Capacitors What They Do In A Circuit

[Todd Mulske]

I just want to explain the use of capacitors in a circuit; what they do and how they affect the circuit. The folowing image illustrates a capacitors design.



There are two conductive plates: one side of the plate has a positive charge and the other side of the plate has a negative charge. Protons carry a positive charge while electrons carry a negative charge. Protons and electrons attract to one another; when they collide electrical current is produced. In the above image (A) represents the two plates of a capacitor; one being the positive plate (proton carrier) and the other being the Negative plate (electron carrier). (D) represents the dielectric, which is a space between the two oppositely charged plates. The dielectric dissipates heat and dumps it.
How does this apply to a battery mod. I will explain it the best I can. When capacitors are placed between the positive and negative side of the battery, protons (positive) charge one plate and electrons (negative) charge the other plate. Energy is always lost through this application because there is no such thing as a perfect capacitor. The dielectric is a space between the two plates. The two oppositely charged plates cause the dielectric to get hot and energy is lost or dissipated. When energy is released it dumps. As far as battery life is concerned; because the dielectric heats up and dissipates heat=energy, batteries will be drained faster.

This is what I know about capacitors and their function in an electrical circuit. Let me state that I am in no way criticizing anyone's circuit design; I am simply explaining capacitance and its effect in a circuit according to the knowledge I have from research and technical school, I am not an electronics technician; just have a wiring certificate which emphasizes ac/dc wiring; not electronic design.

HAPPY vaping

 

[MadmanMacguyver]

Not trying to appear critical but I hate disinformation and I'm sure you would like to know that statement is not entirely true...Protons really don't have much of anything to do with electricity...which is composed of electrons moving from electron shell to electron shell of the molecules or component atoms of a conductive material...you had the general Idea right tho...

and I am not an Electrician I just am very good at assimilating information...the correct method of describing that escapes me at the moment but maybe one of the resident EEs or a mod god will produce the correct description...

BTW congrats on building yourself an OKR VV mod...Aint switching reg vaping great?

 

[pnguin]

OK, you have the structure correct. You can make a capacitor out of two sheets of any conductive material with a non conductive material between them. Say 2 pieces of tin foil and a sheet of paper between them, it won't work very well but it could be used. Now the easy way to visualize what a capacitor does in a circuit is it is like a water tower hooked to a pipe (water in this example = electrons). When demand is low excess water is stored in the tank and when demand is higher than the water system can supply, water flows from the tank to keep the pressure up. A capacitor stores electrons and can then release them later.

 

[Todd Mulske]

Thanks for the input; I was just remembering physics and tried to apply it to electricity, may have got it a little wrong. As far as the OKR goes; I love the thing; it is awesome, blows the ego-t away; hands down.

Not trying to appear critical but I hate disinformation and I'm sure you would like to know that statement is not entirely true...Protons really don't have much of anything to do with electricity...which is composed of electrons moving from electron shell to electron shell of the molecules or component atoms of a conductive material...you had the general Idea right tho...

and I am not an Electrician I just am very good at assimilating information...the correct method of describing that escapes me at the moment but maybe one of the resident EEs or a mod god will produce the correct description...

BTW congrats on building yourself an OKR VV mod...Aint switching reg vaping great?

 

[MadmanMacguyver]

No Problem...and Happy modding...if the modding bug really starts to set in you might have to pay a visit to Doc Gummy...

 

[ScottinSoCal]

My company makes ultra low power infrared cameras designed to go on satellites. Power requirements are strict - satellites don't have extra power to spare - but heat dissipation requirements are even more strict. Excess heat can blind the camera, masking all the IR the camera is supposed to be looking at. Every one of our designs features multiple capacitors. They mostly serve as line filters, to reduce the "noise" generated by power spikes and surges.

The analogy up above about water pipes and tanks is an excellent analogy. If you've got a well to supply the water to your house, your plumbing is subjected to all kinds of surges in pressure. It can blow out seals and create leaks in joins. Have the output of the pump go into a tank, and it smooths things out. It also acts as a reserve for when the demands are higher than the pump can meet. You get a more consistent, even water pressure, and a steady supply even in high demand situations. A capacitor works the same way in a power circuit. That's why really big car stereos use them; when the amplifier demands more power than the car's wiring system and battery can provide, the capacitor fills the gap and keeps the amplifier from clipping, which can blow the speakers.

