# How do I increase energy flowing into a Capacitor?

Discussion in 'General Electronics Discussion' started by Electro132, May 26, 2015.

1. ### Electro132

261
3
Feb 12, 2013
Hi,

I am trying to discharge energy to a 2200 uF -400V Capacitor. The transformer circuit i have is actually generating a total of 330 V output. However, when i connect the negative lead from the transformer circuit to the neg (-) of the Cap, it is only transferring small amounts at a time, like 1 V per sec. Then it begins to slow its charging down around the 100 - 120 V area. It is very frustrating since my aim is to get up to 330 - 380 V tops.

Does anyone have a clue why it does this? And can anyone give advice as to how i can increase the amount of energy flowing through to the cap so i am not waiting for 30 mins just to get 100 V?

Thanks

2. ### Harald KappModeratorModerator

12,334
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Nov 17, 2011
Is this 330 V AC or DC? Show us a complete circuit diagram plus the specs of the "transformer circuit" (max. current etc.).

How about connecting both leads to the capacitor? You need a closed circuit for current to flow. You may observe a small leackage current e.g. through any conducting material with high resistance (e.g. your body) charging the capacitor slowly.

How do you think you are going to charge a capacitor to 380 V when the transformer circuit outputs only 330 V?

What is your experience with electricity? From your recent posts I doubt that you are well versed. Dealing with such a high voltage is potentially lethal and my advice is that you first get a firm grasp of some basics in electronics using only low, safe voltages e.g. from batteries before you handle this kind of energy.

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3. ### davennModerator

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Sep 5, 2009

How about connecting both leads to the capacitor? You need a closed circuit for current to flow. You may observe a small leackage current e.g. through any conducting material with high resistance (e.g. your body) charging the capacitor slowly.

How do you think you are going to charge a capacitor to 380 V when the transformer circut outputs only 330 V?

Hi Harald
good responses

Ohhh dear ... I really shake my head in disbelief sometimes .... how about you ??

Dave

4. ### Colin Mitchell

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Aug 31, 2014
330v AC is more than 400v DC when rectified.

5. ### Harald KappModeratorModerator

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Nov 17, 2011
No, I dare not - I'm afraid I might loose what little hair is left

Right, that's why I asked for AC/DC.

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6. ### poor mystic

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Apr 8, 2011
Hi Electro
speaking for myself, you probably scare us all.
Do you realise what will happen once that capacitor is fully charged? It'll carry a potentially lethal charge of energy, perhaps for days or weeks.
And you'll probably think I'm kidding here, so check it out: even a 9V battery can kill an incautious user! It happens several times a year, here in Australia alone.

You can have way more fun at much lower voltages, and never come close to hurting anybody. I've been reluctant to add to Harald's excellent advice, but I'll say this - that if you were to be killed playing with these horribly dangerous things, and I'd shown you how to maximise the danger to yourself, I'd feel responsible.

Do you have an electrician or technician friend? Wouldn't it be a good idea to join some kind of club or group which is interested in electronics, and get some experience with a bit of help from someone who already understands the dangers?

Last edited: May 26, 2015
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7. ### Electro132

261
3
Feb 12, 2013
The circuit is from a flash camera. I've checked the flow of electricity from the pos (+) and neg (-) terminals as well. It seems that the flow of electricity is only one way regardless as there is a diode. Also, where the flash capacitor used to be, the neg (-) terminal is showing as 330 V on my multimeter whilst the pos (+) is only showing around 1.2 V. So i think it is DC.

I've tried that as i connected both the pos (+) and neg (-) of the flash circuit to the pos and neg of the cap. However, the cap is connected to a coil and that is where it starts to become a bit confusing because the transformer circuit still charges up the cap but only very slowly like 1 V p/s.

The transformer is continuous, so even though it only has an output of 330 V it can still continue charging the cap as long as there is still some space. However of course, i don't plan on going over the maximum limit.

Yes i am quite aware of the dangers that come with high voltage. But in order for me to reach my full potential i am willing to not let anything get in my way, just as long as i am learning the safe way.

8. ### Electro132

261
3
Feb 12, 2013
Hi Poor Mystic,

haha yes i scare myself sometimes too. Anyways, to answer your question, no the cap will not be charged for days or weeks as i have a tool which brings it down instantly called a metal screwdriver. I simply touch the capacitor on one terminal and BANG - bob's your uncle. Yes i do believe it is quite lethal however, i am conducting my experiments with extreme care. So not to worry. I'll be more worried about anyone out there trying to do what i'm doing.

