OTish Alarm clocks

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I assume everyone has heard of this kid and his clock invention.
http://truthuncensored.net/wp-content/uploads/2015/09/ahmed-mohamed-clock.jpg
The picture of the clock shows a 9V battery hookup but no battery. That means the kid either had to plug the clock in or it does have batteries that are not shown.
If we assume that there are no batteries, can this clock store it's alarm time? I say no, but I don't know.
If not, that means that the kid had to plug the clock in during class and also program it to alarm. The clock can not accidentally go off without battery back up. Right?
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On 9/25/15 6:52 PM, Seymore4Head wrote:

Did you notice the AC plug, wire and transformer ? I have an RS alarm clock similar except numbers are green not red. The 9v battery is for saving settings and time during AC power outage.
That said, how it "beeped" in class unless he had access to an AC outlet is my question.
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In alt.home.repair, on Fri, 25 Sep 2015 19:11:59 -0400, Retired

The battery may have been confiscated by the school's TSO, Technology Safety Officer.

It might not be exactly like your clock and it may be able to beep based only on the battery.
I heard varying versions of the story. Somehow the first one seems the most likely. The first one *I* heard was that he showed it to his science teacher who said not to show it to anyone else. (The guy could predict the future.) And the kid didn't but during English class it started beeping. As everyone knows, a bomb will display the time for hours in advance, but it will only beep during the last 30 seconds. So they were justly alarmed. When they opened it and could find no explosive, that only showed how clever the kid was.
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wrote:

I found this today:
https://www.youtube.com/watch?v=pzUtR5TvuzQ

So the kid's teacher said that it looked like a bomb and not to show it to anyone, but the kid took it to English class and plugged it in the wall.
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On 9/25/2015 6:09 PM, Seymore4Head wrote:

If *you'd* done something that none of your peers had apparently done, wouldn't *you* want to show it off? Why bring it to school if not to do so?
When I was in HS, I built a computerized football game using ANALOG computers and DIGITAL logic kits. An offensive and a defensive player "called their 'plays'". Then, told the machine to "run the play". It displayed the result of the play (gain/loss), current field position, down and yards to a first down -- all using VOLTAGES displayed on analog meters. (It didn't keep score -- I figured humans could do that if they really cared beyond the novelty!)
It fit on a 4'x8' sheet of plywood with wires running all over the place.
I could have *just* shown it to my teacher, let him evaluate my work and assign my grade. But, where's the fun in that? He and I already KNEW that I was getting an 'A'... OTOH, being able to play with it in class was rewarding -- and got the class out of what would probably otherwise have been a boring lecture or exam!
The teacher(s)/administrator(s) is the idiot in the clock story.
(Reminds me of a time the police raided our town dump in my youth. Seized several "Marijuana plants" -- that turned out to be TOMATO PLANTS! Ooops!)
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In alt.home.repair, on Fri, 25 Sep 2015 19:25:28 -0700, Don Y

When I was in the 7th grade, we took wood shop, with about 6 weeks or less devoted to "electric shop". I think it was only class time or reading and no projects were involved. On the test, the teacher asked why the birds on power lines aren't killed by the electricity.
I said it was because they weren't grounded, and he marked it wrong, saying it was because the wires are insulated. -- But not all of them are.
Most of what I knew about electricity came from my electric train, and I knew two wires were needed, but I didn't know too much about how houses were wired or understand grounding to my satisfaction, but I still knew the answer.

Another story said that at his previous school, he brought things in all the time to show teachers and classmates. But he had just started at this school.

Wow.

So you dragged a 4x8 sheet on the school bus?

Tomato stems are poisonous. Everyone would have been up in arms if a child had died. The police deserve your gratitude.
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On 9/25/2015 9:57 PM, micky wrote:

As him if he would be comfortable placing one hand on one INSULATED wire and the other on the adjacent INSULATED wire! :>

When I was a kid, I was given a crystal radio kit. Two "connections" (GND and Antenna). Worked well in the kitchen where I had access to a cold water pipe and the "return" for the telephone (routed up to the phone pole so an effective antenna).
Did NOT work well in my bedroom!
OTOH, there are two "slots" in that electrical receptacle...

