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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.
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 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 I am most proud of the projects that require me to wear my earplugs :)
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).
Registered Member #3766
Joined: Sun Mar 20 2011, 05:39AM
Location:
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
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.
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.
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.
Registered Member #3766
Joined: Sun Mar 20 2011, 05:39AM
Location:
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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