This 555 timer circuit uses a simple 555 IC chip. The 555 timer circuit starts after turning the switch on. The green LED lights up to show that the timer has started. When the timing is over the green led switches off, and the red LED switches ON and the beeper beeps.
The timing of this 555 adjustable timer circuit is up to 10 minutes by adjusting the variable 1 meg pot. You can mark the times on a scale drawn on your enclosure next to the 1 Meg Pot. You can use any form of timer to calibrated the device, and the method I have found best is an app on a cell phone called a kitchen timer.