Hey PP just for you, actually for anyone curious to know the inside of their GoPro GoPro Hero3 Teardown [list type=decimal] [*]Page One [*]Page Two [/list]FYI: [acronym=EYE See! To w00d's Photo Musings, my pages][shadow=grey,left][size=1em]w[/size][size=1.25em]00[/size][size=1em]d[/size][/shadow][/acronym] ____________________
I have a feeling that the "brushless" motor might actually be a stepper. I'd sure like to know more about those motors, because I like the shallow profile. No matter what they are, they must also be gearmotors. ...Tiger
Well... Reading a little closer I see "New direct drive Gimbal for gopro". That's pretty interesting. That being the case, one of two things must be true. Either there is a pot mounted on the other side or the sensor electronics is mounted to the camera (but not shown). If you missed it, there is an RCG thread with a little more info here: http://www.rcgroups.com/forums/showthread.php?t=1815204#post23894945 The most interesting thing on this page to me is in the last line: "We will post details for DIY on how to rewind your own motors later on. " UPDATE: The RCG thread above has a diagram that confirms that the sensors are in fact on the camera for position feedback. ...Tiger
Here are a couple videos that perhaps show the development of this thing: http://www.youtube.com/watch?v=wBJ7xdL8sH4 http://www.youtube.com/watch?v=eIt8dEBqao8 ...Tiger
Is the little chip on the blue board a sensor acting as a pot? (accelerometer) "The prototype shown in our videos are using a KDA2208 12 slots/14 poles with 80 turns of 0.16mm in a 2-layer star configuration. Other people have used similar sized motors with 60 turns of 0.2mm. The KDA´s are horribly made - magnets are unevenly spaced, so they are less than ideal. I would not recommend them, but they do work. Its important to use a motor that has as little magnetic "cog" as possible. More poles and slots are probably good. Aim for a resistance of between 5 and 10 ohms per phase, depending on intended load - we got 8ohms on our prototype."
Tyson - I guess our postings about feedback crossed in cyberspace. I came back here to find your posting about the blue board. Yes, it's providing the feedback. I think these would be gyros rather than accelerometers. I'm guessing they are rewiring the motors in an effort to lower the KV rating as much as possible. ...Tiger
Oh, yes your probably right, seems like you need an accel somewhere, probably on the main board to provide an inital reference and keep the drifting gyros in control.
That was great John. I watched the motor winding video on your link. Doesn't look like much fun! I also watched this other one that's a DIY project someone posted: http://www.youtube.com/watch?v=9_8Kb_fXRrU I get the feeling they are driving these more like steppers and regular BL motors. ...Tiger
I am interested in this gimbal also because of the brushless motors although I am very happy with my gimbal plus my design is lower profile but at the cost of supporting the rotation axis on both ends. I recall there was a project very similar to this but the intended purpose was a hand-held camera stabilisation. I believe that project used servos. Did you determine that they are using potentiometers on the back of the motors, or are they encoders?
There are no potentiometers or encoders actually. They have moved the gyros to the camera platform and use that directly for feedback. This works quite a bit different than the one you were building. It's not just the drive mechanics that have changed. This is more of a closed loop system and has much better resolution. Does anyone know if there is a standard tripod mount on the bottom of the new GoPro (1/4-20 thread)? ...Tiger
Sorry about that, of course there are no potentiometers or encoders. I was looking at the three wires but they are the brushless motors themselves. I should finish my coffee before writing dumb posts.
