WEBVTT

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>> Here we go. I'm going to use the edge of this.

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I'm already wearing protective glasses because this will cause a big spark.

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Please don't try this at home.

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There we go. I'm going to connect it to terminals together.

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Ready? Here we go.

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I had my eyes closed. So I hope you guys saw that.

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That was the entire charge

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in a capacitor going through the short-circuit tip of this.

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You can see it actually damaged the tip of my X-Acto knife here.

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They wouldn't focus on this very well.

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But now you can see that a voltage across

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the capacitor went down all the way to 11 minus seven volts.

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So, let's now do the same thing, but this time,

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let's take this to the oscilloscope and connect the probe on

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the voltage that I was telling you about, and

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the node I was telling you about I'm interested in seeing.

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I'm interested in looking at this voltage right here

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and seeing the oscillation I was telling you about. So, let's take a look at that.

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Okay. Here we are at the oscilloscope.

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I'm going to be using my older scope for

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this because I'm going to be putting a very large voltage,

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and then I don't want to risk damaging my new digital scope.

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You can buy one of these older CRT-based scope from eBay for about $200.

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They're very useful. I highly recommend it.

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So, here's the flash circuit.

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It's already powered up using my power supply on the left.

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I'm not running this at its full capacity.

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I'm running it only from 0.6 volts because I don't want to create a very large voltage.

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I just want to demonstrate the principle of operation.

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So, what I'm going to do is I'm going to use the oscilloscope probe

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and look at the voltage right before and after the diode.

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So, let me see if I can get this to focus.

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There we go, almost.

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Right. So, here you can see the diode right there,

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and I'm going to look at the voltage before and after the diode so we

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can see the peak detection and also the large voltage swing I was telling you about.

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So, what I'm going to do is I'm going to connect

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the negative terminal of

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my 10 to one probe and it's important that this is a 10 to one probe.

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So, I will connect that to the negative voltage of the power supply.

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I will take this cap off,

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and then we will focus,

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zoom in a little bit more on the display.

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So, you can see the display of the scope is set to 50 volts per division,

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meaning each of these vertical lines and vertical divisions is 50 volts.

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So, there's eight of them in total, one,

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two, three, four, five, six, seven, eight.

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So 400 volts, a peak-to-peak signal can fit in this display.

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Right now, the middle line is the ground.

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So the signal in the middle is zero volts.

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So, I will connect it right where I was saying right before the diode,

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but I'm going to have to do that from the opposite side of

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the PCB because I cannot really reach that.

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I flip it over.

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This is after the diode,

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and this is before the diode.

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I'll put this on the ground and then I will connect it.

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Here we go, like that.

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So, you can see there is an excess of 400 volts peak-to-peak of swing there.

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The negative swing is clipped at the bottom.

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You can see the bottom part is clipped.

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The reason is because that's where the diode starts conducting and,

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therefore, the capacitor starts to charge.

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So, that voltage does not go below there because

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the capacitor is so big that clips a voltage at the bottom.

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But you can see that right now,

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the voltage across the capacitor,

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you can tell by where the clipping happens must be around minus 200, minus 250 volts.

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If I connect this right to the capacitor,

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you can see that it goes below the vertical division,

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below the lowest point here is because it's less than minus 200 volts.

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So, there's one other thing we can get from this.

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If I connect it, we can measure the frequency of oscillation.

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Each horizontal division is 50 microseconds.

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So, if I connect it,

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we can see that the cycle repeats once every 100 microsecond.

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That's equal to 10 kilohertz.

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Ten kilohertz is audible because you can hear 10 kilohertz.

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In fact, you must have realized whenever you turn one of these things on,

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then it makes that really annoying high-frequency pitch.

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The reason that happens is because the frequency

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of oscillation is within the audible range,

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and the coil is in the transformer vibrate ever so

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slightly because of so much cranes in them in the magnetic field.

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Shift them left and right very little just enough so that you can hear.

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So, the whole circuit emits sound when it's operating.

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That's another reason why it makes that noise.

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So, what I'm going to do now is that now we

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have spoken a lot about how this circuit works,

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looked at some other voltage or the oscillation and

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a whole bunch of other characteristics,

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what I'm going to do now, is I'm going to connect this to

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a Nixie tube and then see if we can power a Nixie tube with one of these things.

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So, let's move back to the other side and let's try to do that.

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So here, I have a Nixie tube.

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This Nixie tube shows numbers between zero to nine and it has also two decimal points.

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So, the way these Nixie tubes work is that the gas inside

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this tube is low pressure neon sometimes mixed with mercury and argon.

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You have around on the outside,

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you may be able to see it,

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there's this mesh that's connected all the way around,

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and at the back is a solid plating that's connected to one of these pens.

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That's the anode pen.

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What ends up happening is by putting a large potential difference

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between this mesh on the outside and

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the little numbers in the inside that you may be able to see,

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you're going to excite the neon gas that's in there,

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and the neon gas is going to glow.

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The exact principle of operation of how it

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happens and the physics that goes into it is an interesting read.

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I suggest that you take a look at it,

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but the principle of operation is what I said.

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The gas gets excited,

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the electrons move to higher energy bands.

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On their way back down,

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they emit light in the frequency and the wavelength that we are able to see.

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That happens near the cathode elements of this Nixie tube.

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Why does it happen near the cathode element?

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Now, it is a little bit of physics that goes in there too.

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I recommended you, take a look at it.

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But in order to turn one of these things on,

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you need to apply somewhere between 150,

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160 of volts between the anode and the cathode of this particular model,

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and then you'd be able to turn those numbers on.

