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Making a floodlight from the CCFLs from many broken monitors - need >1.2A, 700-1000V inverter

Discussion in 'LEDs and Optoelectronics' started by seanspotatobusiness, Jul 12, 2017.

  1. seanspotatobusiness

    seanspotatobusiness

    193
    4
    Sep 11, 2012
    I want to build a floodlight by combining the CCFLs of many broken LCD monitors (laptop and desktop) The laptops come with nice, compact inverters which I can re-use relatively easily but the desktop screens use massive circuit boards with a load of unrelated stuff which I think is too bulky, considering I'd want to use 15-20 such circuits in a single floodlight. Would it be feasible to make a single large inverter to run something like 60 CCFL tubes at the same time? I'm not sure but I think the voltage is like 700-1000 V and the current would be, like, 60 x 20 mA = 1.2 A.
     
  2. kellys_eye

    kellys_eye

    4,281
    1,144
    Jun 25, 2010
    Wow.... 1.2 amps and 700-1000V is a 1kW+ inverter...... not an easy prospect - not cheap either.

    LCD monitor CFLs aren't the way to do it anyway, fragile, different lengths etc. which may mean different strike voltages and an inverter with multiple outputs.....

    Considering you can buy 100W LED floodlights for $20 is this a realistic way to make a floodlight?
     
  3. seanspotatobusiness

    seanspotatobusiness

    193
    4
    Sep 11, 2012
    Thanks for replying. I think I will persist in trying to use their own circuit boards. I don't mind that the CCFLs are fragile since they're going to be mounted inside a protective housing. The screens all came to me for free because they're broken and not worth repairing.

    I took a close look at one circuit board and it looks like it might be justifiable to include it in its entirety. I could do with someone else taking a look at the below picture but I think the whole of the brown board is just a power supply for a) inverters and b) the display circuitry. I can tap into the 12 V and 5 V supply for my laptop inverters which accept those voltages (they all except either 5 V or 12 V). The only problem is I don't know how many laptop inverters I can power from this board (each inverter typically draws 400 mA at 12 V per CCFL attached). I can do away with the green circuit boards if I provide a 3 V signal to the inverter on signal.

    Any idea how I can estimate the power that can be drawn off the 12 V and 5 V lines of that supply?

    [​IMG]
     
  4. kellys_eye

    kellys_eye

    4,281
    1,144
    Jun 25, 2010
    Have you checked out the drive requirements for CFLs? This article explains how 'complicated' they can be.

    https://www.digikey.com/en/articles...equencing-and-attention-to-emi-pfc-and-faults

    If you use different size CFLs they will require their own inverter - not as simple as using a 'common' inverter and driving them all. You would have to re-purpose the inverter boards from each monitor to drive their own specific tube!

    Finding a supply to power the inverters themselves is straightforward enough - any old PC power unit will deliver the 5V and/or 12V required.
     
  5. seanspotatobusiness

    seanspotatobusiness

    193
    4
    Sep 11, 2012
    That's what I'm already suggesting. I will use the board from the desktop monitors to power their respective CCFLs and then use the 5V and 12V outputs from the same desktop monitors to power the laptop inverters. I can't easily cut off the excess desktop monitor circuitry so I might as well put to use as a power supply for the laptop inverters.
     
  6. seanspotatobusiness

    seanspotatobusiness

    193
    4
    Sep 11, 2012
    I've had a look at the back of a monitor that says it draws 0.7 A at 240 V. What translates to 168 W which is more than I was expecting. Assuming that the four built-in CCFLs use 8 W each, that would still leave 136 W. Assuming the power supply is only 60% efficient that leaves (168 W x 60%) - (4 x 8 W) = ~68 W. I've no way to tell how that's distributed across the 12 V and 5 V but if it's 34 W each then I can draw 2.8 A from 12 V and 6.8 A from 5 V?

    I figure I can probably attach eight laptop inverters to each desktop PSU (four on 12 V (1.6 A) and four on 5 V (4 A)

    [​IMG]
     
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