Meaning of ground in DC/AC in this circuit

Discussion in 'General Electronics Chat' started by jamjes, May 10, 2010.

  1. jamjes

    Thread Starter Member

    May 10, 2010
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    Hi folks

    I'm new here, looks like you've got a wealth of info and people here :)

    Okay now for my question. An example...

    The FIRST circuit on this page:
    http://uzzors2k.4hv.org/index.php?page=flybacktransformerdrivers

    has a 12v rail and some 'ground' symbols. In this circuit, are all grounds going to the same 0v of the power supply??

    The right-hand ground is the secondary coil of the transformer, is this ground really connected to the same ground as pin 1 of the 555?

    I guess my bigger and more general question is what exactly is ground symbol if you've also got 0v reference in a circuit diagram? Is it different depending on whether you have 0v/9v from a battery for instance, or you're using a 3-pin mains AC plug and thus you have Earth ground as well?

    Confused and sleepy,
    JJ
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
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    Yes. The multiple ground symbols are to keep the schematic neat. Less wires running all over the place just to get back to GND. Easier to read.

    No. Anything on the other side of the transformer should STAY isolated.

    You dont want a few hundred or thousand volts accidentally on your low voltage side. Imagine what would happen when you went to turn the potentiometer and you got the HV. no good.

    You should also use a plastic knob on the POT to be safe.

    this also is not a beginners project. If you dont have at least a few low-voltage projects under your belt, and dont follow EXTREME caution, you can EASILY, EASILY, EASILY end up dead.

    Do NOT work on these projects alone. If you accidentally end up zapped, time is of the essence. And it may not be your fault. If you are pulling a flyback out of an old TV, or monitor, the windings may have vibrated some insulation off the flyback. Thats why they are suspended and encased in the TV and monitor enclosures.

    In DC ground is a return path for the electrons. The (-) on a battery. AC it is actually a big spike in the dirt.

    The 0v reference CAN be taken from ground, and is done so to keep all the DC components at the same 0v level. (even if it actually had .02v on it, that would now be the reference)

    SO, dont work on this type of stuff when you are:
     
    Last edited: May 10, 2010
    kingdano likes this.
  3. jamjes

    Thread Starter Member

    May 10, 2010
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    Thanks for the verification retched :)

    As for the HV, I am aware of the lethal nature and treat everything as being death-voltage until everything is switched off and correctly discharged.
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
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    That is a good way to treat it. RESPECT the electron. Especially in such big numbers ;)

    Electrons hunt in packs, its never just the little lone electron that starts trouble with you. He has got to go and get a few million of his brothers and cousins an really start a ruckus. Jerks.
     
  5. whatsthatsmell

    Active Member

    Oct 9, 2009
    102
    4
    Yeah - and they've got a real negative attitude!

    (Sorry - I just couldn't resist :p)
     
  6. retched

    AAC Fanatic!

    Dec 5, 2009
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    Thats what the water soluble marker said to my PCB after it ruined it. (Couldn't resist)

    Ok.Enough.
     
  7. jamjes

    Thread Starter Member

    May 10, 2010
    35
    0
    I dont know what's more lethal: High Voltage or your bad jokes :D :D
     
  8. retched

    AAC Fanatic!

    Dec 5, 2009
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    My jokes. Thats why I dont listen to myself.
     
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