| Electronics > Projects, Designs, and Technical Stuff |
| Isolated mains zero crossing detector: how? |
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| technix:
Since I got that big-ass TRIAC (and I also have a bunch smaller TO-220 and TO-92 ones) I am wondering how to build something with it. I have TRIAC-output optocoupler to drive the gate, now I need an isolated zero crossing detector to control the gate firing time. I wonder if this circuit would work, using a 6N137 optocoupler: (I just have a bunch of them in spare) * Put a 220 ohm resistor in series to the 6N137 transmitter diode, * Put a 5.1V 1W Zener antipatallel to the R-LED series * Put a high voltage high value resistor in series with the circuit above, I am looking at maybe 47k * Put the whole D-R assembly across the mains. Can this produce a square wave at the output of 6N137 with its logic edges corresponding to the zero crossing of the mains? If so I can feed this output to two timers on one microcontroller, with one timer measuring the mains frequency and the other generating the TRIAC firing pulses. |
| langwadt:
could use two optos in anti parallel |
| technix:
--- Quote from: langwadt on November 02, 2018, 03:36:10 am ---could use two optos in anti parallel --- End quote --- Technically yes, but I am a bit troubled at how do I use the two outputs. 6N137 isn’t exactly a cheap component, and I don’t want to let one just go waste. |
| TJ232:
Don't complicate your life, just use an AC opto like SFH620 Details about ZCD implementation, schematic & stuff HERE and HERE. |
| AllTheGearNoIdea:
There are lots of opto coupled Diacs around with zeros crossing detectors |
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