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Rube-Goldberg Type Random Number Generators?
stercor asks: "I've been considering random number generators made with easily-available materials. Living in Oregon might suggest photoelectric cells and rain. Or something to do with slugs (generation rate IS a factor, however)
My question is what other off-the-wall shelf hare-brained brilliant ideas can other Slashdot readers come up with? Please limit ideas to ones that would actually work." When I was younger, I was always intrigued by the rigs used by most State Lotteries. You know the ones: dump balls into a chamber, throw in a fan/vacuum combination to agitate the balls and to allow a random one to shoot thru a tube when the button was pressed (basically, a high tech version of your average BINGO machine). Has anyone else seen or built a contraption that does something similar but in a weird, roundabout or weird and roundabout way?
How about a webcam that is aimed at a black backdrop, with an incense burner hidden just out of frame, below. You light some incense, turn the webcam on, every time you take a picture you get a random black and white image. Do some fancy pixel crunching to generate a number.
"And like that
I've been vexed that the sound card plus CD-ROM drive combination always shows signal at around -50 dBVU in CoolEdit. So, just for grins, I decided to capture a few seconds of the noise and analyze the properties. I was astonished to see that the resulting signal is a white-noise pattern with a slight emphasis at the high end (when sampled at 44 kilosamples per second). In short, it looks like diode noise with a 4 kilohertz square wave thrown in.
That suggests to me that this would make a fair source of random samples, especially after you slot out the interfering signal.
How many computers don't have cheap sound cards and CD-ROM drives?
I can't find my polarizers, so I can't test this, but I think you could rig something up with a cheap CCD webcam. If you look at a poorly lit image from a CCD there's an awful lot of noise, and the image sort of rides on top of this noise. If you took your cheap CCD webcam and kept reducing the light to it till you got mostly noise it'd be simple to capture and generate random data from. I was thinking of a shoebox with the sensor inside, USB cable coming through a small light-tight hole. Make a hole in front of the lens and stick a pair of polarizers in front of that hole. Rotate the polarizers to get a light intensity such that you get lots of noise.
If you snap a frame you'll get some random bits. Somebody could break the randomness by shining a really bright light through the polarizers, but as long as you can control access to the shoe box you'd be fine.
Chris Kuivenhoven is a thief, beware
you know, i was just thinking exactly the same thing.
here's one other:
Post a random comment.
the number of moderation points, given a suitable comment, will probably be completely random.
Just get a Seismograph, and return the heigh of the last reading. Sensitive enough to measure footsteps across the room, so you shouldn't have a problem if you place it right.
I live near a freeway, so I have plenty of randomnees avaiable in the traffic going by my house.
Warning, with this, and many other schemes you need to normalize the data. Otherwise you will tend to get larger numbers during rush hour, and smaller ones during the night. Also a big snow fall (shuts down traffic) will change the values received. Be aware of these issues, if someone else finds out what you are using to generate random numbers they may use that to break your scheme. (Even if you numbers are random, just over a smaller range)
In a nutshell, they pointed a camera at a lava lamp and used an algorithm to reduce the image into random numbers.
... if you sample white noise from any source, you'll have a random value. Analogue synthesizers commonly use a reverse-biased diode of some sort to generate noise as it reaches the Zener region. You used to get special "noise diodes" - basically Zener diodes that were chosen because they were extremely noisy.
A good, simple white noise source is a reverse-biased transistor. Get an NPN transistor, connect the base to negative and the emitter to positive through a large (220k or so) resistor. Look at the voltage on the emitter - noise! Use an amplifier of some kind to get a useful voltage - you're not too bothered about hi-fi here, although theoretically distortion could skew the results (hint - what would clipping do to high and low values? What would crossover distortion do?)