AC Load control using infrared and microcontroller

Hi, i am new in this forum. i am a 3rd year electrical engineering student and trying to build a voltage controller using triacs, microcontroller and a tv remote. but i am facing problem in isolating the ac from dc without using relay and how to control triac using 5V dc signal.
Could anyone please help me on this problem?

Try looking up 'opto-isolator', you can even get them with zero-crossing detectors built in.

Thank you, Nigel. I am trying to vary the speed of fan using microcontroller. how can i change the resistance of variable resistor?
**broken link removed**
can we use moc3020 for just switching instead of relays?