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Why are there only pi nits in a hemisphere? (Or, why do my reflected and...
I just spent about a week trying to sort out why people kept claiming that surfaces with a given radiance (or luminance) emit pi times as much light over a hemisphere, when there are in fact 2*pi...
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Shiny spheres
My friend told me that many years ago, she lost points in an MIT art class for putting the highlight in the wrong place on a sphere. So when she saw my last post about radiance, she posed the question...
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Maker Faire 2014 Highlights: Miscellaneous
AeroTestra has a fully waterproof UAV with 20 minutes of flight time. They’ve instrumented it with water quality sensors and measured local bodies of water for salinity.TechGyrls is a collaboration of...
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Maker Faire 2014 Highlights: Manufacturing
I stopped by the Full Spectrum Laser booth again this year. People often ask me for recommendations on 3D printers, and I usually steer them toward lasers instead. They’re super easy to use and work...
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Maker Faire 2014 Highlights: Electronics
robopeak showed off their $400 360-degree LIDAR unit with 6m range. Not as polished as the $1150 Hokuyo, but about the same size and a whole lot cheaper.They also had a 2.8” USB LCD touchscreen...
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Visible light spectrum as the sun sets
Today I played with a ColorMunki Design, using it with argyll in Linux to record the spectrum of ambient light in the sky as the sun set.I ran "spotread -a -H -s log.txt" to record using the ambient...
View ArticleSeeed Xadow "couldn't find a Leonardo" / "buffered memory access not...
Spent an hour or two trying to figure out why I couldn't upload sketches from arduino to my Xadow board. Turns out the serial port wasn't selected in Tools... Serial Port (even though /dev/ttyACM0 was...
View ArticleXadow analogRead
Updated: figured it outI can't make sense of the pin mapping on this Xadow board to read analog values. Note that analogRead() has funny behavior to start with. But I looped through pins 18-29...
View ArticleXadow connectors aren't interchangeable
Well that wasted an embarrassing amount of time. The xadow boards have flex cable connectors at each end so that you can daisy chain them. I had the breakout board hooked up the wrong way, and spent...
View ArticleXadow PWM only supports 1 (or 2) pins
As far as I can tell, the only pin on the Xadow flex cable that you can do PWM with (at least using the arduino IDE) is SCL. (And if you screw up and plug in the breakout board backward, SCL will...
View ArticleIOIO otg + Ubuntu quickstart
I picked up a IOIO board from SparkFun. I want to control its PWM channels from my Ubuntu workstation (no android involved). Fortunately, I work near Ytai, so I was able to pick his brain when I got...
View ArticlePoint Grey cameras suck.
Spent way too many hours fighting with two different Flea3 cameras from Point Grey lately. All the software is hidden behind a login page, and they'll spam you if you sign up. Lots of different...
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Polaroid Cube sucks
I tried out the new Polaroid Cube camera today, and figured I'd start with the basic outdoor selfie. And this pretty much sums it up:If you're going to make a camera without a display, it probably...
View ArticleUn-bricking a Parrot Ar.Drone 2.0 with a Xadow (arduino)
The Ar.Drone 2.0 creates a wifi access point using network 192.168.1.*, which conflicted with another network I was using on my laptop. I telnetted in and changed bin/wifi_setup.sh to use 10.0.0....
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Radial Mill
I see lots of small CNC milling machines these days, generally built like 3d printers: made of plastic or wood, or aluminum extrusion and bearings. But unlike a 3d printer, subtractive milling...
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Building new drawers
The crappy drawers in my kitchen were falling apart, so I took the faceplaces off and built new drawers. I used 3/4" melamine-backed plywood for the sides, and 1/4" melamine-backed MDF for the bottom....
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Paperclip Maximizer 1.0
The AI does not hate you, nor does it love you, but you are made out of atoms which it can use for something else. —Eliezer YudkowskyA Paperclip Maximizer is an artificial intelligence whose sole...
View ArticleIntuition for Young's Modulus
Today I was trying to remember how to use Young's Modulus. I eventually figured it out (I think), but when I went to check my intuition, nobody else was describing it in these terms. So it's odd that...
View ArticleUbuntu: use syndaemon disable touchpad while typing
As this page describes, syndaemon solves the problem of trying to type on a laptop and having the cursor jump somewhere else because it thinks you touched the...
View ArticleEmpirically testing the "three hats game"
After reading the brain teaser here, I couldn't convince myself that the solution was correct:http://www.futilitycloset.com/2015/02/17/the-three-hats-game/It still seems impossible to me that any...
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