Random Number Generator Usage
The B7 switch on the back of the module should be set before the module is powered on, in or-der to select the RNG mode of operation. Module has three options switched B6 to B4 (see fig-ure 7) for selecting number range. Current version of RNG module can produce 7 different ranges of random numbers.
Set the switches for the range of your choice. Plug one end of the 3.5mm (1/8”) male to male cable into the Digital out of the Analog Geiger counter / Audio out of Digital Geiger counter. Insert the other end of the 3.5 mm cable into the J1 “Digital Out” socket on the DMAD. Turn the Geiger Counter on, then turn the module on. If there is no display on the LCD, adjust the contrast control on the back of the module.
When the module is powered on, LCD Screen will be blank for 1 second (LCD screen is initial-ized during this time) & then a splash screen will be displayed with text “Random Number” appearing on top line of LCD Screen, followed by text “Generator” on bottom line of LCD Screen. Splash screen will be displayed for a minimum of 1 second, after random number gen-eration commences. Module will display the random number generated on LCD screen only when Geiger counter detects the radiation particle. This can take a while (average background radiation particles count per second is 20, if background radiation level is low in your location. Till first radiation particle is detected, LCD Screen will display splash screen.
Once random number generation commences, for each random number generated LCD Screen will show text “Range : 1 to 2” in top line, (range selected here is 1 to 2 for example). Bottom line will display text “Generated :” followed by the random number generated. This display will be present till next number is generated, after which display will be refreshed to display current number.
In reality random numbers generated inside microcontroller for any selected range starts from 0 instead of 1. Before the generated number is displayed on LCD Screen and serially sent out, 1 is added to generated number to shift the range from starting 0 to starting 1. This is done be-cause conventional counting system starts from 1.
As each radiation particle is detected by Geiger Counter, a new random number is generated and displayed on LCD. At the same time number is sent out via TTL serial port that can be ac-cessed by header I/O & 3.5 mm socket on the back of DMAD Module. This allows any system to take the random numbers generated by this module for further use. PC can be connected to this module with optional RS-232 cable and a proper interface to read random numbers gener-ated. Serial Data format is 9600 Baud, 8N1 with a byte wide data for random number.
Random Number Generation Theory
True random numbers are useful for data encryption (cryptography), statistical mechan-ics, probability, gaming, neural networks and disorder systems, to name a few.
Random numbers generated by a computer are notoriously random in an exact defined- pattern. So much so that they are many times referred to as pseudo-random numbers. The random num-bers generated by this module are truly random.
The way the RNG module operates is simple to understand. However, its fundamental function is best described using a mechanical analogy. Imagine a sequence of numbers painted on the outer edge of a revolving wheel. There is a pointer on the outside of the wheel that points to the number at the top of the wheel. The wheel is set into motion, spinning very rapidly. Then at any given “random” moment in time the wheel is instantly stopped, and the number under the pointer becomes our random number. Once read, the wheel is set back into motion again for next random number generation.
The electronics follow pretty close to the mechanical analogy. The microcontroller spins the sequence of numbers internally. The random point in time when the sequence of numbers is in-stantly stopped is generated by the detection of a radioactive particle by the Geiger Counter. Background radiation is an ideal quantum mechanical random time-delay generator because it is impossible to predict with any accuracy the exact moment a radioactive particle will be de-tected. When a particle is detected, a positive pulse is sent to the Digital out of Analog Geiger Counter / Audio out of Digital Geiger Counter. This module is connected to Digital out of Ana-log Geiger Counter / Audio out of Digital Geiger Counter. On RNG Module, the positive pulse is connected to microcontroller input pin. This positive pulse generates an interrupt in the mi-crocontroller that stops the numbers from spinning. The number is read, displayed and sent out serially on the TTL port.
We determine how many numbers are painted on the wheel by setting the jumpers on the back of this module i.e. setting the range of random number being generated.
There is a simple test to find the trueness of random numbers. If you add all the random num-bers that are generated (let’s call this number N) and divide that by number of samples you added together (Let’s call this number S) the answer should be approximately 50% of your number range (Lets call this number R).
For example using a range of 1 – 10, so R = 10. The number of random number samples, is 100, so S = 100. We add those 100 random numbers together, that equals N. So N/S = .5 R In this case the number N when divided by S (100) should equal approximately 5. This would show an even distribution of random numbers though out the range of 1 - 10.
Following link has a test program that will read a file of random numbers and analyze the ran-domness of the numbers in the file. http://www.fourmilab.ch/random/ We have not tested random numbers generated by this module with the above test program.
Background radiation consists of three sources; Cosmic radiation from the sun and stars. Ter-restrial radiation from low levels of uranium, thorium, and their decay products in the soil, air and water. Internal radiation from radioactive potassium-40, carbon-14, lead-210, and other iso-topes found inside our bodies.
