Breakdown voltage ratings also include a time factor - a cap that can hold X volts for a few minutes may fail after a few hours, day, weeks or months. The book ratings are for dielectrics that can hold indefinitely. Supposedly. I've replaced many factory made caps that were rated for higher voltage than their actual situation in-circuit. Nothing is foolproof, and everything has a lifespan. Thanks for a great video, very informative.
Interesting take on it. I gave basics like talking about breakdown voltage and how to figure out how thick to make it for a desired breakdown voltage and how to test it. I gave basics on materials like wax and resin for insulating and avoiding sharp edges and why. And I did show you the steps for one with two copper plates starting at 7:28. But I guess this is more of a "all you need to know to make one of your own design video" than I "step-by-step only for one capacitor video."
The dielectric strength of a dielectric such as Mylar decreases as the film thickness increases. This means that you can't simply double the dielectric thickness and expect double the breakdown voltage. If you download the datasheet for Mylar you will see that the dielectric strength decreases substantially as film thickness increases. The reason is that the electric field does not distribute evenly across all the layers of dielectric film. A solution to the problem is to use a technique refered to as dielectric stratification. This involves placing floating tinfoil between every layer of film (but not right to the edge). This stabilises the electric field between each layer and allows you to stress the dielectric to it's published value. Also, you have to test the capacitors in oil if you work above the corona inception voltage (about 10kV) or they'll fail from corona and not dielectric breakdown.
this is a very interesting (and logicaly explained) piece of information but i cannot find any source for "dielectric stratification". Is there another term for it ?
The online rating is probably dependent on exposure time, if you were to do a longer running test at a bit of a lower voltage you'll probably find that the plastic will degrade and breakdown.
Finally! a video that shows me how to make a homemade capacitor that actually works and I can make from materials that I can find easily. thank you very much.
I saw a really cool video where a capacitor made of a glass jar, and two pieces of foil was charged. The foil was removed while it was still charged, and then touched together with no discharge, however when the foil was replaced the capacitor was still charged. This shows that the charge is not held on the conductor, but on the outside of the dielectric, at least with a simple leyden jar.
Justin Hall Yeah, the charge is sprayed onto the dielectric as the metal electrode is removed. That might have been MIT's video or that might have been my own video. Here's mine about dissectible capacitors ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-gPXv063O5B8.html
Thanks so much for taking the time to share your knowledge and build skills/ design ideas. I'm currently working on building my own capacitor discharge device for magnetizing. I want to experiment with a diy foundry and try some different alloys etc. the goal is to use raw materials/ easily attainable materials for alternative energy experiments. I can't thank you enough for your videos!
+Nathaniel Charles Put a resistor in the circuit in the discharge path. PS There's no Reply button under your comment because of your Google+ settings. - go to your Google+ page, - in the top, right corner click on your thumbnail icon, - in the popup that appears, click on "Settings". - for the 2nd question down "Who can comment on your public posts?" set it to "Anyone".
One of the best video on capacitors, capacitor testing, and workable design. Thank you so much for sharing your knowledge with others. \keep up the good work. Your lab set up is so professional that tells you have a good hand-on experience. Thank you again. I liked your video.
Absolutely, the shape makes a difference. That's what I was trying to illustrate in the video at 6:00. What you're seeing with your wire is what I'd expect you to see. Try it with flat plates and you won't break it down as easily. I don't have any derating factor. I doubt that you'll find derating factors for breakdown voltage. You can find breakdown voltages for different materials, but they're tested with standard shapes. To know for certain with your plate shapes you just have to test.
To get those ratings I just did a google search for the dielectric strength of polyethylene. If you do that you'll find a bunch of tables on different websites. All they say is "polyethylene", nothing about any grade. So I don''t know what grade the numbers were for. Also, for mine all I know is it's used for putting on floors under carpets to act as a vapor barrier. And thanks, I'm glad you find my videos and website helpful. Sorry about speaking fast.
Thanks. I'm glad you like the video. I'll leave it to you to do the dielectric strength tests... now that you know how! :) Make sure to put up a video of the tests. No kidding I'm busy too. Woke up in bed this morning going back and forth on the details for three different videos!
Great now I'm gonna be spending lots of time watching your vids. Even though I understand electronics. Been in it for years, still amazed by the physics of it all. I think you do a great job on explaining and showing it all also. And lastly you just helped me out with a project I've been working on.
