Trouble analyzing circuit

Discussion in 'General Electronics Chat' started by giv know, Jan 10, 2015.

  1. giv know

    Thread Starter New Member

    Jan 10, 2015
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    0
    min_ups.png
    I have the following problems understanding the above circuit:
    • I understand the part where the optocoupler activates transistor T3 acting as a relay driver. I also understand that this would activate relay RL1. But how does relay RL(a) get activated to N/O?
    • Also, when the relay is in the N/C position, how does power from the 12V SMF battery get to the output?
    • The NAND gate N1 has both inputs at the same value. When the ac mains is working, wouldn't the NAND give 0 as output where as it should actually be giving 1?
    Note: This circuit can be found at http://bestengineeringprojects.com/electronics-projects/advance-mini-ups/ along with an explanation. I can not make sense of the explainaion, hence this post.
     
  2. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    hi,
    Look at this marked up diagram, the Red arrows and text are for mains ON.
    E
     
  3. giv know

    Thread Starter New Member

    Jan 10, 2015
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    0
    The labeled diagram is quite helpful. Thanks Eric!
    Could you confirm if its safe to conclude that once RL1 gets energized, all 4 of its contact sets switch to N/O.
     
  4. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    hi giv,
    Yes, the relay has 4 pole change over, sets of contacts.
    N/O = Normally Open, N/C = Normally Closed, this is when the relay is not energised == Off.

    So all the N/O contacts are closed, when the relay is energised.

    E
     
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