IR remote control relay help

Discussion in 'General Electronics Chat' started by HaseebEngineer, Feb 2, 2014.

  1. HaseebEngineer

    Thread Starter New Member

    Aug 8, 2013
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    I have succesfuly made a circuit and its working but whenever i plug in the circuit the relay turn on automatically without even pressing the remote button. I dont know whats wrong with the circuit.
     
  2. ScottWang

    Moderator

    Aug 23, 2012
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    767
    You need a power up reset and another npn driver for LED, it means that you should adding another 4.7K and NPN to drive the 470 resistor and LED, why you should do that, because the output current is too less from Pin 2.

    Or you can try to moving 470 and LED to in parallel with the coil of relay, it will save the 4.7K and NPN bjt..
     
    Last edited: Feb 2, 2014
  3. ScottWang

    Moderator

    Aug 23, 2012
    4,853
    767
    The power up reset as:
    In series with a 47K/0.25w resistor between Pin 4 and Pin 15, and connecting a 0.1uf capacitor from Pin 15 to +6V.
     
  4. HaseebEngineer

    Thread Starter New Member

    Aug 8, 2013
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    Thank you for your help, i will try and will tell you if it helped ...
     
  5. HaseebEngineer

    Thread Starter New Member

    Aug 8, 2013
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    Actually the problem is not with the led ... its with the realy ... When i completely turn off the circuit and then turn it back on, the relay automatically turns on and the bulb connected to it turns on ...
     
  6. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,783
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    [​IMG]

    Where is the relay? I see what appears to be a transformer in the upper right?

    Is that supposed to be the relay? If that is the relay, which contact is moveable, which contacts are the NO/NC ones?
     
  7. HaseebEngineer

    Thread Starter New Member

    Aug 8, 2013
    22
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    no, its a relay ... and the pin to which the bulb is connected is the NC one ...
     
  8. HaseebEngineer

    Thread Starter New Member

    Aug 8, 2013
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    I did what u said but still not working properly ... Still when i turn off and then on the circuit the relay turn on and then i have to turn it off with remote ...
     
  9. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Try adding a small capacitance to the collector of the relay driver. Might be power on transients. 1 uf would be enough to see if that is the defect.
    Try it on the +6 volt power side of your relay coil first.
     
  10. HaseebEngineer

    Thread Starter New Member

    Aug 8, 2013
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    ok let me see what happens
     
  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    You should have a back-emf suppression diode (reverse-polarised) across the relay coil to protect the transistor. Also, a 0.1uF ceramic cap should be connected directly between the supply pins of the IC to decouple it.
    What is the purpose of the 10uF cap? It will slow down the edges of the clock pulse and could make the clocking unreliable.
    Your LED would be better driven from the transistor collector rather than from the IC (which has very limited output current sourcing capability).
     
  12. tubeguy

    Well-Known Member

    Nov 3, 2012
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    197
    The N/C contact will energize the bulb with the relay Off.
    So, it is likely the bulb will light up on power-up.

    To clarify, when you say the relay is On at power-up, is the LED connected to the output (pin 2) also On at this time?
     
    Last edited: Feb 2, 2014
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