0:00:00.230,0:00:03.405
>> So, here's a circuit for the flash.

0:00:03.405,0:00:05.820
So, in order for you to understand how this works,

0:00:05.820,0:00:08.520
you need a little bit of electronics background.

0:00:08.520,0:00:10.965
But I'm going to do my best to try and explain

0:00:10.965,0:00:14.250
at least intuitively how this circuit works.

0:00:14.250,0:00:16.770
So, here's the single transistor I was telling you about.

0:00:16.770,0:00:19.035
Here, the three resistors,

0:00:19.035,0:00:21.150
one is here, one is here,

0:00:21.150,0:00:22.890
and the other one is right there.

0:00:22.890,0:00:26.445
I told you that there is a big electrolytic capacitor. That's this one.

0:00:26.445,0:00:29.690
I said there is a neon electrolytic aluminum foil one.

0:00:29.690,0:00:30.965
That's this one right here.

0:00:30.965,0:00:33.125
I said there are two transformers,

0:00:33.125,0:00:34.550
here's the first transformer,

0:00:34.550,0:00:36.100
here is the second transformer,

0:00:36.100,0:00:37.920
here's the neon flash shoot.

0:00:37.920,0:00:39.600
That's the thing that flashes.

0:00:39.600,0:00:42.465
I'm sorry, not the neon just a regular flash.

0:00:42.465,0:00:44.265
Here is a little neon bulb.

0:00:44.265,0:00:46.170
In the one that I just showed you,

0:00:46.170,0:00:47.325
this was an LED,

0:00:47.325,0:00:49.755
but it doesn't really matter, the concept is the same.

0:00:49.755,0:00:51.900
So, sometimes they use the neon one here.

0:00:51.900,0:00:53.790
Here's the trigger switch,

0:00:53.790,0:00:55.590
then when you close the flash fires,

0:00:55.590,0:00:59.535
here's the on and off switch. Let's go through this circuit.

0:00:59.535,0:01:03.000
So, at the beginning the on and off switch is open.

0:01:03.000,0:01:05.735
So, let's forget about everything that's on this side of the circuit.

0:01:05.735,0:01:07.340
If this switch is open,

0:01:07.340,0:01:09.950
and there is, therefore,

0:01:09.950,0:01:11.120
no current going through the base,

0:01:11.120,0:01:12.425
there is no voltage on the base.

0:01:12.425,0:01:15.370
So, this bipolar transistor is turned off,

0:01:15.370,0:01:17.030
so there is no current going down.

0:01:17.030,0:01:19.445
As soon as you close the circuit,

0:01:19.445,0:01:21.620
you can follow this connection.

0:01:21.620,0:01:24.140
It goes through somewhere in the middle of the transformer and is

0:01:24.140,0:01:26.630
connected to all the way up to 1.5 volts.

0:01:26.630,0:01:29.420
So, you will bring some current and

0:01:29.420,0:01:32.735
some voltage close to 1.5 volt at the base of this transistor

0:01:32.735,0:01:35.630
which will quickly turn this transistor on

0:01:35.630,0:01:39.110
causing a large current to go down from the collector to the emitter.

0:01:39.110,0:01:41.950
Now, as soon as you induce a current,

0:01:41.950,0:01:45.900
to go through this half of the transformer,

0:01:45.900,0:01:52.005
this itself will cause a current to be induced on the other half of the transformer.

0:01:52.005,0:01:53.605
But as soon as you do that,

0:01:53.605,0:01:56.090
the current in here will then lower the voltage of

0:01:56.090,0:01:58.820
the base to go down to even below zero.

0:01:58.820,0:02:01.430
So, then the transistor turns off again.

0:02:01.430,0:02:06.140
But when a transistor turns off this voltage will then eventually go

0:02:06.140,0:02:08.389
back all the way up to 1.5 volts because the

0:02:08.389,0:02:11.060
current will stop, and then the transistor will turn on again.

0:02:11.060,0:02:14.120
So, this transistor turns itself on and

0:02:14.120,0:02:18.335
off through this feedback path in the transformer.

0:02:18.335,0:02:20.810
So, you could say that this portion of

0:02:20.810,0:02:24.020
the circuit is essentially nothing more than an oscillator.

0:02:24.020,0:02:27.710
So, by turning the transistor on and off quickly,

0:02:27.710,0:02:30.360
you can induce a current in the transformer.

