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Forums
4hv.org :: Forums :: High Voltage
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New purchases and side projects thread

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GrantX
Fri Sept 09 2011, 05:12AM Print
GrantX Registered Member #4074 Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
Hey,
First time uploading pictures, hopefully it works out.
Got some new stuff in the mail and have been working on a bunch of minor projects not worth their own thread, so I thought I'd share them all here. Others are encouraged to do the same.

Anyway, first picture:
My new caps and diodes. Big shiny one: 50kV 20nF polystyrene, little shiny one is 80kV 1nF. Ceramic caps are 30kV 1nF. The small diodes are 30kV, 20mA and the monster ones are 40kV 1A.

Next pic:
My shoddy 400V 2.95mF cap bank. For asploding things.

Next pic:
My incredibly primitive ignition coil sparker I slapped together today. Simply charges some caps and dumps them into the primary when you push a button. The resistor overheats badly and your fingers get uncomfortably close to live 350VDC when operating the push button. Not recommended.

Next:
Trying to make a high voltage resistor out of a million 1/4W megohm resistors and some liquid electrical tape, because I'm cheap and got a ton of them "free" from uni.

And finally:
The worst SGTC primary and secondary ever conceived. I've scrapped the idea and am looking for materials for more sensible coils. :)

Hopefully others will add their silly side projects and interesting new bits here.

1315544859 4074 FT0 Imag0084

1315544859 4074 FT0 Imag0081

1315544859 4074 FT0 Imag0086

1315544859 4074 FT0 Imag0090

1315544859 4074 FT0 Imag0096
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buxtronix
Fri Sept 09 2011, 01:59PM
buxtronix Registered Member #4078 Joined: Tue Aug 30 2011, 12:53PM
Location: Sydney, Australia
Posts: 19
Nice toys!

Nice stuff you are doing, looks like lots of fun. I have a very similar range of stuff for various experimenting.

1) big caps are always fun. I have seen those polystyrene caps on ebay but currently see no great use for them in my own stuff. What do you plan on doing with them? A big marx generator is always awesome (see Link2 for mine).

2) Good stuff. Remember, when figuring out how much assploding a cap bank can do, the important figure is the total number of joules stored. Look up "capacitor joule calculator" and you will find out how many joules a cap [bank] can give. More volts is better than more uF. Your appears to be 0.25 joules. I scored a capacitor that holds 150 joules. It makes a CD shatter, see my blog for video. I wish I could get more of these caps..

3) Buy some sidacs from ebay, quite cheap (10 for $US20). Look up "ignition coil sidac" for how to get the most from them. I have a 2kv microwave capacitor charged from a small flyback, and with sidacs dumping into an ignition coil, I get 2inch arcs from it. (Dr Electric was my inspiration)

4) No comment. High voltage resistors are useful :) I have 5000 x 390k VR37 resistors. If you are in .au and need some, I might be able to help.

5) Your secondary is sitting on a Jaycar catalogue. Are you in aus? Your 2ndardy has potential (sorry for the pun), but your primary...yeah you would be better off with a pancake coil. Cylindrical coils tend to have too much coupling which results in excess arcing between secondary windings, destroying it.

I am slowly documenting my own projects at Link2 I am most proud of the projects that require me to wear my earplugs :)
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GrantX
Sat Sept 10 2011, 01:44AM
GrantX Registered Member #4074 Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
Thanks for the comments. Yes, I'm in Australia, I live just outside Melbourne.

1) Well, I don't have any particular plans for the caps, A few will end up in my SGTC if I ever get around to making proper coils (I want a larger secondary so I can pump 900VA into it with my larger NST, instead of my little 180VA 6kV one).

2) I used the online calculator and came back with 236 Joules, its actually 2950 uF (hence 2.95 mF). Is this enough for a small coilgun by any chance?

3) Interesting idea, I believe I've seen something similar on Instructables. I also saw a kit on Information Unlimited for $99 that can produce up to 5 inch sparks from an iggy coil at 100 bps. Im very tempted to pick it up, despite the price :)

4) You've sparked my curiosity, haha. But I'm anxious to see how my jury-rigged and thieved HV resistor holds up to the big NST :)

5) Yes! Im a jaycar regular. Yeah, I built the primary before I actually knew how a TC worked. After passing the Electromagnetic class at uni I realised how silly I was. I'm going to chop the wire spool in half and rewind a pancake coil, and I want a larger secondary, as it's only 50mm x 300mm, so I'm guessing it's not suitable for the 15kV/60mA NST.

I like your site, you've got some awesome projects and parts (I'd kill for a massive cap like that, haha).
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magnet18
Sat Sept 10 2011, 04:50AM
magnet18 Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location: 1307912312 3766 FT117575 Indiana State
Posts: 624
XravenorX wrote ...


2) I used the online calculator and came back with 236 Joules, its actually 2950 uF (hence 2.95 mF). Is this enough for a small coilgun by any chance?

A small, small one.

coilguns tend to be unimpressive unless you go big, like the kilojoule range, because only like 3% of the energy is transferred to the projectile. If you try to make a smaller projectile so it goes faster, efficiency drops further.

I wanna build a coilgun, but I want to wait until I can do it right and make one that's a few K-joules
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Forty
Sat Sept 10 2011, 04:08PM
Forty Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649
236 joules is enough for a coilgun to plink through cans and whatnot. it would be a good starting point
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GrantX
Sun Sept 11 2011, 12:45PM
GrantX Registered Member #4074 Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
Decided to connect the big 50kV 20nF cap to my NST for some arc fun. Results were quite unexpected:

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buxtronix
Mon Sept 12 2011, 05:08AM
buxtronix Registered Member #4078 Joined: Tue Aug 30 2011, 12:53PM
Location: Sydney, Australia
Posts: 19
Be careful about running your NST resonant with a cap. The huge arcs you see are from the overvoltage that this generates (it is a tank circuit after all), and quite a few NSTs have been killed like this.

Still, it does look awesome.
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GrantX
Mon Sept 12 2011, 05:15AM
GrantX Registered Member #4074 Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
buxtronix wrote ...

Be careful about running your NST resonant with a cap. The huge arcs you see are from the overvoltage that this generates (it is a tank circuit after all), and quite a few NSTs have been killed like this.

Still, it does look awesome.


Yeah, I only ran it twice, once when I was testing all the new caps, and once to make this video. I don't want to kill my NST, so there will be no more of those shenanigans.
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sngecko
Mon Sept 12 2011, 02:52PM
sngecko Registered Member #3447 Joined: Fri Nov 26 2010, 11:10PM
Location: North Jersey
Posts: 97
Yikes. One of those arcs near the end of the video looked like it originated either at the unseen capacitor leg or *through* the cap wall. Given the lack of glowing chunks and cursing, I guess it must be the former.
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magnet18
Mon Sept 12 2011, 03:57PM
magnet18 Registered Member #3766 Joined: Sun Mar 20 2011, 05:39AM
Location: 1307912312 3766 FT117575 Indiana State
Posts: 624
I've had that happen before, I wasn't expecting anything to happen at all, I just wanted to see if the capacitor could hold a charge.
next thing I knew, deafening arcs were shooting between the cap leads.
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