help needed...basic electronics circuits...

Thread Starter

utkarsh5

Joined Oct 27, 2011
7
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
 

Thread Starter

utkarsh5

Joined Oct 27, 2011
7
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...:)
 

Thread Starter

utkarsh5

Joined Oct 27, 2011
7
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 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...:)
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.
 

samin

Joined Oct 14, 2011
32
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.
 

Thread Starter

utkarsh5

Joined Oct 27, 2011
7
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.
the circuit you mentioned IS THE ONE I AM ASKING ABOUT.i want the schematic for it:)
 

Pencil

Joined Dec 8, 2009
271
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

Maybe a Bistable flip flop made from discrete components?

Here is an example: FLIP FLOP.
 
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KMoffett

Joined Dec 19, 2007
2,903
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...:)
What do you have available to power a switching circuit?

ken
 

samin

Joined Oct 14, 2011
32
the circuit you mentioned IS THE ONE I AM ASKING ABOUT.i want the schematic for it:)
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
 

Thread Starter

utkarsh5

Joined Oct 27, 2011
7
What do you have available to power a switching circuit?
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.
 

KMoffett

Joined Dec 19, 2007
2,903
Do you have access to SCR's (silicone controlled rectifiers)? This would be the simplest component to implement your requirements....I think.

Ken
 
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Thread Starter

utkarsh5

Joined Oct 27, 2011
7
Do you have access the SCR's (silicone controlled rectifiers)? This would be the simplest component to implement your requirements....I think.

Ken
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
 

KMoffett

Joined Dec 19, 2007
2,903
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
 

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sheldons

Joined Oct 26, 2011
613
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......


 
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