Inverter Circuit using 555

Discussion in 'General Electronics Chat' started by imraneesa, May 1, 2015.

  1. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    Dear Sirs,

    I am trying to make inverter circuit using 555 using the attached schematic diagram.
    except i used 33uf instead 100uf (first capacitor) and 3300uf instead of 2200uf.
    the transformer i took from 17w fluorescent emergency light. that had 5 pins. 3 pins output side and two pins primary side.
    i did not use the third pin. i dont know where to connect it.
    my problem when i connect it to the batteries (4x3.7v lithium batteries) i am getting input signal only 0.57ac and output when i tested is 1.1ac only. output is connected to 17w fluorescent tube. i am attaching the picture of what i did also. IMG_20150501_095655.png IMG_20150501_095704.png IMG_20150501_095727.png invertera.png
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,125
    3,048
    Divide and conquer. I would start by verifying that your 555 circuit is working. Break the connection between the output at pin 3 and the bases of the transistors. Put an LED there and see if it flashes. (You'll have to slow down the timer so that you can perceive the flashes.)

    While the two parts - the oscillator and the amplifier - are disconnected, you can also verify that the transistors are working properly. Just touch that resistor to either power rail to see if they switch as intended. It's very easy to get the pins wrong.

    You could also replace the transformer with a speaker, so you can hear your oscillator working.
     
  3. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    when i broke the circuit and added the led and changed the capacitor value to little big to slow down the frequency. the led start to blink good. now i am not sure how to test the pnp and npn transistors. in the datasheet it saying three pins as Base Collector and Emitter.
    why they have added 100 ohm at pin 3? the datasheet of tip41c and tip42c saying that the base current is 2A. if we are supplying 10v then resistor should be 10v/2amps i.e. 5ohms. why they used 100 ohms there. am i making any sense?
     
  4. tcmtech

    Well-Known Member

    Nov 4, 2013
    2,035
    1,660
    I suspect your transformer is a high frequency type not a low frequency type so that's where most of your problem is.
     
  5. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    so can i make use of same circuit with just changing resistor values to make it high frequency. how to make use of that transformer? how to find about that transformer? and what is that additional pin on the output side. is that have something to do with its working?
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    You may have to experiment with C/R timing values to get the best output from the transformer.
     
  7. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    when i check the voltage from the output after 2200uf capacitor to the negative terminal with the voltmeter i got ac current of 5v. but when i connect it to the transformer and then check the voltage on the input pins of transformer i only getting 0.5v. so where all the voltage going. if the frequency is not matching transformer does not behave good?
     
  8. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    That transformer will have a *VERY* low impedance at the frequency you want - you'll have a tough time driving any power into it!
     
  9. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    but the same transformer use to light that fluorscent lamp. i have the circuit but i did not understand. it it was using d882 transistor. how to find what frequency it need. how to solve this problem. give me some ideas. i will follow as you say. thank you very much for your patience and kind help.
     
  10. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    i just want that transformer work. i want to see it work to light that same light it use to light before. please tell me what i can do.
     
  11. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    The magic ingredient is switching frequency.
     
  12. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    how much frequency i can try it with. i am trying with in the range 40hz to 65hz. but no luck. but i notice as the low frequency output also reduced. so i dont know much frequency to apply. can you give me any idea? thank you.
     
  13. tcmtech

    Well-Known Member

    Nov 4, 2013
    2,035
    1,660
    I would start experimenting in the few tens of kilohertz range.
     
  14. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
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    Assuming your florescent light transformer has a ferrite core - it won't work at mains frequency.

    A few decades ago someone noticed that florescent tubes gave about 15 - 20% more light if they were driven with AC at 20kHz - you transformer is likely designed to work somewhere around that frequency.

    If you want to make a battery to mains inverter - you have to use a big heavy laminated iron core transformer, just like they do in uninterruptible power supplies.
     
  15. takao21203

    Distinguished Member

    Apr 28, 2012
    3,577
    463
    these transformers are notorious not to work right at low frequency.

    at 50 KHz you dont need 3300uF moreover it has no effect.
    The circuit is for iron core transformer.

    Also the tube needs starting voltage which is very high, then burns at maybe 70 volts, CFLs use a choke for that (like a HF ballast).
     
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