triac dimmer

[NixoNiiz]

I am stuck in understanding how this circut works, when i press the A key the ligth will dimmer, but im not sure how the triac works, can someone tell me why it dimmers the light? Because when i put the circut into real componentes. The signal on the right side of the lamp follows the input, but goes to 0 when the signal on the left side is high.. How is this posible?

The atatched pdf show how the signals look.

[A.Rohde]

Hi NixoNiiz

I tried you multisim file in version 2012. But I'm not able to get the same results as you looking at the scope

Without A key pressed I can see the graph with the small triangle signals. But With A key pressed (I assume you mean just flip the swith), I only get a a negative 0 volt on the graph. I tried both with the S3 switch on and off. Are you sure you uploaded the right version of maybe I haven't adjusted the scope correctly? 

Best Regards

Anders

[NixoNiiz]

Hello Anders

Thank you for taking your time to look at my problem.The scope pictures aren't from multisim but from a real oscilloscope in the laboratory. I just can't seem to understand why the oscilloscope in multisim won't agree with the one in the laboratory. The scope picture you get is similar to the one i get, but only in multisim.

Another thing is that C1 only charged once, and that's it. But if i remove it the circuit doesn't work. On the scope picture from the laboratory it looks like C1 is charged constantly, but i'm not entirely sure.

Regards Nikolaj