The lengendary 555 timer in monostable mode

Circuit diagram for connecting LED to NE555 timer, and operating in monostable mode.

LED rating is 12v, but also using 9v is possible but less bright ( to me the brightness is ok?

How NE555 timer operate in monostable mode (delay timer):

  • Power supply is 5 to 16 VDC (Pin 8) and ground is Pin 1.
  • Pin 2 is trigger pin (active low) and always set high by a 10kΩ pull-up resistor.
  • Pin 3 is the output pin with max. current output of approximately 200mA, but gets pretty hot at this amount of current. Therefore a 10kΩ resistor to control the current. The 2N2222 NPN BJT transistor will boost the current to light the 12V LED.
  • Pin 4 is the reset pin,when pulled low will cause the 555 timer to stop all operations.
  • Pin 5 is not in use, and a 0.01uF capacitor is connected to it to prevent pin 5 to be a floating pin.
  • Pin 6 and 7 form a RC circuit which determines how long the LED will stay ‘ON’.
  • The 1MΩ potentiometer at its minimum will light up the LED for approx. 1 second and at its maximum will light up to LED for 2 minutes.