# help me understand ground and when to use it

Discussion in 'General Electronics Chat' started by Dentsu, Jul 18, 2011.

1. ### Dentsu Thread Starter Member

Jul 7, 2011
47
0
hi, i am beginner and just started learning about electronic and this place seem like an excellent place to start. i have watch quite a few video here already and i have a questions. i think the basic concept of ground is to release static electricity?..but it also could act as a bridge to connect to a circuit? if so how does it work in a schematic with multiple ground? can you simulate one if it is not on a pcb or metal casing?..which lead me to another question. which way does electricity flow? how can you know the direction it will go and can it overlap a path? hope you could ignore how simple those question are and help me understand it.

2. ### lokeycmos Active Member

Apr 3, 2009
432
7
2 basic types of ground: earth ground and chassi ground. earth ground is just what is says. earth ground is common when dealing with transmitters and radio recievers. chassi ground is ground within a circuit. usually when you look at a schematic with multiple grounds, yes they are all connected together, because they are all common to eachother. a great computer program for simulating circuits is multisim. this is a very powerful and easy to use software. you can simulate almost any circuit, digital and analog. current flow can be somewhat confusing. there is whats called conventional flow which is what most people think about. conventional flow says that electricity flows from positive to negative. then there is electron flow. this is where it can get confusing. with electron flow the electrons flow from negative to positive. dont worry about this. if your a beginner just go with what you know. when you say "can electricity overlap?" i think your talking about a parallel circuit, so, yes. hope this helps!

Dentsu and Sparky49 like this.
3. ### Sparky49 Well-Known Member

Jul 16, 2011
835
417
To echo what lockeycmos said, most grounds you see on circuit schematics are a substitution for the 0v rail. In the example attachment, i have circled all of the grounds. Imagine if the designer had to connect all of those points to a single track!

It would be far more complicated than it already is -with lines all over the place, criss-crossing one another.

For that reason, we use the 'ground' as it just makes it look tidier and easier to read.

• ###### Example 1.jpg
File size:
293.7 KB
Views:
32
Dentsu likes this.
4. ### Dentsu Thread Starter Member

Jul 7, 2011
47
0
thanks for taking the time. it really help me to better understand it. i tired putting up a simple circuit together in multisim and the same circuit without a ground would draw significant more current when off. how would i create a ground if the setup is not on a pcb? will a simple metallic plate is all that is needed? a little off topic but i am playing around with led and i can't seem to find photoresistor and how would i simulate a light condition. is there a option to do that?

@Sparky49 can you elaborate on "substitution for the 0v rail" i remember watching a video that explain ground could sent power and another video where it is only neutral. ps your schematic scare me.

5. ### GetDeviceInfo Senior Member

Jun 7, 2009
1,571
230
Yet another example of how the term 'ground' confuses, and our insistance at subscribing to the confusion. The question I have is, why? The chassis symbol used in the linked schematic is just that. It indicates that the vehicle chassis is a 'common' electrical path. The vehicle is insulated from ground, hence has no 'ground'. In the same thought, nuetral is not ground, but a return for unbalanced currents.

When will AAC do it's viewers a service and debunk this myth?

6. ### ErnieM AAC Fanatic!

Apr 24, 2011
7,442
1,628
What "myth" are you referring to?

"Ground" is a much overused and abused term as it means different things in different contexts.

(Is that a Bilge pump in that schematic? Is this a car or a boat?)

7. ### lokeycmos Active Member

Apr 3, 2009
432
7
could you post the circuit you made on multisim? you cant post multisim files so you have to take a sreen shot.

8. ### GetDeviceInfo Senior Member

Jun 7, 2009
1,571
230
It 'can' mean different things, depending on the communicator. However, looking at it from the side of the audience, who may not know what you really mean, unless the term is clearly defined. The 'confusion' behind the term 'ground' is simply the manifestation of those that refuse to review thier 'perspectives'. The definition itself, which ever one chooses, is fine within thier thought process. Clear communication, an essential in real world work, requires a common language.

9. ### Dentsu Thread Starter Member

Jul 7, 2011
47
0
sorry i am new at this and trying to get my head around the basic terms and fundamental.

File size:
170.6 KB
Views:
22
10. ### debjit625 Well-Known Member

Apr 17, 2010
790
186

Don't be so confused, in a schematic when you see a ground symbol two or more places just think that they are electrically connected together, thats why we say it common ground. In your first circuit the negative terminal of the battery, right side of the bulb and the negative probe of the multimeter are all connected together.And the another circuit you have created is totally equivalent. Common ground has nothing to do with PCB or Varoboard or Breadboard its just to show the common point in a schematic. But what about Multisim ,shows that reading on multimeter(XMM2) its an error of multisim, remember one thing when ever you create a circuit in multisim use a common ground.Multisim can’t analyze a circuit without a proper ground.

Want to test it just create a circuit without ground multisim will give you error, note on your multisim project you created two circuit one with ground and another without so multisim is simulating your project with out giving any error but its just simulating properly the first circuit.

Yes ground have different meanings have a look....

Good Luck

Dentsu likes this.
11. ### debjit625 Well-Known Member

Apr 17, 2010
790
186
Simple use a variable resistor in place of your photoresistor (LDR).Increase or decrease its resistance to simulate light variation.

Dentsu likes this.

Dec 26, 2010
2,147
300
This simulation is showing you a tiny voltage which is probably related to limitations in the accuracy of the software. A level of 43 picovolts is over 200 thousand million times the 9V battery voltage. This is not really relevant to a real-world battery light.

Note that some simulators (e.g. versions of Spice) will not work as all unless a ground connection is defined, and may require at DC path to extend to all parts of the circuit.

13. ### Dentsu Thread Starter Member

Jul 7, 2011
47
0
where would one find this photoresistor? i tried searching manually by symbol.

14. ### ErnieM AAC Fanatic!

Apr 24, 2011
7,442
1,628
I'm still looking for what this mythical "myth" is.

But I think it's just an urban legend.

15. ### debjit625 Well-Known Member

Apr 17, 2010
790
186
You didn't got my point,use the basic component i.e.. "POTENTIOMETER".