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I'm trying to convert an ardiuno project over to a Netduino Plus. The original is feed with 20V and that is available on the Vin points. Does anyone think there is a way to modify a Netduino Plus to be able to handle a higher input voltage than 9 volts?
if you don't need that much current, your netduino should just be able to handle 20V, according to the datasheet of the voltage regulator, I wouldn't recomment it though. I think what you need is a voltage regulator, like this one: http://www.parts-exp...partnumber=7809
It's just a few cents more (free shipping), has an adjustable output from 1.5V to 35V (when fed 4.5-40V) and you can pull 2A from it. I got a whole bunch of these and use them in lots of projects. These switchers don't get hot even when you pull 1.5A while a regular LDO would get smoking hot or even burn (depending on the specs).
Simply feed the step-down your 20V, adjust with the pot to 9V to feed your Netduino. Then just bypass the incoming 20V to whatever you need it for.
The point is I need to get enough voltage across the transistors to put them into an avalanche condition.
In looking at the Netduino Plus 2 schematic, the shottkey diode and voltage regulator are both rated high enough. But there is a voltage comparator circuit that I have not yet check for voltage tolerance. There may also be a heating problem with the primary voltage regulator cutting down 20v to 5 v.
in a slightly different direction -- the STM32F has a hardware RNG on-chip. The world will thank you for a firmware mod supporting it if you can swing it. I'll do it myself eventually, but I can't seem to get back to firmware modding just now....
I thought you needed quantum leaps for true random numbers, but maybe that's what RNG basically is?
There's a 12V DC adapter in the BOM so one would think that what is used for Vin in the schematics. If so, there wouldn't be a problem since the Netduino Plus can handle that voltage.
Anyway, I wouldn't risk the board by feeding it 20V, especially not when a dc/dc is less than 2 USD.
@hanzibal, yes you are right, basically, the hardware RNG described is (ostensibly) using quantum phenomenon to generate true random numbers because of avalanche breakdown, wilt self-destruction limited by the resistor to the high voltage, and amplified to a signal the chip can sample and use.
The STM chips use a similar analog technique; they aren't explicit about what it is, but I don't think it's avalanche based.
The 12V is possibly OK instead of the 20. The higher voltage is desirable because it makes more noise, but really since you probably don't want to use the random numbers directly from the generator anyway, its likely OK, since I imagine you are going to do what is traditional and suck a long sequence of them in to seed into a CPRNG like blum blum shub or something like that. If 12v is enough to get you some random noise, but with color that you can diminish sucking more in, then that's probably better than fighting the voltage problem.
Alternatively, if your really want the voltage, you could try making a simple charge pump with some discretes and a free PWM pin if you've got one.
My backup solution is to use a MAX232 chip and bridge across it's plus and minus to get 20. I noticed the Arduino solution has a drifting problem that I wonder if maybe it's heat problem due to the regulator having to chop the voltage down to 5V.
Over the weekend, I hope to build up a prototype circuit to try the lower voltages and different resistor value to create similar conditions. We shall see.
Once I get the solution up and running, it will be interesting to compare the noise based RNG to the STMs numbers and see if there is a difference.
The objective of this project is to create a RNG that anyone can build. The ultimate user for this are researchers who want a true RGN rather and a PRNG.
Sorry, for going on about dc/dc but there are also step-up converters equally priced. Is "[color=rgb(40,40,40);font-family:helvetica, arial, sans-serif;]RNG that anyone can build[/color]" in the form of only using standard parts the reason for wanting to avoid these converters per sé or am I missing the point here?
Why not build a simple charge pump like ziggurat29 suggested, the MAX232 uses one.
About drifting, obviously you must achieve a perfectly white noise to get as a rectangular probability distribution as possible. You could verify that by letting the thing run for weeks under different working conditions respectively to see if the 0/1-distribution really converges to 50:50 compared to a goal set in double precision. In the end that's the only thing that matters. If your device does not meet this requirement, it would be totally useless to anyone, let alone researching scientists.
What's your comment on the 12V DC adapter found in the BOM for the schematics you referred to?
From a philosophical perspective, I personally don't think that we can ever observe true randomness due to the Heisenberg principle of uncertainty. It would be like trying to have a camera take photographs of itself
The objective of this project is to create a RNG that anyone can build. The ultimate user for this are researchers who want a true RGN rather and a PRNG.
and more practically, it's critically important for folks doing crypto.