A capacitor doesn't really use power by itself, it stores it and releases it on demand. It's like a second, very short term battery in the circuit.

 

[jrm850]

This is a great read for anyone wanting to learn about electronics. This has been a hobby of mine for a decade or so and I wish I had found this program when I first started. I found this link on another electronics forum that CraigHB pointed me to a couple of weeks ago. It's a US Navy electronics training program.

NEETS - Navy Electricity and Electronics Training Series

 

[TomCatt]

This is a great read for anyone wanting to learn about electronics. This has been a hobby of mine for a decade or so and I wish I had found this program when I first started. I found this link on another electronics forum that CraigHB pointed me to a couple of weeks ago. It's a US Navy electronics training program.

NEETS - Navy Electricity and Electronics Training Series

Wooohooo, a little light bedtime reading

But really, thanks for the link

 

[jrm850]

lol, my sleep pattern has definitely improved since finding it. I intend to read through the whole program, but somehow haven't made it past Module 1 yet. Maybe I can just find the audio book version and wake up feeling more intelligenter.

Wooohooo, a little light bedtime reading

But really, thanks for the link

 

[Quigsworth]

IMHO caps don't really apply to what we're doing here with these mods...we're dropping voltage across a resistance to make heat...it just doesn't get much more basic than that in the world of electron flow (or hole flow, tomato/tomaaato). Switching voltage regulators (a good example is a computer power supply or an OKR type regulator) very quickly switch the input voltage off and on (fast enough to "clip" or "step" it down to a required output level)...if you looked at this output voltage using an oscilliscope you would actually see the jagged "sawblade" of a cheap switched regulator. For us, this jagged output is a non issue...however, intricate high speed electronic components that must operate within very finite perimeters care a great deal about smoothness and stability of the voltage supply. Caps (without getting into a bunch of math) essentially act as a counter-balance, they charge as the sawblade tooth spikes up and discharge (dump their volts into the circuit) when the saw blade tooth drops down...the net effect is a much smoother output. Caps, in concert with very high frequency switching regs (the faster you switch, the smoother the output, the more money you have to pay for it, lol) are what's in your high end computer power supplies, (which is why you can pay hundreds of dollars for a good one as opposed to $7 for a OKR 10 T which seemingly does the same thing (output ampacity has a lot to do with it to but that's another post)

Some folks much smarter than me are putting caps across their output as caps can dump an enormous amount of energy very quickly, taking the initial hit off their batts...I don't know enough about batt chemistry to say this is that much of a plus but I don't see it being a negitive aside from the fact that caps are a small load to your batts.

 

[CraigHB]

Electrical current is actually a pretty hard thing to wrap your head around. I've been working with electronics since I was a kid, even studied EE in college and I'm still not sure I understand it perfectly.

The grade school explanation is that it's the flow of electrons from point A to B, but that's not entirely correct. It depends on the medium. In an electrolyte, such as a lead-acid battery, it's only positively charged particles that physically move. In most conductors, like copper wires, it's the negatively charged particles that move. The movement of particles itself is very slow, it can take quite a long time for a particular electron to get from one point to another along a copper wire. Though the force that excites them propagates along a wire close to the speed of light.

When we measure current, we are actually quantifying the net movement of both positively and negatively charged particles. Another thing that convolutes understanding is the convention that current flows with respect to positively charged particles when most of the time, current flow consists of negatively charged particles moving in the opposite direction. We quantify current in a way that allows us to model circuit behavior with mathematics. The math gets the job done, but it doesn't lend itself directly to a conceptual understanding.

There's a big difference between a capacitor and a battery. A capacitor stores energy in the form of an electric field. A battery stores energy chemically. The physics behind them are quite different, but both do a similar job, storing energy. You could use a capacitor and a battery interchangeably in some cases. If you had a large enough capacitor, you could power an atomizer with it. However, that would be highly impractical because the energy density of a capacitor is several orders of magnitude lower than that of a battery. You'd need a very large capacitor. They're mainly used in filter or tank circuits where only a small amount of energy is required to do a job. Things like filtering or smoothing inputs and outputs are jobs for a capacitor. You see relatively large ones on switching regulators because those regulators generate a high frequency pulsed output that has to be smoothed to DC.

