Stair lighting electronic project using 555 timer

Using this electronic circuit can be made a very useful circuit that can be used for stair lighting. The circuit is very simple, requiring fewer electronic components and is made using 555 timer.
When one of buttons push buttons is pressed, phase wire ( marked "F" in diagram) provides voltage to lamps connected in circuit. Meanwhile, Tril triac is triggered, so lights remain lit after the button is released. After preset time has elapsed for the state "ON" light will turn off automatically.
Power supply voltage for IC is derived from the network, the resistors R1 and R2, capacitors C1 and C2, diodes D1, D2 and D3
For the component values given in this electronic scheme, the setting can be between 30 seconds and 12 minutes.