1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Grounding

Discussion in 'General Electronics Chat' started by SeanHatch, Dec 27, 2002.

  1. SeanHatch

    SeanHatch New Member

    Joined:
    Dec 27, 2002
    Messages:
    97
    Likes:
    0
    Location:
    Michigan, USA
    Well, I thought I understood it...

    When reading a schematic, grounds (the little triangle of lines) are connected to the negative end of the battery right? So if there is a +9Vdc, you would connect all the grounds to an imaginary -9Vdc. Is this correct, or am I way off?

    So, knowing this I am attempting to wire the pick-ups in a guitar I'm currently repairing. I noticed that some of the leads to the potentiometers, and some of the leads of the pickup are grounded, however obviously there is no battery. My question is, what are these grounded to?

    I guess maybe I just don't understand, so if in addition to these questions somebody could explain to me what a ground really is, that would be apprecitated.
    _______________

    Thanks,
    Sean
     
  2. isaacj

    isaacj New Member

    Joined:
    Dec 20, 2002
    Messages:
    57
    Likes:
    0
    Location:
    Mojave Desert
    Ground is simply a reference point. It is generally considered to be zero volts and has no polarity.

    Think of a circuit as a pipe. If we apply equal pressure(volts) to both ends nothing will flow through the pipe. If we remove all pressure from one end of the pipe ("ground" it), we get flow from the pressure side to the non-pressure side.

    So if there is a +9Vdc, you would connect all the grounds to an imaginary -9Vdc.

    No! These connections are always 0V. If you connect all of the ground connections to a negative -9V, you will have 18V across your circuit and will likely burn something in it.

    A 9V battery can only provide 9V of electricity. If the battery is connected to provide positive voltage, no negative voltage can be obtained.
     
  3. SeanHatch

    SeanHatch New Member

    Joined:
    Dec 27, 2002
    Messages:
    97
    Likes:
    0
    Location:
    Michigan, USA
    Thanks...but

    Thank you very much for the help on understanding grounding and such. I guess I was way off, but hey I'm a rookie in electronics and you guys are here to help me.

    Now perhaps a real-life example, say I am actually building a simple circuit which has grounds, now that I understand that they are all connected to a central point, what should this central point be? I understand the pipe, and the energy difference concept, so if one end of the pipe is a 9 volt batter, what is the other end? Where exactly on a true to life circuit would all these grounds lead to?
    ____________

    Thanks,
    Sean
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. isaacj

    isaacj New Member

    Joined:
    Dec 20, 2002
    Messages:
    57
    Likes:
    0
    Location:
    Mojave Desert

    what should this central point be?

    You had this part right already. I apologize if I confused this issue. The grounds would all be connected to the negative battery terminal.

    A battery has two connection points. The negative terminal and the positive terminal. If you want positive voltage, you connect the positive terminal to your supply connections and the negative terminal to ground. If on the other hand you want a negative voltage, you would connect the negative terminal to your supply connections and the positive terminal to ground.
     
  6. SeanHatch

    SeanHatch New Member

    Joined:
    Dec 27, 2002
    Messages:
    97
    Likes:
    0
    Location:
    Michigan, USA
    About the Guitar

    Thanks, now I'm pretty sure I understand how this works.

    But the one question still remains, how and where to would you ground things on a guitar, since on the inside there is no battery or anything, I've read some schematics and descriptions from some popular pickup companies, and they all said:

    "Connect all grounds to a central point on the bridge of the guitar"

    Does this make sense? If not can somebody please, please tell me where to connect these grounds to when there is no battery. I know this must be kind of hard to understand and grasp if you've never worked on a guitar or played one, but so far the help you guys have given me has been quite descriptive and useful. In any case any help on this guitar thing would be appreciated. Here is a link to a schematic/diagram of a pickup wiring with a couple of grounds.

    http://www.seymourduncan.com/website/support/schematics/S_1singlecoil_1vol_1tone.html

    So basically I just want to know (but mostly UNDERSTAND)where you put these grounds, and why there?
    ____________

    Thanks,
    Sean
     
  7. pebe

    pebe Member

    Joined:
    Sep 24, 2002
    Messages:
    354
    Likes:
    1
    Location:
    Ellon - Scotland
    Assuming your guitar uses a screened cable to connect to the amp, then connect your grounds to the screening of the cable.
     
