 Cymru Cymru sy'n dynnu'r prif. MÔr creu sy'n gwrth o'r clennófodol iddyn nhw phone'r ysbyt. Rhaid i chi'n cael brydy'r ieithod, ychyn ejemplo. So, testa cwrs are quite dangerous, not as dangerous for remote controllers for computers. Basic risks, electrocution, the obvious one. In actual fact, 93% of the chances you are not going to kill yourself, you are much more likely to burn yourself. But, as all of the doctors in the room will attest, when you burn yourself and drill a little hole in yourself at the same time, it cultureises the wound. This makes it less likely to heal, which means you are much more likely for infection. It's the infection that will kill you. Explosion, so it's a little weird, but testa cwrs I've transformed within them, testa cwrs have capacitors in them. Both of which can store quite a lot of energy, one magnetically along the electrostatic. Some of them can be stressed quite a lot. Especially when you are an impoverished testa cwrl and you are running a mat, 150% of their rated values. Not that I would ever do that at all. It happens, they explode. I've gone through burns pretty much. Any radiometers here, and even before they grab hold of an aerial while there's been RF up it. Yes, a few hands go out. Are RF burns pleasant? No, I'm referring you back to the little holes in your fingers with cultureised wounds that don't heal. For you guys, probably the most important thing is pacemakers and cochlear implants. There isn't a huge amount of risk to be fair because these are relatively small colours, but if you have cochlear implants or a pacemaker, please can stand at the back of the room. I really don't want to take any risks. It's really unpleasant if your pacemaker kicks in and it shouldn't have to. There are a couple of other things, but they aren't much less of warnings. If you have asthma, the coils that I run, especially the small ones, produce ozone. Ozone is a known irritant of the throat. You start feeling your throat going, you know when you have an asthma attack. Get out and get some fresh air, you'll be absolutely fine. We've got nobody in wheelchairs, have we? Nope. The only other thing is, if you are getting up and going anywhere, especially with these two here, it's probably going to be hard anyway. Can you please tell me that you need to go or don't just walk into the killings zone. That's just because certainly later on we're going to have to mix parts there. I want to do that. It's a very good question to be fair in the open source. Certainly in the open source hardware, we don't want to do any of it. It's sparse, it's like fire, it's fun. It is, it's really cool, it's good stuff. It's rare as well. You don't often see four meter long sparks in normal everyday life. So there's a bit of a rarity factor here. It's different entertainment. It's different. Yeah, you just don't see it. For me, it's a challenge. I've been an electronics engineer most of my life. When I started coming into Tesla coiling, that sort of, oh, I don't know all about electronics, I can. Holy! There's a lot to learn. If you think you know about a capacitor and an inductor in one circuit being fed by what is effectively a gap in a piece of wire, you're wrong. And I have seen university papers going on from pages and pages about how that simple thing works. It's unbelievably complicated. And then what you do, you attach another transformer to it and an even bigger coil of wire and another capacitor. There's a lot going on. But that's why I keep doing it. If it was easy, I'd have stopped ages ago because I'd been bored. And the biggest thing that attracts me to be is it's dangerous. Yeah, okay, I admit it. I personally think it's about as dangerous driving a motorbike. If you're sensible, you're going to be safe, you're probably going to stay safe. Some stage, something is going to trip you up. But if you're sensible, you've probably narrowed down what is going to happen to you to the nasty boom rather than death. But it's there. So, Tesla Coil. There are a few examples here. There are various different shapes and sizes. We've got a few here. Those were... I'm really going well with this control tonight. I'll tell you guys. Oi. Be happy. Right. Tesla Coil. These are the smallest I've built for the older ones of you. This is, of course, the same icon. They are roughly three inches tall. They all work. They produce sparks. I don't have four or five millimetres, something like that. Then we go to the other extreme, which is a friend of mine. That, from floor to ceiling, is around six metres. There is a bigger coil in the UK, which I've seen recently. More impressive is that. A spark gap coil. This one's electronic. We'll come to that later. So then there's everything in between. A little spark gap coil. A little electronic coil. And one I like to call flat airing for the older of you. Purely because I wanted to build a Tesla coil that was flat. The whole of that except the battery is seven millimetres thick. I did wear a ton of T-shirt ones. Until the insulation broke down. Interesting. Anyway. So. Tesla coil. That is the traditional circuit of a Tesla coil. One that Tesla himself would recognise. Very briefly you have AC mains into a transformer to get it to a relatively high voltage. High voltage capacitor. Primary coil. And a secondary coil. Let me show you some of those bits. I'm here to put them into context. Primary coil is the four bits of rate type down the bottom. By the thousand turns on this one. And then the torus at the top is actually all the capacitor. We'll come back to how that moves in a little while. So that's roughly how a very simple Tesla coil sits. So. What happens? What happens? So. What happens? We've got the mains side. 240 volts. I've got 10. 