Medussa data logger vs Eagle Tree Logger

[TX HM-52]

Originally Posted by tjrtmaster

Does anyone know where I can get a Medussa Data Logger?

Tim

right on the site direct here;http://www.medusaproducts.com/oracle/index.htm

Mike

[Pinecone]

WOW, I just checked, Medusa wants $66.95 for the data logger and another $39.95 for the USB link.

The Eagle Tree is $69.95 for the logger WITH the USB link.

Voltage - Medusa 60 volts max - Eagle Tree 70 volts max
Amperage - Medusa 100 amps - Eagle Tree 100 amp standard, optional 150 amps
Sampling rate - Medusa 1 - 4.4 per second - Eagle Tree 1 - 10 per second

Data logged - Medusa -Volts, Amps, Watts, mAH, RPM, Temp (x2), Throttle signal
Eagle Tree - Volts, Amps, Watts, mAH, RPM (x2), Temp (x3), Throttle signal, Altitude, Airspeed, GPS position, Servo current, and Spektrum data for AR9000.

Display - Medusa - Computer only, Eagle Tree - Computer or LCD Display Panel

Your choice.

I am happy with my Eagle Tree.

[TX HM-52]

power panel rarely works, service sucks at eagletree (to put it mildly) I'd would go with Medusa or one of the other three I posted above (slightly cheaper).

I won't get burned by Eagletree again and I'll do my best to keep them from screwing anyone else with their selective support..

Mike

[tjrtmaster]

Pinecone,
Where is the Eagle Tree with usb link available for $69.95?

[ke6d]

Originally Posted by tjrtmaster

Pinecone,
Where is the Eagle Tree with usb link available for $69.95?

Should be on their web site. I bought a V2 from a LHS for the same price, used it for 25 days, then send it back to Eagle Tree for a free 30 day exchange. My V3 came last week. I just hooked up to the Hurricane to check it out. I flew it for 6:30 min, then let the heli sit for another 10 min before disconnecting the the recorder. The log only used 17% of the recorder's flash memory. There was still over 100KB left for logging. Cool...

Dan

[JKos]

Originally Posted by TX HM-52

power panel rarely works, service sucks at eagletree (to put it mildly) I'd would go with Medusa or one of the other three I posted above (slightly cheaper).

I won't get burned by Eagletree again and I'll do my best to keep them from screwing anyone else with their selective support..

Mike

Mike,
I'm sorry to hear of you bad experience with Eagle Tree. Mine has been nothing but outstanding. I have never had any trouble reaching Bill via e-mail. They have been quite willing to implement customer recommendations as well.

PowerPanel "rarely works"? What are you talking about? It has worked every single time I have plugged it in; no problems at all. I use my eLogger and PowerPanel every single flight.

About RPM sensing... Let's talk about how brushless ESCs work for a moment. There are two independent processes going on. One is PWM which effectively controls the voltage to the motor. Then there is commutation which is how the ESC actually gets the motor to spin correctly. The PWM controls the speed of the motor. The commutation must follow the speed of motor in order for the motor to run correctly. Commutation is based on back EMF pulses from the motor.

Governors on brushless ESCs use commutation rate as the RPM "sensor." Sense the ESC must already commutate, it's just a mater of implementing a governor control loop to control the "throttle" (the PWM).

The EagleTree brushless sensor works just like the ESC does for commutation by detecting the back EMF.

- John

[TX HM-52]

Originally Posted by JKos

Mike,
I'm sorry to hear of you bad experience with Eagle Tree. Mine has been nothing but outstanding. I have never had any trouble reaching Bill via e-mail. They have been quite willing to implement customer recommendations as well.

PowerPanel "rarely works"? What are you talking about? It has worked every single time I have plugged it in; no problems at all. I use my eLogger and PowerPanel every single flight.

About RPM sensing... Let's talk about how brushless ESCs work for a moment. There are two independent processes going on. One is PWM which effectively controls the voltage to the motor. Then there is commutation which is how the ESC actually gets the motor to spin correctly. The PWM controls the speed of the motor. The commutation must follow the speed of motor in order for the motor to run correctly. Commutation is based on back EMF pulses from the motor.

Governors on brushless ESCs use commutation rate as the RPM "sensor." Sense the ESC must already commutate, it's just a mater of implementing a governor control loop to control the "throttle" (the PWM).

The EagleTree brushless sensor works just like the ESC does for commutation by detecting the back EMF.

- John

I don't have time to re-explain it to you after all the wasted time with them already on this...

I ordered all new LCD and logger and they ran me through the ringer for over a month!!!I still doesn't work... Worked a few times then says 3192 watts right on startup and changes randomly before any power nearing even a few watts is drawn (good stuff huh?)

The tech I spoke to there told me (listen close this time John..) that the ESC connected logger will NOT BE ACCURATE if an sort of mechanical drag occurs. maybe he just doesn't know what he's talking about but hey he works for Eagle tree so what can I expect.. Try running w/o motor and I'll bet you still get readings.

