Forums > MaxMSP

flickering from sensors


Nov 23 2012 | 5:00 pm

HI all,

I’m trying to use a bunch of new sensors, but looks like with greater sensitivity comes a major flickering…
So, I know several ways to detect and filter flickering, which is great. Only problem is that in this case is not only flickering, but sometimes, somehow the sensor – which is placed in a very still position and far from movements – sends some random (like one or two) values way bigger or smaller than the avarage flickering, so what i get is a *preceived* movement, which is not, actually…

I don’t think there are some fixes for this, but in the Max world, you never know… ;-)
So i hereby attach three text file I collected with coll which show what I’m talking about, so in case you wich you can reproduce and see if there is a possible fix

Thanks!

Attachments:
  1. flickering.zip
Nov 23 2012 | 5:28 pm

A median filter may help, but after looking at your files I’m not sure it will help much, I don’t see where the datas are way bigger or smaller than a running mean. Sometimes I’d be happy to get as dirty datas as you get ;-)

As always, with median or running mean you’ll get less reactive datas…

p

Nov 23 2012 | 5:52 pm

thanks Patrick, I tried with them but then I get delay, which is not useful at all in my case…
if you look carefully for instance "X"

3, 433;
4, 424;
5, 433;

or "Y"

2, 457;
3, 441;
4, 455;

or "Z"

3, 607;
4, 596;
5, 607;

you find jump from 9-to-16 points, and that was without movement…
but now that i put it this way.. i see that it’s not just one value, but the three of them altogether at the same time..
AND, more interestingly, it is just "one" value, and then it goes back to normal…
So i think there is something i could do with counter, o things like this…
I’ll tinker a little bit more and see if this is the case, and/or if this gets reproduced…
and thanks for your interest Patrick! ;-)

Nov 23 2012 | 6:14 pm

ok, it is confirmed. it is just "one" jump, and then it goes back more or less where it was…
I’m trying to figure out some code, if you have some ideas, please, feel free to spread.. ;-)

Nov 23 2012 | 7:26 pm

This thread might be interesting: http://cycling74.com/forums/topic.php?id=15180


dtr
Nov 24 2012 | 6:49 pm

What kind of sensor is it? Isn’t it something in your electrical circuit that’s causing this noise? Could be easier to fix that than filter it out in code.

Nov 24 2012 | 7:51 pm

In my experience, all sensors jitter a little, even in a well designed system.

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Forums > MaxMSP