If you want a big bang, then I'm *really* surprised no one has mentioned
Tantalum capacitors yet...

On 1/22/06, Peter Todd <pete@petertodd.ca> wrote:
>
> On Mon, Jan 23, 2006 at 07:42:57PM +1300, Jinx wrote:
> > > I also tried some standard low-intensity red LEDs.... They are
> > > very boring to say the least. At 10V they blow for about 10
> > > seconds then die. At 15V they die instantly. In both cases you
> > > can see a bit of a black spot by the die. No fun
> >
> > How inconsiderate of them.......
>
> Yes indeed. I think all electronic componants should fail spectacularly
> with a loud bang, a shower of sparks and leaving highly visible
> scorchmarks.
>
> > If you have enough I/O you could drive the "fuses" by x/y, similar
> > to the simplest keypad arrangement
>
> IO is no big deal, I'll just use i2c IO expanders or whatever else it
> takes. Density will really be the issue, because I want everything to
> fit on the periphery of the grid, yet still have enough current capacity
> to work. From prior experience with LED arrays, that can be rather
> tough.
>
> Yes, you are right about the x/y. For some reason I was thinking for a
> bit that you needed diodes for the interconnections between the x and y
> layers.  But no, I am completely and utterly wrong on that one. :)
>
> > Could you perhaps use thermochromic paint in any way ? You can
> > get both reversible and irreversible types. I know the irreversible
> > stuff is used to record if eg refrigerated food has been exposed to
> > too high a temperature. I think it goes blue or black, don't know
> > what colour it starts at though
>
> Thank you! That's a wonderfull idea. A quick google search for
> "thermochromic irreversible" showed up http://www.chemsong.com/spec.htm
> which states that they have inks that go from black to red, or black to
> blue, at 120C. If that's true I could simply paint the whole backside of
> the PCB with the ink. I'll have to ask the manufacturer about stability
> though, don't want the inks to be the same as in thermal paper...
>
> I just tried experimenting with regular paper too actually. It browns
> very reliably at 500C (measured with a cheap thermocouple) and
> predictably chars or starts to burn when exposed to a red-hot wire. If I
> sandwitch a wire and the paper between two sheets of glass and apply
> current I get a very nice scorch mark, yet no matter how much current I
> apply I can't get it to actually catch fire, presumably because of how
> little oxygen is present. If I can treat the paper somehow so it won't
> support combustion I should be set, and safe.
>
> Well... I think I have my irreversible thermochromic ink for my
> prototype at least. I think a nice pristine white sheet of paper would
> look very beautifull too, carefully sandwiched behind glass, over time
> ending up as a white sheet of paper with 4000-odd burn marks on it...
>
> --
> pete@petertodd.ca http://www.petertodd.ca
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--


Shawn Wilton (b9 Systems)
http://black9.com
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