Led timer circuit ---duration 45 days

[risingcurrent]

Hi guys

had requested help on this topic a month back , i want to implement a timer circuit which would turn on a led's to indicate a time of 30 days , 45 days and 60 days has passed and need the circuit to remember the past value if power is turned off and start counting from the value after power is restored , have ruled out 555 timers after a lot of problems in design with cap size and accuracy issues , is there any other way to implement this circuit .

have tried looking at microcontroller also for this kind of application ,find the fairchild semi ace1101 (attached document) easy to implement , anybody has experience with this microcontroller , or any suggestions for using any other microcontroller ,since would be investing on the progamming board ,emulator and other stuff please suggest a one which is useful for broad range of projects.

all suggestions and comments are welcome.

risingcurrent

 

[VVV]

PIC micros from Microchip have some advantages:
1. the development tools are FREE from Microchip's website
2. you can find schematics for programmers and in-circuit emulators even on this board. It would cost you about $25~$30 to build them (plus sweat equity).

That would keep your investment to an absolute minimum.

An inexpensive device that would definitely work in this application is the PIC12x508 or other from the same family (8 pin).

For battery backup you can simply use a couple of diodes, to keep the micro running in case of a power failure.
Or, using a 32.768kHz crystal would reduce the current so much, that you could run the micro continuously off the battery and just have the LED powered from another source.

 

[XNOX_Rambo]

You could program the MCU to count the time and store it in the data EEPROM.
Whenever the device is re-powered it would read the count from the EEPROM
and continue from there.

The only problem is the durabillity of the EEPROM. If you count with a resolution
of 1 second that will generate 5,184,000 writes in 60 days - but the EEPROM is only
specified for 1,000,000 so you need to have a longer timer "tick".
1 minute ticks will give you 86,400 writes and if you intend to reuse your timer
you can do it 11 times then.

Having some sort of battery backup, as VVV sugests, would do away with this problem.
If that is possible you could have a look at MSP430 from Texas Instruments. It has
a real-time clock mode that runs on only 0.8µA.

 

[risingcurrent]

VVV and XNOX

thank you for taking the time to reply and the suggestions , will try out the things mentioned and post back.

risingcurrent