Light dimmer problem

[FromTheCockpit]

Instead of feeding the mains to the pic pin, drive an opto like the PC814.

This has 2 LEDs in anti-parallel at the input, so you'd get 2 pulses for each mains cycle, one each for positive and negative. This will also give you a bonus of isolating your circuit from the mains.

Regards,

Anand Dhuru

Thanks for the reply. What resistance values normally goes for the opto side of the PC814 and what should be the wattage of this resistance values. I am @ 240VAC

[ardhuru]

I'd used 100K, 1W on 240 VAC.

Reducing the resistance would get you sharper edges, but then one needs a resistance of a higher wattage, so I finally settled on these, and its worked great for me.

[Megahertz]

I wonder if 4n25 can be used the same way?
(with 100k direct to Live and other end to neutral)

[ardhuru]

Looks like the 4n25 has only 1 diode at the input. You'd get only 1 pulse per cycle. If thats acceptable, I dont see why the 4n25 shouldnt work.

Regards,

Anand