theory on fridge door alarm

[edwardgith]

Hi,I would like to know the theory behind the variation of delay time with the changing of the values of C1 and/or the other component in the fridge door alarm project.Could anyone please assist me?

 

[audioguru2]

The datasheet for the project's CD4060 oscillator/counter IC explains pretty well how it works:
http://www.datasheetarchive.com/semiconductors/download.php?Datasheet=533773

View attachment 37644