So we have calculated OFF time above, means after the calculated time LED will be turned ON. We should note here that we have used LED at reverse logic, means when OUTPUT pin 3 is low, LED will be ON, and when OUTPUT is HIGH then LED will be OFF. Similarly to create a 10 minute timer we would be changing the resistor value to 545.4 k ohm.Īs per above calculations, for a 15 minute timer circuit, we need the value of resistor to 818.2k ohm. So to build a 5 minute timer circuit, we would be simply changing the resitor value to 272.7k ohm in above given 1 minute timer circuit. We can easily calculate the resistor value for 5 minute, 10 minute and 15 minute timer circuit:
So to build 1 minute (60 seconds) timer we need resistor of value 55k ohm and capacitor of 1000uF: In monostable mode, the duration for which the PIN 3 would remain HIGH, is given by the below formulae: We need to set 555 timer in Monostable mode to build Timer. All we need to change the value of Resistor R1 and/or Capacitor C1. We can use this property of 555 timer to create various timer circuits like 1 minute timer circuit, 5 minute timer circuit, 10 minute timer circuit, 15 minute timer circuit, etc. It means for some time output pin 3 is HIGH and for some time it remains LOW, that will create a oscillating output.
As the name suggest 555 timer is basically a “Timer”, which create an oscillating pulse.
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