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Ignition Coil Tester Transistor

Discussion in 'Hobby Electronics' started by Craig, Nov 5, 2003.

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  1. Craig

    Craig Guest

    Would anybody know of a transistor that can be conected to a high
    performance ignition coil that caan take the emf plus the amperage.

    What I`am doing is using a lm555 timer set at a known frequency, the ouatput
    of the lm555 is conected to the base of the power transistor in series with
    a resistor.

    I have used standard power transistors but they don`t appear to be able to
    take the current draw of the primary of the ignition coil, even with a diode
    connected across the collector and emitter of the transistor.

    Thanks Craig
  2. Hello Craig,
    I was just reading about that problem on the tesla coil
    enthusiasts web site.

    You will notice that a 2N3055 (that you may have used) is used
    to drive a horizontal output transistor from a monitor or TV, the
    diode also from a monitor.

    Up my way, there is going to be a council cleanup
    collection of discarded household goods and appliances.
    Bonanza time for spare parts!
    Trouble with me, I usually have a go at fixing old stuff
    that I pick up, then I am stuck with it. I must try and be
    more ruthless and just rip out the parts I want and not
    get sucked into fault finding challenges.

    Craig, do not buy those parts retail. You will find
    them easily, (on the footpath in Hornsby.) :)

    Have Fun,
    John Crighton
  3. Andy

    Andy Guest

    G'day Craig,

    In the past it was common to use transistors such as BUX80 or MJ10012
    on ignition coils with primary resistance of 3-4 ohms. A zener of
    anywhere between 180 to 400v (and sometimes a series resistor) between
    collector and emitter to keep transistor within SOA.

    By "high performance" I assume your coil has a primary resistance of 1
    0hm or less?. If so, you are going to have to come up with a circuit
    that limits the primary current to around maybe 6-7 amps (otherwise
    the coil will draw heaps of current and get *very* hot!). This can be
    done by adjusting the dwell time (angle) to keep the max primary
    current at the appropriate level.

    Probably the easiest way to test your coil is to get a used ignition
    module from a wrecker. Mount it on a heatsink and wire it up. A word
    of caution - if you go this way, get a module that is designed to
    trigger from a hall effect (i.e. square wave) signal - NOT from a
    reluctor (quasi sine wave) signal). The reluctor input types may do
    strange things when connected to the output of your 555.

  4. Bong, I was just about to suggest using a horizontal output transistor but
    ol' JC beat me to it. I would be going for a beefy one out of a large TV.

    AS for council clean-ups, well, you do get some good shit in sometimes. I
    always glance out of my car window and say to myself "I should come back and
    grab that", but I never do of course. I should, cause the other day, someone
    convinced me to take a whole heap of PCB's to a scrap merchant becuse they
    would pay me for it, rather than me paying to take them to the waste
    transfer station. Well I'll be buggered but they payed me something like
    $1.50/kg for the shit. Multiply that by the 30odd kg I had and thank you
    very much, i'll go buy me a box off piss.

    SO if you are in sunny Brisvegas and you have shit-tin of PCB's that are
    beginning to piss you off, then you can quite happily dump them off for the
    "help Real Andy buy a box of Piss foundation" or alternativly you can visit
    Admax scrap merchants at Virginia and claim the buck fifty or what ever it
    was per kilo. I think the former is the best option
  5. weco

    weco Guest

    Seems like a whole lot of trouble to run an old ignition coil....

    Had a client who was into ozone generators and he ran the dam things off our
    line voltage (120) with a standard lamp dimmer and a series AC cap and a
    standard ignition coil ..if I remeber right around 1 uf ...Produced a PILE
    of high voltage and he sold this gadget commercially...I ran piles of tests
    on it ...couldn't believe it worked ...but it did and it worked GREAT!

    So if high voltage is the object ..t.his is way easier than messing aroud
    with 555's and flyback transistors!

    cheers from up north
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