Step 4: Making the Transmitter
Start by building the wooden base for the controller. I used two rectangular pieces of plywood, separated by four wooden pylons. The reason for this is that originally, when I was using PIC chips, the transmitter board was much larger and needed somewhere to go (you can see the old one above). The one use currently is the first picture, with the Arduino in frame. Yours can be way smaller, especially the handles -- I just like having really big levers to push around. In fact, if you use smaller levers, you won't need the elastic to hold them in up and in place. In my case, the weight of the handles means that they fall down without support. It is really nice to have an nice elastic response that zeroes the motors, as it makes the blimp much easier to control.
Anyway, cut and sand your wood, then put together some sort of a square base. Once you have that, screw in your metal angles, and space them out as much as possible across the base. Screw in pieces of wood that stand up vertically. Watch the screw length, too -- in my case, the only ones I had were too long, so now I keep stabbing myself because they poke through the wood.
Get your potentiometers out. The shaft diameters of the ones I got were 1/4", but when I drilled 1/4" holes in the handles they slipped and didn't hold firm. If this happens, you have a choice: glue the potentiometers in directly, or do what I did and fit a plastic straw around each shaft: it gives a good fit without slipping. Also make sure that your potentiometers are turned halfway when the lever is vertical; a small deviation can be corrected in software later, but if it's way off you won't be able to turn it in one direction.
Once you've got the first one in position, grab your trusty glue and fix your potentiometer to the vertical piece. Make sure to hold firmly for a bit. Do this for the other two, and then solder wires onto the three attachment points of each pot. I gathered these together and soldered them into a pretty standard connector so that they can be detached easily from the rest of the transmitter components.
Now get your elastic. Screw it into one side of a lever, screw it to the base, and then fix it to the other side at your desired firmness. This step took me a lot of tweaking, but it's worth it in the end when you have a smooth, automatic response.
Now you have the controller base, so you need to put together the board that connects it and the radio to the arduino. You can do this however you want by following the general schematic; I like things that are easily detachable, so I used a lot of connectors between components. I used the board in the picture above as a hub to bring all the wires together, and then used a row of pin headers to connect everything to the appropriate pins of the arduino. The picture above is missing the 9V battery clip, which I added later.
If you've reached this point, attached all the bits per the schematic, and haven't broken everything, I would suggest uploading the transmitter code and looking for the telltale series of square pulses on the radio's data line with an oscilloscope. If you can see it, and can see it change when you move the levers, you're in good stead.