Hi guys,

I received this schematic from my friend, but there's no further explaination. I'm a newbie to electronic stuff, so I need help about this one. So far, I built it 'n everything just fine, although I know from this forum that it's dangerous to light up LEDs directly to main power grid without transformer.

What is the function of RC parallel in the blue box? And what is the formula to calculate their value?

Thanks...

 

The circuit is simply too dangerous to use. Use a wall transformer to power the LED's.

We do not discuss line powered circuits.