# EEVblog Electronics Community Forum

## General => General Chat => Topic started by: t_ryner on April 25, 2017, 02:40:34 am

Title: accidental creation of AC power using a 9 volt Battery?!
Post by: t_ryner on April 25, 2017, 02:40:34 am
I was messing around with a few large coils used in CRT Tvs, and was getting brief (tiny) arcs when brushing it against the wire in a incomplete connection. In the past, I did this with a transformer from a 12v power supply. I must have been touching the connections, as I received a mighty tingling sensation caused by ac voltage  :scared: . Calculations estimate that shock to be around 90 volts (1:10 ratio transformer). Since  DC voltage doesn't tend to pass through transformers. Has anyone else had a similar experience?
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: amyk on April 25, 2017, 02:55:29 am
You are causing a change in current, and thus magnetic field, which is how AC power can be coupled through a transformer. That's also how inverters and DC-DC converters work.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Ian.M on April 25, 2017, 02:56:29 am
Yes.  Inductive kickback is a common source of high voltage transients in DC circuits.  Its been known about for 180 years. See https://en.wikipedia.org/wiki/Induction_coil (https://en.wikipedia.org/wiki/Induction_coil)
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Brumby on April 25, 2017, 07:06:36 am
You might find that the actual voltage you felt was a bit higher than 90V..... but it would only have been a single pulse for each disconnect of the battery.

This phenomenon has been used in the ignition systems of petrol powered motor vehicles for more than a century.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: james_s on April 26, 2017, 09:40:25 pm
You've created a manually operated boost converter. I remember discovering the same thing when I was about 10 and decided to play with a transformer and a 6V lantern battery, it was quite a shocking experience.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: macboy on April 28, 2017, 06:33:58 pm
You've created a manually operated boost converter. I remember discovering the same thing when I was about 10 and decided to play with a transformer and a 6V lantern battery, it was quite a shocking experience.
When I was 12 or 13 we did a unit on electronics in "industrial arts" class in school. I connected the DC power supply through the NC side of a relay then through the coil. So as the coil energized, the relay would turn itself off, then on, off, etc. I connected a couple wires across the coil and dared my classmates to hold one in each hand. A couple of them took turns seeing who could hold on the longest. I didn't take a turn. It looked very painful, and according to them, it was.  >:D
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: IanB on April 28, 2017, 06:43:09 pm
I was messing around with a few large coils used in CRT Tvs, and was getting brief (tiny) arcs when brushing it against the wire in a incomplete connection. In the past, I did this with a transformer from a 12v power supply. I must have been touching the connections, as I received a mighty tingling sensation caused by ac voltage  :scared: . Calculations estimate that shock to be around 90 volts (1:10 ratio transformer). Since  DC voltage doesn't tend to pass through transformers. Has anyone else had a similar experience?

Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Cyberdragon on April 29, 2017, 12:15:26 am
You've created a manually operated boost converter. I remember discovering the same thing when I was about 10 and decided to play with a transformer and a 6V lantern battery, it was quite a shocking experience.
When I was 12 or 13 we did a unit on electronics in "industrial arts" class in school. I connected the DC power supply through the NC side of a relay then through the coil. So as the coil energized, the relay would turn itself off, then on, off, etc. I connected a couple wires across the coil and dared my classmates to hold one in each hand. A couple of them took turns seeing who could hold on the longest. I didn't take a turn. It looked very painful, and according to them, it was.  >:D
Did that with three relays (one dpdt, two power) for 2-phase from a bench supply. Except I didn't put any suppressor/snubber on the primary and it fed AC backwards into the psu making it go nuts. It survived, but probably wouldn't have much longer. Oops... :palm:
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: james_s on April 29, 2017, 12:28:19 am
After my discovery, I remember messing around with schoolmates and getting them to hold the wires out of the transformer. "Come on guys, it's only a battery, it can't hurt you!" These days I'd probably be expelled and go to jail.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Ian.M on April 29, 2017, 01:35:58 am
Heh.  It didn't take me long to realise that a lamp flasher module (complimentry BJT astable) could drive the coil, and for some reason, the frequency was drastically increased.  I know now that it was due to the back-EMF.   Some experimentation to find a transistor that could stand up to the voltage spikes, and heatsink it, and I had something that could drive most small transformer secondaries from a supply between 6V and 12V and sustain a continuous discharge from the former primary.   T then got into Cockcroft-Walton voltage multipliers . . . . . .

