Reply by josephkk June 29, 20132013-06-29
On Thu, 27 Jun 2013 18:27:55 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

> >>As far as some sort of accuracy... It's hail... can there be that much =
accuracy? =20
> >IEC 61215 10.17 comes from a committee of interested parties, that >probably have investments in companies that manufacture the required >test equipment. It is therefore to their benefit to make the accuracy >requirement as expensive as possible.
Typical standards comities are composed of vendors / manufacturers, end users, test equipment manufacturers, academics, and others with an economic interest (or compliance interest) in the outcome. Take LEED standards for an example: http://www.usgbc.org/leed I could just as easily selected ASTM, TIA, IEEE, NEMA, UL, or over a hundred others. ?-)
Reply by Michael A. Terrell June 29, 20132013-06-29
Joe Gwinn wrote:
> > In article <APidnfkuDIdgYlDMnZ2dnUVZ_rWdnZ2d@earthlink.com>, Michael A. > Terrell <mike.terrell@earthlink.net> wrote: > > > Spehro Pefhany wrote: > > > > > > Michael A. Terrell wrote: > > > > > > > > Has anyone ever worked with 'Glass break detectors' for alarm > > > >systems? The old ones were tuned for the sound glass makes when it > > > >breaks, but some could detect the sound it makes before it shatters. > > > >The output was analog. I haven't worked with them for over 35 years, and > > > >don't remember the details. > > > > > > I just remember the ones that were made with foil.. > > > > > > That's late 1800s technology. Back when Ademco used brake drums for > > alarm bells.:) > > I recall a vibration detector design from the 1970s that used a > gold-plated ball bearing nesting in the cavity between three > gold-plated brass screw heads arranged in an equilateral triangle. The > vibration caused the ball to jiggle, breaking the circuit. > > The advantage of the ball was that its weight made it largely immune to > low-frequency vibrations, as from passing trucks. > > The lower-cost variation was two horizontal rods passing through the > center of a big washer, all gold plated. Vibration caused the washer > to jiggle on the the rods. > > The advantage of such designs was that they could be part of a typical > supervised-loop burglar alarm system, were dead simple, and were > electronics-free.
I saw all that stuff, back in the '70s when I helped a friend start an alarm business.
Reply by Joe Gwinn June 29, 20132013-06-29
In article <APidnfkuDIdgYlDMnZ2dnUVZ_rWdnZ2d@earthlink.com>, Michael A.
Terrell <mike.terrell@earthlink.net> wrote:

> Spehro Pefhany wrote: > > > > Michael A. Terrell wrote: > > > > > > Has anyone ever worked with 'Glass break detectors' for alarm > > >systems? The old ones were tuned for the sound glass makes when it > > >breaks, but some could detect the sound it makes before it shatters. > > >The output was analog. I haven't worked with them for over 35 years, and > > >don't remember the details. > > > > I just remember the ones that were made with foil.. > > > That's late 1800s technology. Back when Ademco used brake drums for > alarm bells.:)
I recall a vibration detector design from the 1970s that used a gold-plated ball bearing nesting in the cavity between three gold-plated brass screw heads arranged in an equilateral triangle. The vibration caused the ball to jiggle, breaking the circuit. The advantage of the ball was that its weight made it largely immune to low-frequency vibrations, as from passing trucks. The lower-cost variation was two horizontal rods passing through the center of a big washer, all gold plated. Vibration caused the washer to jiggle on the the rods. The advantage of such designs was that they could be part of a typical supervised-loop burglar alarm system, were dead simple, and were electronics-free. Joe Gwinn
Reply by Michael A. Terrell June 28, 20132013-06-28
Spehro Pefhany wrote:
> > Michael A. Terrell wrote: > > > > Has anyone ever worked with 'Glass break detectors' for alarm > >systems? The old ones were tuned for the sound glass makes when it > >breaks, but some could detect the sound it makes before it shatters. > >The output was analog. I haven't worked with them for over 35 years, and > >don't remember the details. > > I just remember the ones that were made with foil..
That's late 1800s technology. Back when Ademco used brake drums for alarm bells.:)
Reply by Joe Gwinn June 28, 20132013-06-28
In article <ck3ns85un3gj03cd8k22gpjt3kf6m76fl2@4ax.com>,
<mharris@comprodex.com> wrote:

