http://forums.leaflabs.com/topic.php?id=838 A place to share, learn, and grow... en-US Fri, 22 Jan 2016 00:21:48 +0000 http://bbpress.org/?v=1.0.2 q http://forums.leaflabs.com/search.php http://forums.leaflabs.com/topic.php?id=838#post-5122 Fri, 10 Jun 2011 14:31:03 +0000 poslathian 5122@http://forums.leaflabs.com/ <p>You can use an array of ambient sensors (as few as two...) and use the differential readings to determine the gradient of the ambient light (what direction is brighter/darker). </p> <p>The canonical example of this is a drive-towards-the-light robot. Take two take two ambient light sensors on a little horizontal bar. Put a small piece of cardboard in the middle to separate them, then turn your robot towards whichever sensor has the lower output. </p> <p>Not sure what you are doing, but if you just need to know what part of the scene is light/dark, you can play tricks like this. 3 ambient light sensors and you should be able to triangulate the center of mass of the lighting input. </p> http://forums.leaflabs.com/topic.php?id=838#post-5043 Tue, 07 Jun 2011 13:06:40 +0000 josiah47 5043@http://forums.leaflabs.com/ <p>well im hoping i do not need to use a camera since a ambient light sensor might work, but if one part of the scene is darker and another lighter i don't know if the ambient light will sense that i guess it will since its an average, i think maybe ill test it first. </p> http://forums.leaflabs.com/topic.php?id=838#post-5040 Tue, 07 Jun 2011 12:30:28 +0000 gbulmer 5040@http://forums.leaflabs.com/ <p>josiah47 - are you willing to try to program the camera?</p> <p>If you are, look at Canon Hack Development Kit<br /> <a href="http://chdk.wikia.com/wiki/CHDK" rel="nofollow">http://chdk.wikia.com/wiki/CHDK</a></p> <p>In theory, with the right Canon camera, you could do everything in the camera. There are some advantages to this, including a faster processor, and plenty of RAM. Also, no need for anything except a camera. I picked up some Canon cameras at a reasonable price on eBay. </p> http://forums.leaflabs.com/topic.php?id=838#post-5039 Tue, 07 Jun 2011 12:11:34 +0000 robodude666 5039@http://forums.leaflabs.com/ <p>Why would you use a camera to get the brightness of a scene? Use a camera to take a picture. Use an <a href="http://www.pololu.com/catalog/product/1608/resources">ambient light sensor</a> or <a href="http://www.ladyada.net/learn/sensors/cds.html">LDR</a> to determine the brightness in an area. Alas, as for cameras.. I know SparkFun has a <a href="http://www.sparkfun.com/products/10061">LinkSprite TTL</a> camera, but it captures JPEG images. You may need a camera that gets raw values. The <a href="http://www.4dsystems.com.au/prod.php?id=75">4D Systems µCAM-TTL</a> claims to offer RAW RGB modes.</p> <p>Once you get your camera to communicate with the Maple, look at the RGB value of every pixel and calculate the <a href="http://en.wikipedia.org/wiki/Luminance_(relative)">luminance</a>. Sum them up and divide by the number of pixels to get the average luminance of the entire picture. You'll be doing a lot of math, so I'd recommend taking a look at <a href="http://forums.leaflabs.com/topic.php?id=266&amp;page=2#post-3874">libfixmath</a> to help with all those calculations. </p> http://forums.leaflabs.com/topic.php?id=838#post-5036 Tue, 07 Jun 2011 11:38:13 +0000 josiah47 5036@http://forums.leaflabs.com/ <p>Okay, I have a little project that I can't give the full details but, basically what I need to do is get a camera hooked up to the Maple and then make it look at a scene, take the average brightness of the scene, so pixel by pixel calculation and then send the average brightness to the pc via serial.</p> <p>Any clues on how to go about this,<br /> camera choice? anyone currently using a camera with the controller?<br /> code to do the numbering crunching?</p> <p>Thanks </p>