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706  Using Arduino / Project Guidance / Re: Cat Sprayer on: May 18, 2011, 05:32:50 pm
I don't know about a windshield sprayer.  Those shoot a pretty intense beam, I'm looking for light mist.

Just cut the nozzle off a cheap sprayer, and connect the hose from the pump to that.
707  Using Arduino / Project Guidance / Good Hot Melt Gun on: May 17, 2011, 09:49:36 pm
I've almost talked myself into buying a hot-melt gun. I really don't like to buy cheap tools, but I'm not going to spend a couple hundred on an industrial grade gun. Anyone have any experience with any particular guns? Brands to avoid? Brands that are good?

I'm sorta thinking in the short term, maybe the Arrow TR550, though I can't find any specs on the wattage. It appears to be only a high-temp gun (380F), so it's less versatile. Looks kind of tippy.

In a dual-temp gun, there's the Stanley GR25 and GR100, or a Surebonder DT280, or an Arrow TR400DT.

Ad-Tech looks nice, but they're more expensive, especially for a dual-temp (that's not a mini).
708  Community / Products and Services / Re: Freetronics "Eleven": Like an Uno, but with proto area on: May 17, 2011, 05:28:38 pm
You mean like, Frankenduino?

After years of assembling my own PCs, I have lots of those around. Never occurred to me that I wouldn't be able to use them. I'm sure I can come up with something, but I'm not going to make another parts order right now.

ETA: Also, those standoffs are very close, dimensionally, to a 4-40 D-Sub jackscrew. The thread pitch is finer. The nuts for either of those won't fit on the top edge, left side mounting hole, and the female portion of the screw will contact one of the pins on the underside. I don't know what that is there -- the 6-pin group immediately to the left of the AREF label, but on mine, it has a male DIP-6 header in place. Well, before this gets to be too much of a thread-jack, I have a few ideas for dealing with it.
709  Using Arduino / General Electronics / Re: voltage-controlled oscillator on: May 16, 2011, 09:29:38 pm
He appears to be asking about a simple low-frequency 555 circuit.  Something easier done directly with Arduino.

Easier? Depends. You don't need a PC with an IDE and a USB port (or serial port) to build on a 555/6.  smiley-grin
710  Community / Products and Services / Re: Freetronics "Eleven": Like an Uno, but with proto area on: May 16, 2011, 08:56:18 pm
Wish I'd known about this sooner. Well, for future reference, will these types of standoffs work in all the holes?

711  Using Arduino / Project Guidance / Re: Cat Sprayer on: May 15, 2011, 03:05:03 pm
Well, that was funny.

But it did bring to mind using a windshield washer pump instead of a spray bottle. Get one from J.C. Whitney, or your local auto parts store. Maybe 5 amps? Under $20.
712  Using Arduino / Project Guidance / Re: Cat Sprayer on: May 15, 2011, 12:43:02 pm
Maybe something other than a sprayer would be as effective.

Or, turn on a fan?

Maybe a cam driven by a motor could actuate the trigger on the spray bottle.
713  Community / Products and Services / Re: 15 dangerously Mad Projects for the Evil Genius on: May 14, 2011, 10:11:28 pm
That sounds fun.

Completely tangental, but it reminds me that I have, somewhere in storage, an issue of Radio Electronics which I saved specifically because it has plans in it for a low-cost home-grown tesla coil.

I noticed you have an Android book coming out too. Coincidentally, I read recently that Google has chosen Arduino for its open accessory kit.
714  Using Arduino / Project Guidance / Re: Differese between SPI, UART and USART. on: May 14, 2011, 09:53:32 pm
Do I get to say Neener-Neener now?  smiley-twist
715  Development / Other Hardware Development / Re: Core Memory Shield on: May 14, 2011, 09:37:06 pm
I did my first real programming on an IBM 360. Punched cards too.
716  Using Arduino / Project Guidance / Re: Differese between SPI, UART and USART. on: May 14, 2011, 09:35:11 pm
A UART is a Universal asynchronous receiver/transmitter. The most well-known implementation is for serial ports on PCs, where the 16550 is (or was, anyway) ubiquitous. It is an IC. A USART is similar, except that it also provides synchronous serial capability. Whether you could get one to work with an Arduino would depend, I guess, on the which chip you were trying to use, and how much work you wanted to put into programming. Since the Arduino already has TX/RX pins, and there are many existing solutions for serial communication, I don't think I'd be looking around generically for UARTS. I admit that I don't know, for example, whether the Maxim 3322E fits the definition of a UART (I suspect it does), but there's already information on using it. Or search the forum for RS485. I'm sure there are many options for serial communications, but it depends a lot on what you're trying to do.

