This timer makes a LED be on for a certain amount of time after pressing the switch.
This time is adjustable from 3 seconds to 2 minutes using the potmeter.
Instead of a LED other load can be connected to this circuit, a relay for instance.

TinyCAD file of this circuit

R1 = 100 Ω
R2, R3 = 10 kΩ
R4 = 500 kΩ potmeter
C1 = 220 µF/16 V
D1 = LED
T1, T2 = BC 547B
S1 = Switch, normally open