On Wed, Aug 24, 2011 at 6:48 AM, Tom Parker <[email protected]> wrote:
> On Wed, 2011-08-24 at 07:38 +1000, James Cameron wrote: > > On Tue, Aug 23, 2011 at 10:39:38PM +1200, Tom Parker wrote: > > > Nice! I made a simple "position the turtle based on accelerometer x and > > > y" and found the sensor to be quite noisy. > > > > Could you quantify that please? > > > > Normal shaking of hand, or the earth under you in your case, or nearby > > sound, may generate what appears to be noise. > > I must say I hadn't thought about where the noise might be coming from, > I merely wanted to process it out. Is it really sensitive enough to pick > up normal sound (not just boom sounds!)? > > Going back to what I was trying to do, I was trying to make a spirit > level, so I'm not interested in vibration. I'm interested in enough > averaging to smooth out the noise (whatever the source) while retaining > enough speed to such that the turtle moves smoothly. > > I'm not really familiar enough with Turtle Blocks to know if the > performance I am seeing is because reading the sensor is slow or because > computing the average is. I had the blocks turned off because my program > was in the way of seeing what was happening and I did discover this > greatly speeds things up, but updates were still slow enough to make > finding the zero point difficult. > > I suppose exposing the raw data is good for teaching about the > properties of the sensor and the real world (if it is indeed picking up > small vibrations). However I suspect many applications would like some > signal processing and a lot of those would like fast signal processing. > If the sensor is up to it but turtle blocks itself isn't, perhaps some > signal processing could be built in. Either as a separate "average n > values" block, or a property of the accelerometer block? > You could create such a block in Python and import it into your Turtle Art project. See http://wiki.sugarlabs.org/go/Activities/TurtleArt#Programmable_Brick You can also do in-line math using the 'Python' block, as per Tony's example or: http://wiki.sugarlabs.org/go/File:Sine.png > > Then you can have a conversation about the sensor and signal processing > without having to introduce loops and boxes? > > There might also be a use case for a "zero" transformation where you > declare the current orientation as zero and thereafter return the offset > from that. My vector math isn't quite good enough to work out how to do > that, never mind express it in Turtle Blocks. I say this because the > first thing I did was wonder why only one axis was near zero with the > laptop sitting "flat". I quickly realized the sensor is in the screen > and the screen was tilted backwards! > > Can you make subroutines in turtle blocks? My program was a bit unwieldy > with just two loops in it. I guess I should look at the examples. > Yes. See the blocks palette: http://wiki.sugarlabs.org/go/Activities/TurtleArt#Blocks_Palette > > Also, we're more than 750km from Christchurch, I didn't feel any of the > big earthquakes, never mind the (still numerous) aftershocks. > > good luck. -walter -- Walter Bender Sugar Labs http://www.sugarlabs.org
_______________________________________________ Testing mailing list [email protected] http://lists.laptop.org/listinfo/testing
