Picric acid DOES taste bitter! Posted May 12, 2008 Share Posted May 12, 2008 Made myself a CW generator powered from a microwave oven transformer that outputs round 30kv DC. Ive tried to use it to power one of those Ion-hover-triangles made out of foil, toothpics and copper wire. Is smells interesting and i'm almost having liftoff, but something is keeping the CW to charge/recharge at a sufficient rate. It is full-wave with 10kv. caps in three stages, with double capacitance at the medium stage, and triple at the first in an attempt to solve the recharge problem, but with no luck. Tips, ideas, questions etc... Link to comment Share on other sites More sharing options...
Richtee Posted May 12, 2008 Share Posted May 12, 2008 . Is smells interestingThat's a BAD thing. Well, as far as your lungs and free radicals go. Also increasing capacitance increases the recharge time. I have no idea WTF yer doing... never heard of the effect you mention, but sounds like what you need is either more voltage or current, not more capacitance. Link to comment Share on other sites More sharing options...
JCrewPyros Posted May 13, 2008 Share Posted May 13, 2008 From what it sounds like to me is off the Mythbusters episode.. Levitation? They use different types of things to get free levitation and this was one of the contraptions that they built... correct me if I am wrong... Link to comment Share on other sites More sharing options...
lja Posted May 14, 2008 Share Posted May 14, 2008 Are you sure you're getting 30 KV? Each stage of a CW multiplier adds the input voltage again, it doesn't double it over and over. That's why the caps and diodes only need to be rated at 2x the Vin. Most of the microwave transformers I've played with have only been around 2KV. So what you've built may only be around 6KV not 30. I'd get rid of the doubled caps and just add more stages to the CW multiplier. Pot in some wax if you start to get arcing across parts of it. I've made them many stages with decent results. The smell is probably ozone. Not good for you but it will certainly freshen up the air in the room. Careful with the MOT, those transformers are really dangerous and will kill you very quickly if you're not careful. Link to comment Share on other sites More sharing options...
Boomer Posted May 14, 2008 Share Posted May 14, 2008 Is it 50/60 Hz or switch mode? A CW multiplier looses juice very quickly at mains frequency, anything above 10 stages is in vain.The biggest I built was 24 stages (12 positive and negative vs. earth), it used a shoe box of 3,3µF RFI foil caps. Gave quite a bang but also grilled my meter (only connected to ONE pole, the other floating!). Link to comment Share on other sites More sharing options...
Picric acid DOES taste bitter! Posted May 20, 2008 Author Share Posted May 20, 2008 Thnks, realy helpfull! Ill start re-soldering my diodes and caps in notime! Im a little ashamed that i misunderstood such a fundamental thing as the voltage increase level. As for the MOT: Its 1850 volts between one tap and the gound, thus 3700 between the two. I persume it still works like that even in an full-wave design CW. Again, thanks, and i do know that smell was ozone. *Update* Re-soldered the caps and diodes so now i got 5 stages with a single cap for each stage. Longer spark at the test run and more corona-effect, but still didn't solve the recharge problem. Also, if the electrodes arent close enough to eachother it starts sparking between two of the top stages( ill fix that, dont worry) It runs from 50/60 Hz mains transformed through a microwave oven transformer, if i didnt make that clear, and the amps in the transformer should be well over enough to charge the whole thing in notime, what am i doing wrong!?! Link to comment Share on other sites More sharing options...
Purpley Posted July 7, 2010 Share Posted July 7, 2010 If I have a high voltage neon transformer that gives out 15000 volts and 30 mA wil that work for the levitation device? Link to comment Share on other sites More sharing options...
frosty90 Posted July 11, 2010 Share Posted July 11, 2010 If I have a high voltage neon transformer that gives out 15000 volts and 30 mA wil that work for the levitation device? For a tiny one maybe. The voltage really needs to be a bit higher. You will need to rectify the output of the neon transformer, and diodes to do this need a reverse breakdown rating of minimum about 22000 volts (15000 volts is rms, so peak DC is sqrt2 times this.). You can string together a series of cheap 1000v diodes to do this, but insulation is tricky! Most people use voltage multiplier circuits driven from lower (a couple of thousand) voltages, then the components dont need to see the full output voltage, and you can get higher voltages easier than with a transformer. Link to comment Share on other sites More sharing options...
