Fancy Switching Circuit

Hi guy's, just stumbled across your site, its brill! !

Not well up on electonic's but do a lot of messing about. need a little help here!

I need a small circuit to latch together for 1 sec after being triggered by an audio triggering circuit.

How do i avoid the same thing happening over and over again, i would like a period of about 15 mins before it would trigger again. Possibly without using pic cause im not well up on writing code.

What my plan is:


When the audio dection detects sound it will hold the "1" key on a phone down for one sec to call a pre-programmed number. Been playing around but keep having the 1 key being pressed on and off continuisly by sound

Cheers

James

What sort of setup do you have for pressing the key? Using a 555 timer set for about 15 minutes and a normally closed relay you could disconnect the audio input so that it would not re-trigger the key-press. The 15min 555 could be turned on by a second 555 whose time period is set for 1 second. The only issue we must get around is the triggering of the 15 minute 555 AFTER the 1 second
555 has completed.

***
Check the "Two Stage Time Delay Circuit" at the following link:
**broken link removed**

I think this will do the trick.

This is a plan.

You would need a monostable with a 15 minute period. The monostable control the DC power to the relay that you are using to "press" the 1 key on the phone.

The relay power supply line also have a 2,200uF capacitor connected for charge storage.

As soon as the audio signal is detected, the monostable cut off the supply to the relay circuit. But with the 2,200uF capacitor still connected and charged, the relay will operate for a short time until the capacitor charge has been exhausted. Larger capacitor value gives you longer time upto a few seconds.

No more audio signal will trigger the monostable until it resets, after 15 minutes.

Thanks guy's, what a brill forum, really contructive help, im off to play for a bit. ill let you know how i get on!

Just in case any one hasnt copped onto what im doing is im trying to use old cheap handsets for "intruder" alerts around the place, the audio detecter was only one idea, im sure it wouldnt take huge figuring out to change it to something more suitable, ill post a schematic if i get working!

@ ionic--- i'm using an 4 pin optocoupler for pressing the button, when it detects a voltage at one side it joins the 2 pins at the other, really handy things, i love them!

J Reidy said:

Just in case any one hasnt copped onto what im doing is im trying to use old cheap handsets for "intruder" alerts around the place, the audio detecter was only one idea, im sure it wouldnt take huge figuring out to change it to something more suitable, ill post a schematic if i get working!

@ ionic--- i'm using an 4 pin optocoupler for pressing the button, when it detects a voltage at one side it joins the 2 pins at the other, really handy things, i love them!

Click to expand...

I had thought you were up to something like that! And as you said, audio may not be the most suitable detection method. A simple noise from the house could cause a false alarm. Maybe motion sensors would do better.

By the way, the phone number that would be dialed, are you thinking of the Police Department or your cell phone. If it called your cell phone I know there are some answering machines that allow you to call home and monitor the sound. At that point You yourself could call the police department with the
"Actionable Intelligence."

Optocouplers are indeed great buttons/switches...