dc-dc voltage step up HUGE!!!

Nice! That answers my question. I have never worked with this much voltage before. Are my wires going to explode/degrade? I dont want to build this thing and then have it die instantly. What wire gauge should I use for the pancake coil and for all the other leads?

Thanks so much man! I could never do this without you!

Just out of curiosity, is your system portable? I eventualy want to configure mine as a rifle.

Use as thick a wire as you can find. I use 2awg for the test linking of the capacitors. You wont need as heavy guage a wire as your making a smaller machine. Wire size goes up with the size of the capacitors. Mains flex should be suitable for some camera caps. I used 2awg as I am using bean can sized caps . Dumping a bank of caps into a target involves huge currents (in the order of 100's to thousands of amps. When experimenting keep one hand in your pocket at all times

edit: spelling - silly iphone

Great advice! Thanks! I think I am all set for now.

Dont forget to have a freewheel diode across the bank antiparallel. There will a back surge when your bank fires that can easily destroy your capacitors. The diode will need to be able to absorb the entire estimated power of the shot. Usually for a camera cap based bank, a big stud diode will do.

Once your bank is charged you need to provide a way to disconnect the charger from the bank prior to firing. If your antiparrallel diode fails, the caps are next in line followed by your charger. If you blow up a few caps who cares, but I'd be pretty annoyed if I had to rebuild my charger. A contactor will suit this task.

How are you going to fire your bank?

Ok, I had planned on disconecting the charger, but what does "anitparallel" mean? And where am I supposed to get a diode which wont explode when I "shoot" it.
As for firing, cant I just use a switch?

Thanks,
Liam.

A switch will last one or two shots before the contacts either weld shut or vapourize. Your best option (and probably the cheapest) is a home made contactor.

Another option is an SCR, which would obviously need to come before the antiparallel diode, so it is protected. An SCR is like an electronic switch. You feed it a trigger voltage and its anode and kathode terminals go short circuit, like a switch. Since theres no moving parts in one, it wont "weld shut" or vapourize (unless you use a little 60V scr ) You can find these on ebay for about $20 for something to suit your project. They look like a stud diode with an extra lead.

Antiparrallel - sorry I'm used to these terms. It means reverse polarity across the bank (i.e. negative end of diode to positive end of caps). You can find stud diodes on ebay pretty cheap. Look for one that has a big surge rating (current). Most of the cheaply available diodes on ebay will handle your max 200v bank. They will be about the size of a c sized battery, with a thread on one end. Diodes will have two currents. Their constant power handling and peak or surge. The constant may only be like 60 or 70 amps, but the surge rating will be in the order of 100's to 1000's of amps.

This is a strange request, but I realy dont want to buy the wrong thing (I am almost out of funds for this project) is there any way you could send me a link to the items in question? I know I am asking a lot here. Sorry!

Thanks,
Liam.

No worries - dont mind helping out.

Cant get on it now though, have a few things to do first then I'll track down said items on ebay for you to look at

:angel::angel::angel::angel::angel::angel::angel::angel::angel::angel::angel:

I cant thank you enough!

hehehe pleasure mate - just dont go blowing yourself up with the caps

Did you take a look at my thread (big capacitor bank) - it'll give you some ideas of what I am playing with (a tiny bit bigger than what you plan to be messing with *grin)

Heres a line for you:

You have a huge capacitor bank!

Seriously though, that thing is sick. Where did you get the capacitors?

The reason didnt go that rout is that I wanted something portable. And the fact that 110v is a lot less likely to kill me then what you have going

So, limited to 110 volts, how many uF would be ideal? Is there a point where more uF becomes irelevent? I have 8000 in my bank right now, how many would you recomend?

Thanks,
Liam.

You can never have enuf uf, especially for your purposes. The more power you can dump into the coil (without vapourizing it) the more energy will be transferred by lorentz force to your projectile. Think about it - if you take a bigger engine and put it into a car, the car will go faster/better, but only provided the drivetrain (your wires) and the chassis (your coil) is up to the job. If you have a really nice chassis and drivetrain (copper bus bars and a heavy guage coil), you could stuff a helicopter engine into the car (trust me, its been done, to a minivan ) Theres a point tho where you have to stop, either because the project is getting too big, or adding more caps has no additional effect, and just increases the time it takes to charge up the bank.

You think I have some mean caps - check out grenadeirs bank on about page 3 of that thread - hes got 96, of which he only wired up 42 from memory. Hes blown a few parts too

I got the caps off ebay

I just found a cap in my junk box that alone is 6800uf at 160V! It has a nice big "Danger - High Voltage" sticker on the side Perfect for an ion laser psu

Nice! So, I will double my capacitor bank size. Any more then that and I will exceed what can fit into a space the size of a rifle stock Let me know when you find those items! Ima study till then!

Thanks,
Liam.

Edit: When dis-connecting the power supply, do I need to break both leads, or just one? Thanks!

sensible to break both.

Are you planning to make a "rifle" em projectile gun? check out the electromagnetic projectile accelerators section on 4hv.org - they have a wealth of info there

4hv is like lpf for all things high voltage or just stupidly high current (or both).

Yes I am. Great link btw! My plan was to put the mini 12v gell battery as a shoulder but (that way the weight has less effect) then have all the capacitors as a stock,then a grip with a trigger etc, then a tube, in which I will fire my aluminum disk, and then a barrel down which my aluminum ball bearings will fly I am still working on an elegent way to transfer the momentum from the disk to the projectile though.

Think it will work? It is simportant to me that it be light weight and higly transportable. Not like the clunky coil guns most people seem to favor.

Thanks,
Liam.

Do you think house wire will work? I just found probly a hundred feet of it in the basement.

Just been doing some research on this. 110v is not really going to be strong enough to get much momentum.

That and theres a lot more maths involved in an EM accellerator. You need to know your maximum pulse current, and select a diode thats suitable, along with an SCR as well. Due to the fact that your not going to be destroying the coil every shot, your caps will go negative if not protected properly. Since I will be destroying (most) objects placed across my bank (including empty beer cans - that should be fun) I shouldn't need to worry about the diode, but will be fitting it anyway; it that shot where some of the target remains that will put my $200 cap array at risk.

I would suggest looking up "camara capacitor coil gun" and working from there. The coil gun works in similar fashion to what you want to do, just a different style coil. Sticking with your current caps, I'd charge them up to their rated voltage (or slightly shy, such as 190V), and go from there. Make a remote box for testing, and once your satisfied with the outcome, then fit the assembly to the insides of the rifle stock.

Forget about the rifle body until you have the electronics working properly and safely. Then ensuring the caps are discharged (and then put a clip lead across them to keep them that way) go ahead and make your gun.

If you use isolation electronics (where the operator is seperated from the high voltage by a beam of light etc), you can be quite safe from being shocked by such a thing. Mine will be using contactors, opto-isolators and at most the operator will be near 135 volts (feedback signal from the bank volt readout). The rest of the nasty hv stuff is contained inside the cap bank box, well away from the operator. (for obvious reasons - blowing stuff up involves very loud bangs, and hearing protection should be worn, even though the operator will be up to 10 m from the bank).

I cannot simply suggest a diode and SCR. That depends on the inductance of your coil. Since every coil is different, every semiconductor requirement will be different.

Some test equipment you'll need for this is a volt meter, a inductance tester and that java program mentioned on the 4hv forum for calculating your pulse length / voltage / current. IF you dont do the math your going to be sorely disappointed as you blow scr after scr etc, which could get quite expensive. Once you know your peak current you'll be able to select an SCR and diode once (perhaps twice if you have a wiring boo boo), and not spend a fortune on fried components