How to implement a timer set on 30 days

[risingcurrent]

hi guys

am trying to implement a circuit to turn on a led after 30 days , want the circuit to be small , know that with 555 timer the circuit can get big and cap sizes can be a problem , is there a alternative way to implemen this using rc or lc timers or a smaller 555 timer circuit.

would appreciate if you could post a test circuit , all comments welcome

thank you
rising current

 

[maxwellequ]

Re: timer 30 days

I don't know how such things are usually implemented, but I would use a cristal oscilator and digital dividers. I don't think that you can get something accurate with the 555 (variation on the cap value, leakage currents...)

 

[penrico]

Re: timer 30 days

Why don't use a microprocessor with a 32.768Khz cristal???

 

[IanP]

Re: timer 30 days

Try:
Timer and divider 74HC5555
**broken link removed**
Regards,
IanP

 

[risingcurrent]

Re: timer 30 days

thank you Ian for taking the time to respond , will try the programmable delay counter from phillips .

just curious for a further modification of the project i am doing , the circuit has to function as a indicator for the application after 30 days , if it is not a repetetive task would there be a simpler way without using a 555 timer at all or microcontroller options where there is way for the circuit to turn on the led automatically after 30 days .

all comments appreciated .

rising current

 

[eltonjohn]

Re: timer 30 days

Don't ever think to do this with a 555 .This is the future already .micros are under a dolar .A pic12c509 can do this with very little lines of code .
1) set up a timer interruput or poll a counter
2)increment the variable senconds
SECS >60 :
3)increment the variable minutes
MINS > 60 :
4) increment the variable hours
HOURS > 24:
5) inmcrment the variable DAYS
DAYS = 30 do yout thing

If you want to do it the analog way . Detect the night and day with an optotransistor and count 30 transitions and that will be the same accuracy that with an 555