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Energy power metering circuit with ADE7753 problem

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harmoncia

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Hello,

I'm trying to build a power consumption meter using ADE7753. I've designed a circuit (see the picture), made PCB and put it all together. First of all, I tried to run the circuit from external 9 V battery, to see if ADE is ok. It was, so I've programmed driver for it for my ATmega. Then I've wanted to try some measuring. Measuring circuit was still powered by external 9 V battery and ATmega circuit was in bread board powered by it's external PSU. ADE7753's energy register was shown on LCD connected to ATmega. Everything was set to start measure. So I've connected 230 V input mains (phase and neutral) and no load was connected and some shortage happened in my circuit. Resistors R1 and R2 are burned and ATmega is probably dead. Do you have any ideas how could this happened? Power circuit was not closed (no load). Any ideas? Thanks for answers.

Circuit image
 

FvM

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To work correctly, the circuit would need a jumper between the mains N terminal and AGND.

You're operating the energy meter chip without isolation from mains voltage. So all circuit parts connected to it, e.g. the microcontroller are carrying 230V mains voltage. They must not be touched and can't be connected to other equipment (oscilloscope, computer) without respective isolation. Alternatively, the mains connection can be made through a safety transformer for test purposes.

But I don't know what's your isolation concept for the energy meter. It's a basic project question, that should be answered at the very beginning.
 

harmoncia

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Ok, thank you. So if I get correctly what you mean, you suppose to connect N and AGND together. However wouldn't it be causing problems when AGND is connected to GND and GND is digital ground from 7805, which is supposed to power MCU?
 

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