Where is earthing?

Discussion in 'General Electronics Chat' started by nradam123, Dec 9, 2013.

  1. nradam123

    Thread Starter New Member

    Dec 3, 2013
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    0
    I know this is not an electronics question, regardless i thought i will ask it here.

    How do i earth a DIY CFL lamp? The CFL only has two terminals for hot and neutral and i have just connected it to a plug and into power.

    Its just one 15W CFL. I havent earthed it nor attached any fuse to it. Is that required? And if yes, how is the connection for eathing?
    My logic is incase of short circuit, the MCB will trip and i dont have to worry about fuse. And no earthing terminal too.

    Will be nice if u guys can clarify this for me
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,386
    1,605
    There is no earthing on this device. Period.

    Power comes in on two wires: "hot" and "neutral".

    Neutral is "grounded" (earthed) in one place in a local (ie: house, building) area. All voltage is then relative to neutral and is on the hot line.

    So connect hot and neutral to the CFL.

    Ground could go to the metal box encasing the base of the lamp IF there is such a box.
     
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  3. nradam123

    Thread Starter New Member

    Dec 3, 2013
    10
    0
    Thanks! So i am safe :)
    As for fuse, when is a fuse required generally? I have heard that just power by voltage (230V) here will give an estimate of the kinda ampere fuse is required.
     
  4. Shagas

    Active Member

    May 13, 2013
    802
    74
    It depends if 15 watts is branded as the input wattage or output wattage .

    If it was input wattage then you could just say 15watts/240 volts would give you about
    65mA so you would pick a 80ma fuse (if it exists) . Most probably 100mA fuse.
    If 15 watts is the output wattage (which I'm guessing it probaby is) then the input current is going to be higher to account for the losses in heat etc .
    Try finding out on the back of the bulb if they write what the input current is and choose a fuse according to that.

    But i'm unsure if it even makes sense to fuse a light bulb ... it either works or it burns out.
     
  5. WBahn

    Moderator

    Mar 31, 2012
    17,737
    4,789
    If I understand you correctly, you have made a lamp that uses a CFL bulb and that plugs into a normal power outlet, right?

    If so, then the thing to consider is whether there is any way plausible for someone to easily come in contact with one of the two connections (such as the outside of a typical Edison-base bulb), especially when the bulb is not installed? If so, that one should be your neutral and you should use a polarized plug. Is there any way for the hot line to ever connect to any place on the lamp that someone could touch? For this you want to assume that the hot wire's insulation has been removed and that the wire could be broken anywhere along its length. If the answer is yes, then you want to connect a ground wire to those places and route that to the third (ground) prong in a three prong plug.

    The fuse (a circuit breaker) should already be installed in the circuit you are plugging it into.
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,526
    2,369
    Where are you located?
    If somewhere that uses a similar system to the UK (230v) with an independent fuse in each plug-top then you select the fuse according to the load the plug is attached to.
    Max.
     
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