I packaged the whole circuit up with a 9V battery in a lantern battery shell and took it to school.  Oddly enough charged HV capacitors (small enough to be reasonably safe) didn't make the teachers very fond of me once they'd made the mistake of confiscating what I was fiddling with and getting a 'bite' off them.
However the Physics master and the rest of the science department were vastly amused, and my detention was IIRC a lecture on practical electrical safety, followed by the return of the offending device with strict instructions not to bring it to school again without written permission from the Physics master, or he wouldn't be so lenient the next time.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: blueskull on April 29, 2017, 02:32:58 am
If you can see arcs, then it's not 90v. It's more likely to be a few kv.
That's how flyback converters work. Store energy in coil, then disconnect input. The inductor tries to continue its current, but due to increased impedance, it has to increase output voltage to catch up with previously applied current, so you get higher voltage.

https://en.wikipedia.org/wiki/Boost_converter
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: CatalinaWOW on April 29, 2017, 02:40:38 am
Now you know how those prank books that shock you when you open them work.  Exactly the same idea.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: blueskull on April 29, 2017, 02:44:07 am
After my discovery, I remember messing around with schoolmates and getting them to hold the wires out of the transformer. "Come on guys, it's only a battery, it can't hurt you!" These days I'd probably be expelled and go to jail.

Did exactly the same when I was in grade school.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: rrinker on April 29, 2017, 06:05:44 pm
LOL my best friend made something of the sort to keep his (younger) sisters out of his work room in the basement. Made one of those shockers that uses the BEMF from a relay wired as a buzzer, and then controlled it with a 4 button capacitive touch combination lock circuit from one of the big circuit annuals I had. Hit the right combination and you could freely open the door. Put in the wrong combination and you got a nice zap if you tried touching the door knob.

Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Kilrah on April 29, 2017, 06:40:31 pm
A friend of mine used to make use of disposable digital(WTF?) camera flashes on people.

I was more of a "make a show" type than "hurt for fun", so I'd rather short them on random metal objects with a loud BANG surprising everyone.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: t_ryner on May 01, 2017, 02:12:54 am
:-\ 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).
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Brumby on May 01, 2017, 02:32:56 am
A friend of mine used to make use of disposable digital camera flashes on people.

I was more of a "make a show" type than "hurt for fun", so I'd rather short them on random metal objects with a loud BANG surprising everyone.

I've got a couple of hundred of those boards in a box around here somewhere....   ;D
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Red Squirrel on May 01, 2017, 04:08:57 am
I remember playing around with a 17v AC adapter once as a kid.  Discharging a capacitor through the low voltage end could give you a nice shock on the prong end.  :-DD
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Brumby on May 01, 2017, 09:44:31 am
A friend of mine used to make use of disposable digital camera flashes on people.

I was more of a "make a show" type than "hurt for fun", so I'd rather short them on random metal objects with a loud BANG surprising everyone.

I've got a couple of hundred of those boards in a box around here somewhere....   ;D

Found it.  The boards themselves were neatly laid out on sheets of paper - but the box fell.

(https://www.eevblog.com/forum/chat/accidental-creation-of-ac-power-using-a-9-volt-battery!/?action=dlattach;attach=312145;image)

This seems to have all the same design board.  I know I collected whatever was available and found there were 3 or 4 different boards.

I must have some more somewhere......

Some interesting caps....
(https://www.eevblog.com/forum/chat/accidental-creation-of-ac-power-using-a-9-volt-battery!/?action=dlattach;attach=312147;image)
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Brumby on May 01, 2017, 09:49:04 am
Any project suggestions?
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Kilrah on May 01, 2017, 12:03:50 pm
Wow, how the heck did you end up collecting that many!  :scared:

Parallel all their supplies and outputs to common buses?  >:D

Series-wiring them (with batteries then of course) might end up problematic after a number too small to use up much of the bin...
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Brumby on May 01, 2017, 12:36:01 pm
Asking a few photo processing places to hang on to them for me ... and then going back to collect periodically.  Some of them refused because they have had other requests to hang on to stuff - like empty film cannisters - but people never came back for them.  Since I was true to my word, those who said 'yes' continued to save them and I continued to collect.

A few years ago, I traded about 1,000 of them for merchandise from Oatley Electronics.  I still have this box - and I think I have another stash somewhere.  Possibly another 1,000 all up.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Kilrah on May 01, 2017, 12:51:02 pm
Interesting. I had always thought they were being reused.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Brumby on May 01, 2017, 01:13:24 pm
Obviously not with the places I scored from.

