basic general question

First, this will kill you no problem.

How will you convert DC to AC?

Last, this will kill you no problem.

Your point? A gun will kill him too if he points it at his head(first he will need to make sure it is loaded).

Breakdown of air is about 30kV/cm so its not like this thing will jump out at him. Obviously if he's storing charge on the cap then he will need a safe way to discharge it before sticking his hands in there.

In any case 10mA isn't, in general, enough to kill.

You would have been more helpful to try to answer his questions instead of stating the obvious.

Most people know a gun will kill them. Not as many know a sign transformer will do this as well.

The fact that he's confused about what a transformer will transform is a red flag that he is in the unknowing group.

You wanna take a chance on that?

I asked him a basic question and I warned him of the danger. You'd have done better to mind your own business since your knowledge is so slim.

Oh!! Great come back. You asked him a question... did he ask for a question to his question or to answer his question? If you know so much about this s*it then surely you could supply more information. Your question about how he will convert DC to AC shows just how ignorant you are... Your trying to act like your intelligent by misdirection. The crux of the matter is not that how he will get AC from DC(which I assume he will do by an inverter like everyone else) EXACTLY what he asked.

Unlike you I do not know the true answer so I did not respond. I wouldn't want to give him bad advice. Maybe you should take that advice instead of trying to act like you know something about something you don't.

My answer would be to add about 100kohms in series with the cap to generate a peak instantaneous current of V/R ~= 2k/100k A = 1/50 A. While this is over is rated max of 10mA it is only 10mA above it and will die down to 7% of that within ~5 RC's. For his application this might be to long. He mentions that it is for a pulsed laser but how long between each pulse does he need. How big is the cap? In anycase he could work down from the 100kOhm resistor to increase the charge rate. Although having a resistor of 1ohm produces an instantaneous peak current in the secondary of about 2000 A and that means its over 4M in the primary. I'm sure that he will definitely not get this out. But even if it pulls just 10 amps from the 12VDC supply it could eventually cause problems. (depending on how fast and how many times it is pulsed) Obviously there will be a saturation point that will limit the peak inverse current and most devices can handle a substantially higher peak inverse current but I have no specific answers.

But unlike you have I have no practical experience with the subject so I did not answer... You also obviously have no practical experience but answered with nonsensical questions trying to act like you know something that you don't(which you do a lot of).

I mean, come up... WTF is up with "How will you convert DC to AC?"??? WTF do you think you can ask such stupid questions. You are assuming the guy is a total idiot... and this really means you are the idiot. He did not ask anything about that and you should assume that he as a little bit of a clue what he is doing. Now maybe it is the case he will hook up the 12VDC supply directly to the sign transformer and it won't work... GUESS THE F*CK WHAT??? YOU KNOW THEY MAKE 12VAC POWER SUPPLIES TOO? Your f****ng question is moot and just a waste of time. If he does have that problem he will post back and say it doesn't work and then someone will solve that problem very quickly and he will just have to run to wal-mart and by a 12VAC adapter or tear out the rectification in his 12VDC adaptor.

Now instead of that bs you should have tried to answer his real problem but no, since you have no clue you misdirect like a magician. A magician has no real magical powers so they pretend. You are nothing but an intellectual magician. I see your BS all the time in this NG and you do more harm than good and I think its time someone pointed it out. Surely though there will be those that will jump on me because they too are intellectual magicians and everyone knows you guys stick together.

Also, it is true its a probably a good idea to point out that it could kill him but if he doesn't know this already then maybe natural selection needs to take place. Also, every time someone plugs in a device you need to warn them they might die too. Do you know that only about 200 people a year die from electrocution? Of those how many do you think are not electricians or kids?

"A low-voltage (110 to 220v) 60 Hz AC traveling throughout the chest for a fraction of a second may induce ventricular fibrillation at currents as low as 60 to 100 mA; about 300 to 500 mA of DC are required. If the current has a direct pathway to the heart (e.g., via a cardiac catheter or pacemaker electrodes), much lower currents (>1 mA, AC or DC) can produce fibrillation. Body resistance (measured in ohms/sq. cm)* is concentrated primarily in the skin and varies directly with the skin's condition. Dry, well-keratinized, intact skin has an average resistance of 20,000 to 30,000 ohms/sq. cm, whereas the resistance of moist thin skin is about 500 ohms/sq. cm. "

So assuming the length of is arms to chest is ~30cm gives about

Instead of being a moron about the dangers you should just point out that its not safe and maybe link to a site about the dangers and some saftey precautions. Ofcourse if he's poking around in the circuitry while its life then maybe he deserves to get electrocuted. Its not that bad though, I've messed around inside of life TV's and not be electrocuted. (Maybe it was a stupid thing to do but I'm alive.)