  8. isaacj

    isaacj New Member

    Joined:
    Dec 20, 2002
    Messages:
    57
    Likes:
    0
    Location:
    Mojave Desert
    Looking at the schematic you linked to, all you have to do is connect all ground wires together and that's it. The schematic also indicated there might be a wire comming from your bridge, if so this wire would also be connected to the ground wires.

    "Connect all grounds to a central point on the bridge of the guitar"

    They are telling you to connect all the ground wires to the bridge.

    Procede at your own risk. I've never worked on guitars.
     
  9. jdp12345

    jdp12345 New Member

    Joined:
    Jan 3, 2003
    Messages:
    14
    Likes:
    0
    ground

    I have a question about ground.

    if I have +9v and -9v and I have to create ground. I can simply attach
    the -9v to the chasis of my board right?

    Will that create a 0V connection, perhaps. Here is what I have. I bought a Breadboard from Radio Shack. Part number 276-169. This board has 3 posts. 2 red posts and 1 black.

    I connect the red wire from the battery to one of the red posts. I then connect the black wire from the battery to the black post. Now I have +9V and -9V. How the heck do I create a ground? I've tried connecting the -9v to the last red post on the breadboard and I still get -9v.

    Your advice and help in this area is greatly appreciated.

    Also, how do I measure ground? I have a little voltmeter, also from radio shack. It has a black and red pointers. How do I use them to measure ground 0V?

    Thanks alot. :?:
     
  10. isaacj

    isaacj New Member

    Joined:
    Dec 20, 2002
    Messages:
    57
    Likes:
    0
    Location:
    Mojave Desert
    I connect the red wire from the battery to one of the red posts. I then connect the black wire from the battery to the black post. Now I have +9V and -9V.

    NO. Now you have +9V and a ground(0V) connection(the black post).

    First, lets start with the battery. You said you were trying to use a 9V battery. If thats the case, you only have 9V to work with, negative or positive, not -9V and +9V. You can not use a battery to provide negative and positive voltage at the same time, just one or the other.

    Second, the breadboard. The black post is for ground. The red posts are for supply voltages; could be negative, could be positive. You might have one of each. For example post 1 could be +3V and post 2 could be negative -3V. You could also make post 1 10V and post 2 30V, it doesn't really matter.

    Also, how do I measure ground?

    The short answer is, you can't. Ground is a reference point. It's also where all endpoints in a circuit connect back to the power supply.
     
  11. herbymcduff

    herbymcduff New Member

    Joined:
    Dec 5, 2002
    Messages:
    205
    Likes:
    0
    Location:
    USA
    If your just wanting to check and see if you have a good ground, do a continuity check on your ground strip to see if everything if connected good. Or you could ohm the ground strip, and it should read really low at any givin point. If all you have is voltmeter, place the red lead on supply (+), and place the black lead anywhere on the ground strip. You should be able to read 9V anywhere you place the black lead.

    If thats confusing, sorry. Ignore then.
     
  12. jdp12345

    jdp12345 New Member

    Joined:
    Jan 3, 2003
    Messages:
    14
    Likes:
    0
    Thank you Isaac & Herby

    Thank you for the enlightening answers. Isaac, when I have 1 9V batterym I only have +9V, did I get that right?

    The black post is the ground, right?

    Good. Now. I'm attemping to do a tiny project that amplifies a signal.
    For the amplification, I'm using an LM741 op-amp. It has a +V input as well as a -V input.

    Because, I have 3 posts on my breadboard. 2 Red and 1 black. How can I connect the battery to provide +9V and -9V to this Op-Amp?

    Thank you for your great input.
     
  13. jdp12345

    jdp12345 New Member

    Joined:
    Jan 3, 2003
    Messages:
    14
    Likes:
    0
    thank you Herby

    Thank you for your answer Harby.
    I understood your posting. Now that I know how to get +9V and ground,
    I only need to figure out how to get -9V and supply it to the LM741 Op-Amp?

