Buzzer for a normally closed switch

[MRR]

I'm sure there is an easy solution to my problem, but I very little electronics background and don't yet have a breadboard to even experiment on. In fact, it was only two days ago that I learned a 555 doesn't need to (or can) be programmed by a computer to use.

I want to make a buzzer that will go off for about two seconds when a push button is pressed. I'll figure out the capacitor and resister needs in the future, right now I'm concerned about how to make it work at all. The switch I will use this for is normally on.

Can I use http://www.kpsec.freeuk.com/images/555mono.gif" , but with the trigger taken out (solid connection) and the push button where the reset is? Or does that not allow the capacitor to charge correctly to buzz when pressed?

My other thought was to have the push button connected to a Flip/Flop and have that connected in the "trigger" spot of the above diagram.

Would either of those work? If neither work, please just tell me that (don't post a solution, I want to learn to fish, not be handed a fish) and I'll try other things when I can get a breadboard to work on.

Thank you
MRR

 

[hisham.i]

Hello MRR
Simply you can use the circuit you mentioned and what you have to do is to adjust the values of resistor R1 and capacitor C1 in order to get 2 seconds on state after you press the push button.
You have to put your push button in the place of the trigger.
The output to the buzzer is taken from pin 3.
the equation which gives the relation between the on time and the resistor, capacitor values in monostable operation is as follows: T=1.1*R1*C1

 

[MRR]

Hello MRR
Simply you can use the circuit you mentioned and what you have to do is to adjust the values of resistor R1 and capacitor C1 in order to get 2 seconds on state after you press the push button.
You have to put your push button in the place of the trigger.
The output to the buzzer is taken from pin 3.
the equation which gives the relation between the on time and the resistor, capacitor values in monostable operation is as follows: T=1.1*R1*C1

Even though the button is normally closed (button in the diagram pressed closed), the buzzer will still go one the button is pressed (trigger open)? I thought that would make the circuit buzz when initially powered and then not buzz again until the button was pressed (opened) long enough to charge the system for another buzz. Guess I really need to do some hands-on work before asking my silly questions.

Thanks for the info.
MRR

 

[vk6kro]

The monostable circuit has to be pulled low to trigger. So, yours would trigger when you stopped pushing the switch.

Switches are cheap, so it would be best to just get a normally open switch or just make one where you push two pieces of metal together.

If you really had to use that switch, you could try this:

[PLAIN]http://dl.dropbox.com/u/4222062/555%20with%20N-C%20switch.PNG

I have moved the switch to the high side of the trigger circuit as well as remove a few components you don't need. Seems like it would work, although I haven't tried it.

 

[MRR]

Sadly, the switch cannot be changed.
Thank you for this possible solution despite my request to not post a solution. I never would have stumbled across putting the switch there. If you hadn't posted the explanation, I'd never had figured out why that could possibly work; I'm still not used to electricity being about different volts instead of simply on or off.

Even if you layout doesn't work, it does give me another way to look at this problem.

MRR