There was a bonus, too .... the battery used was an alkaline AA.  After 24 flashes, they still had some life in them.  Didn't buy any AAs for a couple of years...  :D

Even now, I'm looking at a few 120uF 330V photo flash capacitors that could still be good.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: rrinker on May 01, 2017, 04:44:26 pm
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

Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Kilrah on May 01, 2017, 05:18:25 pm
I've used the Polaroid batteries too!

Not so much the AAs from disposable cams though - for those I had another very prolific source, namely occasionally working for a theatre that used a lot of wireless microphones - and rule #1 in that world is you change the batteries for every performance even if they're normally still 80% full becasue you never know who might have left their mic powered for who knows how many hours either before or after the show.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: james_s on May 01, 2017, 05:56:59 pm
Ah yes, the PolaPulse batteries, I remember those. They could deliver very high current due to the flat construction with high surface area. Plenty of energy left in them in most cases after the film was expended.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Red Squirrel on May 02, 2017, 01:22:01 am
Woah with that many flash capacitors you need to put them all in parallel.  ;D

Interesting that the caps are specifically for flash, are they basically just lower ESR?  I'm actually surprised they're Rubycon and not some kind of Wun Hun Lo brand.

Crazy to think how wasteful those cameras were though, when you consider the re-usability of digital cameras or even regular film cameras that you could reload.  I recall using a few myself on a school trip. Their advantage was cost if you don't take much pictures, though as even a regular film camera was rather expensive.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: james_s on May 02, 2017, 03:51:20 am
Another potential source of good lightly used batteries are retirement homes. My brother used to work maintenance at one and they were required by law apparently to replace the batteries in all of the smoke alarms annually even though they were primarily line powered. This meant a box of ~380 lightly used 9V batteries every year. Unfortunately more than half the ones I had went bad and leaked over time, it's hard to use that many batteries.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: CatalinaWOW on May 02, 2017, 04:25:45 pm
And now you see the value in Harbor Freight DMMs.  As a meter they are meh!  But it is a free 9V battery.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: james_s on May 02, 2017, 05:49:05 pm
Is it even an alkaline?

I have one of those meters, I keep it in the emergency kit in my car. It's no Fluke but it does work about as well as my very first DMM which was quite expensive when I got it back in the early 90s. Good enough for diagnosing electrical problems if I break down somewhere or come across someone else who has.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: t_ryner on May 05, 2017, 04:37:06 am
If you use the flash on a receipt, it can sometimes burn wherever there's ink. Tomorrow I plan on making a run over to goodwill to buy a few misc. electronics. I'll see if they have any antique multimeters (I've seen them there before) or things that are worth buying for reverse engineering. I'll also buy a new film camera to see how it compares to the older ones you posted.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: t_ryner on May 05, 2017, 04:44:19 am
I think there's some regulations requiring the replacement of all the alarm batteries in a situation like that (ex., assisted living, medical complex, etc). The battery provides backup power, but I was wondering whether or not a modernized design could be run off of supercaps. It would reduce the requirement/risk of faulty batteries, and prevent unnecessary waste. Battery companies wouldn't like that though!
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Brumby on May 05, 2017, 05:41:56 am
I don't think a partial impact to one niche of the battery companies' market is going to worry them a lot.

There are batteries everywhere.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: john_c on May 05, 2017, 06:01:58 am
Any project suggestions?

Wow, you have a lot of capacitors there. My suggestion for a project: shrink dimes. If you get good at that, you can try shrinking quarters!

Google it - it's a great pastime for those with proper safety knowledge and access to very high C values. ;)
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Brumby on May 05, 2017, 07:19:26 am
My access to US coinage is rather limited - and trying such things on Australian currency is illegal.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Red Squirrel on May 05, 2017, 06:10:05 pm
Build a rail gun and send currency to the moon instead.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: james_s on May 05, 2017, 06:20:47 pm
Technically it's illegal to damage US currency also, and I suspect that's the case in most nations. Realistically though the FBI is not going to haul you off for shrinking a few coins. As long as you are not counterfeiting or buying up large quantities of coins and melting them down for the metal nobody is going to bother you.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: timb on May 05, 2017, 11:55:11 pm
Technically it's illegal to damage US currency also, and I suspect that's the case in most nations. Realistically though the FBI is not going to haul you off for shrinking a few coins. As long as you are not counterfeiting or buying up large quantities of coins and melting them down for the metal nobody is going to bother you.

