To make this simple alarm not even need more time. Yes we should have an NPN transistor that I have chosen them BC547, a rsistor100k and a consumable that you should inform you of any cases dagger .But I also used a plate with two transistors to pass on the issue of sound stood is you can even without the sign that can function.
- Here you have been given schematic for a better information
- Here's what else you need.
- transistor NPN
- resistor 100k
- buzzer,led etc
- pcb and bred board for testing