Questions tagged [ground]

Ground or earth is the reference point in an electrical circuit from which other voltages are measured, or is a common return path for electric current, or a direct physical connection to the Earth.

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123 votes
6 answers
56k views

Should chassis ground be attached to digital ground?

I'm working on a PCB that has shielded RJ45 (ethernet), RS232, and USB connectors, and is powered by a 12V AC/DC brick power adapter (I do the 5V and 3.3V step down on board). The entire design is ...
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75 votes
4 answers
93k views

What is ground and what does it do?

I'm a bit confused about the concept of ground, and perhaps voltage as well, particularly when trying to analyze a circuit. When I learned about Ohm's law in grade school, I learned how to apply the ...
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55 votes
10 answers
45k views

Why is an Ethernet cable not grounded?

There is no dedicated GND in the classical Ethernet 8P8C ("RJ45") pinout.[1] Why does the Ethernet spec not include a ground, unlike many other cable types used for interconnecting devices that may ...
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47 votes
3 answers
44k views

When a battery is your power source, what is ground?

For the sake of not incorrectly connecting my power supply and damaging my board I'm going to ask a relatively dumb question. Is ground on my board the negative terminal on my battery? Explicitly ...
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46 votes
3 answers
224k views

Why do we connect a battery to ground when jumping a car?

This may seem like a very simple question, but I've searched all over the place and haven't found an answer. When jumping a car, we connect the + end of the charged battery to the + end of the dead ...
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42 votes
3 answers
32k views

What are the advantages of having two ground pours?

I've seen many 2-layer PCBs that have a ground pour on both the top and bottom layers, I was wondering why do that ? and wouldn't it be better to use the top layer for power and signals and the bottom ...
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38 votes
4 answers
15k views

Reason of multiple GND and VCC on an IC

What is the reason that most of ICs (e.g. MCU) has multiple (A/D)GND and (A)VCC pins? If it is to increase performance of an IC, how does it help to performance? or is it easier for the IC designer ...
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37 votes
3 answers
140k views

Help me understand the relationship between positive, negative, neutral and ground in AC and DC

This question stems from notations on schematics and seemingly conflicting information I'm seeing. I suspect that I'm seeing different vernacular for the same concepts--but I'm in a place where no one'...
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33 votes
5 answers
11k views

Should I really divide the ground plane into analog and digital parts?

I am about to design my first PCB as part of my graduation project. Of course, as the first step, I try to learn as much as possible. A part of the research I found this 3 part article, that suggests ...
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32 votes
6 answers
113k views

"Ground" vs. "Earth" vs. common vs. negative terminal

This may just be me not having a degree in electrical engineering or electronics, but the whole notion of "ground" and "earth", when used in electrical circuit diagrams (especially integrated circuits)...
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31 votes
10 answers
12k views

AC: Why differentiate between Ground and Neutral?

Current flows through a conductor connecting points at different potentials. Leaving aside multi-phase details, common/conventional AC systems use a 3-wire setup: Wire-1: a line/live/hot/phase wire ...
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  • 313
31 votes
5 answers
26k views

What is causing large oscillations in my DC/DC boost converter? Is this ground bounce or some other effect?

I designed my first PCB for a DC-DC boost converter only to find that it produced very noisy output. The design is based around the MIC2253. Here's a schematic: Although my circuit allows for ...
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26 votes
3 answers
26k views

Why is earth used for ground? Literally earth?

I never considered earth to be particularly conductive. It's just dirt, after all. However, I've seen "earth ground" conductive stakes driven into the ground in order for electricity to be grounded, ...
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24 votes
4 answers
19k views

Are there reasons *not* to have a copper-pour ground plane on a PCB?

I am taking a first stab at designing a PCB from scratch. I am considering using a CNC mill fabrication process, and it seems like with this process I would want to remove as little copper as possible....
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24 votes
3 answers
92k views

Difference between Line and Neutral in AC

I want to find out what is the difference between the AC (220 VAC) lines, (phase and Neutral). As I know that the Alternating Current (AC) has no polarity, so why do we have a "phase" line and a "...
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24 votes
1 answer
6k views

Does anyone know the history of the earth ground symbol

I Googled for hours, asked every EE professor in my college, then checked every electrical engineering book in my university's library (hours), and have found nothing about the history of the ground ...
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23 votes
2 answers
32k views

Extra bare wire in USB cable

Whilst cutting up a USB cable for a project I noticed this extra bare wire within the insulation. Now I'm assuming the foil is shielding of some sort, but do I need to connect this bare wire to ground?...
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23 votes
4 answers
22k views

When to use ground plane cutouts?