> I would like to inquire regarding circuit design options for a > custom-made testing device. > > It is intended to test the breaking strength of glass sheet on solar > panels in the field. Hence, it needs to be portable, running off > something like two 3.7V Li-ion batteries. > > The concept is to use a solenoid-type plunger that is activated one > time by a push button. This strikes the glass with a predetermined > breaking strength to check for durability against hail damage, etc. > > I suspect something like a storage cap would be required, but would > appreciate some suggestions on how best to proceed. I repeat, the > device needs to be small and battery powered (for safety).
Why so complicated? Just drop a ball bearing a specified distance onto the glass sample, just like the test for the breakability of industrial safety eyeglass lenses. What I recall for industrial lenses is that the test used a 16-ounce steel ball dropped one foot. I had an old pair of glasses with industrial tempered glass lenses, so I took a lens out, put it in a horizontal plank, outward side up, and dropped a 16-ounce hammer head on it. The lens survived. So I kept going higher till it broke; don't recall the final height, but it was a lot more than 12". So that's why my father always bought industrial lenses for me. For all eyeglass lenses (non-industrial): "The regulation at 21 CFR 801.410(d)(2) describes the exact procedure for the impact test (See Appendix A). The regulation states, &#2013266099;In the impact test, a 5/8-inch steel ball weighing approximately 0.56 ounce is dropped from a height of 50 inches upon the horizontal upper surface of the lens. The ball shall strike within a 5/8 inch diameter circle located at the geometric center of the lens. The ball may be guided but not restricted in its fall by being dropped through a tube extending to within approximately 4 inches of the lens. To pass the test, the lens must not fracture&#2013266058;.&#2013266098; Joe Gwinn
Reply by Don Lancaster June 28, 20132013-06-28
On 6/27/2013 9:48 AM, Syd Rumpo wrote:
> On 27/06/2013 17:18, Spehro Pefhany wrote: >> On Thu, 27 Jun 2013 23:34:37 +1000, mharris@comprodex.com wrote: >> >>> >>> Thanks for sall the mechanical suggestions. We ruled these out due to >>> inherent variables and aging of parts. >>> >>> Can anyone tell me how to build a solenoid operated plunger that will >>> have the necessary force? Or at least a viable starting point with >>> regard to circuit design. >>> >>> Mark "Hailstorm" Harris >> >> >> They're all mechanical to some degree. >> >> It remains to be seen whether the friction and other temperature etc. >> related variations in a solenoid plunger would be any better than an >> electronically calibrated spring force. >> >> Regardless of how you drive them, solenoids provide a very nonlinear >> force with plunger position.. so they're actually not very well suited >> to your application. The more efficent ones (with a closed magnetic >> circuit when they're actuated) are much worse. Some of the temperature >> related variation could be eliminated with a constant current type >> drive, but I doubt that's your biggest problem with that approach. >> >> Maybe you could fling a mass around with a motor. Or pump up a >> relatively large reservoir with air to a calibrated pressure and use >> an air cylinder. Or if cost is not a concern and you're stuck on the >> solenoid-ish idea, consider a linear motor*. > > <snip> > > A 'voice coil actuator' would be better than a solenoid. I know little > of these but Google has lotsa hits... > > http://www.orlin.co.uk/voice-coil.htm is one such. > > Cheers
Do it pneumatically. -- Many thanks, Don Lancaster voice phone: (928)428-4073 Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 rss: http://www.tinaja.com/whtnu.xml email: don@tinaja.com Please visit my GURU's LAIR web site at http://www.tinaja.com
Reply by Charlie E. June 28, 20132013-06-28
On Thu, 27 Jun 2013 18:27:55 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
> >The tempered glass appears to be strong enough to withstand a nuclear >blast, and will certainly survive an ice cube drop. A quick search >with Google excavates little concern over hail stone damage. However, >I suspect that installers, dealers, and insurance underwriters might >want to know, which may have inspired this project. >
I have a friend who lives in a golf course community. He found out (to around $8K in damage!) that solar panels can not stand up to a well driven golf ball! He put up screens about a foot over his panels to protect them from the golf balls. Would probably work for hail as well. Of course, it does cut back on his production a little bit... Charlie
Reply by Ralph Barone June 27, 20132013-06-27
<mharris@comprodex.com> wrote:
> Thanks for sall the mechanical suggestions. We ruled these out due to > inherent variables and aging of parts. > > Can anyone tell me how to build a solenoid operated plunger that will > have the necessary force? Or at least a viable starting point with > regard to circuit design. > > Mark "Hailstorm" Harris
As I see it, your problem (and the device you want) are inherently mechanical. The electronics you seek are mainly a wrapper around the mechanical bits to calibrate it. So perhaps rethink and repose the question in that manner.
Reply by Jeff Liebermann June 27, 20132013-06-27
On Thu, 27 Jun 2013 20:21:40 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

> has anyone ever worked with 'Glass break detectors' for alarm >systems?
Not worked with, but I do have one on my office windows. However, I didn't have a sensor on the front door. So... <http://www.11junk.com/jeffl/pics/office/slides/broken-glass.html> The alarm did NOT trigger, so I have no clue if the devices actually work.
>The old ones were tuned for the sound glass makes when it >breaks, but some could detect the sound it makes before it shatters. >The output was analog. I haven't worked with them for over 35 years, and >don't remember the details.
Yeah, there are several methods. I found this which might help: <http://www.best-microcontroller-projects.com/glass-break-detector.html> I didn't see anything on predicting if the glass was going to break. I suspect that the major interest is not so much if the tempered glass was broken, but rather whether the solar cells behind the tempered glass sustained any damage. Thin film and amorphous are fairly flexible, but monocrystalline and polycrystalline will break if bent even slightly. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Reply by Spehro Pefhany June 27, 20132013-06-27
On Thu, 27 Jun 2013 20:21:40 -0400, the renowned "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

> > > has anyone ever worked with 'Glass break detectors' for alarm >systems? The old ones were tuned for the sound glass makes when it >breaks, but some could detect the sound it makes before it shatters. >The output was analog. I haven't worked with them for over 35 years, and >don't remember the details.
I just remember the ones that were made with foil.. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com