Iinterface with a microcontroller, a AC load.

Hi. Now, let us see how we interface with a microcontroller, a AC load. Here we have an Optocoupler MOC3041. It could be 3042, 61, 63. They are the Optocouplers with zero voltage crossing. So, in the event of using this IC from the microcontroller, we have connected one LED in series to understand that while this goes high, the current, while the current flows through this route, this LED will glow indicating that our circuit is working as far as the input to the Optocoupler is concerned. This may or may not be used but this gives a good indication that the current is flowing through the internal LED of the Optocoupler. This is the internal LED of the Optocoupler. Since this is an IC and we are not able to see the light of this LED which will be ultimately falling on this TRIAC to make it conductive.

And let’s come again. So, when we make this high, the current will flow this way, this way, this way and this way and complete the circuit. And in that process, this light will fall on this. And once this light fall on this, this main circuit closes. Main circuit closes means, how the supply will flow from here and from, say, this is positive cycle, so, this side is positive. So, positive goes this way, passes through this way. It cannot go this way because the gate is not triggered. So, it goes this way and reaches here and conducts this way only if the light is falling from here to here. So, it conducts this way, comes this way, this way, passes through the gate and M1 terminal, we call it M1 terminal and to the neutral. Then only, the main current flows this route. Until we fire the gate, the main current will not flow.

Now we will see that how, if we suppose disconnect this line, ok, let me disconnect this line. And see, when I give power to it, lets see what happens. AC supply is available. I make it one, I make it one, the current flows through this, internally this light falls on this. But the path is not complete. So, the gate is not triggered, the lamp is not glowing, right? And we join it again, join it again and see, in this situation, once we power this and if I make it 1, you find this lamp is glowing. I make it 0, the lamp is off. I make it 1, the lamp is glowing. I make it 0 the lamp is off. This is how a TRIAC is used in series with the supply and the lamp, interface to the microcontroller. (Video)