Exactly. Otherwise, there wouldn't be those "Penny Squasher" machines you see occasionally in stores. (You put a penny in and turn a crank, which is connected to some gears and a series of rollers. The penny comes out completely squashed and elongated.)
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Ian.M on May 06, 2017, 12:12:08 am
Defacing USA coinage: http://www.thecoinsmith.net/CoinSmithBlog.html?entry=who-s-right (http://www.thecoinsmith.net/CoinSmithBlog.html?entry=who-s-right)
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Brumby on May 06, 2017, 01:00:59 am
That seems to limit the illegal nature to ones where fraud is involved.  A sensible approach, IMO.  That the line is drawn at the point of offering such coin as legal tender for purchase, seems a reasonably clear one.  So, as I read it, a defaced coin offered as an object - and not legal tender - is OK.

However, in Australia, no such provisions exist.  From the Royal Australian Mint:

https://www.ramint.gov.au/using-coin-designs (https://www.ramint.gov.au/using-coin-designs)

This page contains general information about the legal restrictions which apply to the use of Australian currency coins and the reproduction of coin images and designs. The information in this page is provided as a general guide and should not be relied on as a form of legal advice.

Defacing, destroying or altering Australian currency coins

It is a criminal offence under the Crimes (Currency) Act 1981 (Cth) to deface or destroy current Australian currency coins. It is also an offence to sell or possess current coins that have been defaced. Defacing a coin includes coating the surface of the money with any sort of material. The penalty for defacing coins, or selling or possessing money that has been defaced, is \$5,000 or imprisonment for two years for an individual (or both), and \$10,000 for a body corporate. You may also be guilty of the offence of making counterfeit money if you alter a genuine coin.

The destruction or alteration of designs used on coins may also infringe the right of the author of the design not to have an artistic work subject to derogatory treatment. The author's rights to 'integrity of authorship' are protected under the Copyright Act 1968 (Cth). If you do something in relation to an artistic work that is prejudicial to the author's honour or reputation, a court can order you to stop the infringing conduct, make a public apology, or pay damages to the artist.

So, not only are we not allowed to damage a coin as Commonwealth Property for ANY intent, but we could even fall foul of Copyright.  That seems pretty black and white.

OK - so coin zapping on Australian currency is off the table .... any other project ideas?
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: helius on May 06, 2017, 01:22:53 am
Has a Marx Bank already been suggested? I seem to recall some very large spark towers from down under, wish I could remember the url.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Red Squirrel on May 06, 2017, 01:24:54 am
Not really illegal in Canada either, but discouraged. They'll ask you nicely to stop, as is tradition.

Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: blueskull on May 06, 2017, 09:17:41 am
Technically it's illegal to damage US currency also, and I suspect that's the case in most nations. Realistically though the FBI is not going to haul you off for shrinking a few coins. As long as you are not counterfeiting or buying up large quantities of coins and melting them down for the metal nobody is going to bother you.

I believe shrinking US coins is LEGITIMATE, but destroying coins for the metal is not.
At least this is what the owners of coil shrinkers (at an attraction somewhere in RI) told me, and he has a sign board over there referring some US laws to back up his point.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: james_s on May 06, 2017, 04:05:01 pm
Is it legal to give/sell Australian coins to someone else? What if you were to send a few dollars worth of coins to somebody in the US and that person decided to shrink, melt or otherwise damage the coins? Are they going to be dragged over to Australia for punishment?

Really though, I suspect the law is one of those things that is on the books to enable punishment in extreme cases but I really doubt it's enforced. I mean can you find a single case of someone getting arrested and fined for smashing, painting or otherwise deliberately damaging a few pennies? Maybe they really are unreasonable and heavy handed there but it seems unlikely given the general personality of most of the Australians I've known.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Kilrah on May 06, 2017, 08:02:23 pm
Obviously something for "mass damaging" indeed. Often coins, especially low value ones tend to cost more to make than their face value... by destroying them you're costing the state money, simple as.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Red Squirrel on May 06, 2017, 08:31:52 pm
Obviously something for "mass damaging" indeed. Often coins, especially low value ones tend to cost more to make than their face value... by destroying them you're costing the state money, simple as.

That was one of the reasons they got rid of the penny here.   It cost more than a penny to make one.

