no LED to mains but how about fluoro tube to mains?

Discussion in 'The Projects Forum' started by takao21203, Sep 14, 2014.

  1. takao21203

    Thread Starter Distinguished Member

    Apr 28, 2012
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    can I discuss it on the forum? The picture would show a circuit that is not safe at all, thin flying wires, and 1uF capacitor which can charge upto 700 volts, always have to short it manually.
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Posted for 2hours and no reply from a few different Mods that have passed through, I would call that a "green light".
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    That is a lot like talking about no incandescent to mains, not very practical. The real problem we have with transformerless power supplies and LEDs to mains is the electronics used in what should be a low power device. If you have to ask you probably should not be doing it.

    The only reason to make a xfrmless power supply or LED circuit to mains is to save a buck, which is unacceptable. You can run florescent tubes off DC, but it will still need to be high voltage. The device itself is fundamentally a high voltage device.

    In every other case the moderation staff take it on a case by case basis. We still have final authority, even if it is not spelled out in the rules.

    Post it, and then we'll decide.
     
  4. takao21203

    Thread Starter Distinguished Member

    Apr 28, 2012
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    OK here the circuit, I know its bad because the thin wires. DSC02596.JPG
    Basically I generate 700 volts from 230, and charge 1uF in series with the CFL through 47 K Ohms.
    Result the lamps starts several times a second, improved that with a tin foil connected to 700 volts.

    however, it takes a while until the lamps keeps lighting up, and is erratic, goes off after some minutes. Also the tube quickly developed a black zone. Maybe the tube is too long and need permanent heating via the filaments?

    I made the circuit from several schematics on the web, using ideas from all of them, but it is still no good. the capacitor must be discharged manually each time. OK I dont have it running now, and I know its dangerous to charge 1uF to 700 volts.

    Also I have an insect lamp, never use it because I like insects, there is UV tube inside want to take a look at the circuit. Maybe it works with the longer tube too.
     
  5. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    If you wanted to discuss the merits of your design, and/or have questions concerning the source documents that assisted you in your design, go ahead and post the schematics.
     
  6. takao21203

    Thread Starter Distinguished Member

    Apr 28, 2012
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    Well its pretty simple- the tube in series with a 1uF foil capacitors bank, and a voltage tripler with 3 diodes and 2x 56nF, also charging the 1uF capacitor to 700 volts (through 47 K Ohms). Once that is reached the lamp ignites. It should keep burning but it does not, so I connected a tin foil to the 700v. Also I connected the filaments with a small 5nF capacitor.

    When using 2uF behaviour was not better but worse.
    The problem is I think the tube is too long and needs permanent heating perhaps, or a ballast specially designed for it.
     
  7. tcmtech

    Well-Known Member

    Nov 4, 2013
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    I don't see why you are going through the voltage multiplier system and what not. Back years ago it was normal to run four pin florescent tubes under 48" long directly off of 120 VAC power with nothing more than a series inductor and a lamp starter module.

    Simple, highly reliable, and cheap.
     
  8. takao21203

    Thread Starter Distinguished Member

    Apr 28, 2012
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    sure a series inductor, what would be the required value in mH? And they need to be large as some electric power is lost inside them.
     
  9. Brownout

    Well-Known Member

    Jan 10, 2012
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    Thought you were the joule thief king. I'm shocked you're not using a blocking oscillator/transformer to get the HV you need. That's how it's done in the floro lamps I've taken apart. The transformer is small much less than 1 in^3. The circuit amounts to a version of the JT, but it used push-pull transistors aka Royer circuit.
     
    Last edited: Sep 16, 2014
  10. tcmtech

    Well-Known Member

    Nov 4, 2013
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    The size and value will depend on how much current your lamp needs. Most 48" tubes need around 450 - 500 ma to run at full brightness.

    Inductor size wise the one we have over in dads shop has a inductor ballast that is about the size of a 30 - 40 va transformer and most any decently stocked hardware or building supply store still caries them. They cost about $10 - $15 for a new ballast inductor and starter unit.

    BTW other than during power outages that light over at dads has been on continuously for about 20 years now. :cool:
     
  11. takao21203

    Thread Starter Distinguished Member

    Apr 28, 2012
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    yes I looked at a lot of schematic, but dont have suitable cores or magnet wire here. Also these pocket lammps dont drive the tubes at full power i have read.
     
  12. takao21203

    Thread Starter Distinguished Member

    Apr 28, 2012
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    yes some years ago I had larger fluoro fixtures with a ballast inside. The right one for the thin 6W tube might be hard to find. Eventually I will try it with a PCB from a CFL some day.
     
  13. Brownout

    Well-Known Member

    Jan 10, 2012
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    The Royer isn't only used on pocket lamps. I've found it on everything from CFL lamps to copy machine CCFL backlights.
     
  14. takao21203

    Thread Starter Distinguished Member

    Apr 28, 2012
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    you compare the pocket lamps which indeed step up voltage, to CFLs. These just rectify and then generate high frequency, which is sent through a ballast. The transformer on the ringcore is just for oscillation, the larger core only has a single winding. It is effectively a ballast.

    Just to make clear I dont need to engineer this circuit or to use it, just playing around with these parts.
     
  15. tcmtech

    Well-Known Member

    Nov 4, 2013
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    As a kid I had a old desk lamp that used a small 1/2" x 6" fluorescent lamp in it and that had a small inductor ballast in the base on it so I know they exist some place.
     
  16. Brownout

    Well-Known Member

    Jan 10, 2012
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    I didn't compare anything to anything. I said the CFL uses a Royer converter, at least every single one I've looked at does. It runs at full power and full brightness. Whether or not is uses a step-up transformer is immaterial. However, the converter can be used to step up voltage if designed correctly.

    Royer oscillator circuit
    The circuit consists of a saturable-core transformer with a center-tapped primary winding, a feedback winding and (optionally) a secondary winding. The two halves of the primary are driven by two transistors in push-pull configuration. The feedback winding couples a small amount of the transformer flux back in to the transistor bases to provide positive feedback, generating oscillation. The oscillation frequency is determined by the maximum magnetic flux density, the power supply voltage, and the inductance of the primary winding.
     
  17. takao21203

    Thread Starter Distinguished Member

    Apr 28, 2012
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    there are some differences for instance the primary isnt center tapped. Also the transformer is only used for feedback.
     
  18. Brownout

    Well-Known Member

    Jan 10, 2012
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    Not always. In the ballast shown here, the transformer does more than just provide feedback. It uses a split primary rather than a center-tapped one. This is only so that NPN transistors can be used to drive both half-cycles. This difference has no effect on the ability to drive full power.
     
    Last edited: Sep 17, 2014
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