IC LM 555 as eazy and cheap TIMER

IC 555 most popular as multivibrator and can design as easy and cheap timer like this circuit. The TIME that you want as timer be calculate:

1.1R∗C

A relay timer circuit using the 555. On pressing the switch the relay is activated for a time determined by 1.1R∗C, where R∗ equals 100k plus the setting of the 470 kW variable and C is the capacitor value that has
been selected by the switch. Note the use of diodes to prevent latch-up and damage to the IC when the relay isswitched off.

Posted in: Easy and Cheap DIY timer