10 kilovolts. Tesla coil's range. So there's a spot young ones between about 5 kV and about 30 kV on the primary side. On that AC current charges the capacitor. So over half a cycle that capacitor will charge up roughly 10 kilovolts across it. But. Before it gets to that point we have a spark gap. The spark gap is set so that just before the capacitor reaches its maximum voltage the air breaks down in the spark gap and therefore you get current going from the capacitor through the primary coil of what is essentially a transformer. As we've seen we've got roughly 10 in terms of this case and 1000. That obviously is going to multiply the voltage up. But. What also happens is this is still charging it so we get the other side. Hang on. I've stepped over one. Let's go back a stage. Spark gap fires that capacitor discharges through the coil. It's an inductor. You get an induction and together it forms an RF circuit. You would just put one big pulse into an RF circuit. It starts to oscillate. So in actual fact it will then start pushing power back into that capacitor. This will happen a number of times and the spark gap will stay conducting during that phase. Also we've got this secondary transformer here that we'll be taking what is now RF or radio frequency and multiplying it up by the turns ratio. Has been pushed into the secondary and remember that that is a multicapacitor so that is also resonating at the same frequency of this. The spark gap ceases to fire because there is no longer power in that circuit to keep it sparky. Of course at this point the impedance of the primary has gone from a few ohms to almost nothing. That is as much an impedance transformer as it is a current and voltage transformer. So strangely enough this secondary has then got a whole load of power in it and nowhere to go. But you've got some lovely air and usually a little spike on the top and you can see that most of these are rather than a spike on the top. You get a very high voltage and a very small spot for that high voltage to sit in. So you get a spark out of the top. That carries on while there is power in the top load and the secondary and then we're in for the next half cycle. It's usually a main so 10 milliseconds later. And yes in the opposite direction. And that is roughly how a spark gap testicoil works. It really isn't that difficult and it's actually really quite easy to build. The biggest problem is is actually getting hold of 10kV transformers these days. Used to get a lot of them from neon sign places or places that are actually scrapping neon signs. Of course LEDs are taking them out and they tend not to be as common. So it took a little about a spark gap. A spark gap can be quite literally just two points at a gap. The problem with that is we want to promote that radio frequency. If your spark gap stays firing all of the time you don't get a really really good RF from it. You just get a big pause. So all we actually do is if we use a couple of techniques this one you'll notice is a pair of fans at either end. And also we've got multiple gaps one after the other. These are copper pipe and they're done so you can tap the distance that the spark gap goes. So we only use a couple, it's about a mill of piece. Use the whole lot, it's about seven or eight mill. Combination blowing air through the gap literally blows the spark out which means that rather than it staying there and damping that oscillation you can get a lot more efficient oscillation. Having multiple gaps does the same thing. Because if one gap fails they all fail because the current goes. So it makes it a lot more likely for that to sustain a good pulse of RF. The other way we can do it is with a washing machine motor couple of pulleys and what is effectively a very high speed relay. It's not quite like a relay because these don't actually touch anything. They just get very very close. These flying electrodes are usually arranged so that they connect at every half cycle in phase with the capacitor that we saw in the other diagram charging to its fullest voltage. So effectively what you get is a synchronous discharge of the capacitor. You can also run them asynchronous and then you get into the wonderful world of DC charging and because you're all aware arcs don't like to discharge them extinguished when you put DC on them. They much prefer AC. So there are all sorts of ways with diodes and inductors to cleanse the arc on a rotary like that. And sometimes even with a static gap in series with the rotary to again promote that arc during extinguished. Capacitors usually made from only small caps because it's a company called Maxwell. They sell some lovely capacitors. I own a couple. They're about like that. They start at about £500. We're doing this amateur. That is the equivalent of about £1,000 of Maxwell capacitors made out of loads and loads of really small ones. We call them multi-manufacture caps, MMCs, and that is generally what you'll see in the bigger Tesla coils. Purely deep costs down. There is another advantage of that. When you glow those off nope, but when you can replace