accidental creation of AC power using a 9 volt Battery?!

[james_s]

Well the rounding makes sense to me, but that doesn't stop people from arguing about it. As George Carlin said, a lot of people are #%&ing stupid.

The 10th cent thing on gasoline is just dumb, I mean why do it? The *only* reason is that it's a psychological trick that makes a gallon look cheaper. No other consumer product that I can think of is priced down to 0.1 cent. I mean if you're going to go that far, why not charge $2.839250843/gal? What if I buy just one gallon? Can I have my 0.1 cent back?

[Brumby]

You don't want to try any foreign currency conversion, then.

The 10th cent thing on gasoline is just dumb, I mean why do it? The *only* reason is that it's a psychological trick that makes a gallon look cheaper.

There's nothing psychological about two fuel retailers offering petrol for 135.9c/litre and 135.5c/litre.  The difference is real.  Buy 100litres and you'll save 40 cents with the cheaper price.  Those tenths of a cent become significant when they get multiplied out.

[helius]

At gas ("petrol") stations in the US, the price is always plus 9/10 of a cent. That tenths figure is never anything except 9: the digital price signs that you can see from the highway are not physically capable of showing any other digit there.
Like many things I expect it is historical. I remember when the stocks pages in the newspaper quoted prices in fractions: $1.56 3/4 etc.

[yada]

I guess arcs aren't a good word to describe them. The 90 volts were only resulting from passing a pulse through a transformer. I'll try to get measurement for the voltage. Speaking of flyback transformers, passing 12v through one of the coils in the flyback resulted in a 1cm spark (eventually).

I thought you needed one of those big metal power transistors to make that work. I remember taking a flyback out of a computer monitor that my brothers friend (probably) wasn't using only to find out it wouldn't work without a pretty expensive transistor that will probably soon burn out. Also turns out that he was using it and was pretty pissed. I explained to him that it would work without it and they often put in extra parts like they did with transistor (5 transistors, then 6 then 7 then...) radios. Because more equals more better. You should see a 100 transistor radio! He took me seriously and plugged the remains back in.  Unfortunately it popped the breaker before any cool smoke came out. Guess it needed that part.

[jimdeane]

Reminds me of the later Polaroid cameras - the kind that you just watched the photo develop, not teh old ones where you waited and then peeled the picture off the backer. The film cartridges for those used a flat pack 6V battery that had PLENTY of life left in it after the film was used, I used to snag up as many of those as I could. After a while they went with a smaller battery - same size cardboard carrier to the same dimensions as the film, but the bulge int he middle where the cells were was smaller - even THOSE had decent life left after the film was used. Everyone was gunning for the empties though - there as an article by Forrest Mims in Popular Electronics about how useful this battery was because of the cost and the form factor

My first "hacking" experience in my memory is my dad teaching me how to make a flashlight from one of those Polaroid battery packs, a couple of pieces of aluminum foil (or gum wrapper), tape, and a flashlight bulb.  It was so cool to take that camping. Not only a flashlight, but one I MADE.

I'll have to thank him for that, it might have been the spark for my interests.

[Red Squirrel]

Reminds me of the later Polaroid cameras - the kind that you just watched the photo develop, not teh old ones where you waited and then peeled the picture off the backer. The film cartridges for those used a flat pack 6V battery that had PLENTY of life left in it after the film was used, I used to snag up as many of those as I could. After a while they went with a smaller battery - same size cardboard carrier to the same dimensions as the film, but the bulge int he middle where the cells were was smaller - even THOSE had decent life left after the film was used. Everyone was gunning for the empties though - there as an article by Forrest Mims in Popular Electronics about how useful this battery was because of the cost and the form factor

My first "hacking" experience in my memory is my dad teaching me how to make a flashlight from one of those Polaroid battery packs, a couple of pieces of aluminum foil (or gum wrapper), tape, and a flashlight bulb.  It was so cool to take that camping. Not only a flashlight, but one I MADE.

I'll have to thank him for that, it might have been the spark for my interests.

