Hello, I was hoping you all could help me out.

I'm looking for some basic electronics help. Let me describe the application first.

So we have a door with a magnetic strike that is connected to our phone system. We can open the door by typing a code on the phone, the only problem is the strike is silent when it opens, so people don't know when to pull on the door. I would like to place a buzzer inbetween the switching mechanism and the strike that sounds when the door opens. But since the strike is open for say 5 seconds and I don't want the buzzer sounding for 5 seconds I run into a problem.

So what do I need to do to add a buzzer that will only give a short buzz? The circuit the strike is on is 12 volts.

Help is greatly appreciated!

 

Don't know how much you want to built...from a schematic...kit...or off the shelf? Basically you are looking for a monostable circuit...and there a lot of them out there. LM555 integrated circuit versions are very common if you want to start from scratch. Velleman MK111 is a nice ~$5 kit version of the LM555 timer. SSAC makes commercial modules that will do On-Interval timing modules...~$30. This can also be done with a 12v SPST relay, a resistor and an electrolytic capacitor....and a 12v buzzer.

Ken

 

An old-fashioned "ding dong" type doorbell might work for this purpose.
http://home.howstuffworks.com/doorbell3.htm
Just connect in parallel with the striker.

However, for security reasons, you would want it mounted on the inside. Otherwise, a clever crook could energize your striker by using a portable power source (such as a battery) and gain entrance.

 

Don't know how much you want to built...from a schematic...kit...or off the shelf? Basically you are looking for a monostable circuit...and there a lot of them out there. LM555 integrated circuit versions are very common if you want to start from scratch. Velleman MK111 is a nice ~$5 kit version of the LM555 timer. SSAC makes commercial modules that will do On-Interval timing modules...~$30. This can also be done with a 12v SPST relay, a resistor and an electrolytic capacitor....and a 12v buzzer.

Ken

Ken, thanks for the help. I'm looking for something idiot proof. It's been a while since I've done electronics, I honestly do not remember much, if anything. I was hoping for someone to say buy a and b and add to the circuit, but sounds like it may not be that simple. Help is appreciated.

An old-fashioned "ding dong" type doorbell might work for this purpose.
http://home.howstuffworks.com/doorbell3.htm
Just connect in parallel with the striker.

However, for security reasons, you would want it mounted on the inside. Otherwise, a clever crook could energize your striker by using a portable power source (such as a battery) and gain entrance.

I'll take a look, thanks.