Hi all,

I like to design an energy meter, for that I need to choose the protection circuits for the voltage & current sampling circuit. Please give any suggestions on how to choose components for the protection circuits. Here I attached the reference design from Microchip IC ATM90E32AS.

 

Microchip’s circuit assumes that your microcontroller is operated connected to the mains with its 0V terminal connected to neutral.
If you wish to use a microcontroller that is earthed, I suggest you isolate the voltage inputs using transformers, and use current transformers for the current inputs.
if you are happy with your microcontroller “live” then Microchip‘s circuit gives adequate protection, but bear in mind that anything else connected to the microcontroller has to comply with all the necessary safety requirements that apply to live parts.

 

Microchip’s circuit assumes that your microcontroller is operated connected to the mains with its 0V terminal connected to neutral.
If you wish to use a microcontroller that is earthed, I suggest you isolate the voltage inputs using transformers and use current transformers for the current inputs.
if you are happy with your microcontroller “live” then Microchip‘s circuit gives adequate protection, but bear in mind that anything else connected to the microcontroller has to comply with all the necessary safety requirements that apply to live parts.

We can use CT & PT also but Is this protection Circuit is also required for the IC Protection. Any Idea

 

Hi,
Anyone give suggestions about how to choose components for the protection circuits.

 

If your circuit is connected to earth and isolated from the mains by transformers, then you don't need any. The 1k resistors and capacitors will limit any voltage spikes resulting from surge currents through the transformers, and the series resistors on the voltage inputs (which will be on the secondaries of the transformers) will, along with the transformers, remove any transients that have originated on the mains.