Actually that's kind of what got my interest in electricity too, my grandpa showed me using batteries a wire and a light bulb and I thought it was the coolest thing.   Decide to try the same with a household bulb and the socket and it worked.  "unlimited free power!"    Got my first 120v shock at like 11 lol.

[james_s]

I did roughly the same thing, I think I was 3 or 4, my dad got me a couple of those big cylindrical dry cells with the screw terminals on top, some sockets, knife switches and made me a bunch of wire leads with crimp connectors on the ends. I had hours of fun playing with those.

Later I realized a 6V bulb I had would screw into the candelabra socket in the lights in my parents bedroom, I flipped the switch and it went pop, the whole bulb turned silvery black.

[yada]

Remember the flash that would burn out a light bulb every time you used it? So wasteful. How did they make them go out in order?

[james_s]

Are you referring to photographic flashbulbs?

[Brumby]

Remember the flash that would burn out a light bulb every time you used it?

I believe it's this:

So wasteful.

No more wasteful than the same magnesium ribbon flash bulb used before electronic flashes came of age.

... and those bulbs were a bit easier to use than the original system:


Do you like the manual triggering mechanism of the first two?

How did they make them go out in order?

Good question.

[james_s]

Flashbulbs are nothing more than magnesium wool or foil in a glass bulb filled with pure oxygen. They are triggered by a small electric current, even static discharges can do it. I once dropped a flash cube on the carpet at my grandmother's house and half the bulbs fired. I knew a guy who got a nasty burn on his leg because he had a couple flashbulbs in his pocket and one went off.

They were triggered by mechanical contacts in the camera, usually powered by AA batteries for the small stuff while larger professional flash heads often took a pair of C batteries.

[CatalinaWOW]

There were a lot of different mechanisms for those "bulbs".  The ones I remember are:

1.  The flashcube had a bulb on each face.  The film winding mechanism would rotate a new bulb to the front, and this also put it in contact with the electrical connections.  High and low side for each bulb.

2.  Another had a long string of bulbs similar to the picture above, and indexed the cartridge through the camera, connecting one bulb at a time to the camera contacts.  Again, a pair of contacts for each bulb.

3.  Another version of the strip bulbs had a common connection for all bulbs, and a single high for each bulb.  A step switch in the camera indexed through the bulbs.

4.  Some had some form of steering network in the bulb pack.  I don't remember how it worked but believe it was purely passive.

[t_ryner]

I'm enjoying how much activity is going on on this post- I never expected it to go from whatever I started with to disposable flashbulbs and polaroid cameras!

Flashbulbs are nothing more than magnesium wool or foil in a glass bulb filled with pure oxygen. They are triggered by a small electric current, even static discharges can do it. I once dropped a flash cube on the carpet at my grandmother's house and half the bulbs fired. I knew a guy who got a nasty burn on his leg because he had a couple flashbulbs in his pocket and one went off.

They were triggered by mechanical contacts in the camera, usually powered by AA batteries for the small stuff while larger professional flash heads often took a pair of C batteries.

[james_s]

I vaguely remember there were also flashbulbs that were purely mechanically triggered. Seems like they had a tiny percussion cap that would fire when struck by a firing pin.

[CatalinaWOW]

I vaguely remember there were also flashbulbs that were purely mechanically triggered. Seems like they had a tiny percussion cap that would fire when struck by a firing pin.

Yeah, now that you mention it I believe you are right.

[Ian.M]

Yes.  Philips Magicube.
It had a pin protruding from the bulb base and was fired by the pin being struck laterally by a hairpin spring built into the cube for each bulb.  The spring was held back by a little metal pin formed from the other end of it and the camera fired it by pushing the spring up to clear the retaining pin when you pressed the shutter release.  You could easily fire it manually by prodding the spring.
 
Some fishing line for tripwires, some matchsticks to prod the springs and a Magicube on a stake made an interesting deterrent for people wandering around at night where they shouldn't be.

[6PTsocket]

The real high voltage in a CRT TV was generated by the flyback transformer. What you have there is the deflection yoke that magnetically bends the beam across the screen. Scopes did it electrostaticaly.

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