I am busy on 3 projects at once, one is to supply some devices I designed with cmos chips before finding arduino .
The one part is a small timer/transmitter running on a 3v CR2450 coin cel .
Every 24 hours roughly, it must send a battery OK / system check code ( I am using a Holtek HT12E at the moment and a Hope cheap 443 MhzTx )
If an event is triggered it sends an immediate different code.
There is another cmos chip to handle the sensors, and I am using an HCF4060 for the timing, and my total battery current averages 30 microamps, so the 620mAh battery should last 2 years.
There are quite a few components on the board, so I was thinking that perhaps I should switch to an Attiny ?
Could I get the sleep mode to draw 30 microamps ? Actually it could be 100 microamps with no hassle.
Would there be a problem with 24 hour timing, I have had a quick look, but there seem to be quite a few different types, I would need one I can program with arduino code of course.
I was thinking that if it could sleep with a watchdog ? timer on, and everytime it awoke it could increment a counter to get to the 24 hours ? I dont think the watchdog is very long on these things ?.
And is there an interupt to detect the event input ? for immediate transmission -- using WirtualWire .
Before I try anything ( when I get some time ) I just want to know if it is feasible, for the next orders.
The cmos chips are cheap, but the pcb and assemblly costs quite a bit, perhaps it would balance out.
Any advice ?