Thank you for your concern. I understand how you feel in this position but i assure you, my experiments are done in a safe and controlled environment so the risks of me or anyone getting hurt are minimized. I am not that stupid to play with my life without care, but i will also not let anything stand in my way to reach my goals in learning.

As some would say, if you give up when an obstacle stands in your way, then you will never know how far you could of traveled. I am not like this because i have experienced the joys and excitement of breaking through obstacles. In the end i get a lesson or 2 from doing so along with the spoils of acquiring new knowledge. So to me it is worth pursuing

9. ### poor mystic

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Apr 8, 2011
I like your go get 'em attitude.
I think you need a signal generator, an oscilloscope, a low-voltage, dual tracking power supply, and a few hand tools.
An excellent book is still "The Art of Electronics" by Horowitz and Hill.

You can learn about transistors, triacs, op-amps, logic circuitry, and signals, all at low, safe voltages. Even at those safe voltages, you'll possibly have accidents that cause injury.

A safe environment is one without danger; a nearly safe environment is one in which someone very capable is there with you in case things go wrong.

10. ### davennModerator

13,983
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Sep 5, 2009
OK so lets get back on track

1) you didn't answer an earlier Q ... How do you think you are going to charge a capacitor to 380 V when the transformer circuit outputs only 330 V?
2) What is your end goal ... ie what are you trying to achieve ?

Dave

11. ### KMoffett

723
75
Jan 21, 2009
poor mystic,

Can you provide a link to support this?:
Wiki side note: "Killed by 9V Batteries is an Austrian[1] indie rock rock band."

Ken

12. ### Harald KappModeratorModerator

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Nov 17, 2011
A single terminal can't show a voltage on any meter. Voltage is alweays measured between two points Where is your second point?

A few lines earlier you speak about a diode in the circuit (which sounds reasonable), here the cap is connected to a coil. How? You still haven't shown us the circuit diagram. Your written explanations are not too helpful, a picture is worth more than 1000 words.

The circuit is probably designed to charge a comparatively small capacitor within a reasonable time for operatingthe camera's flash. What are the values of the original capacitor and the capacitor you now use?
Charging a capacitor is not only a matter of the voltage of the source, but also of the current capability. The charging current provided by the flöash charger may be rather low (just enough for the original purpose). The charging circuit acts more like a current source (or a voltage source with a very high inner resistance). Assuming the charge current is rather constant (you can measure it with a multimeter between capacitor and charger), the charging time follows the capacitor's law: V=C*I*t where C is the capacitance, I is the charging current and t is time. See how this equation matches your measurements.

I still think you should not tinker with this kind of high voltage unless you get much more experience in basic electronics.

13. ### Electro132

261
3
Feb 12, 2013
My second point is at the 1.5V batt pos (+)

ok, i have attached the circuit diagram (as well as an alternate design) but i am still thinking about whether i should keep the first cap (80 uF 330 WV)

The 1st design

The Alternate

The value of the original capacitor is 80 uF 330 WV and the one i am using is 2200 uF -400 V. i planned on switching the original for the 2200 uF cap but it just didn't charge up quick enough.

My end goal is to project something out of the coil in one direction with the force of the electro magnetic field.

14. ### poor mystic

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Apr 8, 2011
No I can't, I'm sorry. The reason I can't provide a link is that the rumour, that 9V batteries can kill someone this way, turns out to be a myth.

I think I need my embarrassed emoji.

15. ### Harald KappModeratorModerator

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Nov 17, 2011
For this you don't necessarily need high voltage. You need high current sa current is the means to create a magnetic field within a coil.

You sound like you're thinking along the lines of a coilgun, do you?

16. ### Electro132

261
3
Feb 12, 2013

Sorry for the delay but yes that is true and correct. I was studying how to increase current and found out that i just needed a pos (+) and neg (-) as well as to find a track opening somewhere on the circuit. So this is what i did:

I got the same current output as what was coming into the cap's pos terminal which was 0.027 A, even with 4 channels coming off the one track opening. The track opening was at the + of the cap and connected to 4 channels which is connected to the output. From what i was told this should of been 0.027 x 4 which is 0.108 A not the same 0.027 A that flows through each channel. As an experiment, I placed the standard through hole diodes in reverse (towards the input) and got equal amounts of 0.027 A of current but the output was the same as well. When i placed them facing towards the output (not towards the input), i got only 9 V coming out of each channel and the same with the output.

I know i'm doing something wrong but i just can't figure out what yet.

