Arduino
http://www.instructables.com/id/Make-your-own-Arduino-on-Veroboard/
Try using an lcd with SPI, they're cheap on eBay.
Systems
Power
Step Up
- $2.07 : 3v3 step up
- $0.50 : Battery Clip
Can run off a single AAA battery, good for lightweight.
Step Down
- $0.40 : Battery clips
- $0.43 : Step down regulator
Cheaper, lasts longer. I need to try using just the clips to hold a battery to board. Can also swap out the 4xAAA for a 9V. Lasts even longer, and probably lighter overall.
Display
All options are about $2. The 16x2 is a bit larger and more readable but limited to text. The 5110 is more flexible but kind of small.
Setup
Pro-Mini
$4.62
I really liked these at first, but now that I'm getting a better grasp on the stand-alone circuits, it's not as good. It takes us just as much space as the dip would, the analog inputs are hard to get to.
Stand Alone Tiny85
~$1.50
Limited IO, but that can be expanded with 74HC chips. Good for simple, small projects.
Stand Alone Mega328
~$2.00
Full power Arduino, fairly compact. I think this is the best option.
Setups
- $1.00 : Power; 9v | 4xAAA step down
- $2.00 : Display
- $2.00 : Mega328
- $0.13 : Small Perf Board
$5.13
- $2.50 : Power; AAA step up
- $2.00 : Display
- $2.00 : Mega328
- $0.13 : Small Perf Board
$6.63