Grounding issue

hi all.

currently im working on some kind of signal processing. the main goal is grid freq measurement via opamp and microprocessor. Actually its working but im not sure about wiring diagram.

This is the scheme here.

IMPORTANT NOTE: I just realize that i forgot to draw a wire in paper. It 's NEUTRAL connected to 0V. And opamps work with +-8V.

this is the inside of the dual rail power supply:

Only difference between mine and that is chassis connection(and also im using lm7808/7908 against of lm7812/7912). I didnt wire chassis to the transformer's chassis yet.

In this circuit i can get pulses from output of the comparator (lm324). But im not sure about Neutral-0V connection. Im little bit confusing .

Is it true or should i connect to the chassis to power supply's 0V ??

Thanks.QWERTY

To make the op-amp work you need neutral and 0V connected.
Do not connect (power line ground) to neutral. They are almost the same thing but not quite.
Some times I see a outlet with line and neutral reversed. This will make your box "hot".
If you are only measuring frequency then you can add isolation to make it safe.
The optocoupler does not care if L & N are reversed.

ronsimpson said:

Do not connect (power line ground) to neutral.

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Yes i know Ron. But thanks for remind .

ronsimpson said:

If you are only measuring frequency then you can add isolation to make it safe.

Click to expand...

Im also want to comparating with some kind of voltages (maybe after this tutorial), so i need analog circuitry.

ronsimpson said:

View attachment 120119

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This is a good one. I will use it with my other projects. Thanks.

ronsimpson said:

To make the op-amp work you need neutral and 0V connected.

Click to expand...

So your saying that my circuit is true ,right ?

Many thanks for all kind of replies..

QWERTY.

I tend to connect power supply 0v reference to earth GND as is normal in a PC based P.S. etc.
Also when working in a noisy environment such as servo's it is common practice, inc such as setting up a star GND point somewhere on the chassis or enclosure.
The neutral is never connected to any low voltage control circuitry.
Max.

MaxHeadRoom78 said:

I tend to connect power supply 0v reference to earth GND as is normal in a PC based P.S. etc.
Also when working in a noisy environment such as servo's it is common practice, inc such as setting up a star GND point somewhere on the chassis or enclosure.
The neutral is never connected to any low voltage control circuitry.
Max.

Click to expand...

i just find a great website about pc smps's noises. Here it is.

In the documents ground pin of the grid connected to the dc's gnd...

QWERTY.