This avoids accidental triggering of the circuit.
This circuit will ensure automatic switch off of these lights avoiding wastage of electricity.C2 should have low leakage otherwise it will charge very slowly and in cases of excessive leakages may not charge to motogp 2 demo game for pc full value at all.Html Comment Box is loading comments).The capacitor C2 across pin-5 and ground absorbs external noise and avoids abrupt change in time length when the switch is pressed.There is a delay of about 5 seconds with this circuit.Basically the capacitor takes time to charge.Important points to note, the resistor R2 is used to pull up pin-2 to positive potential.Initially, because it takes time for a capacitor to charge up, it's going to have very low voltage initially until it builds up voltage.
Working, when supply is connected to the circuit keeping the push-to-on switch in OFF condition, the output of the IC remains LOW and the circuit remains in this state, until you press the switch Sw1.
Pin 3 is the output pin.
The SCR is then placed between ground and the 340 volt side of the capacitor.The RC network is what determines this delay time.The 555 timer output at pin 3 will be high and the voltage at pins 6 and 2 of the timer will be a little less than the lower trigger point, or about 3 volts.The reason why the circuit turns on automatically is because pin 6, the threshold pin, is initially LOW.Menu 9 Second LED Timer and Relay Circuit.The reverse connected emitter/base junction of a 2N3904 transistor is used as an 8 volt zener diode which creates a higher turn-on voltage for the Darlington connected transistor pair.When the 9th count is reached, pin 11 and 13 will be high, stopping the counter and energizing the relay.