I've been reading more about proper grounding techniques and using ground planes. From what I've read, ground planes provide a large capacitance with adjacent layers, faster heat dissipation, and ...
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21 votes
8 answers
3k views

Single wire (no ground wire) long distance low frequency communication

In a cave we are currently exploring, there is a temporary siphon that sometimes blocks our way. I was thinking about monitoring it (pressure sensor or other level sensor at the siphon, transmitter ...
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21 votes
9 answers
93k views

Why is the chassis used as ground in automotive electrical circuits

Automotive electronics generally use the metal chassis as the negative ground connector for the DC circuits. Obviously this saves something on wiring. Is there an electrical reason for this approach? ...
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  • 313
21 votes
4 answers
59k views

Difference between negative terminal and copper ground?

What's the difference between Negative and Ground? Like a negative terminal and a copper ground? I was reading that they are both the same; one person stated that negative is just more negative than ...
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20 votes
3 answers
29k views

Why most appliances in US don't have third prong

Most other plugs I encountered have three prongs - hot, neutral and ground I assume. For example all BS 1363 plugs have one. Also CEE 7/7 have ground connections and while CEE 7/16 exists it is not ...
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20 votes
6 answers
14k views

How does earthing work when earth is dry?

Earthing is meant to provide reliable contact of an electric appliance to earth so that if there's an insulation fault current goes into earth instead of through a person's body. This requires ...
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19 votes
6 answers
12k views

In this transistor circuit, what is the purpose of the diode across the motor?

I am trying to follow an Audrino tutorial with my kid and I am confused by the role of the diode in this circuit. In particular, I have the following questions: It looks like the circuit will work ...
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  • 307
19 votes
3 answers
13k views

How do you choose an inductor for connecting separate ground planes?

On a board with separate analog and digital ground planes connected at one place, the connection is often made with an inductor. How is this inductor chosen? Obviously it has to be able to handle ...
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19 votes
3 answers
6k views

Static shocks all over the building

I just came from the local library, it’s quite big, and most of it is made of an architectural design using mostly painted metal book shelves painted with some kind of anticorrosive paint along with ...
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18 votes
3 answers
39k views

How to find out if electrical outlet ground is working?

Just want to make sure my outlet's ground is working. How to do that? UPDATE: My main aim is to test resistance of anti-static wrist strap, but since I know it works by testing it with multimeter, I ...
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17 votes
4 answers
39k views

How should I connect AGND and DGND

I have been reading about grounding in a mixed signal systems. Do I get it correct that it is best to group analog and digital elements and then have a single ground plane, as long as the digital ...
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17 votes
3 answers
39k views

Use of ground symbols in circuit diagrams

In this question is the following diagram for a voltage booster intended for small battery powered devices The TPS61200 spec says GND is control/logic ground and PGND is power ground but this isn't ...
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17 votes
2 answers
2k views

What's the purpose of a tactile switch with GND pin?

Some 5 pin or 3 pin tactile switches have an extra GND pin such as this Omron B3W-1150. What's the purpose of this pin?
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17 votes
1 answer
11k views

With shielded twisted pair cable, do you ground one end, both ends, or neither ends of the shield

I've got a project coming up that's to be doing RS-485 communications over shielded twisted pair cable. The project will involve cable length runs of many 10s of ft and the cables will probably have ...
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  • 1,617
16 votes
7 answers
119k views

How a person standing on a floor tile and holding a live equipment can complete the circuit?

Can someone please explain the how grounding / earthing to prevent a person from getting electrical shock using simple illustration of a faulty electric iron connected to the 240VAC mains? I don't ...
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16 votes
2 answers
4k views

What is the purpose of wiring pins 2 and 3 of a potentiometer together?

I build a lot of audio devices - amplifiers, effects processors etc. I've been doing it for about a year and learned a lot of principles. However one thing I still don't understand is wiring pots 1 ...
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  • 654
16 votes
2 answers
3k views

Why are caps configured this way in EMC filters?