0:02:30.360,0:02:33.560
Now, this center tab brings back a small voltage.

0:02:33.560,0:02:35.900
It means that the entire voltage across

0:02:35.900,0:02:39.440
the transformer does not appear at the base of this transistor.

0:02:39.440,0:02:41.990
If it did, the transistor would die.

0:02:41.990,0:02:46.610
So, they've taken only a part of that voltage down to the base of the transformer.

0:02:46.610,0:02:49.985
But the whole transformer has a huge turn ratio.

0:02:49.985,0:02:53.450
By that I mean, if you look at this circuit again,

0:02:53.450,0:02:56.640
you can only see the outer coil,

0:02:56.640,0:03:01.785
the outer coil of this transformer and I can count it has about six or seven turns only.

0:03:01.785,0:03:05.600
That coil on the outside that you can see, that's this one.

0:03:05.600,0:03:12.690
On the inside below that yellow tape is a whole bunch of other turns of this transformer,

0:03:12.690,0:03:17.330
maybe about a thousand or a hundred times more than what is on the outside.

0:03:17.330,0:03:20.150
So, that will cause a huge voltage difference

0:03:20.150,0:03:23.450
between the primary coil and the secondary coil of the transformer, and

0:03:23.450,0:03:30.035
that's how you are able to generate such a higher voltage using only a 1.5 volt supply.

0:03:30.035,0:03:33.230
So, they take the high voltage portion

0:03:33.230,0:03:36.335
of the output of the transformer and they connect it to this diode.

0:03:36.335,0:03:39.840
They do that for a very specific reason.

0:03:39.840,0:03:42.935
It's because the signal that appears here is AC.

0:03:42.935,0:03:45.095
It's AC, why? Because it's an oscillator.

0:03:45.095,0:03:47.150
Because it turns on and off constantly.

0:03:47.150,0:03:54.240
That AC voltage will go below zero by several 100 volts every time on this down cycle.

0:03:54.240,0:03:57.650
This diode will only conduct current when

0:03:57.650,0:04:00.860
the voltage on this side is lower than the voltage on this side.

0:04:00.860,0:04:04.450
So, every time this voltage goes well below zero,

0:04:04.450,0:04:07.580
this big capacitor, which is the main capacitor of

0:04:07.580,0:04:11.240
the flash gets charged a little bit more.

0:04:11.240,0:04:15.500
So, every time during every oscillation cycle you will

0:04:15.500,0:04:20.269
put a little bit more charge into this big capacitor.

0:04:20.269,0:04:23.450
So, the voltage at the output of the capacitor is a DC voltage

0:04:23.450,0:04:26.840
but the voltage on the other side of the diode is an AC voltage.

0:04:26.840,0:04:30.470
So, you essentially have built what's called a peak detector,

0:04:30.470,0:04:31.610
where you'll keep dumping

0:04:31.610,0:04:34.010
more and more and more voltage charge

0:04:34.010,0:04:37.745
into this capacitor and the capacitor begins to charge up.

0:04:37.745,0:04:40.340
We will take a look at it under a oscilloscope so we can

0:04:40.340,0:04:42.410
see the oscillation very clearly.

0:04:42.410,0:04:48.760
So, this guy will then eventually charge up to minus 350 volts.

0:04:48.760,0:04:51.260
The reason I say minus 350 volts is because

0:04:51.260,0:04:53.950
I'm measuring everything with the respect to the ground of the battery.

0:04:53.950,0:04:56.775
So, if you assume that this is a zero volts,

0:04:56.775,0:04:59.500
every time this thing spikes well below zero,

0:04:59.500,0:05:00.980
the diode conducts and

0:05:00.980,0:05:03.950
the positive terminal of the capacitor is actually connected to ground.

0:05:03.950,0:05:08.005
So, this knot can go all the way down to minus 350 volts.

0:05:08.005,0:05:09.885
The other side of this now,

0:05:09.885,0:05:11.690
there's a whole bunch of other circuits that is

0:05:11.690,0:05:14.570
responsible for actually triggering the flash.

0:05:14.570,0:05:16.630
So, there's a big resistor that

0:05:16.630,0:05:20.030
separates this half of the circuit from this half the circuit.

0:05:20.030,0:05:22.810
So, this is a big capacitor here that's charged up,

0:05:22.810,0:05:26.780
and that capacitor is connected on one side of the flash tube,

0:05:26.780,0:05:29.035
the other side of the flash tube is grounded.

