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Sorry. On the mains input you have two 30 *Kilo*Ohm resistors. How do you calculate this value?
OK, my last question: how do you calculate the 30 Ohm? Motorola's 4n25 takes 60mW / 3V and I have the impression that 47 Ohm is better suited for 230V. Am I wrong?
Yet another question. As you write, the zero-crossing detection consumes ~800mW.For a 365 days / 24h device that is a lot (thinking at the coal or uranium burnt for that). So lets save energy: for the important dim-position "switched off" it might be reasonable to operate mains input by an optocoupler-driven relais that cuts this down to 0mW. Does this seem reasonable to you?
Hi diy_bloke,thank you for this very nice and understandable tutorial. In the circuit diagram it is not absoluetely clear to me: you do well control the phase and not null?I would like to drice an AC motor (for house ventilation) with it. But I am afraid that when switching off, the motor induces voltage that destroys the triac. How can I protect it for such use?
Thank you for the quick answer. "Null" was the new language frenglish (mix or french and english:) I meant neutral phase of course, as you guessed. Although electrically it is unimportant where you switch, one would (at least in Europe) always switch live phase to avoid tension on the machine parts when beeing switched off. I am happy to hear that your circuit allows this. Remains the snubber, I will try to learn this. Thank you!