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GFCI circuit design problems

Hello everyone,

I am encountering some problems while trying out the GFCI circuit. I am not using the OpenEVSE design as is - I have removed the safety components but am using the same logic. Please find my circuit attached below.

My problem is as follows: For my circuit I am using a voltage divider network to generate + and - 2.5V for powering the LM358. The inverting amplifier works correctly and I get a 0.5V output at pin 1 of the IC. Now to have this voltage trigger a HIGH from the comparator, I use a trim pot to generate 0.45V which is connected to +2.5V rail in the circuit. This causes the trim pot to act parallel to the voltage divider network (which powers the op-amp) and unbalances it. Now, the rails are no longer + and - 2.5V and hence, the op-amp fails to function correctly. Can anyone help me out with this? I know I could go for a dedicated dual power supply but I am trying to operate using a single supply only. 

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