One of my mental barriers with the Arduino is the idea that any project will cost me at least $30 for the board. So it's a bit spendy if I want to make, say, a photosensitive night-light or some other simple project.
But the idea of making something cool, taking the time to perfect it, and then just disassembling it, that makes me a bit sad.
I hear mentions of taking the microprocessor off the board and using it by itself. Is that a cost-effective way to keep projects alive? Do you have to deal with a lot of tradeoffs in doing so?
I'd suggest you read about Arduino standalone (http://www.arduino.cc/playground/Learning/Standalone). At least for me, the Arduino is a prototyping platform, if I decide to make anything permanent, then I'd make a standalone version.
I hear mentions of taking the microprocessor off the board and using it by itself. Is that a cost-effective way to keep projects alive?
Certainly it is, adding a 328 processor and required supporting components will cost less then $10 above whatever other costs of your specific project has. Use the Arduino board to prototype the application and test the software and then move on to adding a standalone 328 chip to the project. It makes no sense to buy a whole board for each project completed for size as well as cost increase.
Do you have to deal with a lot of tradeoffs in doing so?
None that I can see for a 328 based project. Now a avr1280 project might not be as simple as making a standalone 1280 is beyond most simple hobbyist due to the smd mounting and trace sizes.
Ok - so you now know you can do a standalone Arduino - great! However, this statement of yours:
One of my mental barriers with the Arduino is the idea that any project will cost me at least $30 for the board.
While I can understand it, I have to inject a bit of perspective here:
When I started with the Ardunio, I did so because my OS platform I had switched to (64-bit Ubuntu) no longer supported the byte-code compiler for the Parallax Basic Stamp 2 (due to statically linked 32-bit libraries - ugh!); the compiler was binary only, and Parallax was no longer supporting it, nor did they have the source code or know where the original programmer ran off to. I was stuck.
Looking around, somehow I ran across the Arduino! Here was a system that even from one of the more expensive vendors (say, SparkFun) - was only going to cost $30.00 for the entire board!
The Parallax Basic Stamp 2 in the 0.600 DIP format cost about $50.00 at the time. I though the Arduino was a bargain. After I had done a bit of browsing the site, looking at the schematics, and reading about the standalone version (and price shopping the ATMega168) - I was really sold on it.
So - long story short - it could be worse - a lot worse. While in practice you could easily do a "standalone" PIC system, you would still have to purchase a compiler for it (C or BASIC), as the only open-source compiler for C on the PIC only supports a small subset of the PIC lineup - and those compilers aren't too cheap (I won't lie - they won't break the bank, either), plus they only run on Windows.
Good luck with building a standalone!
I have been building ProMinis into my projects, I just +5V that I get from a regulator or wallwart or battery or whatever I am using to power the rest of the project. $17 from gravitech and whatever connectors needed to wire in the I/O I am using.
If I had seen them sooner, I might have used these slightly less DIP based boards instead:
But for me its been pretty convenient just putting in the 6 pins for programming it, +5V on the Vin, Gnd, Rx, and 6 I/O wires.
I have a Duemilanove for prototyping my designs.
I haven't done anything in sufficient qty to warrant building the uC into a custom PWB.
me also, 4 pins for programming 2 for pwr and gnd and bob's your uncle
(as long as you have a programmer or an extra arduino as a programmer)