Voltimeter

>>1131715
Get two of those red multimeters that harbor freight gives away for free, put them in series in 1kv mode, and add the two voltages.

NOTE: I mean to say wired in parallel (capacitors in parallel work like resistors in series)

>>1131716
will do

where are the coupons to get them free?

They'll be on the front page of their site when they have them. They also have some coupons in the store. I don't think they're offering the multimeter right now though. You can always just buy an analog panel meter from ebay. Should be 5-10 bucks.

>>1131715
Are you trying to measure volts or charge? Volts represents the potential difference between two points, and charge measures the actual charge of the capacitor in Coulomb.

https://en.m.wikipedia.org/wiki/Electric_charge

>>1131727
charge

it will be a total of 5.04 amps at 1400 volts when connected in series

>>1131727
so 5.04 coulombs lol

I basically want to know when the capacitor is full to stop charging it manually

>>1131730
You're going to have to connect the caps in series if you want it to withstand 1400 volts. If you connect them in parallel, you will apply 1400 volts to each cap individually, which is well beyond what they are rated for. Moreover, you don't want to push large caps to their absolute limit. Maybe cut it down to 1kV just to have a safety margin?

Connecting them in series will allow you to apply 1000 volts total, but it will reduce the total capacitance.

Are you sure that you are ready to play with hundreds or thousands of volts DC? If you applied 1400VDC the way you were planning, you'll almost certainly end up in the hospital or dead.

>>1131738
im pretty much a novice at DC electricity

is my best bet to use them in parallel? im trying to get the most joules out of them total

>>1131718
Capacitors equivalent capacitance in parallel works like resistors equivalent resistance in series.
Remember, the voltage of things in parallel is all the same, but the voltage of things in series is split between them.
The voltage in parallel is max 150V, but in series you could get 600V without them exploding.

I suppose you could handle a brief 1600V surge, but that seems like a bad idea to test.

>>1131741
ill try it out with a 350V surge at a total of 14400 uF and then ill try it out at 700V surge with two pairs wired in series being wired in parallel to the other pair

Im testing a small home- project, a railgun and coilgun for fun

I know quite a bit about AC but not DC

>>1131715
>Im going to be wiring 4 of these capacitors in series,
You'll have a 900μF @ 1400VDC capacitor.

>>1131718
>NOTE: I mean to say wired in parallel
If you wire them in parallel you'll have a 14,400μF capacitor good for 350VDC.

If you wire them in series you need to add a high value resistor (~1MΩ) across each capacitor as a 'balancer'. It will also act as a bleeder for the high voltage.

>>1131742
I didnt expand the thumbnail and thought it said 150V.

>>1131738 has the correct numbers.

If you were to charge series or parallel to max voltage (350V/1400V, respectively), they'd both hold the same amount of energy, 392J.

The parallel setup will have more charges with less energy per charge, while the series will have less charges but more energy per charge.

I'm not sure which is more important for your project, energy per charge or total charge.

>>1131743
This may sound autistic, but I need the most joules I can get out of a single surge.

after doing some math im planning on wiring two pairs of series connected capacitors in parallel

which would give me 700 Volts at 3600 uF, no?

>>1131740
Best bet is going to be to charge them in parallel with no more than 300VDC. Again though, unless you are very very confident with your HV skills, remember that you can easily kill yourself in under a second with this much potential power.

>>1131747
fuck, i also thought it was 1600uF. Just double my number for energy.

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>>1131747
total charge

ill try this out charging each pair at around 650 V

>>1131743
the resistors on each capacitor in the picture above are 20KΩ

>>1131754
I can't math today. No matter what configuration, you're getting 882J.

If you want maximum charge, you want maximum capacitance. That means parallel.

If you want maximum voltage, you need series.

If you want in between, do 2x2 parallel/series.

>>1131758
i guess Ill try all three of them and record the results, I want to know which would propell a ball bearing the fastest down a lubricated copper rail


so:
Series: 1400 V at 900uF
parallel: 350 V at 14,400 uF
parallel/series 2x2: 700 V at 3,600 uF

im going to assume that the first transfers energy faster but is less stable and second option is the most stable but transfers the slowest

>>1131782
I need them to discharge completely in a second, wouldnt those resistors delay the discharge to be over 20 seconds?

>>1131784
sorry for deleting

your reply hadn't posted when I did

I saw you were already using resistors.

>>1131784
Ahh. I've built a coil gun in the past. I'll tell you right now those caps aren't going to be the best for your purpose. Those are commonly reffered to as tank caps, usually used with motors, and based on aluminium and paper with electrolyte. Due to a certain amount of internal resistance, you're not going to be able to get them to discharge as quickly as you want.

I got around the problem by using mains power for my coils, but you may have a better solution. I'll tell you though, those caps aren't going to work as well as you are hoping.

>>1131716
This doesn't seem safe, 2kv at a meter rated for 1kv

>>1131789
is there any config where I can minimize the time it takes to discharge?

if not then ill just settle with using multiple rounds per charge

>>1131795
It comes down to the construction of the capacitor itself. You can get a lot of power fast out of a film capacitor, but they don't make film caps with enough capacity to do what you want to do. So then you would think, 'oh, I'll just make up a matrix of smaller caps in to a big cap' but now you're going to suffer from added resistance of all those solder points coupled with the fact that no two caps in your matrix are exactly identical.