a fuel, you can replace a tray. It's a lot better. You don't lose all the caps all at once. So it does make things a lot cheaper. Tesla had exactly the same problem and Tesla had the money, but he didn't have a company that made very, very large capacitors. So Tesla being Tesla and one of the reasons I really like the guy made them out of beer bottles. What he did, he got a tray of water, added some salt to it, put beer bottles in and then put a wire in the top of every beer bottle like a laden jar. He had multiple trays and he even had a way of switching the trays in and out and he could fine tune it by pulling out bottles. I will show you later on the size of the Tesla coil that he actually did doing that and you can then think of what happens to those beer bottles. One of the things I just mentioned is tuning. If we remove or add these capacitors we can actually tune parts of the coil and it is very, very important that this top load and that secondary coil resonate the same frequency as the primary coil and the other capacitor because that's where you get one maximum power transfer and two it becomes a DC sorry it becomes a resistive load. As soon as you get that double resonance you can drive it as a resistive load which makes things a lot easier. Come on to that later. So the top load produces two main reasons for having it. Number one is you need that capacitance. When I say capacitance that's one plate of the capacitor in which you all know that capacitors need two plates. The other plate is everything else in this room for all the ceiling, you, whatever are all that second plate of the capacitor. So its size determines the capacitance. The other reason for it and I've looked for photos that prove this and I've done a few it actually creates a magnetic field. If you have this donor shape it creates a magnetic and electrostatic field that the sparks like to follow. Now that is really, really useful because the one thing we don't want is the spark hitting your secondary coil or worse something further down. But by doing that you actually make it into effectively a magnet for sparks. And using the field lines of a magnet to go up and around and down, that's what it does. So it actually protects the secondary coil and to some extent the stuff at the bottom. Just by having the correct shape. So that's really what top load is for. Primary coil say he easily wants 20 turns there's five on here about 15 on that one and these have got the 10. It is always around that. Even really, really big ones only have a few turns on their primary. It's very, very high current. This one is an example that's about a six inch diameter coil. And we were putting two to three thousand amps into there in RF courses which still amazes me that you can get a sheet of copper and put a thousand amps into it being driven from transistor without blowing anything up. That is an inductor. It doesn't matter how strong it is it's still an inductor. I've put the lowest voltage obviously as we saw before there are about 10 kV. Electronicals maybe 400 volts something like that. Not massively high. And again we can use these for tuning. You can put a crop clip or something and pick how many turns you have to tune coils. So it's another way of tuning the resonant frequency to as I say get them to match. You've got to have it to match secondary to the primary those two resonant circuits to get the best power transfer. Secondary coils three to two thousand turns similar to that one. This is where the high voltage is generated. They are a single layer. They are a single layer purely because of insulation. So when you get two wires that cross over each other one you get in point contact which isn't good. Two you can't guarantee that it's only one turn away from the one before. So they are all single turn. Very low current which actually means the output of the testicle is generally safe apart from the RF. You need somewhere in the region of five milliamps across your heart to do any real damage to yourself. Even the really really big testicle is only getting up into the 10 milliamps range and I'm talking three four four tall one. So even then unless you get it directly across very unlikely you can get home coming out of the top. The first and still the largest ever there isn't an American who is trying to get there but he ain't there yet. Some statistics 200 kilowatts of power. His primary coil was two meters tall and had two turns in it. It was a one inch diameter copper wire. The secondary was um three to four meters tall and only had a hundred to hundred and fifty turns which is really really low. But you only need that when you've got 200 kilowatts of power. The other thing he did, he actually put the top load on a long pole. I'll show you the coil later on but you see there you see that bit there that is actually the coil and then there's a long pole in the middle. But you also have three coils all of these we've got two but he actually had three. He thought it was mirror efficient actually it's been driven mathematically makes no difference. He had one advantage though is that the third coil you can actually take away from his laboratory so all the power stuff and all the big expensive engineering was in a completely separate building and that is a really confusing photo because that is his laboratory that tower is about 20 foot behind the laboratory and then there is a big tube about that