The point is, Homer, is that if your not going to try and answer is questions then why bother to post? I know you need to feel useful but its just a waste. Try volunteering at something your good at like picking up trash.

This was just for a rough approximation. Obviously its an RLC circuit but this should just result in reducing the overall peak instantaneous current which means RC will effectively be larger. I did most of those calculations earlier so they may be wrong. (My memory isn't so good these days). In any case it wasn't suppose to be a detailed analysis but just an overall general idea. The point is that increasing R increases the charge time but decreases the maximum instantaneous current. I would imagine that its not so important because it will be limited by the transformers and as long as the average current isn't to high over the charge time then it shouldn't be a problem but the average will need to include the number of charges per second too.

I would think that if you just use it intermittently then you probably don't need a resistor. If this is pulsed many times a second then you'll need a more detailed analysis. (or just experiment) (also I'm assuming V = 2kVDC but since its suppose to be 2kVAC the above numbers will be off)

In any case I'm not really trying to give any info because I have not done this sorta stuff before and I coudl be wrong. There are many web sites that talk about HV and stuff and you'll find more practical experience there. Also, an important side note, which you probably know, is that the capacitor will probably be the most dangerous thing there. You should make sure you safely discharge the cap if you plan on messing around it. The 2000V could span a mm or so and get you. Probably won't kill you but could hurt.

If your eager to start you might try using a 1M resistor and taking some measurements such as charge time(which you can approximately compute anyways) and run it for a while and see if things get hot(very doubful). Then work your way down from there until you reach your specs. My guess, and its only a guess, that you could probably deal with maybe even just a few hundred ohms or even less and everything will work fine if your not pulsing it hundreds of thousands of times a sec.

You might want to give more information on the specifics so someone that knows about this stuff can give a more informed decision. (although maybe all pulsed lasers follow a specific implementation). I think the two important things are the capacitatance, pulses per second, and operation time.

Jon

You're still an idiot. Hooking up a 12 VDC supply to a sign transformer isn't going to do much of anything. Asking questions is the best teaching method.

And your assumptions could kill him. I've been working with electronics and electricity for over 50 years and I don't fool with sign transformers or the like without following a lot of precautions. For someone with as little knowledge as he shows his next few steps could end his world.

ok, I appreciate all your concerns for safety and believe me all precautions will be taken. the cap size will certianly be more than 100 times more powerful enought to kill myself but i will be doing whatever so that wont happen. So lets not worry about that for now . the basic charge curcuit after ac adapter and fuse is as follows the ac current to charge the cap will be 1/2 wave rectified on + and

i would also prefer to sync charging ( or at least discharging ) as + and - are perfectly out of phase on diferent leads. can i achieve this by charging first to a 3 way cap ( think of leyden jar setup with ground connection each on like how some whimhurst machines are configured, positive - ground chain - negative ) the discharging from them automatically? this circuit would be the same as a Greinacher voltage doubler

thanks, any thoughts or jokes about the guy that will blow himself up is appreciated ;) lol Thanks,

Caltus

Obviously you don't know how to f****ng read.

omg! you must be f****ng l33t all those years of installing ceiling fans and you call yourself an expert. I guess you really think that just because you've been around for 50+ years means your an expert. To bad you don't understand that age != experience. Ofcourse one might think it is correlated but usually arrogance and ego wins out every time.

thanks Jon, that is exactly what i was looking for. you have answered while i was typing that last post it appears.

Yeah, I agree. If your stupid enough not to be careful then your stupid enough to die. (Ofcourse there are always accidents but if one is irrational like homer then they will never get anything done. Sometimes you gotta take a risk to make progress)

Yes, there is things such as inductive kick bad, EMF radiation, etc that can cause problems. I cannot really tell you much because I do not know either. There are several sites I have seen that do discuss this topic though. What you want is some type of path to ground that the feedback can take.

