I'm developing a camera controller using the ATMega8 as my platform. This is my first foray into the whole microcontroller thing and, now i think about it, my first real electronics project.
I've drawn up the schematic, coded the C and tested it all in Proteus. Of course, in the simulation it just has a +5V rail and a ground rail...
The device needs to be portable so this, to my mind, means either using a 9V battery - searching this forum and wikipedia would imply this is bad (low energy density) or 3xAA batteries.
The LCD is a bog standard, JHD162A based on the HD47780 controller. According to the datasheet, it needs a minimum of 4.5V to work (though i imagine slightly less would be ok). The IC is, as far as i can tell, rated up to 6V and requires between 2.2 and 5.5 when running between 0-10Mhz. I'm using an external 8MHz crystal so that's applicable. The only other output will be a couple of LEDs (the device controls the camera via an IR signal).
The battery life needs to last for a while, shooting could take hours so i guess 30 hours is a good lifetime on one charge. I think it's reasonable to assume that the power consumption of the entire device is never likely to exceed 75-100mA. Assuming an AA battery has 2500mAh then that should give a good 30 hours allowing for idle periods. I'm going to put in a switch to turn off the LCD backlight when not in use - say for time lapse shooting where the device is unattended and simply needs to send a short burst of IR light to the camera every so often.
As i'm not going to be running off anything higher than the maximum voltages, would i be able to wire up the AVR and the LCD in parallel directly to the battery pack or do i need to regulate it?