Im very new to electric applications the most i have done is built a small kinda hovering motor thing using very basics like a motor an ac 16v adapter and a few cables with propeller blade mounted to the motor. I found this video extremly interesting and it has definatly expanded my knowlage atleast abit. Thank you great video :)
After looking at your page on making high voltage capacitors, I thought that you MUST see (if you haven't already) the standard on making a simple splice (to connect two wires together) to NASA specs.It would go very nicely with your connection and it is ULTRA-SIMPLE...just about five or six simple requirements. Also, now I see that it looks like it is designed to prevent corona leakage...a way I never looked at it before seeing your link. I don't have a link (there are many) at the moment, but you can just google the likes of "wire splice to NASA standards" or "linesman's splice to NASA standards"...etc. This is something everyone from the beginning hobbyist to professional electrical engineers must see!
The technique I use, the one I show a bit of in this video at 8:55, has worked well for me up to 75kV and high current without measurable leakage. I talk about it more on this page rimstar.org/equip/hvwiring.htm. But mine is more for temporary connections, sort of a way of plugging and unplugging high voltage components. The NASA one looks great for permanent connections. Thanks.
For voltage you can use a meter with a suitable probe. In this video, since I'm measuring high voltage I'm using a high voltage probe connected to my analog multimeter. Some meters, like my Fluke digital multimeter, can measure capacitance. You can see me do it in my "How to Make Capacitors - Low Voltage Homemade/DIY Capacitors" video at 5:01 into it. There's a link to that video in the description below this video and you can find it on my channel page.
That is so clever om, i built a 20 m cu loop but never could get it to resonate ! I had coax and a split rotor cap , never did figure out why ! You have hit on something ! Lets hear it work ! 73 K9UT Jerry Uhte
Great video, learned a lot there. Heck of a bang a few hours ago here, from a substation a couple of blocks away. The power dipped off in the house and a second later heard the boom...I bet they were down to 1 sheet after watching your video LOL
If you mean the place in the video where I'm showing leakage at one of my connections (5:32) those are positive ions since they're at the positive wire. I don't know about positive ions being toxic but I know ozone can be produced in this way. Ozone gives off a pale blue light. It's not an ion since it's a molecule of three oxygen atoms. Ozone can be harmful in over a long period of time. My test was pretty short but anyone exposed to it a lot should do so in a ventilated room or outdoors.
As an addition, you may consider showing how to make a HV tesla coil capacitor/s to form a bank for the proper value... series/parallel, etc. I made one 20 years ago with thick polyethelene sheet and aluminum flashing submerged in mineral oil bath in a piece of 6 in. pvc... Sadly, i never got to build my coil and gave the thing away...
A capacitor won't help you get from under 12V to 50kV. For that you'd need a high voltage power supply or some minimal circuit. Also a Van de Graaff generator or Wimshurst machine will do. But a carefully insulated capacitor like the two I show at the beginning of this video will hold 50kV once you have the high voltage power supply to make it. See the links in the video description for various high voltage sources.
It's funny when u type of people make these video's, and explain/show thing's like we all have these electrical instrument's/machines in our kitchen etc... And ur speedy talk like were all robot scientist's!
great info! nothing helps me to understand something better than watching someone break it down or build it, thx for sharing! could the thickness of the polyethelyne be causing the discrepency between your test and the breakdown info that you found online? general purpose poly is quite thin, whereas construction poly is many times thicker. the poly you used seemed quite dark like construction poly - maybe it's thicker than the poly that the site gave a rating for?
IDK if your PE is 94-v rated, but if not, PE turns to liquid fire (imagine water on fire and running everywhere all the sudden) if it catches fire... big deal around electric applications. This is more for the impatient experimenters viewing this in case they decide not to encase it like you do.
The sell them in sort of large rolls here too. I have a roll that's around 80 centimeters tall but I don't know how much area is rolled onto it - a lot.
This is a very good video. You sir get a tip of the hat on the detail you went into. This information is really good for eco types. We could upcycle what most consider trash to this. Good work sir!
It's used for this purpose quite a bit; it wasn't my idea, I was just following common practice. From wikipedia it's used "in transformers where it is known as transformer oil, and in high voltage switchgear where mineral oil is used as an insulator and as a coolant to disperse switching arcs." It's not considered flammable because its flashpoint is above 100F/38C, but is considered combustible for the same reason.
