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Eagle Tree Systems Onboard data loggers, telemetry, and OSD support |
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12-28-2007, 07:28 PM | #61 (permalink) |
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BTW I just got a reply from one of the engineers at Eagle Tree.
The brushless sensor works by counting the pulses over a time base to determine RPM. That's why it needs number of poles.
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12-28-2007, 09:10 PM | #62 (permalink) | |
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Quote:
"Edit: as far as entering the # of poles this is simply used as a divisor in the formula for determining the speed since the monitor is only connected to a SINGLE pole/phase." |
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12-29-2007, 05:30 AM | #63 (permalink) |
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And you were the guy who also said they mesured the pulse width.
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12-29-2007, 08:51 AM | #64 (permalink) |
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and I still haven't heard anything concrete to contradict what I was told by eagletree, that they do use the PWM..
yea, I'm that guy the one that works on programming PICs day after day. |
12-29-2007, 11:46 AM | #65 (permalink) |
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TX HM-52,
DUDE!!! Measuring PWM is absolutely meaningless. Can you not just understand that! Why is it so hard for you to understand that they are measuring the commutation and that's why you put in the poles on the motor. That gets you to motor RPM and then putting in the gear ratio gets you to the rotor RPM. Why on Earth do you refuse to believe this? Give me your e-mail address and I'll have Bill e-mail you himself. Would that work? As for your assertion that you can do brushless motors without the feedback... Yes, you can do STEPPER motors but not the brushless motors we use in RC. - John |
12-29-2007, 11:58 AM | #66 (permalink) |
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I only repeated it here because a tech at eagletree verified it to me on the damn phone "dude". I tend to believe what manufacturers tell me about their products (call me silly if you like), especially when my knowledge of electronics and programming tells me it's completely possible and reasonable.
Developing for PICs I can absolutely show you H/W and S/W that can easily count pulses sent to a single phase of a BL motor and with simple end user calibration can be pretty accurate doing so. Most of the ESC's EMF monitoring discussion that this morphed into talked about the ESC using EMF for tach and I can buy that, but can also see how simply the logger could just count pulses sent to the motor. Just think about it "Dude".. |
12-29-2007, 06:53 PM | #67 (permalink) | |
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Did you read my post?
Quote:
According to the ENGINEER, the brushless sensor counts pulses. It does NOT measure pulse width. And you stated that the tech only sort of agreed with you, that he did not outright say that they measure pulse width.
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12-29-2007, 07:08 PM | #68 (permalink) |
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I did read it and I would count PWM pulses (well I say pulses I mean positive swings of the wave ,same thing) to compute speed. Either just number of pulses or the duty cycle to calculate the speed, I would have to play around with it a bit. I can do it very simply with a short program to demonstrate, I wish I had more time on my hands I would do it and video but I'd rather fly with my precious spare time.
I really have no interest in ET's logger since they shafted me on mine, I was only repeating what he told me when discussing switching from my optical tach on the phone. They may have told me wrong when they said they sample the PWM as I thought they would and I would myself. Not trying to fight with you here just giving the info I got from a supposed reliable source at ET. Peace Mike |
12-29-2007, 08:08 PM | #69 (permalink) |
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Pinecone / TX HM-52
Dan Akroyd / Jane Curtain Point / Counter-point I miss the good ol' days...
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12-29-2007, 08:16 PM | #70 (permalink) |
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I think an easy way to clear this up is to actually scope the output of the brushless RPM sensor while in operation. I think that would answer the question pretty well. No? Maybe I'll do just that when I get a chance.
I've also sent an e-mail to Bill Parry of Eagle Tree. He's the man behind all these cool ET gadgets so he will certainly know the answer. Here's one argument against it counting PWM pulses... It does not ask what switching frequency you have the ESC set to. And since some ESCs vary the switching frequency while in operation, that wouldn't work anyways. - John |
12-29-2007, 08:49 PM | #71 (permalink) | |
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Quote:
1- I have a good idea of the sinewave frequencies ( I have looked at it with a high end scope), I would have to play with the math (in S/W to make it mean something for RPM based on poles as discussed earlier, if I wanted to do it). 2 -Bill someone is one of many I spoke to in my many frustrating time wasting conversations with ET but not sure if he's the one that told me that's how they do it. (I'm very upset with the way they left me with my new unit and that's the only reason I even posted in this thread to start with) 3- calibration of the unit with another tach would solve that on the prototype (but with my method you might have to calibrate each unit in the field with another tach for the motor in question, but I don't think it would be needed for rough readings). Unless I'm mistaken the frequency will change as the speed increases to increase the duty cycle to make the motor spin faster. I could be wrong here but again I don't need to make an ESC or logger so I'm not too worried really. I do think I could make it happen If I needed to though. Mike Last edited by TX HM-52; 12-29-2007 at 10:51 PM.. |
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12-30-2007, 09:10 AM | #72 (permalink) | |
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Quote:
You were the one that said that they measured PWM, to a tech level person, who didn't know enough to disagree. And it was Bill Parry who told me that they count pulses. And as a designer, I am pretty sure, he didn't agree with you that the mesured pulse width.
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12-30-2007, 09:13 AM | #73 (permalink) | |
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Quote:
The output of the brushless sensor will not tell you how to works, as I am sure it processes the signal and sends just the data to the logger.
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12-30-2007, 09:35 AM | #74 (permalink) |
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sigh...somebody needs to spend less time at the computer and more time outside.
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12-30-2007, 02:44 PM | #75 (permalink) |
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It cold and raining.
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12-30-2007, 10:28 PM | #76 (permalink) |
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> as I am sure it processes the signal and sends just the data to the logger.
It's plugged into the same RPM port that the magnetic or optical sensor plugs into, so I'm pretty sure it's just pulses which the main unit counts/measures. So, why do some say it is not accurate? If our systems have zero slip by definition, how could it be wrong? Noise? I think that's the bigger question. >It cold and raining. Bingo! - John |
01-03-2008, 09:24 PM | #78 (permalink) |
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Need Eagle Tree help
Well, Santa brought me the Eagle Tree V3 for Christmas and I gave it a quick test tonight. I had one problem....my RPM's were reading way too high (around 6000). I have the brushless motor sensor. I stripped some insulation from the end of the motor wire one lead on the sensor and connected it inside the bullet connector of one of the motor wires. I have a Medusa 28-32-3400. During the initial setup I told the data logger that my motor had 2 poles because it is an inrunner. Also, since I have a 12 T pinion and the trex has a 150 tooth gear, I divided 150 by 12 and got 12.5 so I put 12.5 to 1 in the setup. Can anyone tell me what I did wrong?
Also, when in graph mode is it possible to save the graph as a file? Thanks, Tim |
01-03-2008, 09:43 PM | #79 (permalink) |
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Anyone interested in a almost brand new V2? I have the cable and software CD. The unit looks brand new. Probably used 3-4 times. The V3 is $69+shipping. Some people dont need the amount of sensors on the V3 so Im wanting $55 Shipped.
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01-04-2008, 03:17 PM | #80 (permalink) | |
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