    Do you know how?

    -jp
     
  14. isaacj

    isaacj New Member

    Joined:
    Dec 20, 2002
    Messages:
    57
    Likes:
    0
    Location:
    Mojave Desert
    Isaac, when I have 1 9V batterym I only have +9V, did I get that right?

    Partly. A battery can provide - or + power. It just can't do both at the same time. It all depends on how you attach it to your circuit.

    The black post is the ground, right?

    Yes.

    How can I connect the battery to provide +9V and -9V to this Op- Amp?

    You can't do this with one battery, you need two.

    Battery 1 - positive supply
    Connect the - black wire to the black post.
    Connect the + red wire to one of the red posts.

    Battery 2 - negative supply
    Connect the red wire to the black post.
    Connect the - black wire to the other red post.

    I would suggest you label the red posts so you remember which is which.

    Now you have a dual polarity power supply. All ground connections go to the black post.
     
  15. jdp12345

    jdp12345 New Member

    Joined:
    Jan 3, 2003
    Messages:
    14
    Likes:
    0
    ground

    Thank you Isaac.
    I can see the light getting brighter.
    ;-)

    Isaac, does every LM741 have to have 2 batteries?
    This is because the LM741 says it needs a -V and a +V
    on pins 4 and 7.

    Pin 4 : -Vcc &
    Pin 7 : +Vcc

    I have a battery holder for my 9V battery. I bought it at Radio Shack.
    Does this mean that for my LM741 I have to have 2 batteries to jump start it?

    Will it work if it has ground connected to pin 4?

    jp
     
  16. isaacj

    isaacj New Member

    Joined:
    Dec 20, 2002
    Messages:
    57
    Likes:
    0
    Location:
    Mojave Desert
    Yes, all 741s have a negative and positve voltage supply pin.

    Will it work if it has ground connected to pin 4?

    The chip will work if one of the voltage supply pins are grounded. However, doing so changes the output of the chip. If the circuit you are building requires -/+ voltage, you must connect the chip that way.
     
  17. jdp12345

    jdp12345 New Member

    Joined:
    Jan 3, 2003
    Messages:
    14
    Likes:
    0
    Thank you Isaac

    Thank you very much for all your answers Isaac.
    I'm on my way to buying more batteries.
    ;-)

    I hope it doesn't become an expensive hobby to begin to learn.
    ;-)

    -JP
     
  18. isaacj

    isaacj New Member

    Joined:
    Dec 20, 2002
    Messages:
    57
    Likes:
    0
    Location:
    Mojave Desert
    I would suggest buying or building a variable power supply. Batteries will get real expensive real quick if you become engrossed in electronic experimentation. I don't have any links to schematics handy, sorry. You'll have to find your own. Try google.
     
  19. jdp12345

    jdp12345 New Member

    Joined:
    Jan 3, 2003
    Messages:
    14
    Likes:
    0
    good idea

    That's a great idea Isaac.
    Will I get positive,negative, and ground all at the same time?

    I'll look at google and see what I can find.

    ;-)

    -JP
     
  20. isaacj

    isaacj New Member

    Joined:
    Dec 20, 2002
    Messages:
    57
    Likes:
    0
    Location:
    Mojave Desert
    That depends. While all power supplies provide a ground connection, you have to have a ground in order to complete any circuit, not all power supplies provide negative and positive voltage. If that is what you need make sure the power supply has both before you buy it.
     
  21. SeanHatch

    SeanHatch New Member

    Joined:
    Dec 27, 2002
    Messages:
    97
    Likes:
    0
    Location:
    Michigan, USA
    Let's Just run through this once more...

    Alright let's have one short example for the sake of clarification. Here in front of me I have 3 things. The first, a schematic with a few grounds, and a voltage source +9Vdc. The second item on the list is the breadboard discussed earlier, it has one black post, and two red ones. The final item on the list is your average 9 volt battery. So, in terms of the posts (Black, Red1, Red2) where do you connect:

    1. The positive end of the battery.
    2. The grounds shown in the schematic
    3. The +9Vdc shown in the schematic
    3. The negative end of the battery.

    I think this should clear things up once and for all
     

Share This Page