It simply shows the lack of sophistication of the school staff. Where is the explosive charge hidden? Does the guy look like he's ready to meet his maker? etc.
Common sense is sorely missing.

No. Had to be driven to school. Had to haul the plywood sheet out of the basement via the "hatchway" -- wide enough that the sheet could be carried in it's "flat" orientation (so I didn't have to disassemble all the modules and then rewire the whole mess)

The plants were planted by the custodian of the dump. The police weren't smart enough -- or trusting enough -- to believe him *or* bring any of the hundreds of local farmers to view the plants before uprooting them.
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In alt.home.repair, on Fri, 25 Sep 2015 22:33:24 -0700, Don Y

My father, who died in 1955, had a 110 volt tube radio that also ran on (very expensive) batteries.
And he had a crystal radio. Not a kit. Plastic, 3 or 4 inches in diameter and 3/4 inch thick, with holes in one side for the sound to come out. Both halves glued together. And a thin green rubber string to, I think, go around one's head and hold it to the ear.
Brown, with a clear plastic tuning knob on the side. It only got one station, WIBC, which was the strongest station in town, I guess.
It has a long green wire with an alligagor clip, and i guess it had two.
To improve reception, I figured i needed a better antenna, and the only antenna I could think of were the TV's rabbit ears. So I connected one wire to that, and the other wire to the metal grill of the forced air heating duct right nearby. Boy did I get zapped.
I didnt' tell my mother or anyone, and after no further problems, eventually we got a new tv
Also an Emerson table radio with a chip out of the case at the bottom side, a radio which had no bottom and sat on a metal table with decorative holes in it, so that the chassis would touch the metal....
Also the formica counter top had a metal trim in front, before they used more formica. When I touched the table the radio was on, and the metal trim of the formica, got a very weak ac shock. I mentioned that to my mother, but we never did anything about it. I still have the radio, and I might still have the table, but one doesn't sit on the other.
good stuff snipped.
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On 9/25/2015 10:45 PM, micky wrote:

Could be. Sound (power) output is really low. E.g., an old fashioned "earphone" was commonly used as the output transducer.

A crystal set can be tunable -- or not. At a bare minimum, all you need is an antenna, ground and "detector" (effectively a diode -- though it can be reified in many different ways: cat's whisker, razor blade, germanium/silicon, etc.). They are so simple that you can fabricate one out of practically nothing (and have been fabricated by prisoners in the war, etc.)
Adding a tuning coil gives you *some* tuning capability. But, the sets have really low selectivity -- any nearby signal can easily swamp the desired (tuned) signal. So, in practice, they really only receive one station.

be happening in the TV to allow that!

Our kitchen had the "formica with stainless edges". We also had large portions of the kitchen walls covered with sheets of formica (e.g., behind the stove/oven).
I was surprised later in life to encounter formica with *rolled* edges!
We rescued a large 220VAC window ACbrrr when I was a kid. It supposedly was broken. With it installed in a bedroom window, we ran a length of BX across the cellar floor to the main fuse panel to provide temporary power.
Nothing.
I was outside peering in the back of the unit. As I was a little tike at the time, I ended up standing on the "area well metal retaining wall" (not sure how to describe that if you don't know what it is -- think of it as an EXCELLENT GROUND!) to gain a few inches of elevation.
Eventually, I shuffled my feet around until a hole in my sole allowed my foot to come in contact with the metal wall -- and got laid back on my *ss!
When asked what had happened, I exclaimed that I'd caught a healthy shock from touching the back of the unit. Dad gingerly tried to repeat my action but had no problems. Until he placed *his* foot on that metal wall. "See?! I *told* you!"
(parents do not like it when you are "right")
Turns out, the guy who had it previously had never wired up a 220V appliance. "OK, this is hot, this must be neutral -- so, this *third* wire must be the *other* hot!"
No, that wire is GREEN... it is EARTH! It is the chassis of the unit. Connect *that* to one of the AC legs and you can pretty much guarantee the unit WON'T work -- and *will* lay you out on your *ss when you touch the enclosure!
Correct the "power cord" on the unit and all is well.
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On 09/26/2015 01:27 AM, Don Y wrote:
[snip]

