Five Second LED

This circuit allows an LED to emit for 5 seconds with the push of a switch. By using (t = 1.1 × R × C seconds), RC equals 4.545. The values of R = 10 kΩ and C = 470 µF were selected based on standard values of resistors and capacitors. The momentary push button switch is connected to ground and to the trigger input with a 10K current limiting resistor pullup to the supply voltage. When the push button is pressed, the trigger pin goes to ground. An LED is connected to the output pin with a current limiting resistor in series to ground. The reset pin is not used so it is connected to the supply voltage.

published 10 years ago