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ballast for small flourescent tube help

Discussion in 'General Electronics Discussion' started by aidan, Jul 17, 2011.

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  1. aidan

    aidan

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    0
    Jul 15, 2011
    so i go this small fluorescent tube from a scanner, and it has a ballast and everything on its own circuit board, but the problem is, being from a scanner, it takes a weird voltage like 18volts or something. now this is very inconvenient for me, something more so would be like 12 volts or 5, is there any way to make it accept 12volts as an input and still light the tube all the way? maybe switch out a cap or inductor?

    It has a model number if that helps,

    Cotek - 01-b117-0010
     
  2. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Cotek is a Taiwan manufacturer (since 1986). The fluorescent tubes are usually referred to as CCFL tubes. Did you try to Google it?
    Undervolting a CCFL-inverter is usually not a problem, though it may not give full output. I'd figure the voltage spec' is determined by the HV-transformer itself.
     
  3. aidan

    aidan

    29
    0
    Jul 15, 2011
    yeah, that was the problem I had had, 12volts on the longest of the two tubes didn't even make the whole length light up. I would like to find out exactly how many volts its designed to take but it is not listed anywhere, even on the power supply iteself there is no list of output voltages or anything of the like.
     
  4. daddles

    daddles

    443
    3
    Jun 10, 2011
    If it's a DC input, finding an 18 V wall wart shouldn't be too much of a problem. I've got two 20 V warts with 2 A output each; if you were a neighbor I'd just give you one of them. Easy to step down with e.g. an LM317.
     
  5. aidan

    aidan

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    Jul 15, 2011
    hm. Yeah, I hate not having something i need. It sucks.
     
  6. aidan

    aidan

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    Jul 15, 2011
    also, how much of an over voltage would hurt it anyways? if it was meant for 18, would 20 hurt it?
     
  7. TBennettcc

    TBennettcc

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    2
    Dec 4, 2010
    Just to be clear, you're attaching your input voltage to the transformer, not to the bulb itself, correct?
     
  8. aidan

    aidan

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    0
    Jul 15, 2011
    oh yeah, there is a DC input on the ballast itself (the circuit board has a couple of transistors and a transfprmer among other small components on it.) ia m applying th voltage to that not the bulb.
     
  9. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Just for reference: a Cold Cathode FLuorescent tube runs on a constant current of 5mA (high- frequency AC) and drops around 1kV or so (depending on its length).

    I'd expect the inverter input voltage tolerance to be at least +/- 10%, so I figure some 16-20V should be perfectly acceptable.
    The inverter will adjust its internal PWM to give a constant current to the lamp, so it'll light with a constant brighness as long as the input voltage is within reasonable limits.
     
  10. aidan

    aidan

    29
    0
    Jul 15, 2011
    ok, cool, thanks for the info.
     
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