For example, metal oxide varistors are used when a voltage spike on the mains is larger than a certain amount and the mov sorta opens up and proves a least resistive path to ground. This prevents that spike from going through the transformer. You could use somethinglike that but not sure if they make them for that high of a voltage. (although maybe you could use several in series) Theres probably a better method and ofcourse theres a whole industry built around HV stuff and they all have these very special techniques and exotic devices for dealing with these kinds of issues. You might look into how they handle this stuff in power distribution. (usually though its for high currents but maybe something will work).

I would say maybe you could just ignore it for now and see but you might not want to take the chance and ruin your components.

Maybe you can put a relay switch between the cap and diodes to completely remove it from the circuit? The relay can be triggered to open when the cap has reached a certain voltage. Might be a good solution. Ofcourse when it closed there would be an inrush of current and this could effect the contacts.

So you want to charge up one side while discharging the other? (so you would increase the pulse rate by a factor of 2)

No, I have no issues with you doing this. Its better than sitting on your hands or twiddling your thumbs cause your too afraid. There are a lot of weenies out there. If it wasn't for people taking risk we wouldn't be where we are. Ofcourse its not that big a risk and you seem like you know the risks. There are many things you can do such as wearing insulated gloves or even a suit but this isn't really necessary if you just pay attention(which I think you will and its not really my place(or anyones) to tell you what you can and can't do)

Have fun.

Jon

Do. Use one hand only and stand on an insulated surface - even a stack of dry newspaper will do in a pinch. Try to use well insulated tools and think the thing you are going to do through.

i think ill do the throw switch like you suggested to prevent that feed back. Im going to making my own relay switches to insure proper insulated and safely encased . basically all my work will be contained in pexiglass with a few redundant grounding options in case a path burns out.

this is not really necessary for the lazor project. Im looking however for a simple solution to to sync the negative and positive pulse that i split from the same output. the negative ac phase must match the exact positive phase. End result i want for this seperate project is pulsed dc that is equal and opposite + & -. this is for hv tests regarding field polarization effects. Non phase is usless for this test as the oppsite current is gone or stored before the other pulse comes out. That why i was thinking on using the doubler using the ground . just not sure on a circuit that will pulse out from that . that curcuit " i think" just maintains HV voltage if we dont use too much load where i want pulses like discharges instead. I thinking my best option might be to wrap my own transformer with 2 equal output windings. for the sync, any better suggestions? If i wrap one winding in one direction and the next in the opposite direction would each output winding be opposite polarity in sync? im not 100 % sure tho i think thats how it works. of course if this works i woudl run it on a figure 8 laminated core with input on centre and oppsite outs on either end to prevent it from shorting across the increased diference. in voltage. how does that sound? Again thanks for all your input.

Caltus :)

here is the transformer i bought and i have 2 of them.

I got the recomemded 1.5 amp power supply however other findings show that is a bit much current for this devic and i got another adapter that outputs 1 amp , again i dont want to burn anything out. i got an asortment of resistors and diodes as i was not sure what to get.

as for the home made cap i made from 6mil polyethelene which someone else used, surface area for diferent caps for now are ony small for testing now and will get bigger later. ( dangerous either way im sure ) foil surface area is about 30 cm x 5 cm for each pos and negative plate and tightly rolled around a dowel.

other caps are same materials but smaller surface area . later for good discharges i may have to go 10 or 50 times the size as the one i mentioned. i dont expect you to do all the math as im lazy however just want you to have a better idea what i have to start with other then loads of pexiglass

--- You're a liar.

All _you_ tried to do was to piss all over the OP in a self-aggrandizing effort without offering anything other than pejorative comments.

You obviously don't even have the capacity to envision the system he was describing (as evidenced from your retort about 12V into the primary of a transformer, when the OP clearly stated that the _supply_ was 12VDC in and 2KVAC out) and yet you pretend to know what you're talking about?

You're an utter disgrace to decent Canadians everywhere, eh?

-- JF

Don't sweat the extra current capacity, the circuit will draw what it requires. If your voltage is regulated to the correct value but your circuit needs more than the available current, expect the voltage to sag. Otherwise, you're good to go.

