24 hrs. clock clock cycle in a 555 timer

[rajaram04]

Hello sir
Tell me about the circuit diagram of 555 in a timer mode so as to make a high clock pulse of 6 hours & a low clock pulse of 18 hours.i want the circuit to be run repeatdly with these clock pulses only.
thanks

 

[ZekeR]

I'm assuming you want a decent amount of accuracy, so that it will remain synchronized with the earth's rotation (I'm assuming you want to turn a light on and off, or something similar?)

Unfortunately, while the 555 is fun, useful, and flexible, it's not very accurate. And even if it were, the components around it would limit its accuracy. It's typical to get resistors with 5% accuracy and capacitors with 20% accuracy. This means that it would only take 3 days for your timer to be wrong by half a day!

It's best to go with either:
a) If you have access to the power line, you can count the power line cycles (it's 60Hz in America, 50Hz elsewhere). The power company keeps a pretty stable frequency.
b) If you don't have access to the power line, you can use a 32kHz quartz crystal used in watches. Most microcontrollers have accommodations for crystal oscillators, and if you opt not to use a micro, it's not especially difficult to make a resonator for yourself.