MOTOR SPEED ERROR MAVIC MINI
- Thread starter RyanDG
- Start date
Hi there & welcome to the forum ?
As the forum language is English it's much better to use Google translate before posting ... not all master Turkish ?
As for the Mini2 in particular, the motor RPM's are included in the craft & mobile device stored .DAT logs, not the mobile device stored .TXT log ... unfortunately both these .DAT logs are encrypted & can't be read by any others than DJI staff.
) also thanks for your understanding.For the Mavic 2 Pro & Zoom the Mobile device stored .DAT logs are readable ... it's also possible for the Mavic Pro, Mavic Air family (all generations) & for the Mini1. The Mavic Pro was the last one that also allowed us to read the craft stored .DAT log.
So in order to gain access to the motor RPM's you need to be able to read either of the 2 .DAT logs ... raw sensor data & motor data aren't included in the .TXT log.
Preferably you use a tool like CsvView to depict the data in the .DAT log ... here below only the RPM's from one of my own flights.
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Hello: thank you for all the info. So apparently the mini case is no longer usable. Until DJI provides me with a functioning case, lol, does anyone have a recommendation for a case? Also, what do you think of the snap on protectors for the propellers? Thanks in advance.
I ended up buying a 2800 size hard case from Harbor Freight and then making a pocket for the MM with a bar down the middle so the lower props could straddle and have space underneath so as not to put pressure on the props. Then I used some of the excess foam to make a piece for the top to hold the MM in place but still left room for the upper props. This worked out well because I could leave the controller joysticks installed and have room for my go pro and batteries for it also.
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On behalf of all the logical people in this world, we feel your pain.
Just bought a new Mini Combo, and the back left props are clearly different than the others ("flatter"). I haven't run into any problems (yet) and will try to check the motor RPMs just out of curiosity.
Well, maybe. You're probably right, but for all I know, the other three props are going to dramatically lose lift at higher speeds ("cavitate"), and the left rear one is going to be the only one that keeps performing. I don't think we know what DJi's specs are, so it's kind of hard to say. But, it seems reasonable to try to even out the differences and it seems clear that new, previously uninstalled props do that so again, you are probably right.
Anyway, another data point, and food for thought.
Cavitation doesn't happen in gaseous media - that's purely an effect in liquids. The loss of lift with these props is due to deformation of the prop, reducing the aerodynamic lift.
Which is why I used quotes, but my point being the propeller shape that has the most air resistance/drag (slower rotational speed) is not always the best general shape for creating thrust for a given motor. Looking at the data you might say that RBack is the best since it is slower, but that is likely not true since it is probably warped too.
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The right back prop is generating the required lift at lower speed. Warping is unlikely to have improved its performance.
The Mini is almost perfectly balanced with the centre of gravity just a smidgen forward of the intersection of two diagonal lines drawn between the motor centres. It's just a touch nose-heavy.
In a stable hover unaffected by any crosswinds, if the propeller blades are equally capable of producing lift, there's no reason why all four motors shouldn't be turning at equal speed. If anything, the front motors might spin just a touch faster to support the tiny bit of extra weight toward the nose.
I posted these photos somewhere earlier, maybe even in this same thread. Draw a line across the body of the Mini diagonally between motor centres and suspend the drone from that intersection point. You'll see the centre of gravity is actually a touch forward (~1/8") of that intersection point.
Had the Mini stored in its case for 18m or so, just got it out this week. Saw the error after the firmware update, and replaced Rear Right blades as per beep error. Next flight showed Rear Left, so replaced those too. No errors since. CSvView clearly shows rear blades at 12 - 15000 rpm, with fronts at around 9500. After replacing both rears, all 4 are below 10000.
Sorry for a late post, but I thought it worth saying, since this seems to show a) that it wasn't just a "firmware affects left rear" issue and b) replacing the indicated blades worked for me and c) the CSvView traces agreed with all of these observations.
I spent way too many hours reading up on this stuff before I just did the changes - which worked - so maybe my experience will help someone else.
Sorry for a late post, but I thought it worth saying, since this seems to show a) that it wasn't just a "firmware affects left rear" issue and b) replacing the indicated blades worked for me and c) the CSvView traces agreed with all of these observations.
I spent way too many hours reading up on this stuff before I just did the changes - which worked - so maybe my experience will help someone else.
I see a lot of graphs showing the bad motor being faster than the others. Mine shows the Rfront significantly slower than the others (or else the other three are running faster?). How can I interpret this?
For comparison, below is what the motor speeds looked like on my Mini with fresh propeller blades installed. With new blades my motor speeds at hover all averaged out to about 9600 rpm. So that would appear to indicate that your Right Front is good, while the other three are running faster.
Is it a significant difference, or something to worry about? I dunno. But it is a noticeable difference. You could repeat the test with the Mini facing 180° in the opposite direction, as that would indicate whether any crosswind draft was affecting the motor speeds if the Mini is leaning into the wind. If the graph ends up looking consistently the same, no matter which direction the Mini is facing, that would be more conclusive.
The Motor Speed Error warning message seems to be triggered only if the motor speed exceeds something like 16,000 rpm. So it looks like you still have lots of room before that happens. But the motor speeds obviously will momentarily be much higher doing any aggressive flight manoeuvres compared to simply hovering.
Note, the average speeds displayed in my graph were calculated using an Excel spreadsheet after trimming off the slow startup and shutdown portions of the data. Note also that, to get an even more accurate number, one should probably also trim off the first 30 seconds of the hover test and let the test run longer than merely one minute, as it takes about 30 seconds for the motor speeds to calm down once the Mini settles into a stabilized hover.
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