Every EMC filter I've seen has capacitors between the AC lines and earth, configured like this: simulate this circuit – Schematic created using CircuitLab Why are the caps not configured like ...
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16 votes
8 answers
56k views

Common vs. ground

I've been trained to use the word ground and the ground symbol to refer to the earth, the dirt on which we stand. Circuit common is considered to be a separate concept, with the symbol . My ...
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16 votes
3 answers
22k views

Grounding and why charge leakage occurs

A basic nugget of info is missing in my end-to-end picture of how grounding works and why it's important. When a voltage is applied in a circuit the electric current starts flowing (or the field ...
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  • 269
16 votes
3 answers
18k views

Placement of Vias to Connect Ground Planes

I've been wondering a lot about grounding practices on PCB layouts. My first question about it deals with vias. I've noticed that on a simple 2 layer PCB with ground planes on both sides, there will ...
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16 votes
1 answer
11k views

What's the use of ground coupling on digital oscilloscopes?

What's the practical use of ground coupling on modern DSOs? I know that it can be useful on analog oscilloscopes to adjust the ground exactly to a graticule line, but from what I've seen, most of the ...
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15 votes
4 answers
3k views

Is ground connection in home electrical system really necessary?

I know that the answer to my question is "Yes, it is!". The ground connection is needed to avoid a person touching a metallic part of faulty equipment to be electrically shocked. So the ...
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15 votes
6 answers
11k views

Decoupling capacitors on the bottom layer?

I'm using 0.01 uF decoupling capacitors in a 0805 package, on each Vcc/GND pair of my CPLDs. So, around eight capacitors in total). I find it a bit easier to route the board if the decoupling ...
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14 votes
3 answers
22k views

Physically, how does connecting a PCB to chassis ground reduce noise?

I realize this may seem to duplicate Should chassis ground be attached to digital ground? but the answers in that thread don't explain why one should connect the chassis to PCB ground, aside from ...
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14 votes
1 answer
2k views

Should the unused areas on the top layer of my RF PCB have ground pours?

I realize there are some questions that are related to this topic but I didn't see any that are really RF specific. I am working on a 2-layer Bluetooth module and I have some unused spaces on the top ...
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  • 1,077
13 votes
3 answers
2k views

What is mecca ground?

I came across few different ground names (digital, analog, signal, power, mecca, EM, shield, etc). I do understand most of them - but mecca is a new one for me. Can someone please explain this mecca ...
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13 votes
5 answers
8k views

Antennas and Ground Planes

I'm looking at this datasheet for the ANT-433-HETH antenna. In the box labeled "Suggested Board Layout" I see a dimension labeled "Minimum Distance to Ground Plane" of 0.5 inches. I always thought ...
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13 votes
7 answers
38k views

Why does the power company provide a neutral line?

I understand that power is often transmitted in 3 phases (with no neutral). Then, when we get to a certain substation, the power company basically gives house 1, L1, house 2, L2, house 3 L3, and ...
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  • 139
12 votes
5 answers
4k views

2-layer PCB design, through hole technology and ground plane

I am designing the layout of a PCB for audio applications (no digital electronics, only analog). All components are through hole, the PCB is pretty large (about 16cm x 10cm) and has 2 layers. Plated ...
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12 votes
3 answers
4k views

What does the pill-shaped 'X' mean in electrical schematics?

I'm not familiar with this symbol. Does it have a name? What does it imply when reading an electrical schematic?
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12 votes
2 answers
4k views

How many ground and power pins to have in a connector?

I'm designing a daughter board for a project. There are 35 I/O pins that need to go to the board. How do I determine the number of ground and power pins to include? How do I determine the placement of ...
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  • 436
12 votes
5 answers
7k views

Why would a power supply unit with insulating case and galvanic separation need a grounded power cord?

Recently I witnessed an external IBM laptor power supply that looked like a usual switched-mode power brick (rather small and lightweight for it more than 50 watts power) in plastic case but had a ...
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  • 12.1k
12 votes
2 answers
60k views

When does and when doesn't current flow to ground?

I was thinking about when current can and can't flow to ground. I came up with that current will only flow to ground when we have at least two grounds in the circuit, since then we have a complete ...
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