How to synchronize acquisiton with the 50Hz power line (detect sine wave zero crossing - 0° phase)

Thread Starter

jean_jean

Joined Apr 2, 2016
10
Dear all,

I have a project that requires (among other things) that I trigger a new acquisition as soon as the 50Hz sine wave from the power line crosses zero (or 0° phase).
I found some ideas on the web using some comparators with OpAmps, but I wanted to know if there are devices already on the market.

Best regards,
Jean
 

AlbertHall

Joined Jun 4, 2014
9,310
There are many references. Search google for 'zero crossing detector'. Some microcontrollers have zero crossing detectors built in - PIC and Atmel for instance.
 

DickCappels

Joined Aug 21, 2008
6,187
The circuit below should work pretty well for zero crossings in one direction. For both zero crossings per cycle you can use to opto couplers and tie the collectors together or "OR" the outputs.

Have to imagine that it would work better without the 1N4148, but people usually add parts for a reason. I suggest that if you try this circuit drive the optocoupler through a transformer for safety's sake.


http://electronics.stackexchange.com/questions/60435/zero-crossing-detector-do-i-really-need-the-7w-resistor

upload_2016-12-5_21-55-27.png
 

Thread Starter

jean_jean

Joined Apr 2, 2016
10
The circuit below should work pretty well for zero crossings in one direction. For both zero crossings per cycle you can use to opto couplers and tie the collectors together or "OR" the outputs.

Have to imagine that it would work better without the 1N4148, but people usually add parts for a reason. I suggest that if you try this circuit drive the optocoupler through a transformer for safety's sake.


http://electronics.stackexchange.com/questions/60435/zero-crossing-detector-do-i-really-need-the-7w-resistor

View attachment 116432
a reason. I suggest that if you try this circ
Hello,
Thank you for your message. I have seen this schematic and it should do the job. I am actually looking for a zero crossing in one direction, as I use the output signal to sync an acquisition card. Also, I will use a 1:1 transformer, as the input signal will be small (it will not be the actual 230V, but from a sensor attached to the 230V line). Any ideas on an actual 1:1 ot max. 5:1 transformer?
Regarding the optocoupler, I was thinking about the Vishay 4N25 (I originally went for the Vishay H11AA1, but it is in both directions, for me 1 direction is fine).

Again, thank you all for your replies.

Best regards,
Jean
 

WBahn

Joined Mar 31, 2012
25,258
The circuit below should work pretty well for zero crossings in one direction. For both zero crossings per cycle you can use to opto couplers and tie the collectors together or "OR" the outputs.

Have to imagine that it would work better without the 1N4148, but people usually add parts for a reason. I suggest that if you try this circuit drive the optocoupler through a transformer for safety's sake.


http://electronics.stackexchange.com/questions/60435/zero-crossing-detector-do-i-really-need-the-7w-resistor

View attachment 116432
Depending on the amplitude of the input voltage, that diode might be very important to prevent a large reverse voltage from destroying the LED.

One concern I would have with this circuit is glitching at the switching points. With a 50 Hz input waveform, the output (which is analog) is going to be changing relatively slowly and so whatever it is driving may see lots of noisy transitions since there is no hysteresis. If nothing else, this should probably be followed by a comparator that has a Schmitt trigger input.
 
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