I believe the guy at eagle tree before you and it doesn't matter to me anyway since I'll never buy that crap again and as I have here I'll try to save others the trouble I had with this horrible company.

Mike

[bugdozer]

I a bit confused why, especially EagleTree, would say that mechanical drag would effect your RPM readings. Um, last I checked the load on my motor, while flying, was always changing. What is the difference between mechanical drag and drag from the rotor? What I do know is that every time a magnet in a brushless motor passes one of the motor coils, the ESC knows. It's called back EMF. Brushless motor ESC's DO NOT function like brushed motors and just put out X amount of voltage/current and the motor goes to town. The ESC must know the position of the magnets in relation to the coils so it knows when to turn them on and off. If the ESC did not know this, the round and round would never happen. These pulses are what the Logger watches and other than timing advances which are very minor, are very accurate. More info here-> http://en.wikipedia.org/wiki/Brushless_motor

[TX HM-52]

hey , you guys cheer lead for whomever you like and buy what you want, I'm just trying to pass on my bad experience with this company as well as a few alternatives (SUE ME!) bugdozer, I explained this was PWM yesterday...(obviously not brushed) and I have a very good understanding of it. I've designed microconteller hardware to drive devices with this method so I'm pretty familiar with how to run a brushless motor..

If you don't believe what I've been told then as I've said about 3 times now.. unplug you motor leaving the logger connected to the ESC and see if you get readings, it's that damn simple! If it doesn't work then I've been told wrong by Eagletree and my guess as a hardware and software developer (seeing how easy it is to monitor PWM). I really can't see how anyone could possibly measure the tiny amplitude of the feedback of the motor while driving it constantly with PWM at over 75 watts! at least not for $70, this makes me tend to agree with what I was told by the tech at ET.

I really haven't got the time or energy to keep repeating myself to you, I'm just posting my experience with ET in this public forum (just like you) to try to save some other poor soul the trouble I've had.

[bugdozer]

Ok, did some testing. CC35 with no motor and Logger in live mode. Nothing registering on the RPMs and CC35 blinks due to no motor connected. Align ESC, no motor. A few bumps on the RPMs and then nothing registering on the logger. My conclusion, no motor, the ESC does not know what to do.

RPM accuracy - Heli clamped to the bench, Logger in live mode and an optical tach. No load / 0 pitch RPMs dead on. Full negative pitch, RPM's fluctuate around 5 to 10 RPM's and then settles in about 4 RPM's off the optical tach.

Based on price, what the Logger can do and my personal experiences with EagleTree, I'm will stick with them for now. If something better comes along or their support fails me like I have heard several people say they have, I may change loyalties. I'm out....

[TRex888]

When I received my V3 and installed the s/w on the PC the s/w insisted on updating firmware on it. After installing the firmware itself the whole thing just hung. I thought t*ts. Looked up forum on rcgroups and it seems other people had the same problems. Solution was to download the latest s/w from their site, yet another firmware update later and all was well.

However, my LCD panel would not work either!!!

After much pain and playing around I hit the reset to default on the LCD panel menu and everything was OK after that.

My guess it that there has been a bad firmware version and it corruptted a lot of the flash memory, luckily the bootroom survived and the new firmware could be installed but some of the flash (settings) were still screwy.

Now that it is working I would not want to do an firmware upgrade again.

[Pinecone]

Hmm, a $70 logger can't read back EMF, but a $13.50 (cheapest ESC at HobbyCity) ESC can?

[JKos]

> I really can't see how anyone could possibly measure the tiny amplitude of the feedback
> of the motor while driving it constantly with PWM at over 75 watts!

That statement indicates you do not know how a sensorless brushless motor ESC works. The feedback is anything but small and is very easily sensed and detected. It is this very feedback which the ESC is 100% reliant on to commutate the motor. It does not commutate based on anything but that feedback.

- John

[TX HM-52]

actually the motor can be spun without feedback and simply by timing the pulses to the phases of the motor without any tach...Wake up!

As far as the the tech at ET telling me another lie (that the thing can be screwed up by drag), I can't help that! The test without a motor may not be accurate since the ESC may look for the impedance of the windings before arming!

"Hmm, a $70 logger can't read back EMF, but a $13.50 (cheapest ESC at HobbyCity) ESC can?" where can you show me that the speed controller uses feedback pulses? smartass!

again this all goes back to bad info from your good pals, the ET techs! (if I'm even wrong)

I don't just talk about electronics, I actually design and build dedicated controllers and home automation gear all the time so get real and don't try to belittle my knowledge!

[bugdozer]

Originally Posted by TX HM-52

"Hmm, a $70 logger can't read back EMF, but a $13.50 (cheapest ESC at HobbyCity) ESC can?" where can you show me that the speed controller uses feedback pulses? smartass!