WSM Posted September 5, 2010 Share Posted September 5, 2010 (edited) Thnks, realy helpfull! Ill start re-soldering my diodes and caps in notime! Im a little ashamed that i misunderstood such a fundamental thing as the voltage increase level. As for the MOT: Its 1850 volts between one tap and the gound, thus 3700 between the two. I persume it still works like that even in an full-wave design CW. Again, thanks, and i do know that smell was ozone. *Update* Re-soldered the caps and diodes so now i got 5 stages with a single cap for each stage. Longer spark at the test run and more corona-effect, but still didn't solve the recharge problem. Also, if the electrodes arent close enough to eachother it starts sparking between two of the top stages( ill fix that, dont worry) It runs from 50/60 Hz mains transformed through a microwave oven transformer, if i didnt make that clear, and the amps in the transformer should be well over enough to charge the whole thing in notime, what am i doing wrong!?! From my training, and remembering DC electricity/electronics fundamentals; think of a capacitor as a cup - the bigger it is, the longer it takes to fill it up (which is why they're used in timer circuits). Have you considered using smaller capacitors of the same rating? I'm wondering if it will solve the rate problem? Let us know if that works. WSM Edited September 5, 2010 by WSM Link to comment Share on other sites More sharing options...
WSM Posted January 1, 2011 Share Posted January 1, 2011 From my training, and remembering DC electricity/electronics fundamentals; think of a capacitor as a cup - the bigger it is, the longer it takes to fill it up (which is why they're used in timer circuits). Have you considered using smaller capacitors of the same rating? I'm wondering if it will solve the rate problem? Let us know if that works. WSM Has any progress to this project happen? I'm just curious since no comments have appeared since I last wrote. Please let us know. Thanks! WSM Link to comment Share on other sites More sharing options...
WSM Posted January 12, 2011 Share Posted January 12, 2011 (edited) Has any progress to this project happened? I'm just curious since no comments have appeared since I last wrote. Please let us know. Thanks! WSM I have a friend who made a CD firing system but lamented the long recharge time after firing. His solution was to replace the (physically) larger capacitor with a (physically) smaller capacitor with the same voltage rating. The recharge time went from many seconds to much less than one second, allowing him to use the CD unit in a multi-fire system; even though the smaller cap supplied fewer joules of power. A similar approach may solve your rate problem. Any thoughts? WSM Edited January 12, 2011 by WSM Link to comment Share on other sites More sharing options...
frosty90 Posted January 13, 2011 Share Posted January 13, 2011 I have a friend who made a CD firing system but lamented the long recharge time after firing. His solution was to replace the (physically) larger capacitor with a (physically) smaller capacitor with the same voltage rating. The recharge time went from many seconds to much less than one second, allowing him to use the CD unit in a multi-fire system; even though the smaller cap supplied fewer joules of power. A similar approach may solve your rate problem. Any thoughts? WSM As a rule of thumb, smaller caps have a lower internal resistance. All capacitors have some internals resistance, electrolytics are pretty bad capacitors in this regard. If you connect a capacitor to a voltage source, with a resistance in series, the cap will basically be nearly fully charged to the supply voltage in the time 4*C*R where C is the capacitance in farads and R is the resistance in ohms, the answer is in seconds. If you want it to charge faster without changing the cap however, you could increase the charging voltage. say you charge a cap with a 10 volt supply. After C*R seconds the cap will be charged to about 6.3 volts (or in general about 63% of the supply votage). So you can use a larger supply, and only charge the cap to a fraction of the voltage. Link to comment Share on other sites More sharing options...
Richtee Posted January 13, 2011 Share Posted January 13, 2011 s. If you want it to charge faster without changing the cap however, you could increase the charging voltage. say you charge a cap with a 10 volt supply. After C*R seconds the cap will be charged to about 6.3 volts (or in general about 63% of the supply votage). So you can use a larger supply, and only charge the cap to a fraction of the voltage.You can also make some cool confetti by over-charging said cap :{) Wheeee! Link to comment Share on other sites More sharing options...
WSM Posted January 14, 2011 Share Posted January 14, 2011 As a rule of thumb, smaller caps have a lower internal resistance. All capacitors have some internals resistance, electrolytics are pretty bad capacitors in this regard. If you connect a capacitor to a voltage source, with a resistance in series, the cap will basically be nearly fully charged to the supply voltage in the time 4*C*R where C is the capacitance in farads and R is the resistance in ohms, the answer is in seconds. If you want it to charge faster without changing the cap however, you could increase the charging voltage. say you charge a cap with a 10 volt supply. After C*R seconds the cap will be charged to about 6.3 volts (or in general about 63% of the supply votage). So you can use a larger supply, and only charge the cap to a fraction of the voltage. I should add that these were photoflash type capacitors! There's something different about the electrolytics used for photoflash applications! WSM Link to comment Share on other sites More sharing options...
WSM Posted January 14, 2011 Share Posted January 14, 2011 You can also make some cool confetti by over-charging said cap :{) Wheeee! Hmmm! Report to confetti, sounds like a new party effect . WSM Link to comment Share on other sites More sharing options...
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