Ac light dimming using microcontroller

[ammarooo]

Hello,
I want to design a circuit that can control light dimming using microcontroller
I have searched alot and i found 2 ways:

1: use a zero-crossing circuit that can tell the microcontroller when to trigger the triac using
OptoCoupler.
2:using a OptoCouplers that has internal zero-crossing circuit (MOC3063)

https://catcatcat.d-lan.dp.ua/wp-content/uploads/2013/03/forum_illissi02.png


I would like to understand how the second way works.
https://catcatcat.d-lan.dp.ua/wp-content/uploads/2013/03/preview_forum_illissi06.jpg

how to know when to trigger the triac using the internal zero-crossing circuit.
Can it be done using PWM in the microcontroller?

thanks

 

[KlausST]

Hi,

For light dimming you need to trigger the triac every halfwave.
After every zero cross you need to delay the trigger according to your dimming level. The less you delay the brighter the light.

To do that with a microcontroller the microcontroller needs the exact timing of the zerocrossing. Then it internally starts the delay timer, after timeout it triggers the triac.

This all is true for way 1.
**********

In my eyes way 2 is not possible for light dimming.
The optocouplers with zerocross switching are good for switching on or off loads like heaters, valves and so on.
No dimming application.
The switching at zerocross (low voltage) is to reduces emc.

Hope this helps
Klaus

 

[ammarooo]

Thanks a lot for you help.
I was really confused about the second way,that is why I asked this question

I would like to ask you if PWM concept can be applied to AC lights ?
Can the optocouplers with zerocross be used as a relay ?
it would be much smaller and more silent


thanks again

 

[KlausST]

Hi,

Pwm concept for dimming light, but you have to restaert your timer with every zero cross. Exactely.
Or you have to calculate the compare value every zero cross.

Zercross optocoupler: there are zercross trac drivers you should not use. Butvthere are true zerocross triacs you can use.


Klaus