Arduino True Random Number Generator

Step 5: Detect Radiation

Once the arduino has been programmed, you can run the processing sketch. The geiger counter should detect about 20 counts of radiation a minute, as natural background radiation. This equates to about 5 bits a minute, which is pretty slow. To increase the number of counts per minute, I bought salt substitute, which contains potassium chloride. A small percentage of potassium atoms are naturally radioactive (its still perfectly safe) , and we can actually measure the increased radioactivity with the geiger counter. I was able to get up to 60 counts per minute, or a bit over twice background radiation (again perfectly safe). The increase in radioactivity allows the counter to produce bits at a faster rate.

Comments

[kelseymh]

This is an awesomely cool project :-) I especially like your use of NoSalt as a ⁴⁰K gamma source. You could also use bananas if you're so inclined ;-)

[codongolev]

I think for the purposes of encryption and the building of an encryption key, I'd definitely use bananas. that way I could tell people that my data is "banana encrypted."

either that or say it's guarded with bananas. or something else ridiculous.

[kelseymh]

If you use it to encrypt your digital voice communications, then you can talk to people on your bananaphone!

[codongolev]

ring ring ring ring ring ring ring ring bananacryption!

[nwlaurie]

Brazil nuts (for reasons completely beyond my understanding) contain at least two isotopes of radium - one of these, mounted in a suitably steampunk holder could be set at variable distances from the tube to give an adjustable - and cheap - radioactive source.
Perhaps.

[kelseymh]

Really?!? I can understand the multiple isotopes (chemistry is fairly insensitive to isotopic differences except for very light elements), but why would radium be accumulated in Brazil nuts specifically? I'd be very interested to learn more; can you point me to a reference?

[nwlaurie]

Wikipedia will get you started - here is 'their' explanation:
Brazil nuts contain small amounts of radium. Although the amount of radium, a radioactive element, is very small, about 1–7 pCi/g (40–260 Bq/kg), and most of it is not retained by the body, this is 1,000 times higher than in other foods. According to Oak Ridge Associated Universities, this is not because of elevated levels of radium in the soil, but due to "the very extensive root system of the tree."[22]

[kelseymh]

Ah, okay, so there's no weird biochemistry involved, just a huge collecting surface. Wiki reference 22, from ORAU, has more details to confirm that, e.g., "higher radium concentrations are found in the leaves and cork of the tree than in the nut," as you'd expect from simple environmental concentration.

The article also points out that Brazil nuts are also high in barium, which is chemically quite similar to radium (just above it on the periodic table).

[nwlaurie]

'twould still be fun to try using nuts as a radiation source in this 'ible!