Im making a simple triac lamp dimmer using an ATtiny. I need some help understanding these AC Input Phototransistor Output Optocouplers! Im looking at some from fairchild: http://www.fairchildsemi.com/sit...
I believe I understand the concept of properly biasing the optocoupler, correct me if im wrong please: You select a current limiting resistor that that works in the range of the specs and indicates a cross as close to the real zero cross as possible.
Taking the H11AA1-M for example:
If max is 60mA. When dealing with US mains you have a max of 172V, which we will safety factor to 190V. So I will pick a current limiting resistor for the emitter to keep current below 60mA, in this case a 3.1k resistor. What I don't understand is how to determine from the spec sheet at what current the emitter essentially shuts off, giving me my zero crossing signal. With a 3.1k resistor at 31 volts the current is 10mA.
Another thing that im not sure about is for 190v at 60mA that's 11.4W of power. That's a damn big resistor.