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How to sense mains AC?

johninjax

Hey,

I need to know if a latching SPDT relay is on the A or B side. The relay has a 5V control, but it will have 120VAC on it. I was planning to use a half wave rectifier and RC filter with large R to tap off ~5V into a gate. Am I crazy? Is there a better/simpler way?

 

Thanks,

 

John

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    Well labelling you as crazy is a conjecture at this point. Reducing AC mains to a lower voltage by using a dropping resistor might put you in the running.

     

    I'm not confident I have a full understanding of your circuit. You have a 5VDC powered SPDT latching relay you are going to use/test. You want to tap the AC mains using a dropping resistor, rectify and filter the output to power the relay?

     

    Why not just test the relay contacts for continuity? That can tell you what side is engaged.

  • 0 in reply to johninjax

    Hi John,

     

    Could you explain your actual goal / use-case?

    The trouble is, with the small bit of information, any answer may not be appropriate or may not help you, because the answer can be different based on context.

    Some example things that can usually help (not all may apply):

    1. My Goal in detail

            (e.g. climb a mountain next year)

    2. What things I'm trying to solve

             (e.g. establish how high I am)

    3. What constraints I have

             (e.g. cost, software experience, hardware experience)

    4. What hardware, tools and software I'm using

             (e.g. part number, link to the tools and software)

    5. Diagram or sketch to show the scenario, and what I've attempted

    6. Where I believe the problem lies, or which part I need help on

              (e.g. unexpected response from the part I'm using)

    7. Non-blurry photographs of the set-up (zoomed out for context, and detail), and video if needed

    Non-fuzzy, focussed Overview Photo (for context)

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  • 0 in reply to johninjax

    Hi John,

     

    Could you explain your actual goal / use-case?

    The trouble is, with the small bit of information, any answer may not be appropriate or may not help you, because the answer can be different based on context.

    Some example things that can usually help (not all may apply):

    1. My Goal in detail

            (e.g. climb a mountain next year)

    2. What things I'm trying to solve

             (e.g. establish how high I am)

    3. What constraints I have

             (e.g. cost, software experience, hardware experience)

    4. What hardware, tools and software I'm using

             (e.g. part number, link to the tools and software)

    5. Diagram or sketch to show the scenario, and what I've attempted

    6. Where I believe the problem lies, or which part I need help on

              (e.g. unexpected response from the part I'm using)

    7. Non-blurry photographs of the set-up (zoomed out for context, and detail), and video if needed

    Non-fuzzy, focussed Overview Photo (for context)

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