Poor sensitivity too. The crystal radio I had growing up got 3 stations, and I was near a couple of big cities.
That was still true when I added an (audio) amplifier powered by a lemon.
[snip]
--
90 days until the winter celebration (Friday December 25, 2015 12:00:00
AM for 1 day).
  Click to see the full signature.
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On 09/26/2015 01:33 AM, Don Y wrote:

Many laws and rules exist because of the absence of common sense.

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On 9/26/2015 9:01 AM, Percival P. Cassidy wrote:

Yup. When you design a product, you have to keep that SIMPLE FACT in mind!
Worked for a hand-tool company long ago. The sorts of horror stories you'd hear from Legal! And, the things you would have to anticipate in terms of misuse...
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In alt.home.repair, on Sat, 26 Sep 2015 09:34:31 -0700, Don Y

Supposed to be true: Seen on a child's Superman costume. "Caution. Costume does not enable wearer to fly."
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On 9/26/2015 12:57 AM, micky wrote:

Sad that the teacher was wrong. Back then, probably no way to correct a teacher. Might have written the power company and asked them the same question. See if they answered, and what the power company wrote.
- . Christopher A. Young learn more about Jesus . www.lds.org . .
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In alt.home.repair, on Sat, 26 Sep 2015 07:46:53 -0400, Stormin Mormon

If I'd fully understood grounding, I still probably wouldn't have said anything, but I can remember that I wasn't used to teachers making mistakes, and again, because I didnt' fully understand it, I wondered who was right. Although, how could I have partially but not fully understood it? From my Lionel train, which I had had for 2 or 3 years, I knew you needed a return wire, and I knew it was often called the ground.
In the ninth grade, the geometry teacher wouldn't even answer my questions. I had asked two questions which were not hard, but I wanted confirmation that I was right. But they weren't the kind of questions he was used to hearing and one or both stumped him. He seemed to decide I was doing that on purpose, because the third time he wouldn't even answer me. Classmates said I should complain to the principle, but I could have asked another math teacher if I really needed an answer. And he gave me an A every 6 weeks. But one thing he didn't do is recommend me for honor algebra 2, in the 10th grade, which was in another building miles away. Even though I got an A every 6 weeks.
When 10th grade started, I wasn't in class with any of the same kids who had been in 8th grade algebra and 9th grade honors geometry, but I didn't think much of it. Later I found out that the class they were all in went faster than the other classes, and did what took us 4 weeks in about 3. At the end of 4 weeks, everyone in all the classes got the same test, and when the teacher or teachers saw that, competing against mostly juniors plus the 24 sophomore kids I had been in class with, I got the highest score, they invited me to join the honors class after all. So I did. We had a test two days later, on 7 days of material, 5 of which I'd spent in the other class, but I got an A on that too.
The book had a question about figuring out the height of an industrial chimney using angles and distance from the base of the chimney and it mentioned in passing that tall chimneys draw better. Another guy in class -- we were all friends -- asked why, and the teacher didn't know, but he found a book that said they drew better, and made the kid stand in front of the class and read it, even though the book didnt' say why, and my friend had never expressed doubt that it was true.
So the geometry teacher made the wood shop teacher, who only made one mistake, look like a prince.

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On Fri, 25 Sep 2015 21:09:12 -0400, Seymore4Head

Yeah, it all makes sense. Lets build something that looks like a bomb because anyone planning on bombing the school would surely bring in a bomb that looks just like a bomb! And lets do a "dry run" WITH a Mission Impossible "bomb" to tip the authorities off to what we plan to do. "Dry runs" do NOT include bringing teh bomb with you which would, of course, make what you are doing obvious if caught.
I can't believe the idiocy that has sprung up surrounding this.
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In alt.home.repair, on Sat, 26 Sep 2015 10:18:50 -0700, Oren

Obama sent an addendum to the invitation: , Don't bring the bomb.
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On 9/25/2015 3:52 PM, Seymore4Head wrote:

There are different technologies that are used to "retain" settings.
"Volatile" memory requires power to retain settings. This is like the RAM in your PC -- turn off the PC (no hibernate) and the contents of memory (whatever you were doing at the time you pulled the plug) are irretrievably lost.
"Nonvolatile" memory retains settings in the absence of power.
*Current* technologies (I'll ignore historical technologies like core, wire recorders, etc.) for this include FLASH memory, PROM memory, NVSRAM (non-volatile/battery backed up static RAM), BBDRAM (battery backed DRAM -- seldom used), etc.
The "RAM" technologies require on power -- but, include the power source *in* the technology (e.g., a battery packaged in with the device/assembly). A device that expects to be plugged in virtually all the time and experience only *brief* outages can rely on a short term power source (e.g., a "super capacitor" that is designed NOT to retain charge indefinitely but, rather, "long enough" to bridge the expected outage).
FLASH, PROM (seldom used in this way) are truly nonvolatile technologies that retain settings in the absence of power. Think of them as blowing fuses to encode data -- a blown fuse means one thing, an unblown fuse means something else. FLASH has the added advantage that the fuses can be *reset* (unblown) and, thus, reused.

Depends on how the clock was designed. If memory is volatile, what state does it "power up" in? Does it KNOW that it has just been powered up and, as such, display a flashing "12:00"? When it does so, what time is the "alarm register" set to -- 12:00 as well?? Is the "alarm enabled" setting ON or OFF?
I.e., I can make a clock that will behave however you would like it to behave in that situation. What *he* chose to do is something that would depend on his particular implementation (e.g., did he use an off the shelf "clock chip" and just connect a display and a few buttons to it? Or, did he start with a general purpose microcomputer and write a "program" that pretended to be a clock? In that case, what assumptions did he put in place?
One could argue that a clock should power up with the alarm RINGING! Imagine if you've got it set to wake you in the morning (for work or an appointment) and the power fails sometime during the night. It won't know what the current time is (unless it was designed to maintain time in the absence of power). So, even if it remembers the alarm time and setting (on/off), it won't know WHEN it should wake you! Why not wake you when power comes on, again? If this is too early, then you'll grumble a bit, notice the clock is flashing 12:00 indicating the power was lost and, possibly, reset it. You stand a chance of making your appointment later that morning.
OTOH, if the power stays out *past* your desired alarm time, it can't wake you up in time, regardless. So, if it wakes you *late*, it's better than NEVER! (?)
(I've not examined his work)
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On 09/25/2015 06:46 PM, Don Y wrote:
[snip]

But it COULD wake you up when the power goes out, and you still have a chance to get up on time.
I used to have a simple circuit to do that. It kept a capacitor charged, and had a transistor that disabled an electronic buzzer while power is on.
Another solution is to have a fan running constantly in your bedroom. You get used to the sound and don't notice it except when it stops.
--
90 days until the winter celebration (Friday December 25, 2015 12:00:00
AM for 1 day).
  Click to see the full signature.
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On 9/26/2015 12:52 PM, Mark Lloyd wrote:

This only works if your annunciator draws significantly less power than you have stored (cap, battery, etc.).
I had a temporary roommate in college who had an alarm he'd built (standard AC synchronous motor alarm clock -- but the alarm contacts were wired to a sonalert). He'd packaged it in a lexan case so you could see the big "computer grade" electrolytics (many 100's of KuF).
When it went off, there was nothing you could do to silence it until the caps bled dry.

Some folks are light sleepers; others *sound* sleepers.
The water fill line to the toilet in the guest bathroom broke one night. I was awakened in time to shut the water *off* before the floor was even covered with water!
OTOH, we had a domestic violence case 4 house down, one evening. SWMBO slept through the ambulance, 4 police cars and firetruck that arrived with sirens wailing and lights flashing for the duration of the "standoff".
Go fig'...
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