Really they need to change the way sales taxes work, they should be part of the final price.  Stores could charge even amounts for stuff and what you see is what you pay.  Could pretty much get rid of nickels and dimes too.  Not sure how it would work for natives that have status cards though, could just round to the closest 25 cents when deducting the tax from the price.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: john_c on May 06, 2017, 10:39:44 pm
So, not only are we not allowed to damage a coin as Commonwealth Property for ANY intent, but we could even fall foul of Copyright.  That seems pretty black and white.

OK - so coin zapping on Australian currency is off the table .... any other project ideas?

That makes sense, given that they all portray Queen Elizabeth II. Here, it would be George Washington and FDR, both long dead. Using a metal stamped with something familiar helps to see the result of the experiment, as I understand it. And I think the dime and quarter have basically suitable size and metal composition for getting good EM induction, as I recall.

Other projects that use high currents in short pulses? Well, I wouldn't recommend converting it to RF. Your local hams will be none to pleased about that. Besides, if you make it big enough it will be dangerous to nearby electronics. Such devices are produced, that can from a distance disable cars with electronic ignition even.

You could go kinetic. Time honored route. Not for everybody.

Maybe light? You could scrounge for gas discharge tubes used in stadium lighting, or something like that. Then see if you light it for 1 second!
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: james_s on May 08, 2017, 05:54:32 pm
That was one of the reasons they got rid of the penny here.   It cost more than a penny to make one.

Really they need to change the way sales taxes work, they should be part of the final price.  Stores could charge even amounts for stuff and what you see is what you pay.  Could pretty much get rid of nickels and dimes too.  Not sure how it would work for natives that have status cards though, could just round to the closest 25 cents when deducting the tax from the price.

There have been efforts to do the same in the US, but unfortunately they have not been as successful as in Canada. I can understand the nostalgia of the penny but it really is a pointless denomination these days. When I was a kid you could actually buy a gumball from a dispenser in the mall for a penny but it's been a long time since you could go buy anything that I'm aware of. I mean I guess you could get a few 0603 resistors for a penny but you'd probably have to buy hundreds of them to get that price. Some fret that without pennies prices will all be rounded up and it will add up, ok that's true, but then why not have 1/10th pennies because even now prices are rounded up. All the gas stations sell fuel with that stupid 9/10th cent, it's stupid.

I also completely agree that taxes should all be rolled into the price printed on the shelves in stores, it would make it so much easier to just show the price out the door and then for situations where one is tax exempt it could have the details in small text on the tag showing how much of the displayed price is tax. Same for tips in restaurants, I absolutely hate tipping, I do it anyway because that's how the wage structure is set up but seriously, if it's expected to tip, just roll it into the menu prices and pay the staff accordingly. Don't make me guess how much I should pay.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: t_ryner on May 10, 2017, 04:12:12 am
According to the laws in the US- It's OK to destroy a penny- as long as you are not going to try and spend it. The keywords in the law concerning that is "fraudulent intent". I doubt the secret penny police will gulag you over the destruction of our smallest currency.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: t_ryner on May 10, 2017, 04:20:06 am
That was one of the reasons they got rid of the penny here.   It cost more than a penny to make one.

Really they need to change the way sales taxes work, they should be part of the final price.  Stores could charge even amounts for stuff and what you see is what you pay.  Could pretty much get rid of nickels and dimes too.  Not sure how it would work for natives that have status cards though, could just round to the closest 25 cents when deducting the tax from the price.

There have been efforts to do the same in the US, but unfortunately they have not been as successful as in Canada. I can understand the nostalgia of the penny but it really is a pointless denomination these days. When I was a kid you could actually buy a gumball from a dispenser in the mall for a penny but it's been a long time since you could go buy anything that I'm aware of. I mean I guess you could get a few 0603 resistors for a penny but you'd probably have to buy hundreds of them to get that price. Some fret that without pennies prices will all be rounded up and it will add up, ok that's true, but then why not have 1/10th pennies because even now prices are rounded up. All the gas stations sell fuel with that stupid 9/10th cent, it's stupid.

I also completely agree that taxes should all be rolled into the price printed on the shelves in stores, it would make it so much easier to just show the price out the door and then for situations where one is tax exempt it could have the details in small text on the tag showing how much of the displayed price is tax. Same for tips in restaurants, I absolutely hate tipping, I do it anyway because that's how the wage structure is set up but seriously, if it's expected to tip, just roll it into the menu prices and pay the staff accordingly. Don't make me guess how much I should pay.

