Why not just use Google, it's been done many times, you can even buy small cheap modules to do the job,
here are some circuits..
https://www.google.com/search?q=det...g&ei=K6lEYfDNC8ig7_UP3sCM0AM&bih=996&biw=1760
Here is a real isolated solution. See the tutorial from Instructables or Youtube
https://www.instructables.com/Contactless-Voltage-Detector/
here are some circuits..
https://www.google.com/search?q=det...g&ei=K6lEYfDNC8ig7_UP3sCM0AM&bih=996&biw=1760
Here is a real isolated solution. See the tutorial from Instructables or Youtube
https://www.instructables.com/Contactless-Voltage-Detector/
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