First Big Arduino project, Need help!

So, looking to start my first few arduino projects. However, since I'm looking at doing more than one, it seemed much more cost effective to purchase one arduino, and use it to bootload/program several other atmega328 chips as opposed to purchasing multiple arduinos, which will also hopefully allow for this to be a more permanent setup. So, several questions:

First, I have read that there are issues using the arduino Uno to burn the bootloader (acting as an isp?). Are these issues still relevant? Would I be better off purchasing a Duemilanova from ebay or somewhere else?

Secondly: Here is the design for the "cheap arduino" that I have running through my mind. With this design, will it function any differently than a off the shelf arduino, and is any functionality lost? (Besides usb communication). Is anything here unnecessary?

For the main project I'm working on, the arduino will be receiving temperature readings from 3-4 (still undecided) Max6675 chips. If I have read the arduino library below correctly, I can use multiple SO and CK pins, and then simply have them share a CS pin? Again, very new to this and am still a bit confused. But, is there any issue reading from 4 separate thermocouples/max6675 chips every 5-10 seconds? Next, what to do with the information? Ideally, it is going to be transmitted wirelessly to a computer 30 feet or so away. Figuring bluetooth was the easiest way to do this, and trying to stay as cheap but effective as possible, I came across the RN-42 bluetooth chip. Should this chip work effectively? Are there any better chips in the same price range (~$20)? If I wanted to add a cheap, 2 line LCD screen to this setup at a later point, is there likely still to be room for it? Lastly, all of this being said, can all of this together fit on an arduino? Moreover, can it fit on the hackduino design described above?

Any help would be greatly appreciated! Thanks! Schuyler

Schuyler: I have read that there are issues using the arduino Uno to burn the bootloader (acting as an isp?). Are these issues still relevant?

My Uno works fine as an ISP.

Someone smarter than me will have to answer your other questions ;)

If you're looking for cheap short range radio comms, there are several options such as Wifi, BlueTooth, ZigBee mesh radio, 434MHz Transmitter/receiver pair or nRF24L01+ transceivers.

The nRF24L01+ is only short range (without using an external aerial I can get a signal through one 9" brick wall but not two walls) but is dramatically cheaper than the other options. If you don't mind waiting for a week or so while they get here from China you can get them for a couple of quid each.

You talk about starting with a UNO and then buying separate chips for subsequent projects. I think there is a well trodden path starting with a standard Arduiono, using smaller/cheaper Arduino clones, putting the chip on your own solderless plugboard circuit, soldering it into a protoboard circuit and finally getting your own PCBs made. I'd suggest you take a small step at a time. Certainly you don't need to buy a UNO and build it permanently into each gadget you make.

Yes, parallel MISO/MOSI/SCK to all devices, give each its own chip select.

Build up clone, will work just fine, pre-load '328s & drop into your circuit.

Try the Optiboot bootloader here for burning blank chips.
Connect Uno’s D10 to blank’s Reset, D11 to D11, D12 to D12, D13 to D13, power to power, gnd to gnd.

If you want PCBs, contact me later, can help you out.

RF comm’s using virtualwire library work great with <$10/set 434 MHz Tx/Rx hardware, for example use 17cm wire for antenna - wirewrap wire works fine.
Default pins are 11,12, you will need to use a couple of the commands to use other pins instead.

I like wirewrap pins for perfboard work:

Try a Serial interface LCD, don’t need to tie up tons of pins.

Thanks for all the tips! Definitly helps. Only question regarding RF is though, I need to have the information transmitted from the arduino to a pc, where it will be interpreted in a C# application. Is there a feasible way to do this with RF?

Sure, have the receiving '328 send the data over serial/RS232/USB to the PC.

What advantages does RF have over bluetooth? Stronger signal?

Yes. Longer range.

I built a bare-bones arduino clone; the BareDuino

It's open source so maybe it will help you design your own..

So, I'm back to work on this project! However, looking for some advice again. The end goal of this arduino project is to receive data, and upload it to a mysql database. Now, my original plan was to use RF to transport the data to a computer, which would upload it to the database. However, how much more work/money would it take to do this from the arduino itself, both wirelessly and using ethernet? This could be done using php or a direct connection to the mysql database. Thanks, Schuyler

Well, a wifi shield will set you back about $50, as will an Arduino ethernet. After that it's just a matter of deciding how you want to send the data to mysql. I did it using a LAMP server and a bit of perl, but there are plenty of alternatives.

Would this device work for what I am trying to do? All it really would have to do is be able to run a GET webrequest.