Threshold Pot doesn't work

[h9361]

OK, but then if you will get a negative response if:

1. you slightly lift the coil off the ground
2. you sweep the coil over uneven ground
3. you sweep over a negative hot rock
4. you sweep over a target (the "bounce-back" response)

I think the LED will be constantly flashing. I thought you added ground balance to the HHD, that should have solved this problem.

For this, i want to add a threshold for the LED.
According to my tests, a vacuum void decreasing is very very stronger than you mentioned above. The voltage will be at the lowest possible amount.

[Carl-NC]

Probably the best place to add it is at TP5. Add another opamp stage similar to IC8b (including threshold) and have it drive an LED. You will have to figure out all the details.

[h9361]

Probably the best place to add it is at TP5. Add another opamp stage similar to IC8b (including threshold) and have it drive an LED. You will have to figure out all the details.

I attached a schematic, is it possible to check it and if possible, suggest me correct values for tp5?
Thank you

[Carl-NC]

That's a good start but everything needs to use +5V/-5V, not +12V. I have no idea about component values, it will depend on the offset at TP5 and how strong the signal is.