I need a setup that will enable a Piezo 12V buzzer/alarm to be triggered to sound after a given time. This is not going to be hooked to any other device. I will need the Piezo to sound 2 hours after set. What are my options? I am a novice with circuits, but would be willing to make a project out of this if there is a solution. Thanks very much in advance!

Drew

Also, posted this in the wrong forum to begin with. This shouldn't be in "Homework Help".

 

Is this a Piezo element that you're driving with an oscillator or is it a DC powered Piezo Sonalert? If it's the latter, what's the required DC supply voltage?

 

Hello djridgeway17

You mention in your post that the "Piezo Buzzer or alarm" is for 12V.
But do not mention what type it is. As CDRIVE is asking you.

Assuming your "Piezo Buzzer or alarm" is a black box and it has an Input to enabling it’s sound,
So what is required is to make a timer to enable the black box 2 hours after the start.

If this period of time (2 hours) will be fixed the circuit would be more or less straightforward.
It takes a time generator (555), a counter circuit, some gates, oh, and of course the start button and the power supply.

Now
Which Integrated circuits for the counters you like to use?
You would use the family integrated circuits: CMOS or TTL?
You have a circuit simulator?

Greetings
at your service

 

Thanks for quick responses. Yes, the Piezo buzzer is and off the shelf one from Radio Shack. Black box with a hot and ground from it. The voltages are 6-16V DC. Like I said, I am a newbie at this stuff, so excuse me for my lack of knowledge or terminology with this.

 

Actually, I apologize for missing your reference to a 12V Piezo Buzzer in your first post. It was 0130 hrs here when I replied. Anyway, what triggers the 2 hour timer?

 

The trigger for the two hour timer will be myself. I can set/arm the countdown.

 

The trigger for the two hour timer will be myself. I can set/arm the countdown.

Back in the 70's there was an IC manufacturer that incorporated a basic 555 and two counter blocks within a single 14 or 16 pin DIP. They easily produced time delays into hours. Unfortunately I haven't seen this chip in years.

The easiest (off the shelf solution) is a programmable plug in timer which are available at home centers. Connect the Sonalert to the output of a 12V wallwart, plug the wallwart into the timer and plug the timer into the wall outlet... done.

What is the application?

 

Now for the application: no wall plug will be available.

This is for a high altitude/near space balloon launch. I want an audible beacon after landing, but this landing will not occur until 2-2.5 hours. To ensure battery life of the beacon is not exhausted on the way up I was looking for a way to delay the power to it. If I am chasing the wrong solution let me know. I am open for any and all suggestions.

Thanks!

 

It just occurred to me that a digital kitchen timer already has an integral Piezo. They make them with count downs up to a 24 hrs.

http://www.partshelf.com/kitchen-timers.html

EDIT: This post was made prior to knowing the OP's application, which was posted just minutes before this.

 

Now for the application: no wall plug will be available.

This is for a high altitude/near space balloon launch. I want an audible beacon after landing, but this landing will not occur until 2-2.5 hours. To ensure battery life of the beacon is not exhausted on the way up I was looking for a way to delay the power to it. If I am chasing the wrong solution let me know. I am open for any and all suggestions.

Thanks!

This is a text book example of why it's so important for an OP to tell the whole story in the first post! Why in the world would you have withheld such vital information?

The Mods should make a Sticky of this!

 

Unfortunately, this item doesn't provide audio output (dB) specs. I assume you need a very loud Piezo.
http://www.partshelf.com/taylor-5828.html

 

You are right. I definitely should have given that FIRST. Sorry. So... Could I replace the speaker in the kitchen timer with a louder Piezo?

 

Also, thanks for your help so far. You could have been more help quicker if I would have done my part.

 

Yeah, looking for around 100db. I will be tracking the landing with GPS, but this will be my backup if the GPS accuracy is worse than anticipated.

 

Hey Guys, Does anyone know if timers like the one in my link are available with a jack that supplies a contact closure or a solid state switch?

 

I found it, 100dB....and cheap!!

http://www.bodytronics.com/p/timers/CC5014

 

Awesome!

Thanks. looks like that will do the trick. I will let you know how it works out. I owe you a sponsor on my launch.

 

Best of luck with your launch!