Wonko Labs

[Noob_386]

I built the Pentupler diagram you supplied. Thanks. It doesn't quite work yet but I think it's just because my caps suck. When I touch the meter's leads I get hundreds of volts for a split second and then awlays a steady 77 Volts. I think it's kind of like with the Villard Cascade. I simply have to get better caps. My only question now is are you absolutely sure that polarized capacitors can be used? I blew a few up when I first tried this with polarized ones. Maybe I managed to get the polarity wrong... The longer of the two leads on a capacitor is the "-" and the shorter is the "+" right?

[Tipp]

If you seem to be having trouble, it's easier and safer to start small. Buy a cheapass (3-4$) wall wart that outputs 12v AC at and see if you can build a working multiplier for that. Once you start to understand all the values and whatnot, then you can aim a little higher. The key point here is safety. Working around mains is extremely dangerous, even moreso when troubleshooting a circuit such as this.
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[Noob_386]

Voltage drops have prevented me from using a low voltage AC source. I originally started with 10 V AC. I have already worked with the mains many times in the past few days and I do take extra precautions. Thanks for the concern though.

I went to get some serious capacitors and found the selection to be limited. For now I have 3 capacitors rated for 400 V and 7500 uF. These are the big types with the screws/bolts for leads and a nice big "+" to clearly indicate polarity so I can't get confused

I'm not going to try to get much current out of it though because my diodes are a little weak, rated at 800V 1A. I'm considering buying a few 6A diodes for this. I also googled diodes in parallel and it's said that you can get more current but not say... 2A out of twin 1A diodes in parallel. Any experience with parallel diodes out there?

I can only make 2 stages for doubling the input voltage (120V RMS gives a peak of 169V. 338V output is as high as I can go with these caps.) So the third capacitor is free for actual coil gun use. I've also bought a web cam so I can show you if I get anything working.

[Noob_386]

Oops! I blew a fuse in my house when I tried to charge my 7.5 mF capacitor. I will need to put a nice big resistor (high wattage) in there. I might try the 10V AC power supply I have again because with these caps so huge the voltage drop might not be an issue until current becomes quite high. I never did plan to get 7.5mF, the store simply didn't have anything smaller like the 200 uF that Joe has been recommending to people. Still, 400V 7.5mF for $20.00 a piece - Canadian currency! Not bad 'eh?

[Tipp]

20$ isnt bad but you could certainly get much lower off eBay or swap meets!

Small FYI: Anothercoilgun is not Joe

Parallel diodes will indeed pass more current.
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[Noob_386]

Er.. what's up with the "God Like Joe" avatar? Sorry Anothercoilgun. I'll refer to you by that alias from now on if that's fine with you.

Thanks for confirming the diodes issue, Tipp.

On small items like this e-bay would cost too much for S&H I think. I also don't want to wait long. I know e-bay "can" be good but I've seen the dark side.

[Tipp]

Yeah but the good side is 99% better And oh yes, I know all about the waiting part...heh...
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[Noob_386]

Okay I tried plugging my 10V AC into my circuit. It finally works! 10 is the RMS value, peak is 14. I get 28 output!

I also placed a 470 Ohm resistor on the 28 Volt output and got 24.5 Volts after that. Seems like current draw of < 100mA creates some voltage drop. Still, as a capacitor would fill up, the current would go down, and the voltage up, so it would probaly reach the peak 2x voltage eventually. It would just chagre a little longer than predicted by T=RC due to the power supply voltage changing based on current.

Here's pictures (my webcam is a piece of pooh, sorry)

AHHHH!!! Crappy free hosting! Here's the page
http://noob386.bravehost.com/
Enjoy

[Noob_386]

Okay, I finally got a 250 Ohm, 100 Watt resistor. It's a mean looking bugger. I put it between my Mains & my Voltage Doubler. This lowered the current draw on the initial charge-up of the capacitor so I wouldn't blow a fuse like last time.

Sucess! I got up to 324 Volts. - A little lower than the expected 338. (169 is the peak of a 120VAC mains, times 2 = 338)

It took a surprisingly long time to get to that point though, the resistor had a greater effect than I expected. After about 250 it was going up volt by volt on my multimeter. I am hoping that this is only for initial charging of the voltage doubler's capacitors. My fear is that it may create a very long charge time for the gun's capacitor.