...From a philosophical perspective, I personally don't think that we can ever observe true randomness due to the Heisenberg principle of uncertainty. It would be like trying to have a camera take photographs of itself
I would even argue the mentioned entity is but a commonly used metaphor for the dice themselves.
well discussions on the topic of the mentioned entity can certainly generate a lot of noise, but I don't know if there's enough entropy in that source, haha, but now we are truly off topic! haha
Is "[color=rgb(40,40,40);font-family:helvetica, arial, sans-serif;]RNG that anyone can build[/color]" in the form of only using standard parts the reason for wanting to avoid these converters per sé or am I missing the point here?
Yes, the objective would be to publish a set of directions to build one. The target audience is most likely mathematicians and statisticians, so I want to make it as purchase and assemble as possible. The entropy circuit will have to be built so I'm ultimately looking for as low a part count and easy to acquire as possible.
Why not build a simple charge pump like ziggurat29 suggested, the MAX232 uses one.
That is a variation of the backup plan of using the MAX chip. I'll definitely consider both and see which one works out as esayist to implement. After experiments on lowering the voltage I'll know if I need to consider a pump up solution.
You could verify that by letting the thing run for weeks under different working conditions respectively to see if the 0/1-distribution really converges to 50:50 compared to a goal set in double precision. In the end that's the only thing that matters. If your device does not meet this requirement, it would be totally useless to anyone, let alone researching scientists.
I'm already started implementing software testing the output of RNGs to the NIST standard. Part of the package would be a set of test the user can run at a regular period to verify their RNG is running up to standards.
What's your comment on the 12V DC adapter found in the BOM for the schematics you referred to?
Its a step in the right direction, but it's still 30% over Secret Lab's specs for the Netduino Plus 2. Over is over, so 12V vs 20V doesn't change the subject of running the board over voltage. Now if I can bend their circuit down to 9V, then we have a solution.
If you guys are interested, I'll keep updating with what I find. I don't want to be wasting band width of no one cares.
...Its a step in the right direction, but it's still 30% over Secret Lab's specs for the Netduino Plus 2. Over is over, so 12V vs 20V doesn't change the subject of running the board over voltage. Now if I can bend their circuit down to 9V, then we have a solution.
Yes, I was thinking of the regular NP which can handle 12V plus it would indicate that the design you referred to runs off 12V and hence doesn't require 20V but I'm not very knowledgable when it comes to avalanched transistor circuitry.
Good luck and keep us posted!
The power then goes to an MC33269DT-5.0G Low Drop Out voltage converter (on the left of the Barrel connector on the schematics). The MC33269DT-5.0G has a max voltage input of 20.0volts. IMHO, you want it lower than that.
BTW, the zener and the LDO will have to convert the input voltages down.
When they do that, they generate heat.
The more current that is converted, the more heat that is generated.
So, basically, do not run a shield/SDcard/etc from the N+2. It wouldn't hurt if you glued the Zener to the N+2 board. In fact, it would help with heat dissipation from the zener.
haha, nice; actually, using zener noise is another common hardware RNG source, so maybe you can save even more parts!
Another pedantic point while I'm apparently on some kind of roll is that what we call zeners out of convention, usually actually work more by avalanche effect, which is what the O.P.'s circuit is doing, ha!
Lastly, simply converging on a 50/50 distribution (or any flat distribution) is not a good measure of randomness. You can imagine the degenerate case of a counter -- it will average 50% above the middle value, and 50% below the middle, and with equal distribution of all values in between, but a ramp function is surely not random. Establishing randomness quality is fairly difficult, and a lot of science has gone into devising tests. And so many crappy generators over the years, its the stuff of fable...
I never get tired reading your posts Dave, there's usually a couple of good laughs in them and I bet you've read "The hitchhikers's guide to the galaxy" more than once.
Surely, perfectly rectangular distribution is not a good measure since a^=1 would produce that, while perfectly white (Gaussian?) noise would but I don't know how to measure that other than in terms of variance or period length.
In school we rolled a hundred dice a hundred times and after each roll we counted the numer of ones, twos, threes,...sixes and found (quite naturally, or?) that the relative frequency converged to 1/6th. Quite unsurpricingly but at the same time fascinating when you think of it and really ask your self "but why exactly?". I guess its a force of nature really. What we did was creating a histogram which is pretty much the Fourier transform, basically saying that any signal (stochastical or otherwise) can be broken down to a number (possibly infinite as in the case of square waves) of sinusoidals. In our case, I guess the "sinusoidals" were stochastical signals, simultainiously strectching in all possible directions but projected onto a vector in a six dimensional universe - the dice ;-)
Now, you must be even more tired of me than of Dave and therefore I promise not to write any more in this post :-)
I would even argue the mentioned entity is but a commonly used metaphor for the dice themselves.