SPI is SoyuzPlodImport, a Russian company known for being the producer of Stolichnaya vodka. I prefer Ketel One myself, but Stoli is pretty good stuff too.

Or, it could be the Serial Peripheral Interface Bus, which defines an electrical and communications standard for serial communication among devices. There is a SPI library for Arduino.

There's a handy search box at the top of every page. It will find lots and lots of info for you. smiley
717  Development / Other Hardware Development / Core Memory Shield on: May 14, 2011, 09:00:57 pm
I guess this is for when you need just 2 more words of memory ... (that's without ECC or a parity bit)

Arduino Gets Core Memory Shield.

Fully open design, so you can download the pcb drawing, parts list, etc. Core Memory Shield
718  Using Arduino / Project Guidance / Re: Please recommend a kit - can't decide and need your input on: May 11, 2011, 07:33:25 pm - is a nice free book but there are more.

New version:
v.4 is 404
719  Using Arduino / Project Guidance / Re: True Random Number Generator on: May 11, 2011, 07:06:38 pm
I think you might be asking whether there is some structure to the random numbers (perhaps a sinusoidal oscillation, for example) that, despite the distribution of 1's and 0's being the same, does not truly lead to a random sequence of integers.

I had some thoughts a while back about what I could try for generating TRNGs, mostly running to something resembling an electrostatic tweeter, except reading from it. Obviously, the "element" would have to be something very low mass. I usually consult Schneier on questions such as this. Here's a remark [not from Bruce] in randomness from quantum noise that rings true to me (which isn't particularly meaningful, since I'm not a cryptographer -- but I do read about this stuff).
As people are finding out TRNG's are not as good as they appear on paper, and are extrodinarly sensitive to influance from the environment they operate in. And importantly it is not always easy to tell the TRNG has been influenced by an external entity via a modulated RF carrier etc.

As was shown a little while ago by a couple of bods over at the Cambridge Labs, an unmodulated RF carrier can take a TRNG from 32bits to 8bits equivalent.
Which I'll leave as an exercise for interested parties to look up.

A 'long wire' sounds to me like an AM radio antenna. As such, I'm not sure there's any way for it to be non-deterministic. One obvious crack an attacker could employ would be to set up another long wire and read the same local RF noise you are.

And, somewhat echoing others here, a 50/50 distribution of ones and zeros could be the repeating pattern '10101010', or 1001110011' or some other longer repeating pattern. Sure, seems unlikely from RF noise.

Is your project just for demonstration, or are you planning some important real-world application for it? I found interesting reading searching Bruce Schneier's blog for 'random number generator'.

Also, I'm reminded of LavaRND.
720  Using Arduino / General Electronics / Re: Wiring a Z80 to Arduino... on: May 10, 2011, 06:08:48 pm
After I got bored toggling in programs (no cassette storage and no UV-EPROM programmer), I bought a Nascom 1, but still couldn't afford an assembler, so I became very adept at hand-assembly - I still remember that "INC HL" is 0x23.
How sad is that?

Not sad at all. Hey, I still think back fondly on my days writing Macro-11 on PDPs. How can you not like an instruction set that contains SOB (Subtract One and Branch). Back then, we worked pretty hard to write really good, clean, elegant, efficient code. I'm guessing any newer embedded system these days has more RAM than we did, and we ran the OS and DECnet, plus our applications. Those were (mostly) fun times.
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