Delay Timer circuit using 555 IC

Circuit Design:

1. 555 Timer Connections:
   • Connect the VCC pin (pin 8) of the 555 timer to the positive supply voltage (e.g., 9V).
   • Connect the GND pin (pin 1) of the 555 timer to the ground (0V) of the circuit.
2. Monostable Mode Connections:
   • Connect the trigger input (pin 2) to the junction of the resistor and capacitor in series.
   • Connect the threshold input (pin 6) to the discharge pin (pin 7).
   • Connect the discharge pin (pin 7) to the capacitor side of the resistor-capacitor series.
3. Resistor and Capacitor Values:
   • Connect a resistor (e.g., 10kΩ) from the trigger input (pin 2) to the positive supply voltage.
   • Connect a capacitor (e.g., 10μF) from the trigger input (pin 2) to the ground.
   • Connect the other end of the capacitor to the discharge pin (pin 7).
4. Potentiometer Adjustment:
   • Connect a potentiometer (e.g., 10kΩ) between the threshold input (pin 6) and the positive supply voltage.
   • Connect the wiper of the potentiometer to the discharge pin (pin 7).
5. Feedback Diode:
   • Connect a diode (1N4148 or similar) from the discharge pin (pin 7) to the junction of the resistor and capacitor.
6. LED Indicator:
   • Connect an LED in series with a current-limiting resistor (e.g., 330Ω) from the discharge pin (pin 7) to the ground. This will serve as an indicator for the timer output.
7. Normally Open Push-Button:
   • Connect a normally open (NO) push-button switch from the trigger input (pin 2) to the ground. This is used to trigger the timer manually.
8. Output:
   • The output is taken from the discharge pin (pin 7) of the 555 timer.

Working Principle:

• When the push-button is pressed, the capacitor charges through the resistor and potentiometer until it reaches the threshold voltage, triggering the 555 timer.
• The timer then enters a monostable state, and the discharge pin goes high.
• The LED lights up during the timing period, determined by the values of the resistor, capacitor, and potentiometer.
• After the timing period, the output goes low again.