Adjustable Delay Timer Using 555 Timer IC | Set 1–3 Minute Off Timer

[Sekhohub.online]

Create an adjustable delay-off timer using the 555 timer IC. Control fans, lights, or relays with flexible timing from 30 seconds to several minutes. Ideal for exhaust fans, alarms, or automatic switches.

Adjustable Delay Timer with 555 IC

In this project, we’ll build an adjustable delay timer circuit using the 555 Timer IC. This circuit allows you to set various delay times—from a few seconds to several minutes—by changing the resistance or capacitance in the timing network.

Features:

Fully adjustable delay (30 seconds to 5 minutes or more)
Works with 5V–12V DC supply
Can drive relay, LED, fan, buzzer, etc.
Based on monostable mode of NE555 timer IC

Materials for the Project

1x 555 TIMER IC
1x PC817 OPTO COUPLER
1x BC547 TRANSISTORS
2x 1N4007 DIODES
2x LED
3x 1K RESISTORS
2x 10K RESISTORS
1x 47K 3W RESISTOR
1x 470K RESISTOR
1x 1M RESISTOR
1x 22uF CAPACITOR
1x 470uF CAPACITOR
1x 12V RELAY
1x 2 PIN MALE HEADER
1x 2 PIN HEADER JUMPER
2x 2-PIN TERMINAL BLOCKS
1x 3-PIN TERMINAL BLOCK
VERO BOARD
JUMPER WIRES

Download Circuit Diagram

Circuit Diagram

⚙️How It Works:

When the push button is pressed, the 555 timer is triggered.
The output goes HIGH and activates the relay or load.
The timing duration is controlled by:
Delay Time = 1.1 × R × C
(R = potentiometer value in ohms, C = capacitor in farads)
When the time expires, the output turns OFF, deactivating the load.

⏲️Example Delay Times.

Potentiometer (R)	Capacitor (C)	Approximate Delay
500 kΩ	470 µF	~25 sec
1MΩ	1000 µF	~1.1 minutes
1MΩ	2200 µF	~2.5 minutes
1MΩ	4700 µF	~5 minutes

Video Tutorial

Tips & Customization:

You can use a multi-turn potentiometer for fine adjustment.
Replace the relay with a MOSFET for silent switching.
For longer delays, use a lower leakage capacitor.

Real-Life Applications:

⏱️ Kitchen exhaust fan that runs for 3–5 minutes after cooking
Bathroom exhaust with auto shut-off
Room lights with auto-off feature
Buzzers or sirens that stay on for a set time
Delay OFF relay module for appliances