[Anothercoilgun]

100 watts is too high of a wattage. If you get close to needing a 100 watter you need to change the design. 250 ohms is too high of a resistor. 250 ohm resistor connected directly across mains 120v ac will as a singular load only dissipate 60 watts; hence the prior reason for 100 watts being too large. Remember I said a mains charger < 200 watts is not worth the time? The multiplier took a long time to charge for 2 reasons. One, you deprived it of current. 250 ohms + the reactance of your caps adds up to ALOT of resistance. The smaller the charging current, the longer the time to charge a capacitor. You are always quoting T=RC religiously, how come you did not see this comming? Two, the other reason why the charging time was excessive, more precisely why they did not reach full voltage, is because a 250 ohm resistor in series with the series resistance of the caps reactance functions as a voltage divider.

Fear not but be certain. If you now add a Bank to be charged by the multiplier, the charge time will be unreasonably long. Use the Rlimit resistor as a current clamp for peak current. If 5 amps is the decided peak, use a 25 ohm Rlimit. 25 ohm at 20 watts is more than fine for now, why? The peak charging current only exist from 10's if milliseconds to 1 second, Farads dependent. Small banks < 500 joules will be in the mid 100's of milliseconds peak time. Large banks > 1,000 joules will be in the 1 seconds range. I believe you are in the small banks class; therefore a 20 watter resistor works just fine.

So either a 25 ohm 20 watter or (2) 50 ohms at 10 watts in parallel. Doublers are so not worth the trouble.




The top row shows a 40 ohm resistor used to limit a mains tripler to 4 amps. The consequence is a slow 5 seconds charge time.

Ipeak = Vpeak / R, so 3.8 Amps = 384mV / 0.1 (power resistor)




The second row shows how with no resistor the curret is naturally limited by the charger to 25 amps. The consequence is a marginal tripping of house fuses for the benefit of a 2 second charge time.


Ipeak = Vpeak / R, so 25.4 Amps = 2.54mV / 0.1 (power resistor)
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28,000 + Views in support of Joe!! His spirit lives on!!!!!

!!!!FYouCK Ebay!!!!!!!
Any one using Basic or C to program a PIC -w-i-l-l- -b-e- -s-h-o-t- -o-n- -s-i-t-e-!-!

[Noob_386]

My caps are 400V 7.5mF, holding 3 Coloumbs. I think that makes them 1200J each. Only one will be for the coil gun, two more are simply my voltage doubler. I might try replacing them with smaller caps in the future. As for the resistor: I like my power rating to be high so that I don't produce lots of heat. The 250 Ohms being too high though... you're right. However, 25 is too low for my purpose.

The reason is something that I haven't mentioned... In the final product I plan to use a "Motomaster Eliminator" as my power source. It's a large heavy semi-portable battery. It's rated for 400W, though I don't want to push the envelope on it. I think about 3A for 360W would be as high was I want my peak to be. So I'm looking at 40 Ohms, 50 Ohms would be fine too.

I have been using Motomaster Eliminators to take notes at college on my laptop in every class. I HATE PAPER WITH ALL MY HEART!!! As a result I have become quite experienced in their transportation. The unit weighs about 23 pounds, and has broken pathetic camping backpacks. I finally got an army backpack from a military surplus store that has held up for a long time. The only thing that broke on it was a plastic part of the strap which I knew would break from the day I bought the thing. 23 pounds is a fair bit, but with a backpack you can still move around fine unless you're a lightweight :p Not much running though... I have done a slow jog for a short distance. I'm not a good runner in general though.. I'm not in shape.

So the end result is going to be a big bad coil gun drawing power from a big bad backpack.

[Anothercoilgun]

Is this correct, 7500uF x .5 x 400V^2 = 600 Joules? If you are using 600 Joules caps for a charger then all my suspicions of you being mental are now varified.
_________________
28,000 + Views in support of Joe!! His spirit lives on!!!!!

!!!!FYouCK Ebay!!!!!!!
Any one using Basic or C to program a PIC -w-i-l-l- -b-e- -s-h-o-t- -o-n- -s-i-t-e-!-!

[Noob_386]

My supplier didn't have any lower rating caps around that voltage and they were only $20 Canadian a piece. Trust me, if I could I would get 200uF like you recommended to someone else, and only the the actual gun's bank would be in the thousands of uF. In fact, I mentioned this a few posts back...

By the way, why is there a multiplication by 0.5 in the equation? I thought P(Watts) = V * I would translate into P(Joules) = V * Q for a Capacitor, where Q is the amount of Coloumbs of charge the capacitor holds, which is equal to V * C where V is caps' voltage rating and C is the capacitance in Fardads ofcourse.

[hectorloshuk]

Hi,

Im moving to Oman in the next few weeks and would like to know what the voltage/amps is used and what sort of electrical adapter I should take with me. Eg. two round pins, etc,...


Thanks.

Steppy-boy.