[SOLVED] Connecting Grounding

[venkates2218]

Hai,
While grounding the PCB
Method 1:Created an PCB,mounting hole with PAD and conductive material is used to mount the PCB on machine.Whole body of the machine is connected to ground.continuity between the ground and earth is available while checking with multimeter.
Method 2:Created an PCB,mounting hole without PAD and earth is connected to single point.An "Ferrite Bead, 70 ohm, 3 A, 0.04 ohm, ± 25%" is connected in series with GND and EARTH pin.


Please suggest which one is best or any other method to connect the earth to PCB

 

[KlausST]

Hi,

it depends ... on what you want to achieve.
And what is the source of noise ... if you want to attenuate the noise or if you want to give the noise (current) a low impedance path not to cause high noise voltage.


in other words:
* If noise_voltage is the problem, then use a low impedance path.
* If noise_current is the problem, then use a high impedance path.

Klaus

 

[venkates2218]

There is an power circuit in that machine.+12VDC is given as input and 2kv is generated on another side of power circuit.Current consumption of whole circuit will less than 1A.

And providing earth to board by using multiple points(using mounting holes) is better or through single point is better.?

 

[KlausST]

Hi,

And providing earth to board by using multiple points(using mounting holes) is better or through single point is better.?

It also depends on the situation.
Multiple points may reduce overall impedance and delay
..but may generate GND_loops which may cause additional problems.

It´s not that simple. There are no general solutions like: "do xxx and everything is fine"

Klaus

 

[FvM]

Most instruments like generators or oscilloscopes, also PC desktops have direct GND to case connection. The main disadvantage of this option is that external signal connections are creating ground loops through protective earth. Ground loops can inject common mode noise and also cause overload of signal ground connections by DC and mains frequent currents due to PE potential differences. In this situations, a capacitive grounding is preferred.

 

[senilicus]

Grounding on PCB's is a difficult issue. Rick Hartley has a very nice presentation on this subject.

 

[D.A.(Tony)Stewart]

Hai,
While grounding the PCB
Method 1:Created an PCB,mounting hole with PAD and conductive material is used to mount the PCB on machine.Whole body of the machine is connected to ground.continuity between the ground and earth is available while checking with multimeter.
Method 2:Created an PCB,mounting hole without PAD and earth is connected to single point.An "Ferrite Bead, 70 ohm, 3 A, 0.04 ohm, ± 25%" is connected in series with GND and EARTH pin.


Please suggest which one is best or any other method to connect the earth to PCB

It is not possible to solve this equation as there are at least 4 spectral impedance unknowns and only 2 suggestions that have no Specs. ! It does not define; spectrum for attenuation, impedance, susceptibility, or direction of interference.


Ground is just a common potential we call 0V as a reference point to potential in loops of current. Ground has no impedance unless there is a current loop. Ideal ground is 0 Ohms only means relative to itself or nearby (neglecting LC effects) and that also neglects what it is shielding or radiating as like a patch antenna. When you connect different 0V systems together the signals suffer from noisy ground loops. Earth ground means 0V but only where it is connected to that earth rod.

Nor does it define the environment of traces, wires and interface sensors or inter machine communication errors from SMPS noise and unbalanced cables and unbalanced signal impedances.

EMI may occur in both directions and by two methods; air (radiated) or conducted.

Please understand this before you must specify the environment, cable interfaces, power sources (linear or switching) There is also a requirement to understand how ESD can damage semiconductors from an exposed external ground and PCB ground and cable shield ground and define this.

What you don't want is to solve one requirement and create a new problem.