darkchemist Posted February 19, 2006 Posted February 19, 2006 Well, I'm interested in constructing EBW dets as I'm actually quite skiddish when it comes to primaries so I've been gathering all the necessary materials to make them. I currently have all sorts of capacitors: 1 X 20kv 54uF oil filled cap (my fav), 6 X 420v 2700uF 'lytics, 6 X 400v 3900uF 'lytics, 2 X 160v 8200uF, and 8 X 75v 99000uF 'lytics. I have all the necessary chems to produce ETN: 1L of 70% HNO3, 1L of 98% H2SO4 and a pound of eyrthritol. Ok, now problem is I keep blowing through and burning up power supplies for cap bank charging (tried MOT to charge the 400v and 420v caps). I'm actually quite interested in an easy ~150vdc charger as I would like to make use of the 75v caps (in series) first. If anyone knows of one off hand I could throw together that would be great as I can't seem to find one in the scope of my expertise. Anyway I'm convinced if I throw enough energy (even at a 150v) I can make a decent EBW system.
evilgecko Posted February 20, 2006 Posted February 20, 2006 You need an inductive ballast to charge capacitors of this value. Another MOT can be used for this purpose. Just connect it in series with your charging MOT and short out the seconderies.
darkchemist Posted March 2, 2006 Author Posted March 2, 2006 Alright, still new to electronics and having a hard time understanding what an inductive ballast is/does. This will decrease the peak amperage (I'm assuming) or does it lower the peak voltage...or both?
evilgecko Posted March 2, 2006 Posted March 2, 2006 Inductance causes impedence in an AC circuit. It restricts current because of the magentic field it produces and also because of its internal resistance (however not much when where using MOTS). By the way your rectifing the output of the charging MOT before you charge the capacitors, right? Otherwise you'll be subjecting them to AC voltages which will kill the caps. And did I read your using the MOT to charge the 420V lytics? Unless you've modified the MOT's secondaries, they output a voltage of around 2000V, way to high for a 420V cap. Maybe you should read up a bit more before you start playing with high voltage/ high currents. Output from a MOT can and will kill you!
darkchemist Posted March 2, 2006 Author Posted March 2, 2006 I see...thankyou. Yes, I've been using some of those (can't remember the serial #) 1000v diodes from radio shack in series to rectify but those are generally the first thing to go. Probably because of way too much current. Hmmm...maybe a mot is a poor choice...what should I use then I wonder? Yeah, in retrospect I should probably just go to the library again and read up a little more.
evilgecko Posted March 4, 2006 Posted March 4, 2006 Yes those diodes will be going from to much current...when you first charge a capacitor it's like a dead short! If you made a diode bridge (it would require 8 diodes though) you'd get a better DC supply. But a MOT is proberly not the way to go. If you are going to be using to explode bridge wires you will want something portable. One way is to use a inductance charger. They run of 6-30V and pulse current through a inductor. This creates sharp voltage spikes much higher than the input voltage which pass through a diode and into the cap bank. These are self current limiting as well so you wouldn't require a inductance ballast. See http://forum.4hv.org on how to build them. A crude way would be to build your own step up transformer (say 40 times more secondry windings than primary) and use a 555 (simple osscilator) to pulse current through the primary at a low voltage (so you can run it of a 12V battery), and rectify the secondry into the cap bank. This would charge to around 400V. You could even add a zener and a resistor to prevent the voltage going over a set limit. Again see 4hv on how to do this. I'm quite interested in EBW devices to and share your thoughts on primaries!
dragonman586 Posted March 19, 2006 Posted March 19, 2006 At what amount of joules is a set of capacitors considered EBW worthy. Because I have a contraprtion here that can put out around 15 joules and blow a section of steel wool pretty nicely. EDIT:I ment to type in 13 Joules Not 15
Boomer Posted March 21, 2006 Posted March 21, 2006 "I'm quite interested in EBW devices to and share your thoughts on primaries! " The idea behind an EBW is to use NO primaries. Or did you mean that? And yes, 13-15 Joule is more than enough. The trick is to deliver the energy in the shortes time possible, think a millionth of a second till full current. This takes high voltage rather than high capacitance. Plus, the wire must be really thin: 1.5 mil gold wire starts working at 200 Amps, while 10 mil wire fails at a kiloamp. IIRC burst action (I^2t integral) rises with the 3rd or 4th power of wire diameter (will look it up)!
dragonman586 Posted March 21, 2006 Posted March 21, 2006 Sweet that means I might have an EBW it dumps the power of a total capacitance of 320 microfarads at somewhere between 280-300 volts Here is a Pic of my doom machine.
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