Set output frequency of UPS

Discussion in 'The Projects Forum' started by libra, Aug 18, 2012.

  1. libra

    Thread Starter Member

    Jul 27, 2012
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    i have ups and the output frequency is 200+hz and remain variable when it is inverting from 12vdc. there is one variable which is used to adjust the frequency to 50hz, but i have adjust it but the frequency is above 200+Hz without load.


    Thanks
     
  2. libra

    Thread Starter Member

    Jul 27, 2012
    62
    0
    i have change the transformer of my UPS from 300W to 500W and after that the output frequency is 200+Hz and the frequency is variable not stable. i have tune the variable resistor with is 300kohm, but no success. 8 transistor irf3205. In the circuit ic used are 555, 4047,741 are used.
     
  3. bertus

    Administrator

    Apr 5, 2008
    15,647
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    Hello,

    Can you post a schematic?
    The frequency will have changed due to the other properties of the "new" transformer.

    Bertus
     
  4. libra

    Thread Starter Member

    Jul 27, 2012
    62
    0
    I have attached the picture of ups and also the pcb schematics.


    Thank you.
     
  5. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    What you have posted ts the PCB layout and not the schematic.
    Do you have the schematic?

    Bertus
     
  6. libra

    Thread Starter Member

    Jul 27, 2012
    62
    0
    On paper I have drawn, but it is not in proper manner. I am also attaching that.
     
  7. Audioguru

    New Member

    Dec 20, 2007
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    896
    Maybe the circuit is simple and cheap so the output frequency changes when the load resistance is changed.
     
  8. praondevou

    AAC Fanatic!

    Jul 9, 2011
    2,936
    488
    Please post a usable schematic.

    You mean you had a working UPS and then you swapped the transformer and this changed the frequency?
     
  9. libra

    Thread Starter Member

    Jul 27, 2012
    62
    0
    No i do not have the schematics :(
     
  10. libra

    Thread Starter Member

    Jul 27, 2012
    62
    0
    the transformer is burn and the transistor are also burned so i brought new transformer and transistor.
     
  11. libra

    Thread Starter Member

    Jul 27, 2012
    62
    0
    if i do not change the resistance the frequency is not remain the same.
     
  12. debe

    Well-Known Member

    Sep 21, 2010
    946
    184
    Hello,

    This is copied from the hyjacked thread by libra.
    This is possible the schematic of the kit used by libra.
    I will also add the posts in the hyjacked thread to this one.
    I can NOT change the order of the posts, they will be sorted by date/time stamp.
    Please continue to use THIS thread and stop using the thread of an other user.
    Unfortunately the threadstarters name changed to debe as that is teh first post now.

    Circuit of a 300w inverter kit i built that uses a 555 IC & a test point you touch & adjust till the led stops blinking, this should match local mains freq. Note iv only posted it for interest as i found it not very efficient so its part of my workshop mess. I purchased a comercialy made unit for very little more & works a whole lot better.
     
    Last edited by a moderator: Aug 19, 2012
  13. libra

    Thread Starter Member

    Jul 27, 2012
    62
    0
    what are that properties
     
  14. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The impedance and resistance of the transformer will be different.
    Ringing could lead to the experienced higher frequency.

    Bertus
     
  15. libra

    Thread Starter Member

    Jul 27, 2012
    62
    0
    Hello,
    By attaching more resistances can i decrease the frequency. Thank you for the reply bertus. i am also attaching the schematics, please see it.
     
  16. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    EEK! The schematic looks awful.
    It is a simple square-wave inverter without voltage regulation.
    Pins 1, 2 and 3 of the CD4047 are its oscillator which should be pretty stable if the 822 capacitor (8.2nF) is a metalized-poly type. If it is not available then a 10nF metalized-poly capacitor can be used.
    But it is probably a cheap unstable ceramic capacitor "made over there where cheap things are made poorly".

    I think pin9 of the CD4047 should connect to ground of the circuit.
     
  17. libra

    Thread Starter Member

    Jul 27, 2012
    62
    0
    I made the schematic through pcb which is very difficult for me. can i connect the pin9 with ground and transistor drain.

    Could you have some other schematic of UPS, then please share.

    Thank you
     
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