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Newbie question.

Discussion in 'Hobby Electronics' started by The Raven, Jul 15, 2004.

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  1. The Raven

    The Raven Guest

    I hope someone can help me with what would have to be classified as a
    relative newbie question.

    I'm reasonably OK when it comes to playing around with 12V automotive stuff
    but 240VAC is something I've been very wary of. Once bitten, twice shy

    Anyhow, I'm working on a basic conversion of a computer power supply for use
    as a 12V source for some specialised battery chargers. I've found plenty of
    good step by step articles on how to do this conversion and the unit is
    running mocked up... So far so good, now comes the time to package it all up
    neatly and safely.

    My dilema is this, I have replaced the standard computer grade power switch
    with a basic 10A 240V SPST switch. The switch contains a neon power
    indicator but I'm unsure as to how this should be hooked up for the neon. If
    this were 12V stuff no worries, but I'm hesitant to start probing around to
    figure out what works on 240V.

    Switch has three spade connectors labelled 1 through 3 and, I've sorted out
    which do the main switching. The third spade needs to go somewhere for the
    neon to operate but I'm not certain where. Any ideas?

    To make this more interesting, I'll consider this a challenge. "Who can
    correctly answer a basic question the fastest". First prize is a US style

    Thanks in advance. Your time starts now....
  2. If you are only switching one line (not generally recomended for this
    application) I would assume the third spade would have to be the end of the
    neon that needs to go to neutral since the other is most likely connected to
    the 'load' side of the switch contacts.
    You may have the active connected to the 'load' side, but the switch will
    still work without the neon working.
    Should that be the case then change the leads on the switch over (the mains
    Also perhaps consider using a dpst switch with neon.
  3. The Raven

    The Raven Guest

    I appreciate that using a DPST will provide an additional layer of safety
    but, beyond that, is there any reason to do so? I don't want to cut corners
    but I would like to know what the implications are.
    As would be the case now.
    Not sure if I follow you on that.
    Yup, will do.
  4. thegoons

    thegoons Guest

    I think he was saying you need to ensure the "mains side/active in" and
    "load side/active out" are not transposed, otherwise the neon would stay on
    continuously - see below:

    / switch
    --------------------/ ---------------------------------- LOAD SIDE
  5. Marty

    Marty Guest

    And also make sure he IS switching the active and not the neutral, otherwise
    the neon would be connected between neutral and neutral!!!!
  6. Ken Taylor

    Ken Taylor Guest

    As a matter of interest, it is 'neutral', not 'negative' in mains

    'Raven', use a double-pole switch, but use a separate neon or other light.
    They do tend to burn out in switches and it's a damn inconvenience to then
    have a perfectly good switch with a dud light. Also recommend you use a good
    quality crimper for the terminals, don't use the el-cheapo ones as they do a
    dirty job, and can leave metal exposed. That said, still heatshrink all the
    terminals, *particularly* the unused ones on the switch.

    On, and just a single fuse, in the active line.

  7. Hey Raven
    Your email addy is bouncing
  8. The Raven

    The Raven Guest

    Hi folks,
    Thanks for the email/posts with suggestions. I found a
    website that helped clarify 240VAC wiring and deciphering the active and
    neutral (plus what I assume is international markings of L and N).

    I had wired the PSU socket correctly but mistakenly switched the neutral
    side. Caution with testing paid off here, as did getting clarification from
    you guys.

    Rewired the switch tonight and all is working as designed, neon and all.

    All 240V side connectors are fully insulated. I've replaced the spade
    connector insulation with full coverage silicon style insulator boots.

    Just have to finalise the binding posts and 12V wiring and all is done.

    I appreciate the suggestions on changing to a double pole switch and will do
    so this weekend.

    Thanks for the assistance.
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