help needed...basic electronics circuits...

Discussion in 'General Electronics Chat' started by utkarsh5, Oct 27, 2011.

  1. utkarsh5

    Thread Starter New Member

    Oct 27, 2011
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    i am working on a project,for which i want to use a tactile(push) switch as turn the power on,or off,or putting simply,i want to use it as a toggle switch.i want to do it without any ic,with basic components.i dont know much about electrnics,so please help me.thanks in advance.:D
     
  2. chrisw1990

    Active Member

    Oct 22, 2011
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    switching the power on/off for what?
     
  3. shortbus

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  4. chrisw1990

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  5. utkarsh5

    Thread Starter New Member

    Oct 27, 2011
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    let me put it more clearly.i am actually working a burglar alarm.i want to use it as a trigger,if it is triggered once,it goes on "beeping" until the power is switched off.i cannot use any ic,since the place where i live in is like a small town(or even a village).i wont be able to get any ic's.but for simple transistors,diodes and all,i can get them from broken radios,toys, or whatever.please help...:)
     
  6. utkarsh5

    Thread Starter New Member

    Oct 27, 2011
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    instead of the tac switch,i'm going to use a transistor.if the circuit is "completed" by the burglar,the alarm(buzzer)goes beep.
     
  7. samin

    Member

    Oct 14, 2011
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    It's easy enough to make a switch that has two parts ( switches that detect breakages) so that the alarm is triggered the metal tape or wire gets broken and the electrical current is interrupted.
    But i think the best, is to use the switches that detect motion They have two parts: a transmitter that sends out an invisible beam of infra-red radiation and a receiver (usually a photocell) that detects the beam some distance away.
     
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  8. utkarsh5

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    Oct 27, 2011
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    the circuit you mentioned IS THE ONE I AM ASKING ABOUT.i want the schematic for it:)
     
  9. Pencil

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    Dec 8, 2009
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    Maybe a Bistable flip flop made from discrete components?

    Here is an example: FLIP FLOP.
     
    Last edited: Oct 30, 2011
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  10. KMoffett

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    Dec 19, 2007
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    What do you have available to power a switching circuit?

    ken
     
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  11. samin

    Member

    Oct 14, 2011
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    Ok, let's take the example of switches that detect breakages and that are usually fitted to doors and windows.

    As i said those switches had two parts, one on either side of the door frame. When the door is closed, the two parts of the switch are close together and electricity can flow between them; when the door is opened, the parts of the switch are forced apart. No electricity can flow and the alarm is triggered. Some buildings have metal tape or wires running across or through the windows and carrying an electrical current. If a window is broken, the metal tape or wire gets broken too and the electrical current is interrupted, triggering the alarm.

    Switches like this can be made less conspicuous using magnetism detectors called reed switches. You have a magnet on one part of a door and a reed switch on the other. If the door opens, the magnet moves away from the reed switch, breaking the circuit and triggering the alarm.


    Here is a schematic using magnetism detectors founded here :

    http://static.howstuffworks.com/gif/burglar-alarm-circuit.gif
     
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  12. utkarsh5

    Thread Starter New Member

    Oct 27, 2011
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    i have a 9 volt battery made of 6 1.5 v cells.

    and by the way,it would be very simple if it were to simply detect a breakage in circuit.but it has to work as a trigger.if the circuit is broken once,it should go on beeping even if it is connencted again...................

    thnks,utkarsh.
     
  13. KMoffett

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    Dec 19, 2007
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    Do you have access to SCR's (silicone controlled rectifiers)? This would be the simplest component to implement your requirements....I think.

    Ken
     
    Last edited: Nov 1, 2011
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  14. utkarsh5

    Thread Starter New Member

    Oct 27, 2011
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    i searched about it a bit,and it comes out to be like "two tightly coupled BJT transistors".can i use two bjt's for that?:)

    thnks
    utkarsh
     
  15. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    I have no idea how your alarm circuit in configured.
    Attached is a latching alarm circuit with a pair of transistors connected as an SCR. Q1 (2N2907) can be any general purpose PNP transistor. Q2 (2N2222) can be any general purpose PNP transistor. I went with 12V circuit because a 12V relay will be easier to find in scrap parts than a 9V one. Just up the battery to eight 1.5V cells. SW2 is connected on alarm, and the SCR circuit closes the relay. The relay stays closed until SW1 is pressed.

    Ken

    Basic design:http://ecelab.com/circuit-transistor-scr.htm
     
    Last edited: Nov 1, 2011
  16. utkarsh5

    Thread Starter New Member

    Oct 27, 2011
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    thanks!!!!it really helped!!!!now i am going to build it!!again thanks!!:D:D:D
     
  17. radiohead

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    May 28, 2009
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  18. radiohead

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    May 28, 2009
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    Kmoffett, are those transistors connected to act like a triac?
     
  19. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    No. They're connected as an SCR.

    Ken
     
  20. sheldons

    Active Member

    Oct 26, 2011
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    well you could use a suitably rated scr as a very basic set reset latch....the switch to turn the scr off can actually be placed across the scr (anode -cathode) if required......


    [​IMG]
     
    Last edited: Nov 5, 2011
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