I am trying to make something similar to what is called a pull pin or personal alarm, sometimes it is called a baggage alarm. I want it so when you pull or cut a wire it sounds a piezo buzzer, even if you put the wire back in place or reconnect the wire the buzzer doesn't stop. I only want the buzzer to stop when you disconnect the battery. I tried using a 555 timer to do this but haven't had any luck. Does anyone know a circuit or have a schematic for something like this so I can finish this?

 

Welcome to AAC!

It would be helpful if you posted a schematic of your circuit so we know what we have to work with.

 

Yep, just made a quick crude drawing, keep the laughing to a minimum please. I was trying to pull the wire going from the trigger(2) out of the reset(4) slot and have it activate. I guess I am doing this wrong.

 

The trigger (pin 2) is connected to +5V and the threshold (pin 6) is connected to 0V – so it will never work.

I suggest you revisit your proposed circuit.

 

Use the output of the timer to trigger an SCR that switches the buzzer low side.

 

Use a sub-mini audio or power jack, with a built-in cutoff switch. The switch is open with a plug inserted; it closes when the plug is removed. Use this to trigger an SCR as mentioned in post #5, and that will give you what you desire.

 

Here's another option :-

 

Here's another option :-
View attachment 166279

Will that reset circuit work?
The reset can only go high if the output goes high and the output can only go high if the reset goes high.

 

You have two issues that need to be dealt with separately.
1) an oscillator
2) a non-resettable switch

Firstly, work on getting the piezo oscillator working.

For part 2, you need something such as:

OR-gate latch
SET-only flip-flop
SCR circuit

Any such circuit should do the trick.

 

The reset can only go high if the output goes high

No. The 555's internal PNP on the reset pin pulls it up above the critical ~0.7V unless there's a pull-down of <~2k.

 

First, do yourself a favor and use a buzzer that doesn’t need an external osc.

Second, the simplest alarm is probably the SCR or a mechanical relay that uses one of the contacts to keep itself powered, the disadvantage is…you need to push a button to set when powered on. (relay)

But, if you really want to use a 555…here is another option…tested in LTSpice.



EDIT:

Tested on breadboard as well.

 

Do you want the circuit to be wasting 10mA when it is sitting around "waiting"?

 

I don't know if you want to make the circuit for fun or if you just want the product of it, but you can buy an alarm at the dollar store for fairly cheap. They have a reed switch on the main circuit and a magnet on a bar that you put on your window. You could have the pin have the magnet in it and then just have a small door with a spring close over the hole to prevent re-insertion. Just another idea.