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Author Topic: Making a needle glow (1000°C) by Battery  (Read 3960 times)
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Different metals have different ranges at which they melt. I used to be diy forging with different types of materials. The propane fired forge I built could get up to 2500 degrees f or even more If I redesigned it. If good at it you can tell about what temp the metal is by the color of it being heated.    
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Nicads will do it, just one would be enough @ 1.2v, nicads give all they've got in a short space of time, nickel metal hydride on the other hand are made for duration not high drain, so imagine six 1.2v 2400mah nicads in parallel, thats 14 amps for one hour, you can work out the rest, another impressive sight is 6 x 12v 40 watt solar panels wired in series, i used my multimeter probes to short the whole bank, it created a high frequency plasma stream well over an inch long, actually the metal probe tips got so hot they melted and fell off spoiling my fun
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actually a pack of one hundered needles is that heavy *caugh*

avg. needle = 0.075g
E = 33.64J
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With this potent formula: E = 0.5 * U² * C

we know that we want to have energy in the range of about 60 Joules.

At 9V I'd need ~1.5C.

How do get this transformed into Farad? Can I just say:
(1.5 A*s) / (9V) = 0.167F ?
although I'm not sure with the 9V do I have to divide by 9 because I said I'd use 9V in the first formula?
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Quote
How do get this transformed into Farad?
Not sure exactly what you did there. This is what I know:

W = 1/2*C*V2

C = W/1/2*V2

C = 33.64J / (0.5*(9V)2) = 0.8306F

or C = 830,600uF
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Yes you're right... thats what you get from mixing variables...
I actually thought the C was coulomb instead of capacitance..
guess I should get some sleep.
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it created a high frequency plasma stream well over an inch long
What would cause a DC system to oscillate like that?
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It is one thing knowing how much energy it takes but another in getting that energy to be dissipated in the needle and not in the wiring from the power source to the needle. The problem is that as the needle has a very low resistance the wiring's resistance has to be substantially lower. This will be a practical difficulty. You will probably have to use things like large jumper leads to connect to the needle. Even then I suspect that most of the resistance will be in the connections. It is the place of the greatest resistance that will be the place of the greatest heat dissipation.

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What would cause a DC system to oscillate like that?
Lack of understanding of what was going on.  smiley-wink
« Last Edit: June 18, 2010, 05:05:35 am by Grumpy_Mike » Logged

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@Groove
@Grumpy mike
your right it is my lack of understanding so if you know please explain, the only way i can describe it was a huge purple stream but not with hard edges and not in a straight line, more like a stream from a plasma globe and it had a very high pitched hissing sound, im sure it was very high temperature plasma because 1. it melted my probes in seconds and 2. the longer the arc stretched out (over an inch) there was a most deffinate peak in the middle where the superheated air was rising, the strange thing was that it was only about 112volt when i measured the output and the panels are rated at 40 watts
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I think I can solve that with using multiple smaller capacitors like 16 or 25, all with individual wires that lead to one bigger piece of metal, and than the needle.
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Built my first test-circuit with calculated ~1.4J at 25V and is able to create a spark and quite a loud pop. And also to evaporate a short length of copper wire (from a stranded wire).

Any idea on how to close the circuit? a transistor would surely burn out, and a simple switch will discharge the circuit when the switch-connectors meet (great resistance at that point).
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jazzar, you are playing around with things that have a high potential for harm (potentially death); be careful.

You may want to research the "high voltage" community for tips, tricks, and techniques. Probably the area most relevant to what you are trying to do would be "quarter shrinkers", "water exploding", and "coil guns" - all three of these in the "high voltage" community involve shorting large capacitor banks into coils or spark gaps. There would be details on how to "switch" such banks properly.

There are tons of web sites dealing with the subject of "high voltage", and plenty of discussion forums, too. You may be able to get more information and discussion on how to do what you want to do from them (then, when you are able to do things in that case, you can come back here to learn how to hook up the Arduino to it and control it).

Good luck with your glowing/exploding needle project (and please, be careful - wear goggles, and one hand in pocket at all times)...

 smiley
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Thanks for the advice(and the 4hv-link), I'll keep that in mind :-)

On the subject of evaporating...
(32400J of energy ouch...)

[media]http://www.youtube.com/watch?v=M-P9BV0r6QM[/media]
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Not sure if someone has mentioned this yet, but you could instead of using 1 cap, use more than one, this will lower the impedance and allow for more current to discharge through the given object, you will however need to find out how much usable energy is inside your battery and work your circuit off it, make sure you account for all losses in the charge circuit and the discharge circuit because they will of course loose you some energy in heat as well.
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Currently planned are 25 * 4700uF capacitors 35V max @ 30V
With the Energy of ~53 Joules

thats about ~60% more than required.

Now I wonder if the discharge isn't too fast so that I will blast one end of the needle off rather than heating it up...
« Last Edit: June 18, 2010, 07:08:46 pm by jazzar » Logged

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