Good Morning All,
I have no experience in destroying crystals by physical abuse, but they always come with the warning "fragile"
Can anyone clarify how fragile they are? Anecdotal old-timer and new-timer input is most welcome.
David Eather wrote in news:icOdnQyUYtkC2BfTnZ2dnUVZ snipped-for-privacy@giganews.com:
A 0.1 mm thick small sheet of glasslike(quartz) material, suspended on 2 thin wires. Now what happens when you abuse that? (hint, it might shatter?)
snipped-for-privacy@giganews.com:
Kind of like a processor chip, only less wires.
People stick them in model aeroplanes and them plant the plane into the ground at 40mph and the crystals still work (mostly), but I hear dropping one 4ft on a hard floor will kill it - so I don't know what to think
For constant acceleration from rest,
v**2 = 2as,
where a is the acceleration and s is the distance it acts through.
If you drop a crystal a distance S and slow it to rest in a distance s, the delta-V is the same magnitude, so the ratio of the accelerations is
a/g = S/s.
Thus if you drop it 1m and bring it to rest in 1 mm, it experiences 1000 gees. If it's more like 100 um, because a little thing like a crystal won't dent the floor or its own case much, that's 10,000 gees.
A model airplane slowing from 40 mph (18 m/s) in half an inch experiences an acceleration of
a = 18**2/0.012 = 27000 m/s**2, or about 2750 gees.
So a drop on the floor can easily be 3x worse for the crystal than a model airplane crash.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
A lot depends on what kind of crystal it is, how it's packaged, and so on, but I know I wouldn't want _any_ of them to fall off my bench onto the hard (tile, hardwood, concrete, etc.) floor.
I guess a good rule of thumb would be to handle it like an egg.
Good Luck! Rich
"Phil Hobbs"
** You just equated m/S with a drop distance.Realistically, the radio receiver inside a model plane is cushioned against motor vibration in a foam wrap and situated in the middle of the fuselage. That fuselage has to collapse before the Rx come to a stop after a hard impact.
18m/S equates to a drop distance ( in vacuo) of 16.5m and the real distance to stop is more like 0.1 to 0.2 metres.So the impact force experienced by the radio and crystal is about 80G to
160G.The real killer of crystals is severe vibrations at a few hundred Hz - a so I am surprised to see them on PCBs inside high powered speaker boxes used in PA systems.
FYI: they are associated with inbuilt uP control and DSP systems.
BTW: crystals used in RC gear are normally the HC49 style.
.... Phil
That's (18 m/s)(18 m/s)/0.012 m = 27000 m/s**2, which is an acceleration. (It's actually the acceleration due to stopping in a quarter of an inch, because I forgot the factor of 2.)
It's intended as an upper limit, to show that falling on a hard floor is easily as violent to a small crystal as crashing a model airplane.
If the plane comes apart, the acceleration will probably be much less than this, but the point is that even if it doesn't, it's still gentler.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
I used to try and change frequency, and that usually meant fracture.
Greg
A picture can be worth more than a thousand words. So here are the innards of a HC-49 crystal:
It can be ok if the inner guts hit the can. They'll bounce back. But there'll eventually be a limit reached where the disk comes off or the same thing happens that you'll see when a wine glass falls onto tile.
-- Regards, Joerg http://www.analogconsultants.com/
I've done that a few times. Didn't have any breakage. But most were the old style military crystals that you could open with a Philips screwdriver and take the crystal out for sanding and polishing. Only one was a HC-49 but that worked in a radio for more than a decade. Bet it still works but then I married and ham radio went onto the back burner :-)
-- Regards, Joerg http://www.analogconsultants.com/
"Phil Hobbs"
** Invented examples have to be realistic or nothing is demonstrated by them.They are just bullshit.
Like you.
..... Phil
Where was that dimensional error you accused me of, again?
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
On a sunny day (03 Oct 2011 23:37:11 GMT) it happened Sjouke Burry wrote in :
I have not seen them shatter, but I have seen the connections come lose.
Here's something real: one of my students designed a tiny telemetry system built onto a PCB only about 2 square cm in size. He panelized the design, stuffed the panels, and used a milling machine to cut the boards apart. About a third of the crystals didn't survive the process.
-Jim MacA.
"Jan Panteltje"
** There you go again - Mr WOG SHIT HEAD.What you have NOT seen is testament to how ignorant you are.
---------------------------------------------------------------------
Only COLOSSAL FOOLS brag about their own ignorance.
Piss off.
.... Phil
Crystals used in filters in some old telecommunications frequency domain multiplexing gear when I first started my first job were maybe 5mm wide x
40mm long and mounted in a tube similar to an old valve / vac tube. The gear was full of them.
I wish that that saying could somehow be turned into a catchy phrase that would then become a cliche and then used often.
"brent" "Phil Allison"
I wish that that saying could somehow be turned into a catchy phrase that would then become a cliche and then used often.
** Hmmmm - nice suggestion.You mean something along the lines of:
" If wishes were horses, then beggars could ride. "
or:
" If you cannot blind them with science, baffle them with bullshit. "
or how about this one I just though of:
" Truth is often stranger than fiction, while fiction is simply never true. "
... Phil
People stick them in model airplanes, soldered to receiver boards and wrapped in foam (or firmly attached to the structure with double-sticky tape). The shock of any impact gets significantly diminished just by being soldered into a structure.
Leave off the foam packing in an engine-powered plane, and you'll have a free-flight airplane some time before you land. (This I know from experience -- three times, because I was a slow learner when I was 18).
-- www.wescottdesign.com
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