There is no perfect solution with capacitors; it's always a tradeoff between capacity and discharge speed. Since you already have those caps, go ahead and use them. But you should anticipate that they won't be done discharging when you want to turn them off, so you should have a physical way to disconnect them from the circuit when your ammo moves to a certain point on the rail or along the barrel. Back emf and eddy currents can bring the ammo to a halt almost as quickly as they projected it in the first place. I've had shots from the coil gun actually propel backward out of the rifle because the coil didn't turn off at the right time. Of course, I eventually just moved over to mosfets switching power to the coils, which is extremely precise and programmable.

>>1131806
Also, I should mention, I was using a 170vdc power supply, rectified from the 120vac mains. I built in a discharge resistor, a danger led, and a key-lock switch. I kept people and animals away from the area, always let someone know that I was going to activate the high voltage, and then was super super super careful both in my proximity to the supply and in the movement of my hands. 170vdc is enough to easily kill you. The voltages you were mentioning are significantly more dangerous. You can do it, but for God's sake anon, be careful.

>>1131809
Again, not saying don't do it, but here's a few more safety tips for you.

• wear safety glasses. You never know when one of your components is going to explode. Probably won't kill you, but it may hurt you.

• be careful not to reach over the supply. Jewelry, dangling objects, etc, can come in to contact and hurt you and the supply.

• always have a physical switch between you and the power supply. If it happens to catch on fire, you don't want to have to reach over the fire to get to the power switch.

• on that note, it's not a bad idea to have a fire extinguisher nearby.

I know it seems ridiculous to do all these things, but it's also not hard to do any of these things, and it could save you a lot of hassle in the long run.

>>1131751
>high voltage = instant death

It requires several seconds of high voltage AC current to stop the heart. It requires a great deal of power transfer through the body to do more serious damage like burning out nerve endings or cooking you alive, which is part of why people often survive being struck by lightning (~90%).

At full charge you're looking at about 882J/210cal. Even if you took it all through you, you'd probably just burn your hands.

>>1131715
Okay, you're stupid for fucking with this amount of charge. I've been working with live electricity for 2 years now, and I am nowhere near ready for this kind of thing. Go ahead, call me a pussy. You have no clue what you're doing and no idea how dumb you are for trying this kind of thing. Scale everything back by 2 orders of magnitude, test it at that level, find out how painful it is to get shocked like that, and scale up slowly. You are an idiot, and will get killed if you fuck up, which you will. Fuck up on the harmless shit, then try the dangerous stuff later. Or don't, I don't honestly care, please note your geographical location before attempting anything so we can post your obituary and laugh at what a stupid fuck you are after your charred corpse is 6 feet under.

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>>1131870
I agree that my stance leans towards an abundance of safety, but you're better off being more safe rather than less safe.

Also, AC (and lighting which is predominantly AC) won't penetrate you as deeply, even at high voltage. This is why people survive lightning strikes. At infinity hertz, it wouldn't go in to your body even one atom deep, but at zero hertz (DC) it will go right through you.

But, you know, go touch the anode with your hand, and touch ground with your other hand. Post results.

>>1131870
You're talking about the capacitor discharging through OP, but what about what he's charging the capacitor with. 1400 volts is a lot of volts. What kinda power supply do you have OP?

>>1131876
Yes, the skin effect is the reason for the 'part of why' qualifier there when I was talking about lightning fatalities. The skin effect prevents your organs from being (completely) cooked, but you're still enduring VASTLY more energy transfer than most home labs are going to deliver.

Even at several kV, where the current is passing directly through the body, it requires enough energy transfer to actually heat the body to do damage with DC. AC kills by causing neurons to rapidly depolarize until their membrane potential is depleted, but this takes minutes of being continuously shocked. The popular image of people's hearts stopping after a good shock on television scares people, but it's actually really difficult to kill with electric current.

You need to be connected to equipment that's extremely fault tolerant, exposed to high voltage for minutes, and then you're still likely to survive if you're disconnected once your heart stops and you collapse. The heart typically resumes after a brief spell of depolarization.

Most high voltage equipment doesn't deliver enough current to do damage, or can't for more than a few seconds before something burns out after shorting through a human body.

Obviously, I'm not advocating people be unsafe with high voltage. I'm just tired of people who have no understanding of biology repeating that high voltage can kill 'instantly'. Yes, a 100kV power line that can deliver a few thousand amps will cook you faster than you can say 'oops'. But you're not playing with that kind of power.

Obviously, since you're pushing a couple hundred Joules into whatever resists the current flow from your little apparatus, it's going to burn the fuck out of a finger that touches it, but it won't kill you.

Stop thinking your heart is going to instantly stop.

What current do you think I should use to charge the capacitor?

A 20k resistor on a 650V power supply?

This is for the 2x2 parallel/series setup

>>1131715
Nobody this naive should be handling high voltage capacitors.
Use a voltage divider, for fuck's sake, to readuce the voltage to a measurable and safe voltage, use lots of high power resistors in order to exceed by far the voltage ratings of the resistors, insulate everything...
Then, and only then, it is relatively safe to connect a cheapo multimeter.

>>1132087
OP is going to electrocute himself.
If those things can discharge in 0.1s, he'll be looking at a nice 50A flowing through his body.

>>1132040
ehh, don't even bother with the resistor. just charge them as fast as you can with whatever current they draw.

That's a big capacitor

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>>1131905
Noted. You're right.

You have to admit though, OP is going to fuck himself up. He came in here asking how to measure charge with a volt meter, now he's got a 650VDC power supply and is probably connecting it to those caps with headphone wire right now. RIP OP.