diameter going from his secondary coil to his tertiary coil which is the one you see there. So about beer bottles 200 kilowatts of power into banks of beer bottles and capacitors. Sparks, you'll see these photos of Tesla they're entirely done for publicity purposes. He was a great, great guy for doing publicity. He was an engineer the last thing he wanted was Sparks he was planning to transmit power and the last thing he was going to do if he was transmitting power is to make load pretty fast. He was an engineer. I'll also say here there's one mega volt Tesla coil myth the biggest Tesla coil in this country which is about four metres tall, will chuck 15 foot, 20 foot Sparks produces about 250,000 volts. Where that comes from is 30 kV an inch or yeah, um 3 kV a millimetre 30 kV 30 kV is sent to me that better. If you look at the length of these Sparks and you take that yeah, that's roughly what they look like but actually no they're not anywhere near that much I can show you how in a little more so right, according to that it's now so I don't know how well you can see this when it's dark enough what can do with this little coil is to produce some Sparks they are a single discharge as you would get from a high voltage source but the top of there is probably 70,000 volts something like that if I wind this up a little this is notorious for you see those Sparks are a lot bigger, fill the same power but what I'm doing is putting multiple Sparks in one after the other what you get when that happens is you've got an ionised channel of air and then the second spot takes the same ionised channel of air and that starts it that far up to the other one so with these I can actually take this up I think 32 occasionally what I do is I lean in and demonstrate and it gets me all the nodes you'll also notice that all the Sparks are coming out from that spot point on the end we call that a breakout and that is there for precisely that reason okay there is the protection of the top though but you know what really they're not coming around the Sparking down so we try and keep them all coming out to the top so that's little more than that little demo of a small test of coil and then zip back a couple a warden cliff I mentioned that it was a tertiary coil I also mentioned that it was a a Spark gap coil I have a little model now this little model isn't quite true being that although there are three coils I've actually stacked one on top of the other purely to make it easier but there are all three coils there but this model quite deliberately has a few issues with it first one is I can't reach the bottom so let me just run that we can get some Sparks really what the Tesla is trying to do is trying to get all the power to come out to the top of that so if we don't let it come out to the top so this is effectively how Tesla had it with a bit of cut over at the top and some power plus some power into that I mean limit the testing with this coil so you saw the Sparks coming out of the sides and coming out of everywhere which is very interesting because in the photo earlier on if I put the remote down it's really confusing there's that photo you can see Sparks coming out to the top of the coil and I'm going everywhere now I think that that picture I know that he took a few things there but there is another photo out there with it running with just the Sparks coming out to the top I guess they're going to take the projector out probably you'll also see Sparks coming up and down the coil the reason we've got Sparks coming up and down the coil is this one is quite deliberately slightly out of tune and it's slightly out of tune to show you what happens when you get a Tesla coil that's slightly out of tune maybe you play the guitar and haven't got a couple of experts you get a nose and anti-nose on your string don't you and you press your nose to well a Tesla coil from top to bottom is a bit like a string what you're trying to do is to get the major nose to sit onto the the breakout so you've got all the power and it's coming out to the top if you don't get it quite in tune your nose changed position and you'll see that about there we'll actually get a breakout and that's because it's the modern tune and we're getting a note from a slightly different place you'll also notice it's interesting when it comes out of there we're taking the projector out because it's stopped being a nice RF oscillator but one frequency and it becomes an old engineers tend to call squag do you know what I mean by squag it's like a chirp but it's a RF so rather than sitting in a specific frequency it'll go up and down the range projectors obviously don't like that the other problem is as you can see this is really really fine wire you're getting spots coming out of that fine wire it breaks down the insulation all of those things are really really not a good thing for a Tesla coil that's why I've got that demo because I can show you all of those without blowing anything off all of them projectors so the use of Tesla coils obviously Tesla was trying to do power transmission latterly he decided that he wasn't going to manage to do much of power transmission and radio was quite popular at the time so he started to try and beat Marconia into his own game unfortunately he went the wrong way he decided that the best way to transmit a long way was loads of power so all he did was he took something small and he put more and more power into it until he got spots out of the top and he didn't get anywhere which is really annoying and it's really annoying for two reasons one he was so down and close and number two is why he was doing that and number three is for RF transmission for all sorts of radio frequency stuff methods of hearing radio waves, carheras you name it he's even got a patent before and tell me what this sounds like a gas filled tube with two electrodes one about halfway down the middle you put a voltage at either end of the tube or an electrode on your area on that middle electrode as well yes he basically created a triode and he patented it but he didn't know that way he just wanted to put more and more power up the thing Marconia admits on record for saying that his radio uses seven of Tesla's patent seven naming the parts of a radio in that area just ridiculous and Tesla gave them to him does that make any sense I've never worked out why I have but it's true the use of Tesla coils of that era was kind of the medical stuff I have an example admittedly this is a little beyond two of the century this is what's called a violet ray machine they are effectively a Tesla coil in a handle you apply to various parts of your anatomy a coil is you can hear it doing that and these are readily available and most of them that you will buy are absolutely lethal and I'm not joking this one had a microcapacitor that had been clamped to death it was all damp and that was between live and the bottom of that Tesla coil which I'm holding I have made this one safe ish please be very careful if you buy them they're a great thing to play with but they have some they have some real problems so yeah I'll hand this around there is a list of the attachments you can get to these the more perfect of you you can probably read some of them down on the bottom right hand that I really don't suggest the kids ought to read but this is history they exist and four of the places too the cure for every malady so coming into the 1970s 1980s people started realising that transistor technology had taken on enough and we could replace this horrible noisy spark gap with transistors so we started to replace that spark gap with transistors and it was really really difficult to begin with to be fair you would be surprising how resilient the average spark gap is compared to a transistor or maybe not of course before transistors we get transistors in gem jars the valve Tesla coil still done that's one from a couple of years ago usually beautifully built and they look the absolute biz we've got characteristic very straight sparks for those of you who are into transistors in gem jars that's the circuit diagram I'm afraid it doesn't mean a huge amount to me I can just about follow it effectively it's an RF oscillator anyway bit more up to modern day certainly in the last few years our friends the Chinese I say that I say that build these little kits I don't know if that's dark enough for you to see see the little spark on the other top these are the little ones you can buy for about a tenner via e-mail or whatever and they're a fully working Tesla coil or even lighter for the rest of the tubes cool little thing to get started in Tesla coiling one word of warning you can still get little burns off the top of that for it to be fair you've probably used the soldering iron in building them therefore you will actually get a worse burn off the soldering iron that one's audio modulated cool little kit to cut parts like that very simple good start the problem with this circuit though is that it isn't really scalable you can put bigger and bigger transistors in here I've seen it done one of the big problems is you don't have a top load so you can't store a whole load of power in a secondary and also you've got no primary capacitor which means you've got to have very very small amount of turns to keep the inductors down because you can't put any power into a high inductor not that that's a lot of voltage you might really get to the point so now they're going to the solid state testicle which is kind of similar to that circuit but we can now use mains on it we're using a full bridge which gives us about four times the power of a simple transistor we're using power MOSFETs but we're still limited by the resistance of the primary the circuit very simple really some form of control which is usually on or off it might be on or off some frequency but it is basically on or off bridge driver current feedback that then powers your control that goes on and off so the whole of that becomes an RF oscillator flies into a bridge I think most of you know what a transistor bridge is yeah none of you go too much but basically mains in, drives these that way and that way into a load and there is a nice little PCB friends who make purple PCBs he doesn't say it that way but I would do a demo because this is a solid state testicle so this one was built for a steampunk exhibition so it kind of looks a little weird but also we rebuilt a few weeks ago so if it does explode I do apologise so with this we can start they are not very big because we haven't got a lot of voltage multiplication on this we still have not got that primary capacitor to give us a real power but we can push into that now at 2k we can actually get an iron engine actually it is only half an iron engine half an iron engine because there are actually two things one is there is