Design Updates

Today i found an incredible deal on Alphanumeric Displays from goldmine electronics.  A package of 5 displays can be had for $1.00 which makes them come out to only $0.20 a piece!  This is cheeper then all the regular 7-Segment Leds we've been looking at and with the alphanumeric displays we can make any letter we want. 

We also scraped the SCR circuit.  After we got the idea to use LCD displays we ran into a new problem which was that we needed 3.0V and the SCR dropped our operating voltage from 3.0V to 2.1V.  I posted some questions on a forum about having microcontrollers wake from an external interrupt pin and other low power configurations and sure enough their is a new revision of the microcontroller we were using that make the SCR circuit obsolete.  First of all it has an internal 37kHz osc. in addition to the internal 4Mhz osc.  Since our project requires practically no processing the 37Khz osc is suitable.  As a rule of thumb the higher the clock used the more power the pic consumes. 

I'm currently not sure how much of a difference this will make.  I'm not sure if the PIC shuts down the oscillator when it's in sleep mode.  I remember reading somewhere before that when using the internal oscillator even in sleep mode the PIC consumed something like 50uA.  Then today i think i read in the datasheet that when the PIC is operating at 3.0V with the 37kHz clock in only consumes 12uA.  So on our particular battery which has a capacity of 215mAh.  The PIC never even going to sleep would last: 215mAh *  ( 1000 uAh / 1maH ) (1/12uA) = 17916 hours (1 day / 24 hrs ) = 746 days = 2.04 years!