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These guys were invented and used back in the '40s and

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the '50s when seven-segment displays,

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an LCD displays and vacuum fluorescent displays weren't available yet,

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and you could show numbers with these.

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So, if you ever had an old HB or a very old measurement equipment,

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you will be able to find these Nixie tubes used as a display, very, very popular.

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A lot of people build very cool things with these like clocks or some

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display depending on what kind of Nixie tube we can get a hold of.

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I got a batch of 10 of them from eBay a while back.

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I can't remember maybe about $50 or so.

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Very cool things to play with but of course because they

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need 150 volts or so to turn them on,

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they are not the easiest things to use.

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So, you will need a DC-DC converter.

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So, I thought why not,

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let's try and power one of these things using a flash circuit

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because the flash circuit is capable of giving us that kind of voltages.

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So, what I've done is that I've taken one of these guys,

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and I have just placed that on

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top of one of these breadboards so that all the legs are nicely separated.

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There is a little resistors connected to the anode.

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So, this wire right here is going to connect

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to the anode and every one of the other wires,

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the cathodes are going to be connected to

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the potential that will turn it on and you should be able to see those numbers.

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So, I'm going to connect everything up,

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show you how it's connected, and then let's see if we can power it on.

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Then, the last thing,

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we're going to measure the efficiency of

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the DC-DC converter based on how much power is delivered to the Nixie tube,

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and how much power is required for the flash circuit to run.

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So, let's do that.

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So, let's see what I've done here.

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I have connected the flash circuit to the power supply,

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so it's powered on.

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I'm monitoring the voltage of the capacitor

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simultaneously like I was doing before on the multimeter.

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I am connecting the anode to ground and I'm connecting one of

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the cathodes to the negative terminal of the capacitor.

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This is because, remember this produces

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negative voltages with respect to the ground of the power supply.

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So, at the same time,

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I am measuring the voltage that is connected to the flash,

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the current that's connected to this that it is being provided to the flash,

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the voltage across the capacitor,

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and the current that is given to the Nixie tube.

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So, if I were to multiply this current by this voltage,

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that's the power delivered to the Nixie tube.

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If I were to multiply this number with this number,

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that's the power delivered to the flash unit.

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So, by dividing the result of this to this,

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I can get the efficiency of the DC-DC converter afterwards.

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But let's first turn on the Nixie tube and see what happens.

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So, let me go all the way down and we bring the Nixie tube into view, like so.

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I'm going to increase the voltage in the power supply until this guy turns

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on. Here we go.

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There we go. Here it is and it's showing the number eight.

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I can show other numbers by connecting it to the other numbers.

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For example, here's number two, three, four,

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five, six, seven, eight,

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and the back that's nine.

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You can also turn one and other ones but I don't want to reach the back,

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all the way back just in case I will short-circuit the wires.

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So, let's connect it back to number eight.

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So, the thing that makes this Nixie tube is really

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cool is the fact that the numbers are not all on the same plane.

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So, it gives it this weird 3D look.

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As I go across the numbers,

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the numbers go back and forth and I think that's

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a really cool retro look and you could incorporate in one of your future projects.

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So, you can see when we're a bit closer,

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the number eight is glowing.

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Very nicely, it has a very nice orange glow color to it.

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So, I'm going to put this down on the ground,

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leave this number eight on so we can measure now the efficiency of the DC-DC converter.

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So, let's put this back down here.

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While it's on, let's go up and look at these numbers. Here we go.

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So, the power supply is set to 0.8 volts and is drawing 386 milliamps.

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So, let's say for the sake of to make it easy in the calculation,

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let's say this was 400 milliamps.

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So, that will be 0.32 watts.

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320 milliwatts of power is being delivered to the flash DC-DC converter.

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The voltage across the capacitor is 133 volts, negative 133 volts.

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The current going to the Nixie tube is 1.2 milliamps.

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So, if you multiply 1.2 milliamps by a 133 and divide that by about 320 milliwatts,

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you get just over 50 percent.

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So, the efficiency, the DC-DC converter efficiency for turning one of these Nixie tube

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on using a flash from a disposal flash camera is only about 50 percent,

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which is very bad because you can make

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DC-DC converters that are easily more efficient than 80 percent.

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But, for hacking purposes and for something

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that would have otherwise been thrown out and for educational purposes,

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I think this is a great project that

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if you have some experience dealing with high voltages,

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I strongly recommend that you try it out.

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Especially, if you've never played with Nixie tubes,

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this things are really, really neat and they're not that expensive.

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You can get them in all kind of patterns.

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Doesn't have to be numbers.

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Sometimes you can have them as bars or something else.

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So I strongly recommend that you try this out, and then you see what you can do with it.

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Just be very, very, very careful.

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>> Well, I hope you enjoyed this episode playing with flash circuits and

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Nixie tubes and I hope that we learned a thing or two about how these things operate.

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Unfortunately, I'm going to have to break this video up again into

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multiple sections because YouTube doesn't allow

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me to upload anything that's more than 15 minutes.

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But if you guys watch these videos and upper rank them,

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then YouTube will eventually allow me to put

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the entire episode in one video so you don't have to keep clicking.

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So, please make sure you discuss this in

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the comment section and also don't forget to answer

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the quiz that I asked about why the neon light flashes as opposed to LED that doesn't?

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Whoever gets the answer right,

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will choose the next topic of the next episode.

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We have a lot of videos,

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a lot of equipment to review,

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and a lot of interesting things coming in the future.

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So, make sure you check back,

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subscribe and I'll see you soon.