Detecting zero crossing point

Porter

This is a hardware question but i did not know where else to ask.· I'm working on a AC diming project with multipule channels (ok christmas lights).· I need to detect the zero crossing point of the AC line.· I've read Picref-4 but gut feel says AC straight into a uM with just a 20m resistor will set off smoke alarms.· Any help or comments appreciated.

Bean

Porter,
That would work, but it is VERY dangerous. I'd go for an opto-isolator.

Bean

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www.iElectronicDesigns.com

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Porter

I did not like the resistor idea either. and had not realized there is an AC input optoisolator.

Any ideas on a part number.· I looked in Digikey and found MID400 but data sheet says it's for line monitoring and Zero crossing would be ignored.· any suggestions???????????

Shawn Lowe

If alll you want is the product, look at EFX-Tek FC-4 boards.

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Shawn Lowe


Maybe I should have waited to do that......

PJAllen

http://forums.parallax.com/showthread.php?p=693647

Porter

Thanks PJ. thats the type thread i've been looking for.
tried doing a search on zero crossing but nothing came up.

to everyone else thanks i learned a lot with this request

JonnyMac

I created an eight-channel lighting controller for my November column in Nuts & Volts magazine. The relevant files are attached and my prove useful to your project. You'll see in the schematic that the AC and DC sides of the project are isolated from each other for safety.