555 Timer with On/Off Indicator

Building a 555 Timer Circuit with On/Off Indicator for your Projects.

To create a 555 timer with an on/off indicator, you will need the following components:

• 555 Timer IC
• Resistors: 1kΩ, 10kΩ
• Capacitors: 10μF, 0.01μF
• LED
• Transistor (NPN)
• Diode (1N4148)
• Battery (9V)
• Breadboard
• Jumper wires

Here are the steps to create the circuit:

1. Place the 555 Timer IC on the breadboard and connect the positive rail to the VCC (pin 8) and the negative rail to the GND (pin 1).
2. Connect a 10kΩ resistor between the VCC and the trigger (pin 2) of the 555 Timer IC.
3. Connect a 1kΩ resistor between the output (pin 3) of the 555 Timer IC and the base of the NPN transistor.
4. Connect the collector of the NPN transistor to the VCC and the emitter to the negative rail of the breadboard.
5. Connect a 0.01μF capacitor between the base and the emitter of the NPN transistor.
6. Connect the anode of the LED to the collector of the NPN transistor and the cathode to the negative rail of the breadboard.
7. Connect a 1N4148 diode in reverse polarity between the output (pin 3) of the 555 Timer IC and the positive rail of the breadboard.
8. Connect a 10μF capacitor between the trigger (pin 2) and the negative rail of the breadboard.
9. Finally, connect the battery to the positive and negative rails of the breadboard.

When the circuit is powered on, the LED will turn on and stay on. Pressing the button or switch connected to the trigger (pin 2) will cause the LED to turn off and stay off. Releasing the button will cause the LED to turn back on.