There is really not much current flowing through the LED in series with the 22kohm resistor, so it is not a lot of heat sloshing around in there. But there would be a maximum power point, i.e., not much IV power dissipated in a high threshold green diode due to low I, and not much either in a low threshold silicon diode due to low V . The threshold is temperature dependent. The PAUSE 1 is probably not enough time for the capacitor to charge all the way back up, and the interval after the RCTIME is not enough for the capacitor to discharge completely. So the initial conditions each time around the loop will fluctuate. There will be soakage in the capacitor too.
The RCtime circuit is quite sensitive to wiring practice. Poor wiring with a roundabout ground trace can also make a pretty good randomness generator.
I was in grad school when a lot of thought was being given to chaotic dynamics. How very simple difference equations could generate apparently random noise. This could be applied to circuits with several different time constants and a nonlinear element like a diode or a threshold element. I did a lot of experementing with programmable unijuction transistors.
So it is heat.· And I did pick 1 ms for it's affect on the randomness. I did notice that an ungrounded circuit gave good randomness but bad repeatability. Changing the length of the wire made any signal disappear. So when I started playing with this circuit I made I did target repeatability. I hope I achieved it.
So, my question for you Tracy is, do you see this circuit as a viable, repeatable solution for randomness? And this question goes out·to anyone who's tested the circuit. If so I will post it on completed projects as a tool for everyone to use.
I am leaning towards·using the Infrared instead of the Red LED so noone trying to build the circuit has problems selecting a diode?
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Have Fun
TR
Post Edited (TechnoRobbo) : 9/11/2007 7:40:12 PM GMT
What do you mean by "repeatable solution for randomness"? I presume not "repeatable" in the sense of pseudo-random as produced algorithmically by RANDOM, but one that will work repeatably with any IR LED and reasonable circuit layout. I don't know. Absent a good handle on how it produces its randomness and how components and layout affect the result, it's cut and try to gain confidence that it "always" works!
Yes, I meant one that will work repeatably. I guess I'll put it out there for peer review. I'll include a caveat that I'm not exactly sure why it works but it seems to work good. Let others add their theories. As far as I'm concerned, it's now public domain.
Comments
The RCtime circuit is quite sensitive to wiring practice. Poor wiring with a roundabout ground trace can also make a pretty good randomness generator.
I was in grad school when a lot of thought was being given to chaotic dynamics. How very simple difference equations could generate apparently random noise. This could be applied to circuits with several different time constants and a nonlinear element like a diode or a threshold element. I did a lot of experementing with programmable unijuction transistors.
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Tracy Allen
www.emesystems.com
So, my question for you Tracy is, do you see this circuit as a viable, repeatable solution for randomness? And this question goes out·to anyone who's tested the circuit. If so I will post it on completed projects as a tool for everyone to use.
I am leaning towards·using the Infrared instead of the Red LED so noone trying to build the circuit has problems selecting a diode?
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Have Fun
TR
Post Edited (TechnoRobbo) : 9/11/2007 7:40:12 PM GMT
What do you mean by "repeatable solution for randomness"? I presume not "repeatable" in the sense of pseudo-random as produced algorithmically by RANDOM, but one that will work repeatably with any IR LED and reasonable circuit layout. I don't know. Absent a good handle on how it produces its randomness and how components and layout affect the result, it's cut and try to gain confidence that it "always" works!
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Tracy Allen
www.emesystems.com
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Have Fun
TR