When reed switch is opened, pin 2 of Arduino goes high with the help of the pull-up resistor R2, and the alert signal is available through the piezo-speaker PZ1 (not an active piezo-buzzer). At the ...

Here is a simple Arduino Camping Light project. In this design, only one push button switch is used to control the light output ... OUTPUT); pinMode(switchPin, INPUT); digitalWrite(switchPin, HIGH); / ...