I want to make a timer that has a monostable with a time of around 690 seconds. In that 690 seconds, I want my buzzer to sound for 1 second, then stop for thirty second. I want this repeated until the 690 seconds are done. I have attached a picture of a circuit diagram of what I wanted to make.

I have tried making it but it doesn't seem to be working. When I trigger the monostable, the buzzer just sounds for 45 seconds and then goes off (until the button is pushed.

Many thanks..........

 

Hi,

If you use 29 seconds and 1 second instead of 30 and 1 you can do 23 cycles exactly.

I suppose you could do this several different ways.

 

Welcome to AAC.
The 555 is not really suitable for time periods as long as this, because the capacitor charging current is not much different from the capacitor leakage current. That results in erratic timing. Have you considered using a CD4060-based circuit, or a microcontroller, instead?

 

Hi,

The way i pictured it was a 29 second one shot followed by a 1 second one shot, then each triggers the other for an endless repeat cycle. A counter could count the cycles and stop after 23 cycles.

Yeah there are a lot of ways to do this. I would throw a microcontroller at it too, but some people are not into that kind of technology. With a microcontroller the time settings are infinitely variable and it can even be made adjustable with a pot or up/down switches, etc.