Hi friends, how are you?
in this video we are going to recover a circuit of that series "useful circuits"
it was the "useful circuits # 2", a power regulator for A.C. in 220V and also 125V, actually for any voltage less than 300 Volts
that circuit could govern up to almost 4 KW (depends on the triac used)
but that video had a lack: To have available a layout, to easily make the PCB either with exposure box or with the ironing method
with this video today I will solve that lack, I will make the layout, to disclose it...
and above all, I'll check that the layout is 100% error-free and so you can trust it to build your own circuit
Let's look at the electronic scheme of this circuit that is basically the same as the first video
The main part of this circuit is the Triac
through the triac will circulate the current that we put in the input, and this is the regulated output ...
the main circuit is this, a high current can flow through here. Everything else in the circuit is low current
here we will put a fuse, to protect the circuit
when the triac triggers through the diac,
the triac will conduct the current, both in one direction and in the other. Remember that it is not a thyristor, it is a triac, so it drives in both directions
these graphs show how the triac will behave depending on the position of potentiometer P1
this is an R-C circuit, where the capacitor C2 is gradually charged
with a certain speed
which will depend on the resistance value of this resistor, which is variable (potentiometer)
suppose that P1 is now selected at a very high resistance value
that would correspond to this drawing
C2 takes a long time to load, and it will also take time for the impulse to reach the triac gate since the Diac needs to see a certain voltage value exceeded
we see that when the positive half-cycle arrives at the anodes of the triac, it does not conducts, until it reaches...
...the moment of the shot (represented by this vertical line) and we see that the triac only conducts this small portion of time.
this would correspond to a regulation to "minimum power", that is, the device that we put at the output would work very weak or nothing
all that is said also applies to the negative half cycle of alternating current
if on the contrary...
we adjust the value of P1 to a minimum resistance value ...
now the current that passes through the R-C circuit will be greater, and C2 will load faster, in less time
this corresponds to this graph, as soon as the positive half-cycle begins, the triac is triggered, and the conduction corresponds to this shaded area in the drawing, which, as you can see, represents almost all the power
it can be seen that voltage is not actually regulated, no current is regulated, but actually it is TIME that is regulated: The time it takes to charge capacitor C2
Well, after using different tools, equipment and techniques that you already know, an idea has become a real object
the PCB is already assembled and ready
before testing it I want to comment on three issues in case you want to build this circuit
first: Heat sink. Inside or outside the PCB?
I have chosen the option to incorporate it into the PCB, I see it more compact and simple
the only drawback is having to use a slightly larger PCB, but it's not a problem since we talk about very little money. This saves us having to pull three cables from the PCB to the triac
Second issue: Fan and thermostat
in the first video I put a thermostat attached to the heatsink
if the heatsink exceeded a certain temperature, the thermostat would close and start a fan facing the heatsink, and cool it
but we saw that this was not really necessary because the heatsink was barely warming up.
therefore, this time I will dispense with fan and thermostat although I have planned the components in case someone does want to include them
Here we have the position for these two connectors, one for the fan, another for the thermostat
You will also have to put this jumper in case you are going to use a fan and thermostat, represented by this dashed line
third issue: potentiometer P1
we can put P1 directly on the PCB since the distance between its pins is the same as the blue connector you are seeing
in this case the PCB should also be fastened, otherwise its weight would be excessive for the potentiometer
Another option for the potentiometer is the one I have adopted: A three-way connector on the PCB, and with three cables we connect it
Well, that's what I had to say. We're going to try it
all arranged, as when I tried it on the breadboard, except for this tester configured as a thermometer, with the probe placed on the heat sink of the triac
This is the temperature right now, by the way, what a winter !: I have 22ºC at home, in December, and without turning on the heating
Look how sensitive is the thermal probe, that just by touching it with my hand the tester quickly accuses the temperature
now as I have withdrawn my hand, the temperature drops ...
OK, I connect the current, 220V
as potentiometer P1 is at minimum (maximum resistance), the lamp does not shine
we are turning P1 ...
the lamp will start to shine a little ...
that is, well, very little ...
we are regulating P1 and the brightness increases continuously
right now, at its maximum: 100W
Now I will regulate in the opposite direction, and the brightness decreases. That is, this works
This is precisely what I wanted to check with this video and with this montage: That the layout is correct and has no errors
now I set it to maximum (100W) and ... the temperature of the heatsink does not rise
these 100W are far from the 3800W that the circuit can handle, but 100W is already enough, and the temperature does not rise one degree
but if I touch with my hand ...
then the temperature rises
when released, the temperature drops again. I do not think it is necessary to fan and thermostat, it will suffice with the own heatsink
I'm not going to do a series of tests with different loads because the intro of this video was just that: A series of tests
I remind you that in the description of this video there are several links that take you to very useful documents if you want to build this circuit: Layout, diagram, list of components, measures of the heatsink ...
and that's all friends, see you in the next video
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