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This application note states that zero crossing detection can be achieved in an AVR with just a couple of resistors. However, it forgoes galvanic isolation and this is not acceptable for me.

I would like to supply CMOS control signal to a triac, in the same time monitoring mains voltage for zero crossing. Is there an opto device, capable of both these tasks at the same time. Preferably a small, DIP, not exceeding $1 device?

This is an AC input optocoupler:
enter image description here

And this is an optotriac, used for controlling power triacs:
enter image description here

Having them both in a sigle package, pointing in opposite direction, would, IMO, simplify and make cheaper implementation of simple AC load control.

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  • \$\begingroup\$ This question has been answered here before. electronics.stackexchange.com/q/4679/9079 or just search for "zero crossing" - you'll find tons of good info. As for single device, I think you'll have to use two inexpensive optocouplers - one "AC input, open collector output" and one "triac output" \$\endgroup\$ – miceuz Feb 24 '13 at 22:10
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    \$\begingroup\$ @miceuz, from the stevenvh's answer in the pointed thread, I will be needing a special opto-coupler, one with two diods in parallel. My question is further asking if there can be found such a thing, in a combination with a triac output (to drive my triac). I imagine this will be a cheaper and simpler solution than using separate chips. \$\endgroup\$ – Vorac Feb 24 '13 at 22:24
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Yes, there are plenty of optoisolators that can do what you want. Look around at the usual suspects, like Mouser, DigiKey, or whatever your favorite supplier is. There should be plenty to chose from, especially if you can live with a few µs delay.

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I've looked, and I haven't found any devices which combine optoisolators in both directions. You had best use 2 devices.

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