0:05:29.035,0:05:33.290
On this side here we have the neon light or the LED,

0:05:33.290,0:05:34.760
and a big resistor in series.

0:05:34.760,0:05:40.265
So, if this voltage gets high enough, meaning when the flash is ready to be fired,

0:05:40.265,0:05:43.820
the light turns on, it's just an indicator to let you as the user

0:05:43.820,0:05:47.545
know that the flash will fire once you push the shutter button.

0:05:47.545,0:05:51.135
So, this portion of the circuit is only an indicator.

0:05:51.135,0:05:55.190
Then you have another capacitor here much smaller than this one that will

0:05:55.190,0:05:59.430
charge to about the same voltage as this capacitor.

0:05:59.430,0:06:02.120
So, as time passes and the flash is charged up,

0:06:02.120,0:06:04.280
slowly current will flow through here and charge

0:06:04.280,0:06:06.605
up this capacitor to the same voltage as this one.

0:06:06.605,0:06:08.150
This is a much smaller capacitor,

0:06:08.150,0:06:12.010
and here's the triggers switch on the other side and another transformer.

0:06:12.010,0:06:15.440
So, the way that flash tube works is that even though we are

0:06:15.440,0:06:18.890
putting zero volts here and minus 350 volts here,

0:06:18.890,0:06:21.880
that's not enough to initiate the flash,

0:06:21.880,0:06:26.750
because the potential is not big enough for a spark to form inside the flash tube.

0:06:26.750,0:06:28.205
So, you need to kick it.

0:06:28.205,0:06:29.840
You need to initiate

0:06:29.840,0:06:35.080
it for the current to start flowing and once the current starts to flow,

0:06:35.080,0:06:37.490
then the path, the short-circuit happens in the middle of

0:06:37.490,0:06:39.890
the flash, and then you get the flash which is a spark.

0:06:39.890,0:06:42.800
So, in order to kick it and initiate the current,

0:06:42.800,0:06:44.300
you need to put a very,

0:06:44.300,0:06:46.010
very large voltage, in this case,

0:06:46.010,0:06:50.870
a very large negative voltage right here to dry the electrons into the tube.

0:06:50.870,0:06:54.530
Once you dry the electrons in the tube, then you will fire the flash.

0:06:54.530,0:06:58.250
This is done through this transformer and this capacitor.

0:06:58.250,0:07:00.605
So, if I close this circuit quickly,

0:07:00.605,0:07:06.530
which is done by connecting these two wires together very briefly,

0:07:06.530,0:07:10.340
it will discharge this capacitor through

0:07:10.340,0:07:14.150
this inductor half of the transformer and to ground.

0:07:14.150,0:07:16.700
So, there will be a burst of current,

0:07:16.700,0:07:20.090
a lot of it but for a very short time right through

0:07:20.090,0:07:23.595
this transformer which will then cause even a bigger,

0:07:23.595,0:07:25.950
because this transformer has a big turn ratio,

0:07:25.950,0:07:27.770
a bigger voltage on the other side.

0:07:27.770,0:07:30.590
So, for a very brief time,

0:07:30.590,0:07:33.920
something close to minus 2,000 volts appears

0:07:33.920,0:07:37.670
here for a very short time and that initiates the flash,

0:07:37.670,0:07:39.530
causes the electrons to be drawn into

0:07:39.530,0:07:42.155
the tube and all the way to the other side and to ground,

0:07:42.155,0:07:44.600
and then you get the big bright light that you see.

0:07:44.600,0:07:47.900
So, this entire circuit is everything that's on this.

0:07:47.900,0:07:52.610
I haven't omitted anything that is on this circuit that you just saw.

0:07:52.610,0:07:54.680
So, by looking at this,

0:07:54.680,0:07:57.500
we should be able to make some predictions well,

0:07:57.500,0:08:00.805
we should be able to put our oscilloscope at this node,

0:08:00.805,0:08:03.670
and look at the waveform that I told you.

0:08:03.670,0:08:07.520
We should be able to measure a very large negative voltage at this node.

0:08:07.520,0:08:10.630
Of course, we should be able to see this light turn on.

0:08:10.630,0:08:12.450
We will do all of those things right now,

0:08:12.450,0:08:15.950
and we'll also take a look at how you would measure something like that.

0:08:15.950,0:08:17.450
Then, at the very end,

0:08:17.450,0:08:19.550
we'll see how we can use this in

0:08:19.550,0:08:23.190
combination with a Nixie tube and do some experiments there.

0:08:23.510,0:08:26.520
So, in order to make the experiments safer,

0:08:26.520,0:08:29.325
I've taken one of these flash and I've removed

0:08:29.325,0:08:32.655
the components that I don't need to and I have some wires to it.

0:08:32.655,0:08:34.830
So, it can be easily connected to a power supply,

0:08:34.830,0:08:37.485
and we can measure currents and voltages and so on.

0:08:37.485,0:08:40.210
So, for example these battery holders, I don't need,

0:08:40.210,0:08:42.700
I'm not going to be using the flash itself

0:08:42.700,0:08:45.730
anymore because I want to use it for Nixie tube,

0:08:45.730,0:08:48.760
so I can remove that and sought of some wires to it so then,

0:08:48.760,0:08:52.300
I ended up with something that looks like this.

0:08:52.300,0:08:55.435
So, exactly the same circuit, everything is the same.

0:08:55.435,0:08:57.805
I've removed the flash, the capacitors there,

0:08:57.805,0:09:00.925
and you can see this one actually uses a,

0:09:00.925,0:09:03.125
this thing will focus.

0:09:03.125,0:09:06.030
This thing uses a little neon tube as

0:09:06.030,0:09:09.030
opposed to an LED to tell you when the flash is charged.

0:09:09.030,0:09:11.520
So, a little bit different but it's the same circuit.

0:09:11.520,0:09:14.715
I have also connected a piece of metal size,

0:09:14.715,0:09:17.600
a piece the metal across the on and off terminal,

0:09:17.600,0:09:20.440
to permanently keep it in the on position.

0:09:20.440,0:09:25.240
So, this would make it a little bit easier for me to do some experiments with it.

0:09:25.240,0:09:30.590
I've also removed the low trigger and put a jumper there in its place.

0:09:30.660,0:09:33.520
Wire that I inserted through, this wires is just

0:09:33.520,0:09:36.130
that across the plus and minus terminal of the flash.

0:09:36.130,0:09:38.605
I can connect this to my power supply,

0:09:38.605,0:09:43.480
and then we can check to see what is the voltage on the capacitor?

0:09:43.480,0:09:44.960
How long does it take to charge that?

0:09:44.960,0:09:47.740
Then we will do one discharge cycle by short circuiting

0:09:47.740,0:09:50.890
the capacitors which is not recommended, just for entertainment.

0:09:50.890,0:09:54.430
Also, then we will show you the wave from the oscilloscope,

0:09:54.430,0:09:56.770
and then we'll get to the Nixie tube.

0:09:56.770,0:09:58.750
So, let's see what I can do.

0:09:58.750,0:10:03.565
So, I'm going to take the positive and the negative terminals.

0:10:03.565,0:10:07.795
I'm going to connect them to my power supply.

0:10:07.795,0:10:09.670
So, here's a positive,

0:10:09.670,0:10:12.640
here is a negative terminal, so I'll put that down.

0:10:12.640,0:10:17.170
I will take the positive and the negative terminal of the multi-meter.

0:10:17.170,0:10:19.510
I'm going to connect it across the capacitor.

0:10:19.510,0:10:24.130
So, I'm going to connect a negative toward the ground of this power supply would be.

0:10:24.130,0:10:27.280
That's the positive terminal of the capacitor,

0:10:27.280,0:10:33.220
and I will take the other wire and connected to negative terminal of the capacitor.

0:10:33.220,0:10:38.620
So, what I'm doing here is that I'm using my power supply to power the flash.

0:10:38.620,0:10:41.740
I am measuring the voltage across the capacitor directly.

0:10:41.740,0:10:45.175
You will be able to move this side away,

0:10:45.175,0:10:53.665
you will be able to see at the same time the voltage that I'm applying to the flash unit.

0:10:53.665,0:10:56.290
You will be able to see a current that the flash unit takes.

0:10:56.290,0:10:57.445
It will show up right here,

0:10:57.445,0:11:00.430
and you will be able to see the voltage across the capacitor.

0:11:00.430,0:11:05.845
So, right now the voltage across the capacitor is minus 5.2 volts approximately,

0:11:05.845,0:11:08.380
it's the residue from the last time that I charged it.

0:11:08.380,0:11:10.030
So, let's do that.

0:11:10.030,0:11:12.070
I'm going to turn the power supply on.

0:11:12.070,0:11:15.925
So, right now it says zero volts at zero amps. Is that makes sense?

0:11:15.925,0:11:20.020
I'm going to slowly raise this voltage at all the way up to 1.5 volts,

0:11:20.020,0:11:24.205
and since I have already started the on and off button shut,

0:11:24.205,0:11:25.825
it will start charging right away.

0:11:25.825,0:11:27.280
So, at the very beginning,

0:11:27.280,0:11:28.750
up to about 0.5 volts,

0:11:28.750,0:11:32.800
you will get nothing because its bipolar transistor hasn't turned on yet.

0:11:32.800,0:11:37.030
So, as soon as you go about 0.6 volts, right there, now,

0:11:37.030,0:11:41.140
the flash is starting to charge up the capacitor and you can see the voltage here

0:11:41.140,0:11:45.295
is already on minus a 115 volts and it keeps rising slowly.

0:11:45.295,0:11:47.155
Minus a 123 votes,

0:11:47.155,0:11:49.045
but this is only a 0.6 volt.

0:11:49.045,0:11:52.810
An alkaline battery, a double A battery can go all the way up to 1.5.

0:11:52.810,0:11:58.195
So let's do that, 1.5 volts.

0:11:58.195,0:12:00.850
We'll wait a little bit until this thing charges.

0:12:00.850,0:12:04.615
You can see draws a lot of current at the beginning of is drawing almost an Amp.

0:12:04.615,0:12:07.765
So, right now the current keeps going down.

0:12:07.765,0:12:09.640
So, that makes sense of course because the current

0:12:09.640,0:12:11.800
keeps going down because the capacitor keeps charging.

0:12:11.800,0:12:13.345
So, resists loading on it.

0:12:13.345,0:12:20.530
At the same time, you can see the voltage appear now is at 324 minus 326-7 volts.

0:12:20.530,0:12:24.835
If I turn this, I have to be very very careful handling this nap very very careful.

0:12:24.835,0:12:26.710
So, if I shift it over,

0:12:26.710,0:12:28.735
you can see that little light flashing.

0:12:28.735,0:12:31.300
That's the little neon light I was telling you about.

0:12:31.300,0:12:33.775
Let me bring it up a bit closer to the camera.

0:12:33.775,0:12:36.710
Hopefully, we'll focus on it.

0:12:38.130,0:12:42.940
Well, you can see the neon flash going on and off.

0:12:42.940,0:12:49.585
There is actually a little quiz in this episode that I like to see

0:12:49.585,0:12:52.390
you guys try and discuss it on

0:12:52.390,0:12:56.590
the forum or on the comments sections of the YouTube channel.

0:12:56.590,0:12:58.420
The question I have for you is,

0:12:58.420,0:13:01.675
can you tell me why does this light flash?

0:13:01.675,0:13:04.360
I can tell you that in the LED version,

0:13:04.360,0:13:06.070
if I were to replace this with an LED,

0:13:06.070,0:13:07.900
the LED would not flash.

0:13:07.900,0:13:10.705
So, let me know why you think this is flashing.

0:13:10.705,0:13:13.075
So, let's put this down.

0:13:13.075,0:13:18.775
So, now I have charged the capacitor to minus 350 volts.

0:13:18.775,0:13:24.640
There's still some about 296 milliamps of current going through it.

0:13:24.640,0:13:26.665
If you leave this for a while longer,

0:13:26.665,0:13:29.290
it's not going to go much more than that.

0:13:29.290,0:13:31.360
It's going to go about minus 358 volts.

0:13:31.360,0:13:33.265
Its probably going to have it around that point.

0:13:33.265,0:13:36.160
So, now that capacitor is fully charged, so

0:13:36.160,0:13:37.960
what I'm going to do is,

0:13:37.960,0:13:40.975
I'm going to turn the power supply off.

0:13:40.975,0:13:43.315
So, there's no more current going in it.

0:13:43.315,0:13:46.720
You can see this voltage will start to slowly fall for

0:13:46.720,0:13:50.665
many reasons that the flashing light is of course is consuming some power,

0:13:50.665,0:13:52.840
there's leakage through the capacitor and so on.

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So, that voltage will continue to go down.

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So, let me get something to discharge it.