On 19 Mar 2007 18:28:57 -0700, snipped-for-privacy@gmail.com wrote:

--- Small inconsistency: The input power is specified as 12 watts, max, while the output power would be 20 watts if the output voltage was RMS.

From the output voltages shown on the PDF data sheet:

It appears that the simple rectified DC is 3kV unloaded, which would make it 2kV, peak, with a 10mA load. 2kV peak is 1414VRMS, so that's 14.14 watts with a 10mA load, which is still higher than the input so there's something gone awry somewhere. In your application, though, it shouldn't matter. One thing to remember, however, is that as the capacitor charges it will draw less and less current from the high voltage supply so when it's fully charged the supply will have risen to its full unloaded value of 3kV and the cap will be charged to 6kV!

---

--- As someone else posted, the high voltage supply (the 'inverter') will take whatever current it needs from the DC supply, so as long as the output of the DC supply stays close to 12V when it's loaded by the inverter you should be OK. That 1.5A part doesn't seem to be regulated, though, which means its output might rise high enough to hurt the inverter if the inverter doesn't load it enough, So I'd use the 1 amp one just to be safe.

---

--- Those two plates, with a polyethylene dielectric 0.006" thick and a dielectric constant of 2.25 will get you a capacitor with a capacitance of about 2nF.

---

--- OK. :-)

Just for grins I ran a simulation with two different doublers you may want to play around with:

Version 4 SHEET 1 880 680 WIRE -784 160 -864 160 WIRE -656 160 -704 160 WIRE -624 160 -656 160 WIRE -496 160 -560 160 WIRE -864 176 -864 160 WIRE -80 176 -112 176 WIRE 16 176 0 176 WIRE 112 176 80 176 WIRE 160 176 112 176 WIRE 272 176 224 176 WIRE -496 192 -496 160 WIRE -112 240 -112 176 WIRE 112 240 112 176 WIRE 272 240 272 176 WIRE -864 288 -864 256 WIRE -496 288 -496 256 WIRE -496 288 -864 288 WIRE -496 320 -496 288 WIRE -112 368 -112 320 WIRE 112 368 112 304 WIRE 112 368 -112 368 WIRE 272 368 272 304 WIRE 272 368 112 368 WIRE -112 400 -112 368 WIRE -656 416 -656 160 WIRE -624 416 -656 416 WIRE -496 416 -496 384 WIRE -496 416 -560 416 WIRE -496 448 -496 416 FLAG -112 400 0 FLAG -496 448 0 SYMBOL voltage -112 224 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value SINE(0 3000 25000) SYMBOL diode 160 192 R270 WINDOW 0 71 28 VTop 0 WINDOW 3 65 26 VBottom 0 SYMATTR InstName D1 SYMATTR Value 1N4148 SYMBOL cap 80 160 R90 WINDOW 0 -39 33 VBottom 0 WINDOW 3 -35 32 VTop 0 SYMATTR InstName C1 SYMATTR Value 2e-9 SYMBOL diode 128 304 R180 WINDOW 0 -38 32 Left 0 WINDOW 3 -73 -1 Left 0 SYMATTR InstName D2 SYMATTR Value 1N4148 SYMBOL cap 256 240 R0 WINDOW 0 47 33 Left 0 SYMATTR InstName C2 SYMATTR Value 2e-9 SYMBOL voltage -864 160 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value SINE(0 3000 25000) SYMBOL diode -624 176 R270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName D3 SYMATTR Value 1N4148 SYMBOL diode -560 400 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName D4 SYMATTR Value 1N4148 SYMBOL cap -512 192 R0 WINDOW 0 47 33 Left 0 SYMATTR InstName C3 SYMATTR Value 4e-9 SYMBOL cap -512 320 R0 WINDOW 0 47 33 Left 0 SYMATTR InstName C4 SYMATTR Value 4e-9 SYMBOL res -688 144 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R2 SYMATTR Value 100k SYMBOL res 16 160 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R1 SYMATTR Value 100k TEXT -42 386 Left 0 !.tran .1

The simulator, if you don't already have it, is "LTSPICE/SWITCHERCAD III", is free, and you can download it from:

One final thing, notice that I used 1N4148's for the HV diodes. Through the magic of simulation that works, but don't try it at home!

-- JF