Myren
Newbie level 2
zero cross detector
i need some way to let my microcontroller know when a zero cross occurs, otherwise i cant keep phase with my little light dimming project.
i saw plans for using a 4n25 (the most primitive of optocouplers: merely a transistor pretty much), but i havent had much luck actually making it go. it pretty much just hooks the LED input up to the AC line then uses a pullup resistor off 5v on the other side to detect.
it triggers alright, but at ~60 khz, which just aint right.
been looking at some solutions: HCPL-3700 seems the best so far for its simplicity, and i /think/ it'll do what i want it to. the On semiconductor ca3059 and intersil fn490 both seem designed for what i want to do, plus a whole helluva ton more... major overkill. i'm afraid to even go check prices on them.
Myren
i need some way to let my microcontroller know when a zero cross occurs, otherwise i cant keep phase with my little light dimming project.
i saw plans for using a 4n25 (the most primitive of optocouplers: merely a transistor pretty much), but i havent had much luck actually making it go. it pretty much just hooks the LED input up to the AC line then uses a pullup resistor off 5v on the other side to detect.
it triggers alright, but at ~60 khz, which just aint right.
been looking at some solutions: HCPL-3700 seems the best so far for its simplicity, and i /think/ it'll do what i want it to. the On semiconductor ca3059 and intersil fn490 both seem designed for what i want to do, plus a whole helluva ton more... major overkill. i'm afraid to even go check prices on them.
Myren