Sampling a Voltage 1

[bpentz]

Hi,

I'm a new poster but I read these forums often. I recently built a circuit that generates random bits from amplified resistor noise. Currently, the output is a voltage of either 5V or 0V, changing very rapidly. I need a way to sample the output to a computer so that I can use 8 bits in a row to produce a number between 0 and 255. What is the best way to do this? I do not have any bugdet concerns, and I want to be able to easily move this Random number generator to any computer. Any tips, links, or help is well appreciated.

 

[itsmoked]

I would probably run your random signal into a serial to parallel shift register then just read out the the shift register when you want the number.

 

[Madcow]

A micro processor and pick an interface.
rs 232 , usb , 10/100 ect..

 

[VEBill]

Just connect your random bit to an input port and assemble the 8-bit number in software. You'll just need a wire (or perhaps two including the return or ground).

Once the numbers are flowing in, be sure to check them using software to make sure that they're truly randomly distributed.

They probably won't be because your random bit probably isn't perfectly distributed between 0 and 1. It might be very close, but almost certainly not quite perfectly 50:50. Maybe the rise time is a shade different than fall time, or any number of reasons. Thus the 8-bit numbers will not be perfectly distributed but will show odd patterns based on what might be called 'parity'.

All great fun as long as you're not expecting perfection.

 

[itsmoked]

You guys HAVE seen this site right?!

http://www.fourmilab.ch/hotbits/how.html

http://www.fourmilab.ch/hotbits/hardware.html

http://www.fourmilab.ch/hotbits/generate.html

 

[bpentz]

itsmoked: Yes I have seen that site. The thing is, I am looking to use odd (perhaps biological) materials as the resistance eventually. I will change it from a DC to an AC bias to do this. Therefore, I need my own RNG. Thanks, though.

Everyone else: Thanks a bunch, I'll try some of these things, and probably end up using a microprocessor with usb or rs232 if the others dont work.

 

[itsmoked]

Sounds like a cool device. Please keep us posted. We love random stuff.