need help please

Discussion in 'The Projects Forum' started by oolesh, Apr 23, 2012.

  1. oolesh

    Thread Starter New Member

    Apr 21, 2012
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    can i activate this transistor like this please??? ll.png
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    What is the wattage or current requirements of the bulb?
    Why do you need the relay?
    Why do you need the 1.5v battery?
    The -ve side of the battery needs to be connected.
    You need to limit the current into the base of the transistor.
     
  3. oolesh

    Thread Starter New Member

    Apr 21, 2012
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    it's a 5v clap on circuit so i want to modify it by removing the led then put a relay to switch a bulb because it's useless like this HELP ME $(KGrHqEOKnIE4Fi3hCt2BOHWOM,3Ug~~_12.jpg
     
  4. MrChips

    Moderator

    Oct 2, 2009
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    What is the voltage and wattage of the bulb?
     
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  5. wayneh

    Expert

    Sep 9, 2010
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    This thread is a continuation of your other thread on this topic. The mods should merge them.

    You need to understand that current can only flow in a loop, a circuit. Connecting just one pole of a battery does nothing - there is no loop. You probably want to connect the "-" poles together, and then your arrangement will work. (Base resistor still needed, as discussed in your other thread.)
     
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  6. panic mode

    Senior Member

    Oct 10, 2011
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    point of any such modification is to leave original circuit operational.
    circuit you posted is designed to drive low power device - n LED.
    you don't want to load the circuit too much by adding relay directly.

    there are different ways to get this done, for example by adding additional transistor driver that turns on relay. or you could remove LED, and replace it with an input of a optocoupler. if optocoupler has high current transfer ratio and output voltage rating of say 35V or more, you can use it directly to drive small 12 or 24V relay (need still need diode across relay coil to suppress kickback and protect optocoupler).
     
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  7. MrChips

    Moderator

    Oct 2, 2009
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    Along the same line, I am assuming the bulb is a 120VAC lamp.
    I was going to suggest leaving the original board as is but drive an SSR (Solid State Relay with an AC load).

    Of course since this requires AC mains wiring, it would require particular attention to safety and proper housing and this forum frowns upon such projects.
     
  8. oolesh

    Thread Starter New Member

    Apr 21, 2012
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    oh yes i will try the optocoupler!!! i will remove the led and put the optocoupler!! can i use any Optocoupler on it? is this model is good 'PC817 Optocoupler'
     
  9. oolesh

    Thread Starter New Member

    Apr 21, 2012
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    no it's a 10 watts bulb sir
     
  10. MrChips

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    Oct 2, 2009
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    You do not have to remove the LED.
    You may be able to drive both the LED and optocoupler in series.
     
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  11. oolesh

    Thread Starter New Member

    Apr 21, 2012
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  12. MrChips

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    I would skip the mechanical relay and use an SSR instead of the optocoupler.
    You still have to stated the voltage requirement of the bulb.
     
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  13. oolesh

    Thread Starter New Member

    Apr 21, 2012
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    can't find the SSR here in mauritius but the optocoupler easy to find here and it's very cheap OPT-PC817-pinout.jpg so the pin 1 is + and pin 2 is - ! what is the maximum voltage can i put on pin 3 'negetive' and 4 'positive' !! i want to put a 12v 8w Tube Light on it ! what do u think if i put the 12v Tube Light directly i use the optocoupler like a switch??thanks alot SIR:)
     
  14. oolesh

    Thread Starter New Member

    Apr 21, 2012
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    i made a circuit please check it OPT-PC817-pinout.jpg
     
  15. MrChips

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    Oct 2, 2009
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    Can your optocoupler handle 1A?
     
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  16. oolesh

    Thread Starter New Member

    Apr 21, 2012
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    i dont know it's a Optocoupler PC817!!!check it for me PLEASE
     
  17. panic mode

    Senior Member

    Oct 10, 2011
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    you should check it. :rolleyes::p

    reading datasheets is part of the job. if you don't understand something, then ask questions.
     
  18. oolesh

    Thread Starter New Member

    Apr 21, 2012
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    i got the datasheet Untitled.png what is Peak Forward Current ??i see it's 1A so it can handle 1A?? the maximum voltage is 35v collector to emitter so i can put 12v?please reply me :(
     
    Last edited: Apr 24, 2012
  19. Audioguru

    New Member

    Dec 20, 2007
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    The datasheet for your low power opto-coupler shows a maximum allowed Continuous Forward Current of only 50mA. Its maximum allowed Peak Forward Current of 1A is for a duration of only 100 millionths of a second occasionally.
    You need a rating of 667mA continuously.

    You must use a high power darlington transistor instead with a suitable arrangement of base resistors.
     
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