a big stream of ions coming out to the point that means so if you are pushing something out it will go in the opposite direction it starts spinning the other reason why that spins is because I am also heating the air up heating the air up to a 3000 degrees and the air tends to expand and go away which also produces a bit of thrust that way which one of the two is the larger I honestly don't know but it makes quite a good demonstration and the electronic tessico will just prove the solid state tessico which is the DR SSDC DR stands for dual resonant and it is purely getting that capacitor back into the circuit that we have removed because we have gone to electronics and it took quite a long time to get the electronics to that point where that could happen obviously we started off with really simple stuff start off with not particularly with transistors but we started using IGBTs which really really love power and the best thing about them is that on resistance is very very low and they will oscillate at the frequencies that we want in a tessicoil I didn't do that which are roughly speaking for this small coil about 300kHz you can even get really really big IGBTs which will do many thousands of amps and that is actually the biggest coil in the UK now and it's electronic it has a bridge of 2000 amp IGBTs in the bottom of it runs at about 70kHz now it's actually better than when I took that photo I've seen it do about 4m it's very very impressive so we've got that primary capacitor we've got feedback current control is another thing that took a long time to develop current control when you get a spot like that it's like shorting out a power supply now remember that you've got thousands of amps hundreds of volts here and you're just going to short it out on a whim the current control became a big thing it's not the IGBTs for exploding and yes I said the word exploding they do I have blown the lid off so many IGBTs I have a shoebox full of them to keep me insulate and get home of the transistor it's a MOSFET designed for power switching sorry dar so very similar circuit you'll notice, apart from the addition of the capacitor there is also another current transformer that actually does the overcurrent protection other than that pretty much the same so that's taken us pretty much up to date I touched on this when I was talking about the warden lift coil primary stripes you don't want the coil spark out to the top and go back in to the bottom because you get some really really nasty spikes and transistors don't like spikes spark out coils don't really care that one was quite happy I mean with some real problems I was very proud of getting that photo two reasons but one is the coil wasn't too badly hurt well it actually goes on so rather than that being a nice resonance to earth it was like running out of a guitar string that wasn't attached to the other end so it just went everywhere but really proud of that photo because I got it not only from there but in that box there with the Raspberry Pi also taking photos of it I got some two angles either way it gets hot but because of the importance of tuning in the electronic coil hard feedback will do the same thing if you imagine you've got that feedback that's trying to keep everything in phase if you use that phase you're then driving something into whatever and it doesn't resonate anymore and remember you've got to keep it in tune with the electronic coils to keep the impedance low and make it a DC load a resistive load soon if you go away from being a resistive load your IDGTs are then switching not at low power anymore and they're switching at the peaks and you get a lot of heat and they're very very fast and that's what they explain that is the result of the photo you saw earlier on and these things here are the Lichtenberg figures and this still happens when it goes wrong sparks will progress and will score the outside of your wonderfully polished coil or in this case if you just go to a piece of insulator that isn't quite up to the task your sparks will generally progress and produce these patterns in wonderful blue Peter style if you remember come and have a look at that later on here's more on my dear William so obviously we're trying to avoid this happening trying to avoid it but the sparks touch anything but over time insulators do degenerate and coils will over time just explode themselves so we come to the use of the test of coils of the present day and yet they have potential I thought I was going to get a man on a tis high voltage transmission a lot of the Japanese now using DC to power their pylons and long distance transmission lines and they're using a test of coil to actually get up to that DC they call it a switch mode regulator or whatever but it's an air core transformer test of coil another one that I see quite regularly and I've done some consulting on this personally is using test of coils to align carbon nanotubes during their creation and there's a Cambridge University and I think it's Atlanta University I'll look at this at the moment and the name of that is called Tesla for races but that's quite a thing and they're making big long lines of nanotubes which obviously conduct all sorts of uses for them I'm sure but the biggest one for test of coils is probably entertainment so talking about entertainment let's see if we can entertain you because I've never actually done this with these coils