Portable Electronic Glass Stength Tester

you've got a long string it's hard to see how you'd get the panel inserted... You could release the string at some point, but that strikes me as scarier than the ice-ball air cannon.

with the ice ball held out the window. Trigger some release mechanism at the right point so the ice-ball drops and impacts the panel. Slightly more portable than than dropping ice cubes from buildings. :^)

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.

As Spehro has pointed out, a solenoid-only drive is unlikely to be able to deliver enough energy, and - in part because a simple solenoid drive applie s a very position-dependent force to the plunger - unlikely to deliver a pa rticularly well-defined impact energy.

As I've already said, I think you have to plan on monitoring the position - and thus the speed and energy - of your plunger as it heads towards the gl ass surface.

You can then make an instrumented automatic centre punch, and - if necessar y - use a magnet on your plunger with a solenoid to modify the speed of you r plunger in the last few millimetres of travel, just before it hits the gl ass.

Because the solenoid will then only be active over a relatively small part of the displacement, the force it exerts will be a lot more predictable, an d close to the maximum available. There will be lots of back-emf in the sol enoid, but you can charge up a capacitor to cope with that for the fraction of a second that you have to deal with it.

the patent :^)

Nope. The new and disgusting FITF (first-to-file) means that if my soon to be patented file-o-matic patent spamming device files for the patent a few milliseconds before Sphero, then it's all mine, as in winner take all. In the past, I had to actually prove that I had the idea first. Now, all I need to do is watch the newsgroups for hints on what people are designing, and immediately file a provisional patent application. I then have about a year to amend the patent into something that will allow me to sue Sphero for infringement:

accuracy?

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.

Photo voltaic is far from perfect. However, the alternatives are far worse. My favorite alternative energy scheme is solar steam power. My plan is to use solar collectors and concentrators to produce steam, which will then drive a dynamo or pump to produce electricity and move water. Possibly a buried thermal reservoir. My calculations show that the delivered energy from the roughly 1kw/sq-meter maximum solar insolation is far higher for steam than for photo voltaic. As a side benefit, the condensed water vapor can be easily purified and can be used to make coffee or tea.

Like all concentrated energy devices, it is difficult to separate it from an explosive device, so some safety issues will need to be considered before mass deployment. Gasoline, which is far more concentrated and dangerous than steam is deemed safe, so I presume something can be done with steam. After that, there's the noise problem, where to get the water, how to deal with the increased humidity, and exactly how to build a government bureaucracy and research paper factory on top of the technology.

Liebermann's 318th law of design: If it moves, it will break. This law has been generally suspected for quite some time, resulting in products with few moving parts, no controls, and no user accessible adjustments. Everything is controlled by software, which somehow is expected to make things safer. Such devices are often conceived in state machines using tables of conditions provided by the company attorneys. Unfortunately, when a state machine is presented with an undefined state, it usually does something rather disgusting. Students are therefore employed in the necessary testing, as they are known for their inability to follow instructions, their creative abuse of devices, and their attraction to dangerous devices. It also helps that they're also disposable.

I have a theory that safety devices cause more accidents than they prevent. Such safety devices make workers and students feel that they are being protected by the safety device, resulting a new classes of imaginative and creative ways to produce an accidental injury. A good indication of the failure of safety devices to prevent accidents and the associated litigation are the voluminous "wholesale repudiation of responsibility" documents and imaginative warning labels found on almost all current products more complicated than a pencil.

I wouldn't worry about protecting students from themselves. Instead, I suggest you concentrate on the documentation that nobody reads and the warning labels, as making a product safe is a futile exercise.

I live in a forest, so PV solar is not very common. I do have friends in the flatlands, that have PV installations including a former lady friend. My interest in the monitoring and data collection of her system has somehow entitled me to scrub and clean the bird droppings, tree debris, dirt, and grease from the panels several times per year. Cleaning the panels is easy. Cleaning out the critters that have moved in under the solar panels is not so easy.

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.

On the other hand, using an airplane for testing has other risks that should be considered: as well as the aircraft adding some errors to the ice fall: There are also falls of fish, frogs, snakes, etc: With about a 1500ft LSALT over populated areas, accuracy will certainly be a problem: Perhaps a fin guided and gyro stabilized ice ball might be worth designing.

I just remember the ones that were made with foil..

Best regards, Spehro Pefhany

Not worked with, but I do have one on my office windows. However, I didn't have a sensor on the front door. So... The alarm did NOT trigger, so I have no clue if the devices actually work.

Yeah, there are several methods. I found this which might help: 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.

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.

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

Do it pneumatically.

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, ³In 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?.²

Joe Gwinn

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

I saw all that stuff, back in the '70s when I helped a friend start an alarm business.

accuracy?

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:

I could just as easily selected ASTM, TIA, IEEE, NEMA, UL, or over a hundred others.

?-)