So many people pay in debt or credit that hard change might eventually be phased out (in the long run). you made a good point- why don't people argue for tenth cent coins for gas? The card is definitely the future. Not as satisfying as a handful of cash though.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Brumby on May 10, 2017, 04:26:54 am
Is it legal to give/sell Australian coins to someone else? What if you were to send a few dollars worth of coins to somebody in the US and that person decided to shrink, melt or otherwise damage the coins? Are they going to be dragged over to Australia for punishment?

Really though, I suspect the law is one of those things that is on the books to enable punishment in extreme cases but I really doubt it's enforced. I mean can you find a single case of someone getting arrested and fined for smashing, painting or otherwise deliberately damaging a few pennies? Maybe they really are unreasonable and heavy handed there but it seems unlikely given the general personality of most of the Australians I've known.

Giving them to someone else isn't a problem in itself.  I don't know if knowing their intention beforehand would constitute an offence.

Certainly, I have not heard of any cases where such an offender has been prosecuted - but that doesn't mean there hasn't been any.  While the law in place allows for any level of defacing, I am inclined to believe that the odd coin or three isn't going to ruffle too many feathers - but the nature of the legislation pretty much cuts off any attempts to "skirt the edge".

My interpretation is "do it at your own risk", but you would be reasonably OK with zapping a few for personal use ... but I just wouldn't do it in the first place.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Brumby on May 10, 2017, 04:39:42 am
That was one of the reasons they got rid of the penny here.   It cost more than a penny to make one.

Really they need to change the way sales taxes work, they should be part of the final price.  Stores could charge even amounts for stuff and what you see is what you pay.  Could pretty much get rid of nickels and dimes too.  Not sure how it would work for natives that have status cards though, could just round to the closest 25 cents when deducting the tax from the price.

There have been efforts to do the same in the US, but unfortunately they have not been as successful as in Canada. I can understand the nostalgia of the penny but it really is a pointless denomination these days. When I was a kid you could actually buy a gumball from a dispenser in the mall for a penny but it's been a long time since you could go buy anything that I'm aware of. I mean I guess you could get a few 0603 resistors for a penny but you'd probably have to buy hundreds of them to get that price.
In Australia, they pulled the 1 and 2 cent coins from circulation in 1992 - and the 5 cent is being talked about in the same way.

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Some fret that without pennies prices will all be rounded up and it will add up, ok that's true, but then why not have 1/10th pennies because even now prices are rounded up. All the gas stations sell fuel with that stupid 9/10th cent, it's stupid.

With 5 cents being the smallest increment when paying by cash in Australia, the rounding rules have been operating ever since 1992.  It's quite simple.  Rounding goes either up or down - to the closest 5 cents.  For example: 58c and 59c are rounded to 60c - just as 61c and 62c are rounded down to 60c.  63c goes up to 65c and so on.  When paying by card, however, the actual cents are used.

As for selling fuel with prices to 1 decimal place - I don't see any problem with that at all.  It's just a RATE at which a product is sold in bulk.  The only thing that matters is the total on the pump.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: james_s on May 10, 2017, 08:08:20 am
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?
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Brumby on May 10, 2017, 10:55:55 am
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.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: helius on May 10, 2017, 01:30:55 pm
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.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: yada on May 10, 2017, 02:39:49 pm
:-\ 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.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: jimdeane on May 10, 2017, 04:31:22 pm
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.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Red Squirrel on May 10, 2017, 05:41:42 pm
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.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: james_s on May 10, 2017, 06:07:22 pm
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.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: yada on May 10, 2017, 08:25:19 pm
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?
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: james_s on May 10, 2017, 09:18:06 pm
Are you referring to photographic flashbulbs?
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Brumby on May 11, 2017, 12:17:21 am
Remember the flash that would burn out a light bulb every time you used it?

I believe it's this:

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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?

Quote
How did they make them go out in order?
Good question.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: james_s on May 11, 2017, 12:32:37 am
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.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: CatalinaWOW on May 11, 2017, 12:38:52 am
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.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: t_ryner on May 11, 2017, 12:40:00 am
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.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: james_s on May 11, 2017, 12:44:36 am
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.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: CatalinaWOW on May 11, 2017, 03:14:49 am
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.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: Ian.M on May 11, 2017, 08:21:40 am
Yes.  Philips Magicube (http://www.flashbulbs.com/philips/ph-8.html).
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.
Title: Re: accidental creation of AC power using a 9 volt Battery?!
Post by: 6PTsocket on August 26, 2018, 04:17:54 am
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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