Fahime,
In the circuit, C5 filters low frequencies and C4 filters high frequencies. The 555 makes a high frequency spike on the supply when it switches and the electrolytic capacitor C5 has too much inductance to be a good filter at high frequencies.
20 hours is too long a timing period for a 555. The timing capacitor must be huge and have extremely low leakage current. An electrolytic capacitor has way too much leakage current.
Use a CD4541 oscillator/timer instead because it has a digital divider chain for long timing periods. It is low power Cmos so it needs a transistor on its output to drive a relay.
Pin 2 of a 555 has a threshold voltage that is at 1/3rd of the power supply voltage. The timing begins when the voltage on pin 2 is reduced to a voltage slightly lower than 1/3rd of the supply voltage.
Pin 6 has a threshold voltage that is at 2/3rds of the power supply voltage. When the capacitor charges to a voltage slightly higher than 2/3rds of the supply voltage then the discharge begins.
C1 is the timing capacitor. The circuit does not need C2. C2 is supposed to be the START switch.
In the circuit, C5 filters low frequencies and C4 filters high frequencies. The 555 makes a high frequency spike on the supply when it switches and the electrolytic capacitor C5 has too much inductance to be a good filter at high frequencies.
20 hours is too long a timing period for a 555. The timing capacitor must be huge and have extremely low leakage current. An electrolytic capacitor has way too much leakage current.
Use a CD4541 oscillator/timer instead because it has a digital divider chain for long timing periods. It is low power Cmos so it needs a transistor on its output to drive a relay.
Pin 2 of a 555 has a threshold voltage that is at 1/3rd of the power supply voltage. The timing begins when the voltage on pin 2 is reduced to a voltage slightly lower than 1/3rd of the supply voltage.
Pin 6 has a threshold voltage that is at 2/3rds of the power supply voltage. When the capacitor charges to a voltage slightly higher than 2/3rds of the supply voltage then the discharge begins.
C1 is the timing capacitor. The circuit does not need C2. C2 is supposed to be the START switch.