I got it from a carpet store. They used it as a vapor barrier under carpets. Though it might also be used in walls during construction for the same reason.
Sir You are Genius. I wind large Ruhmkorff Coils, and started with Layered, at 9 years old. My Coils work fine. Finding the "best" capacitor, is more trial and error then math. Oh to have a brain like Yours.
+Sanskruti Mohanty I'm assuming you're referring to when I said "1 mil = 1/1000th of an inch". The mil I'm referring to is not the metric millimeter. See en.wikipedia.org/wiki/Thousandth_of_an_inch.
That depends on what you mean by larger. To get a higher capacitance you want less layers, but that means it won't be able to withstand as high a voltage. And vice versa, to make it able to withstand a higher voltage without breaking down you add layers, but that will result in a lower capacitance. You need to figure out what your capacitance needs are and how high your voltage will be and then go from there. This video talks about the voltage part, the capacitance part is talked about in my other video ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-GveI9gXIsHw.html.
This was sooo good man Thanks alot Good infos Old video but aloot of good infos Working to make graphene capacitors and this video help me to make good ones
Ah, thanks for clarifying. And I agree that adding layers of insulation between the electrodes changes the capacity. But if you're going to be using a certain voltage range then your capacitor will have to be able to handle those voltages. Since it affects the capacity, you'll have to change something, like increase the surface area, to increase the capacity at the same time. That's why at 1:11 I refer to my video that talks more of the variables.
hi first thank you for the simplified explaination that i could not have found anywhere else on the internet, and i have a question please, that capacitance formula is there a similar formula for batteries i am trying to make a salt water batterie using zink and copper electrodes and i wonder if there is a similar formula to calculate the estimated capacity and voltage 🙏🙏🙏 and thank you
Thanks for the video, I just subscribed. I'm here after blowing 3 cheap Chinese 1000 nf caps and deciding either I'm going to spend way too much or build some myself. I found some teflon sheets used in heat transfer I'm going to tray as my insulator. Do you have any experiance with that material?
I read that the higher the voltage, the smaller the gap between plates... something to do with the odd fact that higher voltages actually form smaller fields. You can't really serially stack dielectrics and expect them to hold up to the total high voltage, each dielectric will be hit with the total voltage.
I have a 2mm thick glass and roughly 1.5kV... My calculations show that I'd require at least 28kV for dielectric breakdown of the glass. I am looking for another substitute for glass with lower dielectric strength. Any ideas?
Not off the top of my head. I'd have to look it up, the same as you. I usually do a google search for breakdown voltage table or dielectric strength table.
You can definitely find it, but just made by a different company. It's use in electronics for helping prevent voltage breakdown. Look in electronics stores and electronics supply websites for "corona dope". It has a very high dielectric strength/breakdown voltage. Look in electronics stores and electronics supply websites for "corona dope". I just put a link for you in the description for this video to the webpage of the manufacturer, MG Chemicals, part number 4226.
I can sort of understand why. Repetitive pulses wouldn't give the dielectric much time to relax between pulses. It's probably pumping up the energy in the dielectric.
Hello, very interesting, can you tell me were can I find how to calculate to make a super capacitor that substitutes the battery of my car? it would have to support 15 volts and at least 1000 farads, is it possible?
Since you're using AC and not DC, the capacitor is being constantly charged and discharged and with alternating polarity. I suspect the vibration is the plates being attached to each other when charged and then relaxing when discharged. The way I suspect there's a loss is that since the plates are free to vibrate a bit, they must not always be as close as they can be. If they're as close as they can be then they'd always have as high a capacitance as they can have.
Thank you for your great videos. They are well planned, thought out, and explained so people can easily understand them. I have a question regarding home made capacitors. When building a capacitor, which is the bigger limiting factor - the plates or dielectric? Meaning is the size of the plates a bigger requirement to meet certain parameters? or the dielectric? Also, If I build a capacitor for a certain use, and the voltage is higher than what can be handled, do I just put a resistor and fuse to limit the power? For example, I build a 200V capacitor, and use it in a circuit with a 50V motor. Do I put a 50V resistor and maybe a fuse to limit the power to the motor? I am new to the details of electronics. I am informed enough on building off the shelf stuff, but individual circuits and components are a new world to me. Thank you for your help! I really appreciate your helping people with your videos. I watch them first, research more so I understand it better, then show my kids.
