AC mains measurement

[francis29]

What is the best circuit for AC mains(230V) measurement. The circuit should have output voltage swing between 0-5V for microcontroller input.

 

[schmitt trigger]

If you are not experienced with working with mains- level voltages, the best is to use a small step down transformer. Let's say 230 to 6 volts.

Then with an opamp, make a precision rectifier. Use a resistor divider afterwards to lower the voltage such that the sinewave peak is lower than the 5 volt microcontroller supply. About 20% lower should provide margin for high line conditions.

 

[KlausST]

Hi,

this has been discussend many times here.

This is my preferred solution: https://www.edaboard.com/threads/355515/#post1520931
This is a non isolated solution! Take care about safety!

Klaus

 

[francis29]

what is the rating of transformer?? it is just for sensing right?? so how much small i can make it??

 

[smijesh]

There is no requirements for output current so you can select output voltage 6V and less current transformer. so the size of the transformer will become small.

Try this or less power

https://media.digikey.com/pdf/Data Sheets/Pulse PDFs/BV020-5411.0~5434.0.pdf

 

[BradtheRad]

I built my own house voltage monitor using an inexpensive 'wall wart' type transformer, 7VAC. It drives a simple DC supply. The entire circuit draws less than 100mA. It has a 3914 IC which lights one of 10 led's.

 

[treez]

i think you can get hall sensors specifically for mains measurement too.

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if you are sensing for mains with a transformer and dont need to draw current as such, you still need fairly some size because of the build up of magnetising current.