PIC USB ADE7753 Ground Problems

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markdem

Joined: 16 May 2006
Posts: 33

03 May 2008 5:14 usb ground problem

Hi All, I have now got my energy meter working using the ADE7753, almost.
The last problem I have is that I want to use USB as the interface to the meter.
However, the problem is, because the ground for the meter is tied to neutral on the 240VAC side to make the ADE7753 work, and the USB connector needs to also be connected to the ground of the meter, I am getting USB connected directly to the neutral 240VAC. As soon as I connect the USB cable, the RCD (GFCI for you not in Australia) in my house will trip.

I need to run the ADE and PIC of the same power supply, and I can not provide power by USB, as the computer will not be connected very often.

What can I do to fix this problem?

Thanks, Mark

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FvM

Joined: 22 Jan 2008
Posts: 5157
Helped: 767
Location: Bochum, Germany

03 May 2008 11:18 pic problem ground

Regular solution would be to use an opto isolated SPI between PIC and ADE. Another option is to try, if ADE could work with a fully differential voltage divider, as I already mentioned in your previous thread. This would be achieved by using the same circuit for V2N as for V2P and connecting the second input to neutral. But cause V2 input common mode properties are unspecified by Analog, I'm not sure about the results.