Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: frank26080115 on April 14, 2009, 07:43:31 PM
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I just received this in the mail
http://www.walkera.com.hk/walkera-dragonfly-ufo-4-spare-parts-ufo4z16-pcb-receiver-p-2064.html (http://www.walkera.com.hk/walkera-dragonfly-ufo-4-spare-parts-ufo4z16-pcb-receiver-p-2064.html)
I got it just for its three ENC-03J gyros and MMA7260 triple axis accelerometer
(http://i156.photobucket.com/albums/t31/frank26080115/walkeraboard.jpg)
(http://i156.photobucket.com/albums/t31/frank26080115/walkerasensors.jpg)
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Walkera... watch out, the quality of their stuff is crap.
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Do let us know if you interface to this and get useable data. I was just looking at a six axis sensor package from sparkfun for $124.95.
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This was on RC Groups
The picture below shows the underside of the sensor board (its the smaller one on the left-hand side):
http://www.rcgroups.com/forums/attachment.php?attachmentid=2333870 (http://www.rcgroups.com/forums/attachment.php?attachmentid=2333870)
On it you can see a bunch of SMT resistors and caps, and not much else - suggesting there's only some passive low-pass and high-pass filtering going on.
I did some crude 'waggle' tests with the sensor boards directly wired to the Arduino's ADC inputs (with a 3.3v Vref into the sensor board, and the AVR micro), and got the following:
GYRO Max Amplitude from the analogRead function whilst 'waggling' (shaking the board in my hand as hard as I could in all directions, whilst logging values to a PC)
Roll: 25
Pitch: 27
Yaw: 54
compared to the other sensor which gives a much better signal:
ACCELEROMETER Max amplitude variance when the sensor board is turned upside, from side to side, back to front (calibrated to zero when board was flat, still & upright)
X: 359
Y: 369
Z: 170
I'd be good to see if (a) you get similar ranges from your board, and (b) it may well help you design the gain of your op-amp circuit (the gyros could probably do with a 5x gain as a reasonable starting point, 10x looks like it might saturate the yaw reading - even if very carefully biased)
Pip
I haven't had a chance to test it myself yet though, hopefully I can build my quadrotor without amplification. Will try tonight.
Pin locations found here
http://www.rcgroups.com/forums/attachment.php?attachmentid=2327509 (http://www.rcgroups.com/forums/attachment.php?attachmentid=2327509)
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:'(
accelerometer not outputing any voltage, double checked everything (powered at 3.3V, sleep mode off), might have been overheated in the desoldering process
gyros are fine, but the accelerometer means another $20 for a replacement from sparkfun
i've never been more pissed at myself :-/ this thing costed $60 CAD and took over a month to be delivered
i have two of dimension engineering's dual axis buffered accelerometers though, i can use arcsine instead of arctan if i am missing the z axis, not sure how well that would work in comparison though
EDIT
i think it's responding now if i apply pressure to the chip, i was checking whether the board may have a hairline crack on a joint or a trace
i definitely have at least one axis responding, meaning the chip is not dead yay
either a cracked joint or a cracked trace, there's a lot of SMD components on the back, i'll reheat them and see what happens
all three responding to gravity correctly if i press hard enough, so i think it needs repair but it's fine