Light ballasts - other uses than for lights?

Discussion in 'General Electronics Chat' started by RogueRose, Dec 24, 2015.

  1. RogueRose

    Thread Starter Member

    Oct 10, 2014
    I was at a second hand shop the other day and they had a number of very large items which were either ballasts or transformers. They were very heavy (10-15 lbs like a MOT) or even maybe 2x the weight of a 1200w MOT (20-30lbs). The box was really non-descript but showed some diagrams of wires that might be found on a light ballast.

    Anyway, I am wondering if there is anything that these can be used for other than their intended use?
    Is there much difference between a flourescent, UV or metal halide light ballasts?

    Also, I have a 2' flourescent light which case is VERY light (it almost seems empty except for a switch). I thought that these bulbs needed a ballast. I have also seen the little cylindrical things, about the diameter of an incadescent bulb screw base, with maybe 2 metal feet/connectors at the bottom. Are these ballasts as well and if so, do they work as well as the heavy ones?
    Last edited: Dec 25, 2015
  2. #12


    Nov 30, 2010
    They do, and it's in there. It has merely been converted to a high frequency switching style ballast.
    Those are called, "starters". They provide the first spark which penetrates the length of the bulb so the next electricity can ride through on the ionized gas the first spark caused.
    RogueRose likes this.
  3. DickCappels


    Aug 21, 2008
    For very small luminaires one can use a series capacitor. Same idea -use a reactance to limit current rather than a resistance.
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
    The big ballasts are internally wired as a step-up auto-transformer with an output voltage approaching ~1kV. They provide no isolation from the AC line. Be damn careful if playing with them....
  5. tcmtech

    Distinguished Member

    Nov 4, 2013
    Given their modular core and coil construction they are pretty easy to take apart and rework for other applications plus given that they are designed to operate continuous duty at maximum rated power while in high ambient temperatures they take a thermal beating and overloading far better than any microwave oven transformer could ever dream of!
  6. MaxHeadRoom


    Jul 18, 2013
    Those sound like the starter switch from older fluorescent lamps.
    They connected the heaters together initially to warm up the tube gas, and opened by bi-metal strip.
    I recall in the very initial installations of fluorescent's, it was common in large work shops where the heat had been left off over the weekend to use a paraffin lamp or propane torch wafted along the tubes to heat the gas up to get them to strike.
    Last edited: Dec 26, 2015
  7. #12


    Nov 30, 2010
    Maybe I'm wrong about the starters providing the first spark. Maybe I was thinking about a gas ignitor.:oops:
  8. tcmtech

    Distinguished Member

    Nov 4, 2013
    There were a number of different types of fluorescent lamp starters over the years. The oldest ones I am aware of used the bimetallic strip to warm up the bulb filaments then opened up to get the arc to start in the tube.

    The later ones replaced the bimetallic strip with a small neon or similar rare gas type of voltage break over device that initially let enough current through to warm up the filaments then once it got warm enough itself went into a sort of higher voltage break over pulsing mode that caused the iron core type ballasts to create short HV pulses well above their line voltage generated output levels that would further improve the fluorescent tube arc striking when cold or as it got older.
    #12 likes this.
  9. ian field

    AAC Fanatic!

    Oct 27, 2012
    It would be a spark if there was a gap for it to jump across.

    A florescent starter shorts the gas in the tube so the heaters and the ballast are all in series across the mains, when the starter contacts open, the ballast produces a back emf to strike the tube.