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Why does a LED tube light need a ballast?

Discussion in 'LEDs and Optoelectronics' started by Braeden Hamson, Oct 6, 2018.

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  1. Braeden Hamson

    Braeden Hamson

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    Feb 18, 2016
    So I was at home depot and I laid eyes on a nice 4ft LED tube light for $7.

    https://www.homedepot.com/p/Philips...-Light-Bulb-Cool-White-4100K-468702/301154647

    I figured this would be great for projects because they have the tube and everything, I figured I don't need a fixture for them, I can make my own! I know electronics. Hubris, hubris seems to have bit me. I got home and connected wall voltage right to the pins of the light, nothin'. After scouring the internets I saw that they needed "instant start ballast" which makes zero sense to me because ballasts are for fluorescent bulbs to make sure the current doesn't run away. What strange twist of fate made the thing need a ballast?
     
  2. Bluejets

    Bluejets

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    Oct 5, 2014
    Could be many reasons.
    LED tubes are a bit like video tape players, audio tape cassettes, dvd's and all the other competing system types that come about.
    LED tubes have many and varied types, each trying to corner the market with specific characteristics, not the least being safety(pin live examples) remote drivers due to heat build-up, efficiency, life expectancy etc. etc.

    I have seen some LED tubes "directly fitted" by amateurs, thinking they would "save heaps of money".
    Fact is it makes little difference to the running cost versus the short life of these new technology thingos.

    That plus they require some type of driver to control the mains supply as LEDs as you know run at lower dc.

    One particular group of around 150 light fittings with 4 tubes in each, died rather spectacularly in a cloud of smoke and sparks over a short period of time due to the internal driver blowing it's guts. Was a great show for the kindergarten kids woken from an afternoon nap not to mention the stink from the burning plastics.

    That plus the original fly-by-night supplier forgot/didn't know, to include the line fuse with each tube.
    $40 a tube at that time x 4 tubes each fitting x 150 fittings....... mmm , that plus less than 12months return on investment, PLUS fittings had to be repaired before new tubes fitted.
    Two tradesmen for 4 days not cheap especially since work not allowed during normal daytime hours.

    Everything is not as it seems.
     
    Braeden Hamson likes this.
  3. Braeden Hamson

    Braeden Hamson

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    Feb 18, 2016
    Hahaha, part of me hopes that one of those kids was dreaming that they had super powers. Then they woke up to that electrical storm, and have been trying to prove they have super powers ever since.

    It also kinda makes me want to go back and buy one, just to make the damn thing work. But $20 for 5 meters, it'd be kinda silly to try XD
     
  4. dave9

    dave9

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    Mar 5, 2017
    They need a ballast because they are designed to be drop-in replacements in existing fluorescent fixtures with a ballast that produces a few hundred if not KV range to drive fluorescent tubes, so they have a buck voltage regulator circuit that drops the high fluorescent tube needed voltage down to what that specific bulb series/parallel LED array needs.

    If you want to roll your own just avoid those that are retrofits, but if you want to roll your own, unless you "want" to use an existing fluorescent tube housing (I can see merits in it to lower cost and design time) and you need a minimal to no change in wiring (which doesn't seem to be the case) then there are also retrofit bulbs that allow rewiring the fluorescent housings to take the ballast out of the equation and just wire the 110VAc straight to the "bulbs".

    To be clear, even if you have fixtures with ballasts, if you are reading this forum then you should be capable of, and should choose bulbs that have you wire the ballast out of the circuit. There's no sense in continuing to use ballasts with LED "EXCEPT" if you plan to move in a few years and want to be able to just pop the old fluorescent tubes back in and take the LED bulbs with you.

    However, if you have a working fixture with a ballast, it doesn't make economical sense to replace fluorescent tubes with LEDs. If you are running lights that many hours, the fluorescent lifespan is good and efficiency not different enough to justify the conversion.

    If the fixture was in a very cold area or one where lights were turned on and off a lot that could make sense, but what wouldn't make sense was if a fluorescent fixture was put in those environments in the first place.
     
    Last edited: Oct 7, 2018
    Braeden Hamson and Bluejets like this.
  5. Braeden Hamson

    Braeden Hamson

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    Feb 18, 2016
    I actually don't have any fixtures, I was actually trying to give my aloe vera plants some indoor lighting. After this ordeal I just went ahead and bought a $40 grow light. Which in retrospect, was a stupid idea because its just white lights... That's gonna bug me now.

    Anyway, thanks for the information. It's now kinda obvious to me that if it's supposed to go into a ballasted system it'll run on 100/1000's of volts.
     
  6. Bluejets

    Bluejets

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    Oct 5, 2014
    No, does not work like that either.
     
  7. Braeden Hamson

    Braeden Hamson

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    Feb 18, 2016
    Crap. You know what, I'm just gonna stay away from those infernal things.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    A traditional florescent bulb is a device with a breakdown voltage and a negative resistance. Getting your head around these is not trivial.

    Led bulbs are completely different but have their own issues.

    Neither can be connected to AC mains directly, requiring a driver of some sort. Fluorescent lights are older and have a traditional electromagnetic solution (a ballast). Led "fluorescent" bulbs are often designed to fit into existing fixtures, either with internal drivers or replacement parts which look like the traditional starter or ballast. Regardless of the names given to them or their shape, they are totally different and electrically non interchangeable.
     
  9. hevans1944

    hevans1944 Hop - AC8NS

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    Jun 21, 2012
    When we bought a house here in Florida it came equipped with fluorescent "curly bulbs" in every light fixture, except for two two-lamp, 4-foot, fixtures in the laundry room and garage. So we spent the first year here slowly replacing the curly bulbs with LED bulbs, not for improved efficiency but simply because we like the LED lamps better. Up north, the curly bulbs took a long time to warm up in cold weather, but that is obviously not a problem here.

    I planned on replacing the fluorescent tubes in the two 4-foot fixtures because the ballasts were somewhat noisy (my wife has very sensitive hearing), but I decided to do the laundry room first because (1) wife doesn't spend a lot of time in the garage and (2) I want to install new LED shop lights over my workbench in the garage. The LED replacements worked fine, and we did not have to change (or bypass) the ballast wiring. Unfortunately, the ballast still makes an audible noise when the LED lamps are on, so I may have to rewire the fixture and "bypass" the ballast to give my wife peace of mind while she does laundry. More research is needed before I commit to this. I wouldn't want to bypass the ballast and then discover that a prospective future buyer really likes genuine glass-bulbed fluorescent lamps... assuming those are still made later in this century.

    I think @dave9 is 100% correct about why the LED lamps are made to be backward compatible with fluorescent lamps. The current batch of LED replacements for incandescent bulbs is much better than the earlier versions: more reliable, electronics runs cooler, LEDs are now dimmable (pretty much), and the cost is becoming competitive with incandescent. Since the US Government has practically banned 100 W incandescent lamps, about the only alternatives on the shelf at Wally World are LED lamps. This seems to have inspired a "retro look" back to original Edison lamps, but I'm not biting. I did discover (accidentally) that I can break the plastic "bulb" on an LED lamp that imitates the frosted-glass envelope of an incandescent lamp, thereby exposing the individual LED emitters, and the lamp continues to work just fine... maybe even better without the plastic absorbing some of the light emitted by the LEDs.
     
    Braeden Hamson likes this.
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