Here ---> http://en.wikipedia.org/wiki/Brushless_motors
Here ---> http://www.microchip.com/stellent/id...GE&nodeId=1523
Here ---> http://www.eetasia.com/ARTICLES/2005...EP_REF_WK1.HTM
Here ---> http://www.freepatentsonline.com/5055751.html

[TX HM-52]

still haven't shown me that the controller you're talking about for $17 uses feedback monitoring!

this is straight from the Microchip website you linked (where I spend quit a bit of time..) I quote! "Typically three Hall sensors are used to detect the rotor position and commutation is performed based on Hall sensor inputs. "

Gee, I don't see any sensor wires coming out of my motor.. Maybe they forgot them on the Align motors huh?

I never said there was not a way to measure back EMF (re-read my comments from the top, very slowly so you can take it all in), I simply said that based on my info from a tech at Eagltree and my expericence that it was unlikely that these cheap devices use this method.

[tjrtmaster]

Do I need any additional attachments/sensors to monitor RPM's on either the Eagle Tree or the Medusa Logger?
Is the Eagle Tree V3 available yet? If so where is it available?
Tim

[TX HM-52]

Originally Posted by tjrtmaster

Do I need any additional attachments/sensors to monitor RPM's on either the Eagle Tree or the Medusa Logger?
Is the Eagle Tree V3 available yet? If so where is it available?
Tim

The Oracle Standard Package includes:
1 Oracle Data Recorder (MR-DR-60100)
1 Temp Sensor (MR-TEMP-001)
1 RPM Phase Sensor (MR-RPM-002)
1 POWERLink USB Adapter (MR-USB-001)

w/USB Cable $99.00 on the Medusa site direct

Mike

[bugdozer]

Originally Posted by TX HM-52

still haven't shown me that the controller you're talking about for $17 uses feedback monitoring!

this is straight from the Microchip website you linked (where I spend quit a bit of time..) I quote! "Typically three Hall sensors are used to detect the rotor position and commutation is performed based on Hall sensor inputs. "

Gee, I don't see any sensor wires coming out of my motor.. Maybe they forgot them on the Align motors huh?

I never said there was not a way to measure back EMF (re-read my comments from the top, very slowly so you can take it all in), I simply said that based on my info from a tech at Eagltree and my expericence that it was unlikely that these cheap devices use this method.

Ok, ok, you are the electronics professional and we are all slow readers but according to Thomas at Castle Creations, every last one of their speed controls use EMF back-pulses to control the motor. He also knows of no other way of controling a 'sensor-less' brushless motor without them. As Castle Creations was one the leaders in sensor-less motor control design, I would tend to trust them.

In the future, I feel a good hearted debate would go more smoothly without the name calling and condescending attitude. I will post no further on this.......

[TX HM-52]

I don't recall calling anyone any names (except maybe Eagletree), I came to this thread titled "Medussa data logger vs Eagle Tree Logger" to post my bad experience with Eagletree to try to help other members with my loss..

Then somehow the topic of RPM accuracy came up and I was simply trying to say that in one of my many time wasting long conversations with a tech (no I don't remember who exactly) at Eagletree trying to get my power panel LCD to function correctly I asked what sensor he thought was best for tach and he said ESC sensor, I asked can't that be incorrect since it measures the PWM to determine RPM and he said I guess you're right but it's minor ( as I said many posts ago "the ESC sensor Is fine in most for most people in most cases") so I have gone on the assumption that the loggers (not by the way the ESC that you and a few have completely sidetracked this discussion to..) simply monitor the PWM to a single pole on the motor.

Being an engineer (not having to Google to find my answers and come up with theories) seeing how incredibly cheap these new controllers are (and how hard/expensive it used to be to drive brushless motors with external sensors) I simply drew a basic logical conclusion, that the also very cheap ESCs PROBABLY ( I never said they couldn't or weren't using some sort of EMF feedback) probably used a very simple algorithm (really basic addition from 1HZ up to whatever in controlled steps on each pole) to achieve rotation to a reasonable accuracy for the price (admittedly not as accurate as if using measurements which BTW would have to measure an incredibly tiny noise period due to the fact that each pole is energized about 160,000 Hz with up to 100 watts of power according to crude calcs. in this respect zero crossing is small at least for the clock speed of an inexpensive micro controller under dynamic circumstances).

Also If you look way back at my post #19 I quote very 1st sentence "Governor modes on an ESC is something I hadn't thought about, I would be curious to know how they accomplish that."

I can and would show you with a very simple program and equally simple hardware to demonstrate how a brushless motor CAN in fact surely be run without feedback, granted not as accurately but I need to be making money to support my Ex and so on..

It's amazing how some people can take things so far off topic in forums sometimes.

I'm going to work now, doing hardware design/repair and programming (sorry if my profession ( the reason I commented further in this technical discussion I happen to know a few things about) bothers you but that's life. If this were a discussion on aerodynamics or brain surgery then you can bet I wouldn't be chiming in with Wikipedia and Google results as I don't have any real world or theory experiences with either...

As I said, I was just here to comment on the logger brand to help another. Not to start a fight.

Mike