 

[TomCatt]

lol, my sleep pattern has definitely improved since finding it. I intend to read through the whole program, but somehow haven't made it past Module 1 yet. Maybe I can just find the audio book version and wake up feeling more intelligenter.

If ya find the audio version, send it my way . I have my iPod going all day already with audio books and podcasts; I'll just put it in the lineup


Sent from my iPod touch using Tapatalk

 

[Quigsworth]

Nailed it Craig...I'm so much better actually wiring equipment than writing about the theory behind it...

You mentioned it, and I saw a post on here not long ago from some engineer guy (sorry buddy, you did some fancy math and deserve the by-line) about building a batt/cap cct to essentially provide a steady-eddy load to his batt (it's job was to just keep the cap up to voltage) and use the cap to burst power the atty...I have access to large motor distribution power factor correction cap banks (347/600V and they're actually rated in KVAR's, lol)...if you had an atty connected to a charged one of those and hit the fire button I wouldn't want to be anywhere near it, let alone have it in my mouth...so you obviously would need a sizeable power resistor in series which is defeating the purpose...but I have to admit...the cap whine between vapes would be cool

 

[CraigHB]

I was going to say something like that, but I had already written a pretty long winded post. You can actually store quite a bit of energy in a capacitor that has a high enough voltage rating, as you mentioned, in the kV. You could use an inverter and transformer to step down the voltage. In that case, energy densities are closer to that of a battery. It still would not be practical, but for the sake of discussion, it would be possible. Though, like you said, you wouldn't want to be anywhere near it if you crossed a wire.

I've seen discussions here about using a capacitor to drive an atomizer. The problem is that in order to charge a capacitor in the time you have between vapes, you need a fairly large source of current. You might as well just use the current source to drive the atomizer and forget the capacitor. There's just no benefit to be had there. You can use a capacitor as a battery and it's practical for really low current stuff, like to provide memory retention, but the current demand is just too high to use one to power an atomizer.

 

[Quigsworth]

I think the cap driven atty can (and probably should) be put to rest not only for practicality reasons but for safety reasons, L-ion batts can be hazardous enough let alone have a good sized cap decide to call it a day in a hand held mod. Caps tend to not bother with the "catch on fire" thing, they just skip right to the "explode" thing

...having said that, gonna put some thought into a butane powered mod

 

[CraigHB]

It depends on working voltage. For a low voltage capacitor charged within its rated voltage, it's not an issue. You can short it repeatedly and nothing will happen. It won't even damage the capacitor. When charged over its rating or when a polarized one is charged backwards they can explode.

EEVblog #42 - Exploding Capacitors in High Speed - YouTube

 

[Quigsworth]

LOL, great link...ok, so the other night, driving home in the rain, changing batts in one of my parallel 3.7's by braille (feeling for the nub, come on, we've all done it), I got a pretty good spark and kinda welded a batt in there a bit (yanked it pretty quick thank god), now I see that vid and have made a mental note to myself...no cap's...I don't want to see my crotch blow up at 300fps

 

[CraigHB]

Inadvertant screw-ups make a good case for not running removable batts in parallel. In my own experience, I've found that using a philosopy of, "I'll just be careful" rarely works. I almost invariably become careless at some point. Hehe, I'm actually rebuilding an interation of a project right now that I fried being careless in testing. Happy that I was able to salvage it at all. Thought I fried every chip on the board using incorrect source voltage, turns out it was only one that didn't survive.

BTW, I don't use tantalums or electrolytics anymore so I don't have to worry about exploding capacitors. My latest project is the first one that uses all MLCC caps, I love those things and it's only recently the high value ones have become reasonably priced. The low value ones are even cheaper than SMD resistors. like a penny a piece. What's not to love about them.

 

[pnguin]

I had not considered using MLCC caps since they used to have so many problems with switching regs (frequency oscillation damaging controllers and low capacitance at higher voltages) but it looks like the new materials have cleared all that up and a lot of manufacturers are recommending them now. Great tip. I will get some for my next project.

 

[jrm850]

Screw ups must be in my nature. I just fried 2 AVRs the exact same way. I bought one of those cheap Owan Oscilloscopes which comes with some pretty fat probe tips and bridged the exact same pins on a little qfp AVR. At least I'm getting proficient with the magnet wire desoldering trick.

Re: Caps... Seems like a USB pass through would be a good application.