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20 Watt Tubelight Emergency Light Circuit Diagram

This simple home emergency lights uses very few components yet is able to produce a reasonable amount of light. The components used are very common and can be easily procured from the local electronic retailer.

The idea is simple, the secondary winding of Tr1 and T1 along with the associated components forms a high frequency oscillator circuit.

This oscillations forces an AC in the secondary winding of the transformer which is further induced into the primary of the transformer and stepped up to the corresponding rated value ofthe transformer.

The transformer used is an ordinary 12-0-12 volt 1Amp rated, it can be retrieved from any old, junk power supply unit that might be lying in your electronic junk box.

The transistor also is an ordinary type, here a 2N6101 is shown, but any other similar type will do. You may try a 2N3055 transistor or even a D1351 in place of the specified one.

The 2k5 preset is used for adjusting the frequency of the circuit which in turn affects the brightness of the connected tube.

The preset must be carefully optimized for obtaining maximum brightness on the tube and yet keeping the consumption on the relatively lower side.

The 0.47uF capacitor is also introduced for enhancing the output from the tube light, you may other nearby values for improving the overall brightness.

The battery can be a 12V, 7 AH battery which should last many hours.

However you cannot expect full striking brightness from this circuit. When I tested this circuit, I could never bring the tube light to its actual specified striking brightness.

The following diagram shows how to make a simple 20 watt fluorescent tube, emergency light circuit.

20 Watt Tubelight Emergency Light Circuit

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    1. Hi Swagatam

      2nd paragraph not seems to be related with current circuit diagram. Correction is required.

      thanks and regards


      1. Done!

        Thanks very much Sam for pointing out the mistake.


      2. Hi Swagatam,
        Battery polarity is not mentioned... primary Center tap of the transformer should be connected to +ve and Emitter of transistor should be -Ve terminal of the battery...

      3. Hi Swagatam,
        Battery polarity is not mentioned... primary Center tap of the transformer should be +ve and Emitter of transistor should be -Ve

      4. You are correct, thanks very much.

    2. sir what the backup time if i connect to a 12v 7.5ah battery?

    3. hi sir i have a cfl like this given in the link
      i have a 11watt inverter. bulb is not switching is U-shaped and only a one side is switching on.may be 11watt is less is it true?do i need more watts.and can it be switched with this circuit?

      1. Hi Kiran,

        The circuit shown in the above article is not very efficient, but still you can try it, I think it might work with a 11 watt CFL.

        Keep a metal plate closely stuck with the U of the cFL, or just touch the U bulb with your palm when it's switched ON, it should strike fully on, if still there's no response then probably the inverter is low in power....

    4. I am an electronics and communication enginnering student .......can u suggest me a circuit for my mini project plssssssssss?

      1. You can try this circuit:

    5. Hi,

      I want to light up 10 no. 15W-20W compact CFL using a single circut.
      It should be able to operate the cfl if wired from a distance of 10meters.

      1. Hi,

        You mean from an inverter?

        You would require a 300 watt inverter for that.

      2. I had a few old 40w circut purchased from market which were in non working condition,after re-soldering all points it started to work , but there is a problem after about 30-40sec of operation Transistor and transformer gets too much heated and CFL stops glowing after that. What could be causing this excess heat. Another same circut is working properly, using a 23W compact CFL in both cases. If you can solve this issue these old circuits can be used instead of making a high watt inverter.
        I am using a 12V/25A lead acid battery.

      3. It's probably because the circuits do not have a current limiting feature in them.

        There's not much we can do in the circuit.

        You may try adding a 100 watt bulb in series with the input supply of each circuit, or a 200 watt bulb in series with two circuits.

        The filament of the bulb would hardly glow but will restrict over current from flowing into the CFLs.

        The idea may look a bit clumsy but it'll do the job.

    6. hi sir. can i use MOSFET (IRF540N) instead of transistor . will the circuit work with MOSFET.

    7. sir,will this inverter charge the battery?

    8. sir,will this inverter charge the battery??

    9. Is preset necessary for this circuit?

      1. it's for adjusting the brightness of the tube to the optimal point

    10. Hi friend,
      Thanks again for this circuit.
      I want circuit so it will run 18w tube(2ft tube) with the power of 3v 2A or 6v 2A battery, i have small transformer 6-0-6 500ma , but i dont want to use big one..(like if 1A transformer bigger then 500ma), if any changes i can make from your above circuit so please tell me, or which parts i have to replace??? i will replace the parts from the circuit you showing above.
      Thanks in advance....

      1. Hi Kamlesh,

        the above shown circuit is not very efficient and will not illuminate the tube with full can try the following instead:

    11. Good evening sir!
      can we get 40 watt flour.light by fitting two of these inverter circuit?if yes how to connect it each other?

      1. you can do it simply by using a higher rated transformer, no need of two units.

        but the illumination will be always half due to a half wave conduction in the trafo


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