ABSOLUTELY ! I agree totally with Abdul !

Rovan.
If you have a supply from a transformer creating your 5V rail, the supply floats relative to gnd. You need to tie the gnd to the triac MT2 or MT1 terminals somehow. I DO NOT recommend direct connection. The CPU then sits at LETHAL potential to gnd, and you will usually destroy your oscilloscope if you try and fault find with it.

You could use a pulse transformer to trigger the triac, but this is an electronics issue you will have to address yourself, as I am not prepared to accept liability.

Steve