Random Numbers help

Projects Programming
1

Hey guys, I thought I would drop by here for help.

I am writing a program where I need to generate a random set of lest say 50 numbers from 8 to 11, and have a new set of 50 if I restart the program, or some condition is not met.

Here is part of my code that generates a random set of 50.
while(i<=49){
ledB*=random(8,12);*

  • i++;*
    }
    The problem is that when I restart the program, I get an identical set of 50 AGAIN. But what I need is a new set of 50.
    If the function random(min,max) is not random what is it used for?
    Thank you
2

You need to 'seed' the random number generator in the setup portion of your sketch using the randomSeed(seed) function:

http://arduino.cc/en/Reference/RandomSeed

That reference shows using a analogRead on an unconnected analog pin to get a different seed number for each startup of the program. There is a active posting around here on trying to find a better source for a seed number that is truly random, check it out.

Lefty

3

Thanks retrolefty,

Want to make something sure.

The way random number generator, gets the numbers is by taking a number say 9999 and applying a formula to it.

When you do randomSeed, it randomizes the number that it applies the formula to.

Am I right? If that is the case what is the purpose of not randomseeding?

4

randomSeed just specifies the initial number. I don't know the default, maybe zero.

Why not do it? Well you may be testing some code and want the same test data every time through.

5

The active link to automatically reseed the RNG at startup - http://arduino.cc/forum/index.php/topic,66206.msg537783.html#msg537783 -