Pull Pin security alarm

Thread Starter

Rider_01

Joined Sep 20, 2018
3
Hello all, I am starting to learn about electronics due to a project of mine. I need to make an alarm that when you pull a wire out or disconnect it then it sounds an alarm, basically like some would call a luggage alarm or a pull pin alarm. I need it to be compact and light but also loud, I need help with a proper schematic if anyone knows of one and the components.

I have been doing some research and I would like it as loud as this or louder if possible:


I don't need the tone change but is the 555IC and NPN transistor the best way to accomplish this or is there another setup that would give me that loud, constant frequency while being in a compact package. Thanks for all the help.
 

Thread Starter

Rider_01

Joined Sep 20, 2018
3
If I'm reading you correctly these can be bought for very little money, units such as this?
Yes, that concept but I am putting the circuit in something else to act as a safety device and need to be able to modify it depending on duty cycle of the machine. I need something much louder than those novelty pin alarms also, I tested one and 10 feet away you could hardly hear it.

I found a schematic for one that might work, something like this but I need it to be pretty loud.

http://www.ee.teihal.gr/labs/electronics/web/downloads/Circuits.pdf
 

AnalogKid

Joined Aug 1, 2013
10,988
A traditional speaker is not a very efficient transducer. Other types of acoustic transducers give you more sound pressure level per input watt.

The link doesn't work.

If you don't need variable tone frequency, consider a self-oscillating piezo beeper. They are very efficient in both loudness per electrical watt and loudness per cubic inch. Alarm-grade units will cause permanent hearing damage. Battery - switch - beeper - done.

ak
 

Thread Starter

Rider_01

Joined Sep 20, 2018
3
I think you are right, a speaker is going to need too much power to make it as audible as I need. I did see the piezo beeper and I am considering that because it is very efficient in power usage vs output. Is there any other beeper you would recommend? I would like to have a couple options. I uploaded the picture of the schematic from the link that didn't work. Any opinions on this and I am assuming that a beeper could be interchanged with the speaker in this:

 
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