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Project: Transformer Checker

Discussion in 'Electronic Projects' started by hsab, Mar 23, 2005.

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  1. hsab

    hsab New Member

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    hi

    simple way to test your transformer :lol:
     

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  2. lord loh.

    lord loh. Member

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    Hey...

    Can anyone explain this ?

    The coil is supposed to provide 0 resistance to DC(The cell). So wont it be just a small change in intensity if the coil is short or not ?
     
  3. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    The neon flashes when you release the button, not when you press it, it's due to the back emf caused by the collapsing magnetic field in the transformer. It's the same effect used in car igntion coils.

    If the transformer has a shorted turn it seriously dampens the 'ringing' of the transformer, and the back emf won't be high enough to light the neon.

    It works with any reasonably sized coil (not just transformers), even 1mH RF chokes will do it - just wire a neon directly across a choke and briefly apply a battery across it - the neon will flash as you disconnect.
     
  4. dave

    Dave New Member

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  5. Someone Electro

    Someone Electro New Member

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    if you hold the contacts of an high inductance coil (electromagnet and stuf like that)Wile conecting and disconeting a batery you will get a shock.the higher the indictance the biger the shock.

    this is a fenonemom that is cased by the magnetic field.Wen you conect the batery the coil makes an electromagnetic field around it wen you disconect the batery the field breaks down resulting in an high voltage spike on the contacts.

    in this tester the high voltage spike is used to flash and neon bulb

    This was used and is stil now to make high voltages (an car initon coil is a good exsample)

    my shocker in the projets page uses this fenomenon to to make voltages up to 3000V from an 6V batery.

    I once toced the electromagnets of an operating bell (run from an batery)I got an shock(it wasent wery plesent)
     
  6. positive logic

    positive logic New Member

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    thats true. i see that circuit before in a magazine. :lol:
     
  7. steven

    steven New Member

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    Re: transformer checker

    if the transformer works in reverse mode i beleave it may work in forward mode, a simple circuit to test the reverse mode transformer is a simple scr circuit useing an scr and a resister or 2 and a 12 volts battery and a 12 volts auto indicator flasher unit from a car will do the job
     
  8. moody07747

    moody07747 Member

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    hmm

    i just use my continuity tester to test transformers
     
  9. steven

    steven New Member

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    transformer testor

     
  10. changiz

    changiz New Member

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    transformer tester

    what it will do if there is an open in the transformer primary and/or secondary wiring and my second quwestion is if the transformer is a multi voltage primary and secondary type, should we connect to each of the voltage input/output wires separately
     
  11. Someone Electro

    Someone Electro New Member

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    No flash if the transformer has an broken coil since no curent will run trough.

    If it has taps use the uper and the most botom tap since this way you get more inductance
     
  12. chaisi

    chaisi New Member

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    can any one xplain this circuit
     
  13. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Try reading the previous posts!.
     
  14. Hero999

    Hero999 Banned

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    Be careful, if you apply a pulse like this to the primary of some mains transformers and you can get a very high voltage at the secondary (in the order of 10kV), this can destroy the insulation.
     
  15. sheldonstv

    sheldonstv New Member

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    :D my multimeter set to ohms does the job........
     
  16. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    But only tests if the windings are O/C.
     
  17. sheldonstv

    sheldonstv New Member

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    :D a transformer can only fail in a few ways-oc primary,oc secondary or shorted turns -shorted turns primary will soon result in an oc winding,the same thing may also happen with the secondary.
    if you need to check the transformer is ok,check it by applying ac to the primary,set your meter to read ac volts and connect it to the transformer secondary-if there are any faults with the windings they will show up when checking in this way(without a load on the tx the secondary volts will be a little higher than usual,but not by a great deal)
    if you want,you could always ring the tx primary and check the secondary waveform with your scope.....but why make things too complicated when a simple continuity test or voltage test will suffice?
    regards mike
     
  18. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    This simple tester does ring the transformer, that's how it works - and you don't need a scope to use it. You also don't need to ring the primary and check the secondary, a ring test will detect any windings with shorted turns on the same core.

    You seem to be limiting the testing to mains transformers?, but the ringing test can be used on many more, audio transformers, switch-mode transformers, non-mains power transformers, line output transformers etc.

    It's a far more useful test than a simple ohms test, and faster and safer than a mains test.
     
  19. sheldonstv

    sheldonstv New Member

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    :D there are times when i need to use a scope to check whats going on with a tx-for example when testing lopts for go-nogo due to shorted turns(eht overwind etc)........also scancoils are sometimes checked in the same way.......
     
  20. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Yes, using a scope for that is a VERY old technique, certainly more than 50 years old, some old scopes even had a timebase output you could use to ring the transformer. But it's a LOT easier to use a handheld tester, I build one from a kit that came from Dick Smith Electronics, it's really useful - and was quite cheap as well!.
     
  21. sheldonstv

    sheldonstv New Member

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    :lol: you will have to forgive me as far as ringing transformers goes-be they audio,smps or flyback(and deflection coils )i am very much old school and set in my ways in that respect.
    hand held testers are handy to use ,ive built one specifically for testing flyback transformers and scan coils-it also will check audio txs etc-but being able to view the resultant signal on the scope is sometimes very much a necessity.
    regards mike
     
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