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Author Topic: $40 3 axis gyro + 3 axis accelerometer  (Read 8465 times)

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Offline frank26080115Topic starter

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$40 3 axis gyro + 3 axis accelerometer
« on: April 14, 2009, 07:43:31 PM »
I just received this in the mail
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



Offline Razor Concepts

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Re: $40 3 axis gyro + 3 axis accelerometer
« Reply #1 on: April 15, 2009, 01:16:52 AM »
Walkera... watch out, the quality of their stuff is crap.

Offline msprague

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Re: $40 3 axis gyro + 3 axis accelerometer
« Reply #2 on: April 15, 2009, 05:25:17 AM »
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.

Offline frank26080115Topic starter

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Re: $40 3 axis gyro + 3 axis accelerometer
« Reply #3 on: April 15, 2009, 10:09:25 AM »
This was on RC Groups

Quote from: pipsqueak
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

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

Offline frank26080115Topic starter

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Re: $40 3 axis gyro + 3 axis accelerometer
« Reply #4 on: April 16, 2009, 10:57:16 PM »
 :'(

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
« Last Edit: April 16, 2009, 11:15:47 PM by frank26080115 »

 


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