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AC Line Monitor and/or Opto Coupler (need for 3.3v board)

Hi. I am looking for a component that will alow me to bring a "hot"

230v (but also less, down to 10v) on to my microcontroller board by detecting the presence of the signal, isolating it, and converting it to DC logic. I thought of using a "standard" opto coupler, but understand there are some dedicated components for this application? (AC Line Monitor?). Some of my signals are just change in state of a line (i.e. 230v present or not, and the changes are long in between) while others are up to 200KHz signals.

Specifically, I am looking for a component that would work good on my

3.3v board (I found one for 5v but I want to use only 3.3v).

Thanks!

Reply to
ElderUberGeek
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I used a Fairchild MID400 for 120VAC. The output is an open-collector transistor.

Reply to
hsbrooks

Would it work for 230VAC? Yes, I have seen the MID400 and strangely enough could not find any other type of product like it on the market! (I think this is not likely.... I must not be looking in the right place or using the right name). Any other component suggestions? (By the way, the MID400 is 5v and I am actually re-thinking my 3.3v strategy....)

Reply to
ElderUberGeek

I'm not sure I understand the kind of signals you want to detect. Is it just

230V/50Hz mains? What about the 200kHz? Anyway, I use an SFH620A (Vishay, Infineon) to detect presence of 230V mains voltage in a 3.3V uC system. Series resistors (you'll want 2 of them in series!) values depends on what you can afford, power-wise. Higher values will cause a longer dip at the zero-crossings. HTH

Steven

Reply to
steven

These are called AC optocouplers, but you could also use any Dual-opto coupler, with the outputs paralleled, and IP diodes back-back. Or a single jellybean opto, with an external bridge. In all cases, the external resistor takes the mains voltage, so any voltage is possible, but watch the power and voltage rating of the resistor. The thresholds of optos are not tightly controlled, so expect some variations in the actual edge-voltage, and some small skew on the two half cycles. If you want actual zero crossing sense, the MID400 is poorly spec'd for that.

The simplest Transistor optocouplers do not care about 3.3V or 5V.

Reply to
Jim Granville

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