Inverter for Fluorescent UV lamp

Discussion in 'The Projects Forum' started by skullforger, Dec 10, 2010.

  1. skullforger

    Thread Starter Member

    Nov 3, 2008
    14
    0
    Hi,

    I would like to make an inverter for a fluorescent UV-A lamp, that I took out of a device to polymerise resin. Normally it gets power from this device, where it is in a socket, along with 11 other fluorescent lamps.

    However, we want to use one of those lamps and make it 'portable'. Can it be powered with a 9V battery and an inverter? If so, is it possible to just solder it together in a couple of hours (we need it next Tuesday).

    It is an Osram 9W UV-A fluorescent lamp.

    Thanks for your advice.
     
  2. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
    141
    Fluorescent lamps typically have two tungsten filaments at each end (hence the two pins). When starting the lamp, these filaments have a goodly current through them to heat them up. Thermionic emission combined with a decent high voltage across the tube causes the formation of a plasma inside the tube. When the plasma comes on, the tube's resistance drops many orders of magnitude and the voltage across the tube needs to be reduced and the filament current turned off. The small amount of mercury in the tube causes UV emissions (at around 254 and 365 nm, if memory serves) and these UV radiations cause the coating on the inside of the glass tube to fluoresce; hence the name.

    One way this is done is with a choke (called the ballast) and a switch in an enclosed glass envelope that's backfilled with a gas. These are very clever, simple, reliable, and low cost devices that have been highly engineered over the last 70 years (you can search the web to find out how they work -- they're fascinating). The other way is to do part or all of this startup task with solid state electronics.

    That said, this isn't something you can engineer yourself from scratch unless you're an experienced EE. You can buy the ballasts (chokes), tombstones (to hold the tube), and the starters and construct your own setup, but you have to get the right parts for the tubes you're using. I mounted a UV fluorescent tube on a chunk of plywood for doing some R&D UV measurements and it worked well (be careful about insulation, as there are hazardous voltages present). The other option is to go to an electrical lighting store and see if you can purchase the appropriate hardware.
     
  3. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,675
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    First, a 9V alkaline battery at 0.5 amp has only 300 mAH capacity (http://data.energizer.com/PDFs/522.pdf). That is, it will run maybe 30 minutes at 0.5A. At one amp, you will see maybe 10 minutes of use (the datasheet doesn't include a discharge rate of 1 A), if it will produce that current.

    Portable fluorescent lamps are available. The ones I have seen use AA or larger batteries. I recommend buying rather than trying to make.

    John
     
  4. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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  5. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    8W for $10. Bet you can't build one for that. The BIG unknown is the type of tube (pin type) the OP has.

    John
     
  6. mtripoli

    New Member

    Feb 9, 2010
    44
    8
    Have you considered using UV leds instead of the tube? This might be a bit easier to put together... Mouser has UV leds for short money.

    I'd keep in mind that exposing oneself to UV is dangerous. I'm surprised to hear that the lamp is UV-A for working with epoxy. Nonetheless, UV can cause all kinds of skin and DNA damage. Most UV units have some kind of interlock that keeps them from working when the device is open (and I wouldn't look into one either, unless you really want cataracts).

    Mike T.
     
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