+Bryant Larsen Regarding the limiting factor difference between plates and dielectric, it depends on what factor you're talking about, capacitance or breakdown voltage. You can see all the things that affect breakdown voltage in this video (I won't repeat it all here.) Capacitance is determined by a mix of things which I go over in my other capacitor making ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-GveI9gXIsHw.html video. If you build a 200V capacitor, that just means the capacitor can handle 200V before it breaks. It doesn't mean you'll be charging it to 200V; that's up to your circuit to do. If your circuit can produce only 40V then the 200V capacitor will charge to only 40V.
Not directly. A battery puts out direct current (DC), a steady flow, one-way, uniform flow of electricity. A transformer needs current that's constantly changing such as alternating current (AC). You could, however, add some circuitry between the battery and the transformer to change the DC to AC before going into the transformer.
Oh interesting. I never noticed that before. Even the wikipedia page says "it decreases slightly with increased sample thickness." Almost sounds like there should be a volts/mil/mil value or something.
You can find details in the Equipment section of my website, rimstar.org. Look for "30kV DC power supply (homemade)". I also just put a link to it in the description below this video.
If the power supply is disconnected from the capacitor so that the capacitor is on it's own, then yes, it holds the voltage, though like any capacitor, it loses some over time. If you just unplug the power supply from the wall, then in this case it also holds the voltage. Some power supplies, when turned off, would allow a path to discharge through the power supply.
I don't know for sure. Maybe because by having one plate with a much larger surface area, you eliminate any edge from that plate. The electric field at edges is different so by not having an edge, you eliminate that variable.
Westsyd2pac Were you charging them to a high voltage, thousands of volts? What voltage were you charging them too? What were the capacitors made of? How are you testing their charge?
No. If the breakdown voltage of polyethylene is 500 volts/mil and the polyethylene is 20 mil thick then it can withstand 500 volts/mil x 20 mil = 10,000 volts. If it's 40 mil thick then it can withstand 500 volts/mil x 40 mil = 20,000 volts. So the breakdown voltage increases as thickness increases but the breakdown voltage per unit of thickness (mil for example) stays the same.
The polyethylene.. I saw the rating for it was 481-551, does this include the range for all grades of polyethylene? Was your plastic high grade? I really like your website man, and although you speak a little fast for me (novice at this stuff) thank God for videos and the pause button lol. You are very appreciated sir.
I have on my list to try an ultracapacitor. Of course, if it works I'll make a video. Though a simple way of getting MF is to make a spiral capacitor like I did in my other How to Make a Capacitor video, but with linger strips.
can you help me understand what im dealing with when people say, by just connecting a high output capacitor to a moped spark plug wire, the output spark will be much more powerful?. i would figure, as the engine revs up and more power is stored by the capacitor, the capacitor will just blast out a constant arc and pre-ignite the fuel and destroy the engine. do i need to use a coil in combination for this to work? the point with what im trying to do is a more complete fuel burn. because of 2-cycle engines design, some of the unburnt fuel exits out the exhaust = pollution. i was told to somehow increase the spark power to achieve a "clean" burn. in other words, will juts a capacitor work? output power is 24v. could i acheive 300v output? current output is 150v to spark plug. i need double. haha....thanks for your time.
+Edwin Bickel Thanks! And no, I don't remember the camera settings. Though with the high current from the power supply I used here I may have just had it all on automatic. The corona from this power supply is easily visible to the naked eye. With the low amperage from my Wimshurst machine however, for example, it can be faint to see with the naked eye and I sometimes have to turn up the camera Exposure to get the corona visible on camera. I had to do that when filming my corona motor version 1, as well as turn up the blue and red in the video editor.
Capacitors do not store charge on the conductor, it is stored in the dielectric, take a charged dielectric to build your next capacitor and your finished cap will be pre-charged.
They are run capacitors, as they are designed to operate continuously. Motor starting capacitors have a higher capacitence, but are only intended to operate for the length of time necessary to start an electric motor, typically less than one second. Start caps typically have a value of more than 40 uF, and are used exclusively for motor starting. Run caps typically have a value of less than 60 uF, and are used for more general purposes. We carry both. Rahway Electric Motor Co. (732) 388-2829
