Re: buzzer
Use 3 x 555 timers or 1 x 556 (dual 555) and 1 x 555.
- 1 x 555 as astable oscillator for your sound need, for example 1000Hz.
- 1 x 555 as astabel oscillator with frequency of about 1Hz, or any you want for duration between sounds. This oscillator used to drive the above one.
- 1 x 555 as monostable oscillator (one shot) with duration (pulse length) = 3 cycles of the second astable. This oscillator used to drive the second one.