17. ### hevans1944Hop - AC8NS

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Jun 21, 2012
Ah! Coil guns. Those are fun to play with, and relatively "safe" if proper precautions are made working around the electrical components. The problem is you can't really accelerate a projectile to "interesting" velocities like, say, hypersonic with just one coil. Discharging a capacitor into a single coil delivers an "impulse" of force to the projectile. That impulse contains all the energy that can be transferred to increase the momentum (velocity) of the projectile. If you want a higher velocity you can either try to increase the magnitude of the impulse (more current) or increase the number of coils the projectile passes through. Each coil gets a discharge as a separate impulse, precisely timed of course to occur as the projectile enters each coil in succession.

With just one coil, and a few thousand microfarads charged to a puny three hundred volts or so, you might as well use rubber bands to store energy and to launch your projectile. Do the physics and then do the math.

As you have no-doubt discovered by now, the circuit used to charge the energy storage capacitor in a disposable flash camera is pretty wimpy, running from a little 1.5 VDC dry cell and with everything squeezed into a little plastic case not much larger than a deck of cards. So... why would you be surprised that a circuit that, going "all out" to charge an 80 μF capacitor to 300 V or so in ten to thirty seconds, would take much longer to charge your 2200 μF capacitor to the same voltage... like more than 27 times longer? You don't need to "improve" the circuit removed from the disposable camera: you need a new circuit, i.e., a new power supply that runs on something other than a single AA dry-cell.

I think, given your level of "expertise," most of us here would be unwilling to recommend or provide you with a schematic for a power supply that would charge your capacitor in a few seconds (or less), whether it be line-operated or battery operated. Of course you can Google any of the many "coil gun" projects documented on the Web and find something that will do the job, and perhaps you could even build it and use it without injury to yourself or others who happened by. But I don't think I want to be involved just yet. Sorry 'bout that. It's no reflection on your aspirations to learn about coil guns. Go learn some more about electricity, circuits, and electronics. Then come back here with more questions, since I am pretty sure no one ever learns all there is to know about anything.

Hop

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18. ### Harald KappModeratorModerator

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Nov 17, 2011
Exactly. We do not favor truly dangerous topics - certainly not at this level of understanding. Too high are the risks.

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19. ### hevans1944Hop - AC8NS

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Jun 21, 2012
I have been interested in, and sometimes professionally involved with, electromagnetic launchers since I was a teenager. A few years ago, one of the scientists that I had worked with bragged about a rail gun his team had built that he said was capable of launching "one pound to Jupiter!" At the time I sort of brushed his remark off because this individual was a known drama king... he once bragged about a certain precision optical metrology system that, according to him, was so well designed it could be assembled on orange crates, this when we were spending thousands of dollars for air-suspended granite optical tables. But he sure could sell R&D research projects to the government. He once brought an Australian scientist to work in the States because the Aussy was an expert in homopolar generators. I spent a few years working for him trying to build a flash xray motion-capture camera for underground nuclear tests. The goal was one million frames per second and at least nine high-resolution frames. I failed at this task because I couldn't magnetically deflect the image to nine different positions on a cathode ray tube with sufficient speed and stability to achieve both the resolution and the speed required. The project went away, but I later learned that the image capture problem was accomplished with a different technology than the one I was asked to use. There's always more than one way to skin a cat, assuming you can catch and skin it at all.

In case you don't know what a homopolar generator is, it's something Michael Faraday dreamed up in 1831 while "messin' 'round with magnets." Basically, it's a copper disk rotating on an axle with an external magnetic field applied parallel to the axle (perpendicular to the rotational plane of the disk). When the disk is rotated, a DC electrical field is produced radially between the axle and the outer edge of the disk, polarity depending on direction of disk rotation and orientation of the external magnetic field, voltage depending on how fast you spin the disk.

Now take this simple description and hand it to an engineer who will scale it up to industrial strength: two copper disks rotating in opposite directions so their angular momentum cancels, each disk weighing in at about a ton or so and several feet diameter, a monster electromagnet to apply a one or two tesla magnetic field, electrical contacts at the axle and on the two rims capable of handling several million amperes, a prime mover in the form of a rather largeish three-phase induction motor and you now have a rail-gun power supply. You need only add the rail-gun and a suitable switch capable of passing a mega-ampere or so of current.

IIRC this research occurred in the late 1970s and continues to this day. There is a machine shop here in Dayton that builds rail guns for the U.S. Navy, and also machines test projectiles made from aluminum block cubes about eighteen inches on a side. These weigh considerably more than a pound, so the "one pound to Jupiter!" quote was probably referring to another rail gun in an earlier stage of development. AFAIK the homopolar generator was never built for a rail gun application. I personally thought it would have been a great thing to use in an Army tank, spun up with gas turbines. The Navy powers their rail gun from capacitor banks, conventionally charged from ship electrical power and switched with thyristors.

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