Electronics > Projects, Designs, and Technical Stuff
Isolated mains zero crossing detector: how?
(1/5) > >>
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
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod