Hello all, What is the difference between the MOC30xx's? I've noticed that some have zero-crossing circuitry built in, and some don't. Since the zero-crossing circuitry doesn't appear to connect to any of the external pins of the MOC30xx chips, what purpose does it serve. I've looked at the datasheets, but I don't see the purpose of the zero cross circuitry. Is it so that when I tell the MOC to turn on, it waits until the next zero-cross before actually turning on it's internal TRIAC, or is there some other reason? I was poking around on the net and thinking that building some type of light dimmer might be fun and educational. I'm far from being expert with analog devices, but I think I have a basic understanding of a TRIAC. Since the circuits I've seen already use a TRIAC (in combination with a MOC30xx) to switch the high voltage, why would the MOC need to know anything about zero-crossing? michael brown (confused) -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads