after all fixed and the sensor picks up the actual motor RPM so the calculation can't really go wrong.
/Lars
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Old 09-24-2011, 01:04 PM   #3 (permalink)
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The ET brushless sensor works great, and is a lot easier than the optical sensor (which you have to shield from ambient light). Plus it's cheaper! as I recall. I have both and was using the optical on a glow engine.
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Old 09-30-2011, 05:15 PM   #4 (permalink)
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As far as I can tell the outrunner motors are synchronous, meaning you can tell how fast the motor is going by the frequency applied to it unless it "slips a pole" which should be noticeable, and therefore the rotor speed unless the one way bearing slips, which should also be noticeable. Do I have that right? Would you be able to hear the motor slipping or the one way bearing slipping? The reason I'm looking into the data logging is because one of my helis is "dogging it" and I'm trying to find out where the loss is between the battery and the helis response.

The only thing I know about synchronous motors is about the big AC machines, and if they slip a pole it's very noticeable!
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Old 09-30-2011, 10:04 PM   #5 (permalink)
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If you are worried about slippage in the one way bearing, the the sensorless pickup is that of course it senses the motor rpm, and only calculates the headspeed assuming no slippage.

Even if you measure the head speed with an optical sensor, that also won' tell you if there is slippage unless you also measure the motor rpm at the same time and compare.

Can't you just turn the main gear by hand while holding the rotor fixed to see if the one way is slipping?
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Old 10-23-2011, 01:30 AM   #6 (permalink)
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Align main gears have the little hole for the magnet.
I haven't seen a magnet hole on any of my clone gears.
But that wouldn't stop me from ruffing up the plastic and
glueing a magnet in the same place anyways.
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